Astronomy Picture of the Day |
APOD: 2024 March 8 - The Tarantula Zone
Explanation:
The Tarantula Nebula,
also known as 30 Doradus, is more than a thousand light-years in diameter,
a giant star forming region within nearby satellite galaxy the
Large Magellanic Cloud.
About 180 thousand light-years away, it's the largest,
most violent star forming region known in the whole Local
Group of galaxies.
The cosmic arachnid sprawls across
this magnificent view,
an assembly of image data from large space- and ground-based telescopes.
Within the Tarantula (NGC 2070),
intense radiation, stellar winds, and supernova shocks
from the central young cluster of massive stars cataloged as R136
energize the nebular glow and shape the spidery filaments.
Around the
Tarantula are other star forming regions with
young star clusters, filaments, and blown-out
bubble-shaped clouds.
In fact, the frame includes the site of the closest supernova in
modern times, SN 1987A,
at lower right.
The rich field of view spans about 2 degrees
or 4 full moons in the southern
constellation Dorado.
But were the Tarantula Nebula closer, say 1,500 light-years distant like
the Milky Way's own star forming Orion Nebula,
it would take up half the sky.
APOD: 2023 October 7 - The Once and Future Stars of Andromeda
Explanation:
This picture of Andromeda shows not only where stars are now,
but where stars will be.
The big, beautiful
Andromeda Galaxy,
M31, is a
spiral galaxy
a mere 2.5 million
light-years
away.
Image data from space-based and ground-based observatories have been
combined here to produce
this intriguing composite
view of Andromeda at wavelengths both
inside and outside normally visible light.
The visible light
shows where M31's stars are now, highlighted in
white and blue hues and imaged by the
Hubble,
Subaru, and
Mayall telescopes.
The infrared light
shows where M31's future stars will soon form,
highlighted in orange hues and imaged by NASA's
Spitzer Space Telescope.
The infrared light tracks enormous
lanes of dust,
warmed by stars, sweeping along Andromeda's spiral arms.
This dust is a tracer of the galaxy's vast
interstellar gas, raw material for future
star formation.
Of course, the new stars will likely form over the next hundred million years or so.
That's well before Andromeda merges with our
Milky Way Galaxy in about 5 billion years.
APOD: 2022 November 3 - M33: The Triangulum Galaxy
Explanation:
The small, northern constellation
Triangulum
harbors this magnificent face-on spiral galaxy, M33.
Its popular names include the Pinwheel Galaxy or just
the Triangulum Galaxy.
M33 is over 50,000 light-years in diameter, third largest in the
Local
Group of galaxies after the Andromeda Galaxy (M31), and our
own Milky Way.
About
3 million light-years from the Milky Way,
M33 is itself thought to be a satellite of the
Andromeda Galaxy and
astronomers
in these two galaxies would likely have spectacular views of
each other's grand spiral star systems.
As for the view from the Milky Way,
this
sharp image combines data from telescopes on and around planet
Earth to show off M33's blue star clusters
and pinkish star forming regions along
the galaxy's loosely wound spiral arms.
In fact, the
cavernous NGC 604
is the
brightest star forming region, seen here at about the 1 o'clock position
from the galaxy center.
Like M31, M33's population of well-measured variable stars
have helped make this nearby spiral a cosmic yardstick for
establishing
the distance
scale of the Universe.
APOD: 2022 September 16 - The Tarantula Zone
Explanation:
The Tarantula Nebula,
also known as 30 Doradus, is more than a thousand light-years in diameter,
a giant star forming region within nearby satellite galaxy the
Large Magellanic Cloud.
About 180 thousand light-years away, it's the largest,
most violent star forming region known in the whole Local
Group of galaxies.
The cosmic arachnid sprawls across
this magnificent view,
an assembly of image data from large space- and ground-based telescopes.
Within the Tarantula (NGC 2070),
intense radiation, stellar winds, and supernova shocks
from the central young cluster of massive stars cataloged as R136
energize the nebular glow and shape the spidery filaments.
Around the
Tarantula are other star forming regions with
young star clusters, filaments, and blown-out
bubble-shaped clouds.
In fact, the frame includes the site of the closest supernova in modern times,
SN 1987A,
at lower right.
The rich field of view spans about 2 degrees
or 4 full moons, in the southern
constellation Dorado.
But were the Tarantula Nebula closer, say 1,500 light-years distant like
the Milky Way's own star forming Orion Nebula,
it would take up half the sky.
APOD: 2022 July 18 - Stephans Quintet from Webb, Hubble, and Subaru
Explanation:
OK, but why can't you combine images from Webb and Hubble?
You can, and
today's featured image shows one impressive result.
Although the recently launched
James Webb Space Telescope (Webb) has a
larger mirror than Hubble, it specializes in
infrared light
and can't see blue -- only up to about orange.
Conversely, the Hubble Space Telescope (Hubble) has a smaller mirror than Webb and can't see as far into the infrared as Webb,
but can image not only
blue light but even
ultraviolet.
Therefore, Webb and
Hubble data can be
combined to create images across a wider variety of colors.
The featured image of four
galaxies from
Stephan's Quintet
shows Webb images as red and also includes images taken by
Japan's ground-based
Subaru telescope in
Hawaii.
Because image data for
Webb,
Hubble, and
Subaru are made freely available, anyone around the world can process it themselves, and even create
intriguing and scientifically useful multi-observatory montages.
APOD: 2022 May 23 - The Once and Future Stars of Andromeda
Explanation:
This picture of Andromeda shows not only where stars are now,
but where stars will soon be.
Of course, the big, beautiful
Andromeda Galaxy, M31, is a
spiral galaxy -- and a mere 2.5 million
light-years away.
Both space-based and ground-based observatories have been
here combined to produce
this intriguing composite image of Andromeda, at wavelengths both inside and outside normally visible light.
The visible light shows where M31's stars are now -- as highlighted in white and blue hues and imaged by the
Hubble,
Subaru, and
Mayall telescopes.
The infrared light shows where M31's future stars will soon form -- as highlighted in orange hues and imaged by NASA's
Spitzer Space Telescope.
The infrared light tracks enormous
lanes of dust,
warmed by stars, sweeping along Andromeda's spiral arms.
This dust is a tracer of the galaxy's vast interstellar gas -- the raw material for future
star formation.
These new stars will likely form over the next hundred million years,
surely
well before Andromeda
merges with our
Milky Way Galaxy in about 5 billion years.
APOD: 2022 January 19 - M31: The Andromeda Galaxy
Explanation:
The most distant object easily visible to the unaided eye is
M31,
the great Andromeda Galaxy.
Even at some two and a half million
light-years distant,
this immense spiral galaxy -- spanning over
200,000 light years -- is visible, although as a faint, nebulous cloud in the
constellation
Andromeda.
In contrast, a bright yellow nucleus, dark winding
dust lanes, and
expansive spiral arms dotted with
blue star clusters and
red nebulae,
are recorded in
this stunning telescopic image
which combines data from
orbiting Hubble with ground-based images from
Subaru and
Mayall.
In only about 5 billion years, the Andromeda galaxy may be even
easier to see -- as it will likely span the
entire night sky -- just before it
merges with our
Milky Way Galaxy.
APOD: 2021 August 18 - Rings Around the Ring Nebula
Explanation:
The
Ring Nebula (M57),
is more complicated than it appears through a small telescope.
The easily visible
central ring is about one
light-year across,
but this remarkably deep exposure -
a collaborative effort combining data from three different large telescopes -
explores
the looping filaments of glowing gas extending much farther from
the nebula's central star.
This
composite image includes red light emitted by hydrogen as well as
visible and infrared light.
The Ring Nebula is an elongated
planetary nebula, a type of nebula created when a
Sun-like star evolves to
throw off its outer atmosphere to become a
white dwarf star.
The Ring Nebula is about 2,500 light-years away toward the musical
constellation
Lyra.
APOD: 2021 April 9 - Messier 106
Explanation:
Close to the Great Bear
(Ursa Major) and surrounded by the stars of the
Hunting Dogs
(Canes Venatici), this celestial wonder was
discovered
in 1781 by the
metric
French astronomer
Pierre Mechain.
Later, it was added to the catalog of his friend and colleague
Charles Messier as
M106.
Modern deep telescopic views reveal it to be an
island universe -
a spiral galaxy around 30 thousand light-years across located
only about 21 million light-years beyond the stars of the Milky Way.
Along with a bright central core,
this
stunning galaxy portrait,
a composite of image data from amateur and professional telescopes,
highlights youthful blue star clusters and reddish stellar nurseries
tracing the galaxy's spiral arms.
It also shows off remarkable reddish
jets of
glowing hydrogen gas.
In addition to small companion galaxy NGC 4248 at bottom right,
background galaxies can be found scattered throughout the frame.
M106, also known as NGC 4258, is a nearby example of the
Seyfert class of active galaxies, seen
across the spectrum
from radio to X-rays.
Active galaxies are powered by matter falling into a massive
central black hole.
APOD: 2020 November 1 - In the Center of the Trifid Nebula
Explanation:
What's happening at the center of the Trifid Nebula?
Three prominent
dust lanes that give the
Trifid its name all come together.
Mountains of opaque dust
appear near the bottom, while other dark filaments of
dust are visible threaded throughout the nebula.
A single massive star
visible near the center causes much of the
Trifid's glow.
The Trifid, cataloged as
M20,
is only about 300,000 years old, making it among the youngest
emission nebulas known.
The star
forming nebula lies about 9,000
light years away toward the
constellation of the Archer (Sagittarius).
The region
pictured here spans about 10 light years.
The featured image is a composite with
luminance taken from an image by the 8.2-m ground-based
Subaru Telescope,
detail provided by the 2.4-m orbiting
Hubble Space Telescope,
color data provided by
Martin Pugh
and image assembly and processing provided by
Robert Gendler.
APOD: 2020 August 4 - NGC 2442: Galaxy in Volans
Explanation:
Distorted galaxy NGC 2442 can be found in the southern constellation of the
flying fish,
(Piscis) Volans.
Located about 50 million light-years away, the galaxy's two
spiral arms extending from a pronounced central bar have a hook-like
appearance in wide-field images.
But this
mosaicked close-up, constructed from
Hubble Space Telescope and
European Southern Observatory
data, follows the galaxy's structure in
amazing detail.
Obscuring dust lanes, young blue star clusters and
reddish star forming regions
surround a core of yellowish light from an older population of
stars.
The sharp image data also reveal more distant
background galaxies seen right through NGC 2442's
star clusters and nebulae.
The image spans about 75,000
light-years
at the estimated distance
of NGC 2442.
APOD: 2020 April 14 - NGC 253: The Silver Coin Galaxy
Explanation:
NGC 253 is one of the brightest spiral galaxies visible, but also one of
the dustiest.
Dubbed the
Silver Coin
for its appearance in smalltelescopes, it is more formally known as
the Sculptor Galaxy
for its location within the boundaries of the southern constellation Sculptor.
Discovered in 1783 by mathematician and astronomer
Caroline Herschel,
the dusty island universe lies a mere 10 million light-years away.
About 70 thousand light-years across, NGC 253,
pictured, is the largest member of
the Sculptor
Group of Galaxies, the nearest to our own
Local Group
of galaxies.
In addition to its spiral dust lanes, tendrils of dust seem to be
rising from a galactic disk
laced with young star clusters and star forming regions in this
sharp color image.
The high dust
content accompanies frantic star formation,
earning
NGC 253 the designation of a
starburst
galaxy.
NGC 253
is also known to be a
strong source of high-energy
x-rays and
gamma rays,
likely due to massive
black holes near the galaxy's center.
Take a trip through extragalactic space in
this short
video flyby of NGC 253.
APOD: 2020 February 15 - Carina Nebula Close Up
Explanation:
A jewel of the southern sky, the
Great
Carina Nebula, also known as NGC 3372, spans over 300 light-years,
one of our galaxy's largest star forming regions.
Like the smaller, more northerly
Great Orion Nebula, the
Carina Nebula is easily visible to the
unaided eye, though at a distance of 7,500
light-years it is some 5 times farther away.
This
gorgeous telescopic close-up
reveals remarkable details of the region's central glowing filaments of
interstellar gas
and obscuring cosmic dust clouds in
a field of view nearly 20 light-years across.
The Carina Nebula is home to young, extremely massive stars, including
the still enigmatic and violently variable
Eta Carinae, a
star system with well over 100 times the mass of the Sun.
In the processed composite of space and ground-based image data
a dusty, two-lobed Homunculus Nebula
appears to surround Eta Carinae itself just
below and left of center.
While Eta Carinae is likely on the verge of a supernova explosion,
X-ray images indicate that the Great Carina Nebula
has been a veritable
supernova
factory.
APOD: 2019 October 3 - The Hydrogen Clouds of M33
Explanation:
Gorgeous spiral galaxy M33 seems to have more than its fair share of
glowing hydrogen gas.
A prominent member of the local group of galaxies, M33 is also
known as the Triangulum Galaxy and
lies a mere 3 million light-years away.
The galaxy's inner 30,000 light-years or so are shown in this
magnificent 25 panel telescopic mosaic.
Based on image data from space and ground-based telescopes,
the portrait of M33 shows off the galaxy's reddish ionized hydrogen
clouds or HII
regions.
Sprawling along loose spiral arms that wind toward the core,
M33's
giant HII regions are some of the largest known
stellar nurseries, sites of the formation of short-lived
but very massive stars.
Intense ultraviolet radiation from the luminous, massive stars ionizes
the surrounding hydrogen gas and ultimately produces the
characteristic red glow.
To enhance this image, broadband data were used to produce a color view
of the galaxy and combined with narrowband data recorded through a
hydrogen-alpha filter.
That filter transmits the light of the strongest visible hydrogen
emission
line.
APOD: 2019 August 28 - Messier 61 Close Up
Explanation:
Image
data from the Hubble Space Telescope,
the European Southern Observatory,
and small telescopes on planet Earth are combined in this
magnificent portrait of face-on spiral galaxy Messier 61 (M61).
A mere 55 million light-years away in the Virgo Cluster of Galaxies,
M61 is also
known as NGC 4303.
It's considered to be an example of a barred spiral galaxy
similar to
our own Milky Way.
Like other spiral galaxies, M61 also features sweeping spiral arms,
cosmic dust lanes, pinkish star forming regions, and young blue star
clusters.
The bright galactic core is offset to the left in this
50
thousand light-year wide close-up.
APOD: 2019 June 29 - M83: The Thousand Ruby Galaxy
Explanation:
Big, bright, and beautiful,
spiral galaxy M83
lies a mere twelve million light-years away, near the southeastern
tip of the very long constellation
Hydra.
Prominent spiral arms traced by dark dust lanes and blue star
clusters lend this galaxy its popular name, The Southern Pinwheel.
But reddish
star forming regions
that dot the sweeping arms highlighted in this
sparkling
color composite also suggest another nickname,
The Thousand-Ruby Galaxy.
About 40,000 light-years across, M83 is a member of a group of
galaxies that includes active galaxy
Centaurus A.
In fact, the core of M83 itself is bright
at x-ray energies, showing a high
concentration of neutron stars and black holes left from
an intense burst of star formation.
This sharp composite color image also features
spiky
foreground Milky Way stars and distant background
galaxies.
The image data was taken from the Subaru Telescope,
the European Southern Observatory's Wide Field
Imager camera,
and the Hubble Legacy Archive.
APOD: 2019 May 29 - M95: Spiral Galaxy with an Inner Ring
Explanation:
Why do some spiral galaxies have a ring around the center?
First and foremost,
M95 is one of the closer examples of a big and beautiful barred
spiral galaxy.
Visible in the
featured combination of images from
Hubble
and several ground based telescopes are sprawling spiral arms delineated by
open clusters of
bright blue stars, lanes of dark dust, the diffuse glow of billions of faint stars, and a short
bar across the galaxy center.
What intrigues many astronomers, however, is the
circumnuclear ring
around the galaxy center visible just outside the central bar.
Although the
long term stability of this ring remains a
topic of research,
observations indicate its present brightness
is at least enhanced by transient bursts of star formation.
M95, also known as NGC 3351, spans about 50,000
light-years, lies about 30 million light years away,
and can be
seen with a small telescope toward the constellation of the Lion
(Leo).
APOD: 2019 March 17 - M106: A Spiral Galaxy with a Strange Center
Explanation:
What's happening at the center of spiral galaxy M106?
A swirling disk of stars and gas,
M106's appearance is dominated by blue spiral arms and red
dust lanes near the nucleus, as shown in the
featured image.
The core of
M106 glows brightly in
radio waves and
X-rays where
twin jets have been found running the length of the galaxy.
An unusual central glow makes
M106 one of the closest examples of the
Seyfert class of galaxies,
where vast amounts of glowing gas are thought
to be falling into a central massive
black hole.
M106,
also designated
NGC 4258,
is a relatively close 23.5 million light years away,
spans 60 thousand
light years across, and can be seen with a small telescope
towards the constellation of the Hunting Dogs (Canes Venatici).
APOD: 2019 January 10 - Vela Supernova Remnant Mosaic
Explanation:
The plane of our Milky Way Galaxy runs through this
complex
and beautiful skyscape.
Seen toward colorful stars
near the northwestern edge of the constellation
Vela
(the Sails),
the 16 degree wide, 200 frame mosaic is
centered on the glowing filaments of the
Vela
Supernova Remnant, the expanding debris cloud from the
death explosion of a massive star.
Light from the supernova explosion
that created the Vela remnant
reached Earth about 11,000 years ago.
In addition to the shocked filaments of glowing gas, the cosmic
catastrophe also left behind an incredibly dense,
rotating stellar core, the Vela Pulsar.
Some 800 light-years distant, the Vela remnant is likely
embedded
in a larger and older supernova remnant,
the Gum Nebula.
Objects
identified in this broad mosaic include
emission and reflection nebulae, star clusters,
and the remarkable
Pencil
Nebula.
APOD: 2018 December 17 - M31: The Andromeda Galaxy
Explanation:
What is the nearest major
galaxy to our own
Milky Way Galaxy?
Andromeda.
In fact, our Galaxy is thought to look much like
Andromeda.
Together these two galaxies dominate the
Local Group of galaxies.
The diffuse light from
Andromeda
is caused by the hundreds of billions of
stars that compose it.
The several distinct stars that surround
Andromeda's image
are actually stars in
our Galaxy
that are well in front of the background object.
Andromeda is
frequently referred to as M31 since it is the 31st
object on
Messier's list of diffuse sky objects.
M31 is so distant it takes
about two million years for light to reach us from there.
Although visible without aid, the
featured image of M31 is a digital mosaic of
20 frames taken with a small telescope.
Much about M31
remains unknown, including exactly how long it will be before it
collides with our home galaxy.
APOD: 2018 October 20 - Halo of the Cat's Eye
Explanation:
Not a Falcon 9
rocket launch after sunset, the Cat's Eye Nebula (NGC 6543) is
one of the best known planetary nebulae in the sky.
Its haunting symmetries are seen
in the very central region of
this
composited picture, processed to reveal an
enormous but extremely faint halo of gaseous material, over three
light-years across.
Made with data from ground- and space-based telescopes
it shows the extended emission which surrounds the brighter, familiar
planetary nebula.
Planetary nebulae have long been appreciated as a final phase
in
the life of a sun-like star.
But only more recently have some planetaries been
found to have halos
like this one, likely formed of material shrugged off during
earlier active episodes in the star's evolution.
While the planetary nebula phase is thought to last for around
10,000 years, astronomers estimate the
outer filamentary
portions of this halo to be 50,000 to 90,000 years old.
APOD: 2018 August 5 - Trapezium: At the Heart of Orion
Explanation:
Near the center of this sharp cosmic portrait, at
the heart of the Orion Nebula,
are four hot, massive stars
known as
the Trapezium.
Gathered within a region about 1.5 light-years in radius,
they dominate the core of the dense Orion Nebula Star Cluster.
Ultraviolet ionizing radiation from the
Trapezium stars,
mostly from the brightest star
Theta-1
Orionis C
powers the complex star forming region's entire visible glow.
About three million years old, the Orion Nebula Cluster was
even more compact in its younger years and a
recent dynamical study indicates that
runaway stellar collisions
at an earlier age may have formed a black hole
with more than 100 times the mass of
the Sun.
The presence of a
black hole within the cluster
could explain the observed high velocities of the
Trapezium stars.
The Orion Nebula's distance of some 1,500
light-years would make it the
closest known black hole to planet Earth.
APOD: 2018 July 15 - Rings Around the Ring Nebula
Explanation:
There is much more to the familiar
Ring Nebula (M57),
however, than can be seen through a small telescope.
The easily visible
central ring is about one
light-year across,
but this remarkably deep exposure -
a collaborative effort combining data from three different large telescopes -
explores
the looping filaments of glowing gas extending much farther from
the nebula's central star.
This remarkable
composite image includes narrowband hydrogen image,
visible light emission, and
infrared light emission.
Of course, in this well-studied example of a
planetary nebula,
the glowing material does not come from planets.
Instead, the
gaseous shroud represents
outer layers expelled from a dying, sun-like star.
The Ring Nebula is about 2,000 light-years away toward the musical
constellation
Lyra.
APOD: 2018 March 26 - The Coma Cluster of Galaxies
Explanation:
Almost every object in the above photograph is a galaxy.
The Coma Cluster of Galaxies pictured here is one of the densest
clusters known - it contains thousands of
galaxies.
Each of these galaxies houses billions of stars -
just as our own
Milky Way Galaxy does.
Although nearby when compared to most other
clusters,
light from the Coma Cluster
still takes hundreds of millions of years to reach us.
In fact, the
Coma Cluster is so big it takes light
millions of years just to go from one side to the other.
Most galaxies in Coma and other clusters are
ellipticals,
while most
galaxies outside of clusters are
spirals.
The nature of
Coma's X-ray emission is
still being investigated.
APOD: 2018 March 9 - Horsehead: A Wider View
Explanation:
Combined image data from the massive,
ground-based
VISTA telescope and the
Hubble Space
Telescope was used to create
this
wide perspective
of the interstellar landscape surrounding
the famous Horsehead Nebula.
Captured at near-infrared wavelengths, the region's dusty
molecular cloud sprawls across the scene that covers
an angle about
two-thirds the size of the Full Moon on the sky.
Left to right the frame spans just over 10 light-years
at the Horsehead's estimated distance of 1,600 light-years.
Also known as
Barnard 33,
the still
recognizable Horsehead Nebula
stands at the upper right,
the near-infrared glow of a dusty pillar topped with newborn stars.
Below and left, the bright reflection nebula NGC 2023 is itself
the illuminated environs of a hot young star.
Obscuring
clouds
below the base of the Horsehead and on the outskirts of
NGC 2023 show the tell-tale far red emission of energetic jets,
known as Herbig-Haro objects,
also associated with newborn stars.
APOD: 2018 February 28 - NGC 613 in Dust, Stars, and a Supernova
Explanation:
Where did that spot come from?
Amateur astronomer Victor Buso was testing out a new camera on his telescope in 2016 when he noticed a curious spot of light appear -- and remain.
After reporting
this unusual observation,
this spot was determined to be light from a
supernova
just as it was becoming visible -- in an earlier stage
than had ever been photographed optically before.
The discovery before and after images, taken about an hour apart,
are shown in the inset of a
more detailed image
of the same spiral galaxy,
NGC 613,
taken by the Hubble Space Telescope.
Follow-up observations show that
SN 2016gkg was likely the explosion of a
supergiant star,
and Buso likely captured the stage where the outgoing
detonation wave
from the stellar core
broke through
the star's surface.
Since astronomers have spent years
monitoring galaxies for supernovas without seeing such a "break out" event,
the odds of Buso capturing this
have been compared to
winning a lottery.
APOD: 2018 February 24 - Facing NGC 6946
Explanation:
From our vantage point in the
Milky Way Galaxy, we see
NGC 6946
face-on.
The big, beautiful
spiral galaxy
is located just 20 million light-years away, behind a veil of
foreground dust and stars in the high and far-off
constellation of Cepheus.
From the core outward, the galaxy's colors change from the yellowish
light of old stars in the center to young blue star
clusters and reddish star forming regions along the loose, fragmented
spiral arms.
NGC 6946 is also bright in
infrared light and
rich in gas and dust, exhibiting a high star birth and
death rate.
In fact, since the early 20th century
ten
confirmed supernovae, the
death explosions
of massive stars, were
discovered in NGC 6946.
Nearly 40,000 light-years across, NGC 6946 is also known as the
Fireworks Galaxy.
This remarkable portrait of NGC 6946
is a composite that includes
image
data from the 8.2 meter Subaru Telescope
on Mauna Kea.
APOD: 2018 January 16 - An Elephant's Trunk in Cepheus
Explanation:
With
image data from telescopes large and small,
this close-up features the dusty Elephant's Trunk Nebula.
It winds through the emission nebula and young star cluster
complex IC 1396, in the
high and far off
constellation of
Cepheus.
Also known as vdB 142, the cosmic elephant's trunk is over
20 light-years long.
The colorful view highlights bright, swept-back
ridges that outline the region's pockets of cool
interstellar dust and gas.
Such embedded, dark,
tendril-shaped clouds contain
the raw material for star formation and hide
protostars within.
Nearly 3,000 light-years distant, the relatively faint IC 1396 complex
covers a large region on the sky, spanning over 5 degrees.
This dramatic scene spans a 1 degree wide field,
about the size of 2 Full Moons.
APOD: 2017 November 9 - NGC 1055 Close up
Explanation:
Big, beautiful spiral galaxy NGC 1055 is a dominant member of
a small galaxy group
a mere 60 million light-years away toward
the aquatically intimidating constellation Cetus.
Seen edge-on, the island universe spans over 100,000 light-years,
a little larger than our
own Milky Way.
The colorful stars in this cosmic
close-up
of NGC 1055 are in the foreground, well within the Milky Way.
But the telltale pinkish star forming
regions are scattered through
winding dust lanes along the distant galaxy's thin disk.
With a smattering of even more distant background galaxies, the
deep image also reveals a boxy halo that extends
far above and below the central bluge and disk of NGC 1055.
The halo itself is laced with faint, narrow structures,
and could represent the mixed and spread out
debris from a satellite galaxy
disrupted by
the larger spiral some
10 billion years ago.
APOD: 2017 September 17 - Bright Spiral Galaxy M81
Explanation:
One of the brightest galaxies in planet Earth's sky is similar in size
to our Milky
Way Galaxy: big, beautiful M81.
This grand
spiral galaxy can be found toward the northern constellation of the Great
Bear
(Ursa Major).
This superbly
detailed view reveals M81's bright yellow nucleus, blue
spiral arms, and sweeping cosmic dust lanes with a scale comparable to
the
Milky Way.
Hinting at a
disorderly past,
a remarkable dust lane actually runs straight through the
disk, to the left of the galactic center,
contrary to M81's
other prominent
spiral features.
The errant
dust lane may be the lingering result of
a close encounter between
M81
and its smaller companion galaxy, M82.
Scrutiny of variable stars in
M81 has yielded one of the best
determined
distances for an external galaxy -- 11.8 million light-years.
APOD: 2017 August 17 - NGC 2442: Galaxy in Volans
Explanation:
Distorted
galaxy NGC 2442 can be found in the southern constellation of the
flying fish,
(Piscis) Volans.
Located about 50 million light-years away, the galaxy's two
spiral arms extending from a pronounced central bar have a hook-like
appearance in wide-field images.
But this
mosaicked
close-up, constructed from Hubble Space Telescope and
European Southern Observatory data,
follows the galaxy's structure in amazing detail.
Obscuring dust lanes, young blue star clusters and
reddish star forming regions
surround a core of yellowish light from an older population of stars.
The sharp image data also reveal more distant
background galaxies seen right through NGC 2442's
star clusters and nebulae.
The image spans about 75,000 light-years at the estimated distance
of NGC 2442.
APOD: 2017 July 12 - Messier 63: The Sunflower Galaxy
Explanation:
A bright spiral galaxy of the northern sky,
Messier 63
is about 25 million light-years distant in the
loyal constellation
Canes
Venatici.
Also cataloged as NGC 5055, the majestic
island universe
is nearly 100,000 light-years across.
That's about the size
of our own Milky Way Galaxy.
Known by the popular moniker, The Sunflower Galaxy,
M63 sports a bright yellowish core in this sharp composite
image
from space- and ground-based telescopes.
Its sweeping blue spiral arms are streaked with cosmic dust lanes and
dotted with pink star forming regions.
A dominant member of a known
galaxy
group, M63 has faint, extended features that are likely star streams from
tidally
disrupted satellite galaxies.
M63 shines across
the electromagnetic spectrum and is thought to have
undergone
bursts of intense
star
formation.
APOD: 2017 March 22 - Central Cygnus Skyscape
Explanation:
In cosmic brush strokes of glowing hydrogen gas,
this beautiful skyscape unfolds across the plane of our Milky Way Galaxy
near the northern end of the Great Rift and
the center of the constellation
Cygnus the Swan.
A 36 panel
mosaic of telescopic image data, the scene spans about
six degrees.
Bright supergiant star
Gamma Cygni
(Sadr) to the upper left of the image
center lies in the foreground of the
complex gas
and dust clouds and
crowded star fields.
Left of Gamma Cygni, shaped like two luminous wings divided by
a long dark dust lane is IC 1318 whose popular name is understandably the
Butterfly Nebula.
The more compact, bright nebula at the lower right is NGC 6888,
the Crescent Nebula.
Some distance estimates for Gamma Cygni place it at
around 1,800 light-years
while estimates for IC 1318 and NGC 6888 range from 2,000 to 5,000 light-years.
APOD: 2017 February 24 - NGC 3621: Far Beyond the Local Group
Explanation:
Far beyond
the local
group of galaxies lies
NGC 3621,
some 22 million light-years away.
Found in the multi-headed southern constellation
Hydra,
the winding spiral arms of this gorgeous
island universe are loaded with
luminous blue star clusters, pinkish starforming regions,
and dark dust lanes.
Still, for astronomers
NGC 3621
has not been just another
pretty face-on spiral galaxy.
Some of its brighter stars have been used as
standard candles to establish important estimates of extragalactic
distances
and the
scale
of the Universe.
This beautiful image of NGC 3621,
is a composite of space- and ground-based telescope
data.
It traces the loose spiral arms far from the galaxy's brighter
central regions for some 100,000 light-years.
Spiky foreground stars in our own Milky Way Galaxy and
even more distant background galaxies are scattered across
the colorful skyscape.
APOD: 2016 August 29 - Young Suns of NGC 7129
Explanation:
Young suns still lie
within dusty NGC 7129, some
3,000 light-years away toward the royal constellation
Cepheus.
While these stars
are at a relatively tender age, only a few million years old, it is
likely that our own Sun formed in a similar stellar nursery some
five billion years ago.
Most noticeable in
the sharp image are the lovely bluish dust clouds
that reflect the youthful starlight.
But the compact, deep red crescent shapes are also markers
of energetic, young stellar objects.
Known as
Herbig-Haro objects,
their shape and color is characteristic of glowing hydrogen gas
shocked by
jets streaming away from newborn stars.
Paler, extended filaments of
reddish emission
mingling with the bluish
clouds are caused by dust grains effectively converting the
invisible ultraviolet starlight to visible red light through
photoluminesence.
Ultimately the natal gas and dust in the region
will be dispersed, the
stars
drifting apart as the loose
cluster orbits the center of the Galaxy.
The processing of this remarkable composite image has revealed
the faint red strands of emission at the upper right.
They are recently recognized as a likely
supernova remnant
and are currently being analyzed by Bo Reipurth (Univ. Hawaii) who
obtained the image data at the Subaru telescope.
At the estimated distance of NGC 7129, this telescopic view spans
over 40 light-years.
APOD: 2016 February 26 - The Tarantula Nebula
Explanation:
The
Tarantula Nebula is more than a thousand light-years in diameter,
a giant star forming region within nearby satellite galaxy the
Large Magellanic Cloud,
about 180 thousand light-years away.
The largest, most violent star forming region known in the whole Local
Group of galaxies, the cosmic arachnid sprawls across
this
spectacular composite view constructed with space- and ground-based
image data.
Within the Tarantula (NGC 2070), intense radiation,
stellar winds and supernova shocks from the central young cluster of
massive stars, cataloged as R136,
energize the nebular glow and shape the spidery filaments.
Around
the Tarantula are other star forming regions with
young star clusters, filaments, and blown-out
bubble-shaped clouds
In fact, the frame includes the
site of the closest supernova in modern times,
SN
1987A, at the lower right.
The rich field of view spans about 1 degree
or 2 full moons, in the southern
constellation Dorado.
But were the Tarantula Nebula closer, say 1,500 light-years distant like
the local star forming Orion Nebula,
it would take up half the sky.
APOD: 2015 November 30 - In the Center of Spiral Galaxy NGC 3521
Explanation:
This huge swirling mass of stars, gas, and dust occurs near the center of a nearby spiral galaxy.
Gorgeous spiral
NGC 3521 is a mere 35 million light-years
distant, toward the
constellation Leo.
Spanning some 50,000
light-years, its central region is shown in
this dramatic image,
constructed from data from the
Hubble Space Telescope.
The close-up view highlights this galaxy's
characteristic multiple, patchy, irregular spiral arms laced with
dust and clusters of young, blue stars.
In contrast, many
other spirals exhibit grand, sweeping arms.
A relatively bright galaxy in planet Earth's sky,
NGC 3521 is
easily visible in small telescopes, but often overlooked by
amateur imagers in favor of other Leo spiral galaxies,
like M65 and M66.
APOD: 2015 November 19 - Centaurus A
Explanation:
What's the closest active galaxy to
planet Earth?
That would be Centaurus A, only 11 million light-years distant.
Spanning over 60,000 light-years, the peculiar elliptical galaxy is
also
known as NGC 5128.
Forged in a
collision of two
otherwise normal galaxies, Centaurus A's
fantastic jumble of young blue star clusters, pinkish star forming
regions, and imposing dark dust lanes are seen here in remarkable detail.
The
colorful galaxy portrait is a composite of image data
from space- and ground-based telescopes large and small.
Near
the galaxy's center, left over cosmic debris is steadily
being consumed by a central black hole with a billion times
the mass of the Sun.
As
in other active galaxies, that process generates the radio,
X-ray, and gamma-ray energy radiated by Centaurus A.
APOD: 2015 October 11 - In the Center of the Trifid Nebula
Explanation:
Clouds of glowing gas mingle with dust lanes in the
Trifid Nebula, a star forming region toward the constellation of the Archer (Sagittarius).
In the center, the three prominent
dust lanes that give the
Trifid its name all come together.
Mountains of opaque dust
appear on the right, while other dark filaments of
dust are visible threaded throughout the nebula.
A single massive star
visible near the center causes much of the
Trifid's glow.
The Trifid, also known as
M20,
is only about 300,000 years old, making it among the youngest
emission nebulae known.
The nebula
lies about 9,000
light years away and the part
pictured here spans about 10 light years.
The above image is a composite with
luminance taken from an image by the 8.2-m ground-based
Subaru Telescope,
detail provided by the 2.4-m orbiting
Hubble Space Telescope,
color data provided by
Martin Pugh
and image assembly and processing provided by
Robert Gendler.
APOD: 2015 October 8 - M83: The Thousand Ruby Galaxy
Explanation:
Big, bright, and beautiful,
spiral galaxy M83
lies a mere twelve million light-years away, near the southeastern
tip of the very long constellation
Hydra.
Prominent spiral arms traced by dark dust lanes and blue star
clusters lend this galaxy its popular name, The Southern Pinwheel.
But reddish
star forming regions
that dot the sweeping arms highlighted in this
sparkling
color composite also suggest another nickname,
The Thousand-Ruby Galaxy.
About 40,000 light-years across, M83 is a member of a group of
galaxies that includes active galaxy
Centaurus A.
In fact, the core of M83 itself is bright
at x-ray energies, showing a high
concentration of neutron stars and black holes left from
an intense burst of star formation.
This sharp composite color image also features
spiky
foreground Milky Way stars and distant background
galaxies.
The image data was taken from the Subaru Telescope,
the European Southern Observatory's Wide Field
Imager camera,
and the Hubble Legacy Archive.
APOD: 2015 September 21 - Spiral Galaxy M96 from Hubble
Explanation:
Dust lanes seem to swirl around the core of
Messier 96 in this
colorful,
detailed portrait of the center of a beautiful
island universe.
Of course M96 is a
spiral galaxy, and counting the faint arms extending
beyond the brighter central region, it spans 100 thousand
light-years or so, making it about the size of our own
Milky Way.
M96, also known as
NGC 3368,
is known to be about 35 million light-years distant and a dominant
member of the Leo I galaxy group.
The featured image was taken by the
Hubble Space Telescope.
The reason for
M96's asymmetry is unclear -- it could have arisen from gravitational interactions with other Leo I
group galaxies, but the lack of an intra-group diffuse glow seems to indicate
few recent interactions.
Galaxies far in the background can be found by
examining the edges of the picture.
APOD: 2015 August 30 - M31: The Andromeda Galaxy
Explanation:
What is the nearest major
galaxy to our own
Milky Way Galaxy?
Andromeda.
In fact, our Galaxy is thought to look much like
Andromeda.
Together these two galaxies dominate the
Local Group of galaxies.
The diffuse light from
Andromeda
is caused by the hundreds of billions of
stars that compose it.
The several distinct stars that surround
Andromeda's image
are actually stars in
our Galaxy
that are well in front of the background object.
Andromeda is
frequently referred to as M31 since it is the 31st
object on
Messier's list of diffuse sky objects.
M31 is so distant it takes
about two million years for light to reach us from there.
Although visible without aid, the
above image of M31 is a digital mosaic of
20 frames taken with a small telescope.
Much about M31
remains unknown, including exactly how long it will before it
collides with our home galaxy.
APOD: 2015 June 14 - M101: The Pinwheel Galaxy
Explanation:
Why do many galaxies appear as
spirals?
A striking example is
M101,
shown above,
whose relatively close distance of about 27 million
light years allows it to be studied in some detail.
Observational evidence indicates that a
close gravitational interaction with a neighboring galaxy created
waves of high mass and condensed gas which
continue to orbit the galaxy center.
These
waves compress existing gas and cause
star formation.
One result is that
M101, also called the
Pinwheel Galaxy, has several extremely
bright star-forming regions
(called HII regions) spread across its spiral arms.
M101 is so large that its
immense gravity distorts
smaller nearby galaxies.
APOD: 2015 February 23 - The Milky Way Over the Arizona Toadstools
Explanation:
Which is older -- the rocks you see on the ground or the light you see from the sky?
Usually it’s the rocks that are older, with their origin sediments deposited well before light left any of the stars or nebulas you see in the sky.
However, if you can see, through a telescope, a distant galaxy far across the universe -- further than
Andromeda or spiral galaxy
NGC 7331 (inset) -- then you are seeing light even more ancient.
Featured here, the central disk of our
Milky Way Galaxy arches over Toadstool
hoodoos rock formations in northern
Arizona,
USA.
The unusual Toadstool rock caps
are relatively hard
sandstone
that wind has eroded more slowly than the softer sandstone underneath.
The green bands are
airglow, light emitted by the stimulated air in
Earth's atmosphere.
On the lower right is a time-lapse camera set up to capture the
sky rotating behind the picturesque foreground scene.
APOD: 2015 February 16 - M106: A Spiral Galaxy with a Strange Center
Explanation:
What's happening at the center of spiral galaxy M106?
A swirling disk of stars and gas,
M106's appearance is dominated by blue spiral arms and red
dust lanes near the nucleus, as shown in the
featured image.
The core of
M106 glows brightly in
radio waves and
X-rays where
twin jets have been found running the length of the galaxy.
An unusual central glow makes
M106 one of the closest examples of the
Seyfert class of galaxies,
where vast amounts of glowing gas are thought
to be falling into a central massive
black hole.
M106,
also designated
NGC 4258,
is a relatively close 23.5 million light years away,
spans 60 thousand
light years across, and can be seen with a small telescope
towards the constellation of the Hunting Dogs (Canes Venatici).
APOD: 2015 January 6 - 100 Million Stars in the Andromeda Galaxy
Explanation:
What stars compose the Andromeda galaxy?
To better understand, a
group of researchers
studied the
nearby spiral
by composing the largest image ever taken with the
Hubble Space Telescope.
The result, called the
Panchromatic Hubble Andromeda Treasury (PHAT), involved thousands of observations,
hundreds of fields,
spanned about a third of the galaxy, and resolved over 100 million stars.
In the
featured
composite image, the
central part of the galaxy is seen on the far left,
while a blue spiral arm is prominent on the right.
The brightest stars, scattered over the frame, are actually
Milky Way foreground stars.
The PHAT data is being analyzed to
better understand
where and how stars have formed in
M31 in contrast to our
Milky Way Galaxy,
and to identify and characterize Andromeda's
stellar clusters and
obscuring dust.
APOD: 2014 December 13 - The Infrared Visible Andromeda
Explanation:
This
remarkable synthetic color composite image was assembled from
archives of visible light and infrared astronomy image data.
The field of view spans the Andromeda Galaxy (M31), a massive spiral
a mere 2.5 million light-years away.
In fact, with over twice the diameter of
our own Milky Way,
Andromeda is
the largest nearby galaxy.
Andromeda's population of bright young blue stars lie along its sweeping
spiral arms, with the telltale reddish glow of star forming regions
traced in space- and ground-based
visible light data.
But infrared data from the Spitzer
Space Telescope, also blended directly into the detailed composite's
red and green color channels, highlight
the lumpy dust lanes warmed by the young stars
as they wind ever closer to the
galaxy's core.
Otherwise invisible at optical wavelengths, the warm dust takes
on orange hues.
Two smaller companion galaxies,
M110 (below) and
M32 (above) are also included in the frame.
APOD: 2014 November 19 - Bright Spiral Galaxy M81
Explanation:
One of the brightest galaxies in planet Earth's sky is similar in size
to our Milky
Way Galaxy: big, beautiful M81.
This grand spiral galaxy can be found toward the northern constellation of the Great
Bear
(Ursa Major).
This superbly
detailed view reveals M81's bright yellow nucleus, blue
spiral arms, and sweeping cosmic dust lanes with a scale comparable to
the
Milky Way.
Hinting at a disorderly past,
a remarkable dust lane actually runs straight through the
disk, to the left of the galactic center,
contrary to M81's
other prominent
spiral features.
The errant
dust lane may be the lingering result of
a close encounter between
M81 and its smaller companion galaxy, M82.
Scrutiny of variable stars in
M81 has yielded one of the best
determined
distances for an external galaxy -- 11.8 million light-years.
APOD: 2014 November 11 - Orion in Gas, Dust, and Stars
Explanation:
The constellation of Orion holds much more than three stars in a row.
A deep exposure shows everything from dark nebulae to star clusters,
all embedded in an extended
patch of
gaseous wisps in the greater
Orion
Molecular
Cloud
Complex.
The brightest three stars
on the far left are indeed the
famous three stars that make up the
belt of Orion.
Just below Alnitak, the lowest of the
three belt stars, is the
Flame Nebula, glowing with
excited hydrogen gas and immersed in filaments of dark brown dust.
Below and left of the frame center and just to the right of
Alnitak lies the
Horsehead Nebula, a
dark indentation of
dense dust that has perhaps the most recognized nebular shapes on the sky.
On the upper right lies
M42, the
Orion Nebula,
an energetic caldron of tumultuous gas,
visible to the unaided eye,
that is giving birth to a
new open cluster of stars.
Immediately to the left of
M42
is a prominent bluish reflection nebula sometimes called the
Running Man that houses many bright
blue stars.
The featured image covers an area with objects that are roughly 1,500
light years away and spans about 75 light years.
APOD: 2014 September 25 - NGC 206 and the Star Clouds of Andromeda
Explanation:
The large stellar association cataloged as
NGC 206 is
nestled within the dusty arms of the neighboring
Andromeda galaxy.
Also known as M31,
the spiral galaxy is a mere
2.5 million light-years away.
NGC 206 is near top center in
this
gorgeous close-up of the southwestern
extent of
Andromeda's disk, a remarkable composite of data from
space and ground-based observatories.
The bright, blue
stars of
NGC 206 indicate its youth.
In fact, its youngest massive stars are less than 10 million years old.
Much larger than the open or galactic clusters of young stars
in the disk of our Milky Way galaxy,
NGC 206
spans about 4,000 light-years.
That's comparable in size to the giant stellar nurseries
NGC 604 in nearby spiral
M33 and the
Tarantula Nebula,
in the Large Magellanic Cloud.
Star forming sites within Andromeda are revealed by the telltale
reddish emission from clouds of ionized hydrogen gas.
APOD: 2014 August 13 - Rings Around the Ring Nebula
Explanation:
It is a familiar sight to sky enthusiasts with even a small telescope.
There is much more to the
Ring Nebula (M57),
however, than can be seen through a
small telescope.
The easily visible
central ring is about one
light-year across,
but this remarkably deep exposure -
a collaborative effort combining data from three different large telescopes -
explores
the looping filaments
of glowing gas extending much farther from the nebula's
central star.
This remarkable
composite image includes narrowband hydrogen image,
visible light emission, and
infrared light emission.
Of course, in this
well-studied
example of a
planetary nebula,
the glowing material does not come from planets.
Instead, the
gaseous shroud represents outer layers
expelled from a dying, sun-like star.
The Ring Nebula is about 2,000 light-years away toward the musical
constellation
Lyra.
APOD: 2014 June 18 - NGC 6334: The Cat's Paw Nebula
Explanation:
Nebulas are perhaps as famous for being identified with familiar shapes as perhaps
cats are for getting into
trouble.
Still, no known cat could have created the vast
Cat's Paw Nebula visible in Scorpius.
At 5,500 light years distant, Cat's
Paw is an
emission nebula with a red color that originates from an abundance of ionized
hydrogen atoms.
Alternatively known as the
Bear Claw Nebula or
NGC 6334,
stars nearly ten times the mass of our
Sun have been born
there
in only the past few million years.
Pictured above is
a deep field image of the
Cat's Paw
nebula.
APOD: 2014 May 27 - Star Factory Messier 17
Explanation:
What's happening at the center of this nebula?
Sculpted by stellar winds and radiation,
the star factory known as
Messier 17
lies some 5,500 light-years away in the nebula-rich constellation
Sagittarius.
At that distance, this degree wide field of view spans
almost 100 light-years.
The sharp,
composite, color image
utilizing data from space and ground based telescopes,
follows faint details of the region's gas and dust clouds
against a backdrop of central
Milky Way stars.
Stellar winds and energetic light
from hot, massive stars formed from
M17's
stock of cosmic gas and dust have slowly carved away at the
remaining interstellar material
producing the cavernous appearance and
undulating shapes.
M17 is
also known as the
Omega Nebula or the
Swan Nebula.
APOD: 2014 April 21 - Massive Nearby Spiral Galaxy NGC 2841
Explanation:
It is one of the more massive galaxies known.
A mere 46 million light-years distant, spiral galaxy NGC 2841
can be found in the northern constellation of
Ursa Major.
This sharp view of the gorgeous
island universe
shows off a striking yellow nucleus and galactic disk.
Dust lanes, small, pink star-forming regions, and young blue star clusters
are embedded in the patchy, tightly
wound
spiral arms.
In contrast, many other spirals
exhibit grand, sweeping
arms with large star-forming regions.
NGC 2841 has a diameter of over 150,000 light-years,
even larger than
our own
Milky Way and captured by this composite image merging exposures from the orbiting 2.4-meter
Hubble Space Telescope and the ground-based 8.2-meter
Subaru Telescope.
X-ray images
suggest that resulting winds and stellar explosions create
plumes of hot gas extending into a halo around
NGC 2841.
APOD: 2014 March 27 - Stephan's Quintet Plus One
Explanation:
The first identified compact galaxy group,
Stephan's Quintet
is featured in
this
remarkable image constructed with data drawn from
Hubble Legacy Archive and the
Subaru Telescope
on the summit of Mauna Kea.
The galaxies of the quintet are gathered near the center of the
field, but really only four of the five are
locked
in a cosmic dance of repeated close encounters taking place some
300 million light-years away.
The odd man out is easy to spot, though.
The interacting galaxies,
NGC 7319, 7318A, 7318B, and 7317
have a more dominant yellowish cast.
They also tend to have distorted
loops and tails, grown under the
influence of disruptive gravitational tides.
The mostly bluish galaxy, NGC 7320,
is in the foreground about 40 million light-years distant,
and isn't part of the interacting group.
Still, captured in this field above and to the left of
Stephan's Quintet is another galaxy,
NGC 7320C, that is also 300 million
light-years distant.
Of course, including it would bring the four
interacting galaxies back up to quintet status.
Stephan's Quintet
lies within the boundaries of the high flying
constellation
Pegasus.
At the estimated distance of the quintet's interacting galaxies,
this field of view spans over 500,000 light-years.
APOD: 2014 February 5 - NGC 2683: Edge On Spiral Galaxy
Explanation:
Does spiral galaxy NGC 2683 have a bar across its center?
Being so nearly like our own
barred Milky Way Galaxy, one might guess it has.
Being so nearly edge-on, however, it is
hard to tell.
Either way, this gorgeous island universe, cataloged
as NGC 2683, lies a mere
20 million light-years distant in the northern constellation of the Cat
(Lynx).
NGC 2683 is seen nearly edge-on in
this cosmic vista combining data and images from the ground-based
Subaru telescope and the space-based
Hubble Space Telescope.
More distant
galaxies are seen scattered in the background.
Blended light from a large population of old yellowish stars forms
the remarkably bright
galactic core.
Starlight silhouettes the dust lanes along winding spiral arms, dotted
with the telltale blue glow of young star clusters
in this galaxy's star forming regions.
APOD: 2014 January 17 - M83 Star Streams
Explanation:
Big, bright, and beautiful,
spiral galaxy M83
lies a mere twelve million light-years away, near the southeastern
tip of the very long
constellation
Hydra.
This deep
view of the gorgeous island universe
includes observations from Hubble, along with ground based data from
the European Southern Observatory's very large telescope units,
National Astronomical Observatory of Japan's Subaru telescope, and
Australian
Astronomical Observatory photographic data by D. Malin.
About 40,000 light-years across, M83 is
popularly known as the Southern Pinwheel for its pronounced spiral arms.
But the wealth of
reddish star forming regions
found near the edges of the arms' thick dust lanes,
also suggest another popular moniker for M83, the
Thousand-Ruby
Galaxy.
Arcing near the top of the novel cosmic portrait lies M83's northern
stellar tidal stream,
debris from the gravitational disruption of a smaller, merging
satellite galaxy.
The faint, elusive star stream was
found
in the mid 1990s by enhancing photographic plates.
APOD: 2013 November 28 - NGC 1999: South of Orion
Explanation:
South of the large star-forming region known as the
Orion Nebula, lies bright blue reflection nebula
NGC 1999.
At the edge of the
Orion molecular
cloud complex some 1,500 light-years distant, NGC 1999's
illumination is provided by the
embedded variable star V380 Orionis.
That nebula is marked with a dark sideways T-shape near center in
this
cosmic vista that spans about 10 light-years.
The dark shape was once assumed to be an obscuring dust cloud
seen in silhouette against the bright reflection nebula.
But recent
infrared images
indicate the shape is likely a hole blown through the nebula
itself by energetic young stars.
In fact,
this
region abounds with energetic young stars
producing jets and outflows with luminous shock waves.
Cataloged as Herbig-Haro (HH) objects, named for astronomers
George Herbig and Guillermo Haro,
the shocks look like red gashes in
this scene that includes HH1 and HH2 just below NGC 1999.
The stellar jets
push through the surrounding
material at speeds of hundreds of kilometers per second.
APOD: 2013 October 12 - Cometary Globules
Explanation:
Bright-rimmed, flowing shapes gather near the center of
this
rich starfield toward the boarders of the nautical southern
constellations
Pupis and Vela.
Composed of interstellar gas and dust, the grouping of
light-year sized cometary globules is about 1300 light-years distant.
Energetic ultraviolet light from nearby hot stars
has molded the globules
and ionized their bright rims.
The globules also
stream away from the
Vela supernova remnant which
may have influenced their swept-back shapes.
Within them, cores of cold gas and dust are likely collapsing to form
low mass stars, whose formation will ultimately cause the
globules to disperse.
In fact, cometary globule CG30 (upper right in the group) sports a
small reddish glow near its head,
a telltale
sign of energetic
jets from a star in the early stages
of formation.
APOD: 2013 August 6 - In the Vicinity of the Cone Nebula
Explanation:
Strange shapes and textures can be found in neighborhood
of the Cone Nebula.
The unusual shapes
originate from fine interstellar
dust reacting in
complex ways with the energetic light and
hot gas being expelled by the young stars.
The brightest star on the right of the
above picture is S Mon,
while the region just below it has been nicknamed the
Fox Fur Nebula for its color and structure.
The blue glow directly surrounding
S Mon results from
reflection,
where neighboring dust reflects light from the bright star.
The red glow
that encompasses the whole region results not only from
dust reflection but also emission from
hydrogen gas ionized by starlight.
S Mon
is part of a young open
cluster of stars named
NGC 2264, located about 2500 light years away toward the constellation of the Unicorn
(Monoceros).
Even though it points right at S Mon, details of the origin of the mysterious geometric Cone Nebula, visible on the far left, remain
a mystery.
APOD: 2013 May 30 - One Armed Spiral Galaxy NGC 4725
Explanation:
While most spiral galaxies, including our
own Milky Way,
have two or more spiral arms, NGC 4725 has only one.
In this sharp color composite image,
the solo spira mirabilis seems to wind
from a prominent ring of bluish, newborn star clusters and red
tinted star forming regions.
The odd galaxy also sports obscuring
dust lanes a yellowish central bar structure
composed of an older population of stars.
NGC 4725 is over 100 thousand light-years across and lies 41 million
light-years away in the well-groomed constellation
Coma
Berenices.
Computer
simulations
of the formation of single spiral
arms suggest that they can be either leading or trailing
arms with respect to a galaxy's
overall rotation.
Also included in the frame, a more traditional looking spiral
appears as a smaller background galaxy.
APOD: 2013 May 3 - Horsehead: A Wider View
Explanation:
Combined image data from the massive,
ground-based
VISTA telescope and the
Hubble Space
Telescope was used to create
this
wide perspective
of the interstellar landscape surrounding
the famous Horsehead Nebula.
Captured at near-infrared wavelengths, the region's dusty
molecular cloud sprawls across the scene that covers
an angle about
two-thirds the size of the Full Moon on the sky.
Left to right the frame spans just over 10 light-years
at the Horsehead's estimated distance of 1,600 light-years.
Also known as
Barnard 33,
the still
recognizable Horsehead Nebula
stands at the upper right,
the near-infrared glow of a dusty pillar topped with newborn stars.
Below and left, the bright reflection nebula NGC 2023 is itself
the illuminated environs of a hot young star.
Obscuring clouds
below the base of the Horsehead and on the outskirts of
NGC 2023 show the tell-tale far red emission of energetic jets,
known as Herbig-Haro objects,
also associated with newborn stars.
APOD: 2013 April 18 - Star Factory Messier 17
Explanation:
Sculpted by stellar winds and radiation,
the star factory known as
Messier 17
lies some 5,500 light-years away in the nebula-rich constellation
Sagittarius.
At that distance, this degree wide field of view spans
almost 100 light-years.
The sharp,
composite, color image
utilizing data from space and ground based telescopes,
follows faint details of the region's gas and dust clouds
against a backdrop of central
Milky Way stars.
Stellar winds and energetic light
from hot, massive stars formed from M17's stock of cosmic gas
and dust have slowly carved away at the remaining interstellar material
producing the cavernous appearance and
undulating shapes.
M17 is
also known as the
Omega Nebula or the Swan Nebula.
APOD: 2013 February 6 - The Arms of M106
Explanation:
The spiral arms of bright galaxy M106 sprawl through this
remarkable
multiframe portrait,
composed of data from
ground- and
space-based telescopes.
Also known as NGC 4258,
M106 can be found
toward the northern constellation
Canes
Venatici.
The well-measured
distance to M106 is
23.5 million light-years, making this cosmic scene
about 80,000 light-years across.
Typical in grand spiral galaxies, dark dust lanes,
youthful blue star clusters, and pinkish star forming
regions trace spiral arms
that converge on the bright nucleus of older
yellowish stars.
But this detailed composite reveals hints of
two anomalous arms
that don't align with the more familiar tracers.
Seen here in red hues, sweeping filaments of
glowing hydrogen gas seem to rise from the central region
of M106, evidence
of energetic jets of material blasting into the galaxy's disk.
The jets are likely powered by matter falling into a
massive
central black hole.
APOD: 2013 January 28 - In the Center of the Trifid Nebula
Explanation:
Clouds of glowing gas mingle with dust lanes in the
Trifid Nebula, a star forming region toward the constellation of the Archer (Sagittarius).
In the center, the three prominent
dust lanes that give the
Trifid its name all come together.
Mountains of opaque dust
appear on the right, while other dark filaments of
dust are visible threaded throughout the nebula.
A single massive star
visible near the center causes much of the
Trifid's glow.
The Trifid, also known as
M20,
is only about 300,000 years old, making it among the youngest
emission nebulae known.
The nebula
lies about 9,000
light years away and the part
pictured here spans about 10 light years.
The above image is a composite with
luminance taken from an image by the 8.2-m ground-based
Subaru Telescope,
detail provided by the 2.4-m orbiting
Hubble Space Telescope,
color data provided by
Martin Pugh
and image assembly and processing provided by
Robert Gendler.
APOD: 2012 December 20 - M33: Triangulum Galaxy
Explanation:
The small, northern constellation
Triangulum
harbors this magnificent face-on spiral galaxy, M33.
Its popular names include the Pinwheel Galaxy or just
the Triangulum
Galaxy.
M33 is over 50,000 light-years in diameter, third largest in the
Local
Group of galaxies after the Andromeda Galaxy (M31), and our
own Milky Way.
About 3 million light-years from the Milky Way,
M33 is itself thought to be a satellite of the
Andromeda Galaxy and
astronomers
in these two galaxies would likely have spectacular views of
each other's grand spiral star systems.
As for the view from planet Earth,
this
sharp composite image, a 25 panel mosaic,
nicely shows off M33's blue star clusters
and pinkish star forming regions that
trace the galaxy's loosely wound spiral arms.
In fact, the cavernous NGC 604 is the
brightest star forming region, seen here at about the 1 o'clock position
from the galaxy center.
Like M31, M33's population of well-measured variable stars
have helped make this nearby spiral a
cosmic
yardstick for
establishing
the distance scale of the Universe.
APOD: 2012 October 6 - At the Heart of Orion
Explanation:
Near the center of this sharp cosmic portrait, at
the heart of the Orion Nebula,
are four hot, massive stars
known as
the Trapezium.
Gathered within a region about 1.5 light-years in radius,
they dominate the core of the dense Orion Nebula Star Cluster.
Ultraviolet ionizing radiation from the Trapezium stars,
mostly from the brightest star
Theta-1
Orionis C
powers the complex star forming region's entire visible glow.
About three million years old, the Orion Nebula Cluster was
even more compact in its younger years and a
recent dynamical study
indicates that
runaway stellar collisions
at an earlier age may have formed a black hole
with more than 100 times the mass of the Sun.
The presence of a black hole within the cluster
could explain the observed high velocities of the Trapezium stars.
The Orion Nebula's distance of some 1500 light-years
would make it the closest known black hole to planet Earth.
APOD: 2012 September 3 - M45: The Pleiades Star Cluster
Explanation:
Perhaps the most famous star cluster on the
sky, the
Pleiades
can be seen without binoculars from even the depths of a
light-polluted city.
Also known as the Seven Sisters and
M45,
the Pleiades
is one of the brightest and closest
open
clusters.
The Pleiades
contains over 3000 stars, is about 400 light years
away,
and only 13 light years across.
Quite evident in the
above photograph are the blue reflection nebulae
that surround the brighter cluster
stars.
Low mass, faint, brown dwarfs have also
been found in
the
Pleiades.
(Editors' note: The prominent
diffraction spikes are caused by the telescope
itself and may be either distracting or provide aesthetic enhancement,
depending on your point of view.)
APOD: 2012 July 26 - The Tulip in the Swan
Explanation:
Framing a bright emission region
this
telescopic view
looks out along the plane of our Milky Way Galaxy toward the
nebula rich constellation
Cygnus
the Swan.
Popularly called the Tulip Nebula the glowing cloud of
interstellar gas and dust is also found in the
1959 catalog
by astronomer Stewart Sharpless
as
Sh2-101.
About 8,000 light-years distant the nebula is
understandably not the only
cosmic cloud to evoke the imagery
of flowers.
The complex and beautiful nebula is shown here in a composite image that
maps emission
from ionized sulfur, hydrogen, and oxygen atoms
into red, green, and blue colors.
Ultraviolet radiation from young, energetic
O star HDE 227018
ionizes the atoms
and powers the emission from the Tulip Nebula.
HDE 227018 is the bright star very near the blue
arc at image center.
APOD: 2012 May 26 - At the Edge of NGC 891
Explanation:
This
sharp cosmic portrait features NGC 891.
The spiral galaxy
spans about 100 thousand light-years and is seen almost exactly edge-on
from our perspective.
In fact, about 30 million light-years distant in the constellation
Andromeda, NGC 891 looks a lot
like our Milky Way.
At first glance, it has a
flat, thin, galactic disk and
a central bulge cut along the middle by
regions of dark obscuring dust.
The combined image data also reveal the galaxy's
young blue star clusters and telltale pinkish star forming regions.
And remarkably apparent in NGC 891's
edge-on presentation are filaments
of dust
that extend hundreds of
light-years above and below the center line.
The dust has likely been blown out of the disk
by supernova explosions or intense
star formation activity.
Faint neighboring galaxies can also be seen near this galaxy's disk.
APOD: 2012 April 20 - M57: The Ring Nebula
Explanation:
Except for the rings
of Saturn,
the Ring
Nebula (M57) is probably the most famous celestial band.
Its classic appearance is understood to be due to perspective -
our view from planet Earth looks down the center of a roughly
barrel-shaped cloud of glowing gas.
But expansive looping structures are seen to extend
far beyond
the Ring Nebula's familiar central regions in
this
intriguing composite of ground based and
Hubble Space Telescope images with narrowband
image data from Subaru.
Of course, in this well-studied example of a
planetary
nebula, the glowing material
does not come from planets.
Instead, the gaseous shroud represents outer layers expelled
from the dying,
once
sun-like star at the nebula's center.
Intense ultraviolet light from the hot central star
ionizes atoms in the gas.
Ionized oxygen atoms produce the characteristic greenish glow and
ionized hydrogen the prominent red emission.
The central ring of the Ring Nebula is about one light-year
across and 2,000 light-years away.
To accompany
tonight's shooting stars
it shines in the northern constellation Lyra.
APOD: 2012 January 9 - Facing NGC 6946
Explanation:
From our vantage point in the
Milky Way Galaxy, we see
NGC 6946
face-on.
The big, beautiful
spiral galaxy
is located just 10 million light-years away, behind a veil of
foreground dust and stars in the high and far-off
constellation of Cepheus.
From the core outward, the galaxy's colors change from the yellowish
light of old stars in the center to young blue star
clusters and reddish star forming regions along the loose, fragmented
spiral arms.
NGC 6946 is also bright in
infrared light and
rich in gas and dust, exhibiting a high star birth and
death rate.
In fact, since the early 20th century at least nine supernovae, the
death explosions
of massive stars, were
discovered in NGC 6946.
Nearly 40,000 light-years across, NGC 6946 is also known as the
Fireworks Galaxy.
This remarkable portrait of NGC 6946
is a composite that includes
image
data from the 8.2 meter Subaru Telescope
on Mauna Kea.
APOD: 2011 November 11 - In the Arms of M83
Explanation:
Big, bright, and beautiful,
spiral galaxy M83
lies a mere twelve million light-years away, near the southeastern
tip of the very long constellation
Hydra.
This
cosmic
close-up, a mosaic based on data from the
Hubble Legacy Archive, traces dark dust and young, blue star
clusters along prominent spiral arms that lend M83
its nickname, The Southern Pinwheel.
Typically found near the edges of the thick dust lanes,
a wealth of reddish star forming regions
also suggest another popular moniker for M83,
The Thousand-Ruby
Galaxy.
Dominated by light from older stars, the bright yellowish core
of M83 lies at the upper right.
The core is also bright at x-ray energies
that reveal a high concentration of neutron stars and black holes left from
an intense burst of star formation.
In fact, M83 is a member of a group of galaxies that includes
active galaxy Centaurus A.
The close-up field of view spans over 25,000 light-years at the
estimated distance
of M83.
APOD: 2011 July 23 - NGC 2403 in Camelopardalis
Explanation:
Magnificent island universe
NGC 2403 stands
within the boundaries
of the long-necked constellation
Camelopardalis.
Some 10 million light-years distant and about 50,000 light-years
across, the spiral galaxy also seems to have more
than its fair share of giant star forming
HII regions,
marked by the telltale reddish glow of atomic hydrogen gas.
In fact, NGC 2403 closely resembles another galaxy with an
abundance of star forming regions that lies
within our own local galaxy group,
M33
the Triangulum Galaxy.
Of course, supernova explosions
follow close on the heels of
the formation of
massive, short-lived stars and
in 2004 one of the brightest supernovae discovered in recent
times was found in NGC 2403.
Easy to confuse with a foreground star in our own Milky Way Galaxy,
the powerful supernova
is seen here as the spiky, bright "star" at
the left edge
of the field.
This stunning cosmic portrait
is a composite of space and ground-based
image data from the Hubble Legacy Archive
and the 8.2 meter Subaru Telescope at the summit of
Mauna Kea, Hawaii.
APOD: 2011 July 1 - VAR!
Explanation:
In the 1920s, examining photographic plates from the
Mt. Wilson Observatory's
100 inch telescope,
Edwin Hubble determined the distance to the
Andromeda Nebula,
decisively demonstrating the existence of other galaxies far beyond
the Milky Way.
His notations are evident on the historic plate image
inset at the lower right, shown in context with ground based
and Hubble Space Telescope images of the region made
nearly 90 years later.
By comparing different plates, Hubble
searched for novae, stars which underwent a
sudden increase in brightness.
He found several on this plate, indicating their position with
lines and an "N".
Later, discovering that the one near the upper right corner
was actually a type of
variable star known as
a cepheid,
he crossed out the "N" and wrote "VAR!".
Thanks to the work of Harvard
astronomer Henrietta Leavitt, cepheids,
regularly varying pulsating stars, could be used as standard candle
distance indicators.
Identifying such a star allowed Hubble to show
that Andromeda was not a small cluster of stars and gas within our own
galaxy, but a large galaxy in its own right at a substantial
distance from the Milky Way.
Hubble's
discovery is responsible for establishing our modern concept of a
Universe filled with galaxies.
APOD: 2011 June 9 - The Great Carina Nebula
Explanation:
A jewel of the southern sky,
the Great
Carina Nebula, also known as NGC 3372, spans over 300 light-years,
one of our galaxy's largest star forming regions.
Like the smaller, more northerly
Great Orion Nebula, the
Carina Nebula is easily visible to the
unaided eye, though at a distance of 7,500
light-years it is some 5 times farther away.
This
gorgeous telescopic portrait
reveals remarkable details of the region's glowing filaments of
interstellar gas
and obscuring cosmic dust clouds.
Wider than the Full Moon in
angular size,
the field of view
stretches nearly 100 light-years across the nebula.
The Carina Nebula is home to young, extremely massive stars, including
the still enigmatic variable
Eta Carinae, a
star with well over 100 times the mass of the Sun.
Eta
Carinae is the brightest star
at
the left, near the dusty
Keyhole Nebula (NGC 3324).
While Eta Carinae itself maybe on the verge of a supernova explosion,
X-ray images indicate that the Great Carina Nebula
has been a veritable
supernova factory.
APOD: 2011 May 19 - NGC 253: Close Up
Explanation:
This dusty island universe is one of the brightest spiral galaxies in
planet Earth's sky.
Seen nearly edge-on, NGC 253 is only
13 million light-years away, the largest member of the
Sculptor
Group of galaxies,
neighbor to our own
local
galaxy group.
The detailed
close-up view is a five frame mosaic
based on data assembled from the Hubble Legacy Archive.
Beginning on the left near the galaxy's core, the sharp panorama
follows dusty filaments, interstellar gas clouds, and even individual
stars toward the galaxy's edge at the right.
The magnificent vista spans nearly 50,000 light-years.
The frame at the far right has been compressed slightly
to bring into view an
intriguing pair of background galaxies.
Designated a starburst galaxy because of its
frantic star forming
activity, NGC 253 features tendrils of dust rising from a
galactic disk laced with young star clusters and star forming regions.
NGC 253 is also known to be a strong
source of high-energy x-rays and
gamma rays, likely due to massive black holes near the galaxy's center.
APOD: 2011 April 15 - Messier 101
Explanation:
Big, beautiful spiral galaxy M101 is one of the last
entries in Charles
Messier's famous catalog, but definitely not
one
of the least.
About 170,000 light-years across, this galaxy is enormous,
almost twice the size of our own Milky Way galaxy.
M101 was also one of the original
spiral
nebulae observed by Lord Rosse's large
19th century
telescope, the Leviathan of Parsontown.
This
mosaic of M101
was assembled from Hubble Legacy Archive data.
Additional ground-based data was included to further define
the telltale reddish emission from atomic hydrogen gas in
this gorgeous galaxy's star forming regions.
The sharp image shows stunning features in the galaxy's
face-on disk of stars and dust along with background galaxies,
some visible right through M101 itself.
Also known as the
Pinwheel Galaxy,
M101 lies within
the boundaries of the northern constellation
Ursa Major,
about 25 million light-years away.
APOD: 2011 February 25 - NGC 4449: Close up of a Small Galaxy
Explanation:
Grand spiral galaxies
often seem to get all the glory.
Their young, blue star clusters and pink star forming regions
along sweeping
spiral arms
are guaranteed to attract attention.
But small irregular galaxies form stars too, like
NGC
4449, about 12 million light-years distant.
Less than 20,000 light-years across, the small island universe is
similar in size, and often
compared
to our Milky Way's satellite
galaxy, the Large Magellanic Cloud (LMC).
This remarkable
Hubble Space Telescope close-up of the
well-studied
galaxy was reprocessed to highlight the telltale reddish
glow of hydrogen gas.
The glow traces NGC 4449's widespread star forming regions, some
even larger than those in the LMC,
with enormous interstellar arcs and bubbles blown by short-lived,
massive stars.
NGC 4449 is a member of a
group
of galaxies found in the constellation Canes Venatici.
Interactions with the nearby
galaxies
are thought to have influenced star formation in NGC 4449.
APOD: 2011 January 13 - NGC 3521 Close Up
Explanation:
Gorgeous spiral galaxy NGC 3521 is a mere 35 million light-years
distant, toward the
constellation Leo.
Spanning some 50,000 light-years, its central region is shown in
this dramatic image,
constructed from data drawn from the
Hubble Legacy Archive.
The close-up view highlights this galaxy's
characteristic
multiple, patchy, irregular spiral arms laced with dust and
clusters of young, blue stars.
In contrast, many
other spirals exhibit grand, sweeping arms.
A relatively bright galaxy in planet Earth's sky,
NGC 3521 is
easily visible in small telescopes, but often overlooked by
amateur imagers in favor of other Leo spiral galaxies,
like M66 and M65.
APOD: 2010 July 28 - The Trifid Nebula is Stars and Dust
Explanation:
Unspeakable beauty and unimaginable bedlam can be found
together in the
Trifid Nebula.
Also known as M20,
this photogenic nebula is visible
with good binoculars towards the constellation of Sagittarius.
The energetic processes of
star formation create not only the colors but the
chaos.
The red-glowing gas
results from high-energy starlight striking interstellar
hydrogen gas.
The dark dust
filaments that lace
M20 were created in the atmospheres of cool
giant stars and in the debris from
supernovae explosions.
Which bright young stars light up the blue
reflection nebula is still
being investigated.
The light from
M20
we see today left perhaps 3,000 years ago,
although the exact distance remains unknown.
Light takes about 50 years to cross
M20.
APOD: 2010 July 6 - HCG 87: A Small Group of Galaxies
Explanation:
Sometimes galaxies form groups. For example, our own
Milky Way Galaxy is part of the
Local Group of Galaxies.
Small, compact groups, like Hickson Compact Group 87
(HCG 87)
shown above, are interesting partly because they slowly self-destruct.
Indeed, the galaxies of
HCG 87 are gravitationally stretching each other during their 100-million year
orbits around a common center.
The pulling creates colliding gas that causes bright bursts of
star formation and feeds matter into their
active galaxy centers.
HCG 87
is composed of a large
edge-on
spiral galaxy visible on the lower left, an
elliptical galaxy
visible on the lower right, and a
spiral galaxy visible near the top.
The small spiral near the center might be far in the distance.
Several stars from
our Galaxy are also visible in the foreground.
The above picture was taken in 1999 July by the
Hubble Space Telescope's
Wide Field Planetary Camera 2.
Studying groups like HCG 87 allows insight into how all
galaxies form and evolve.
APOD: 2010 May 3 - Spiral Galaxy NGC 3190 Almost Sideways
Explanation:
Some spiral galaxies are seen almost sideways.
NGC 3190, one such galaxy, is the largest member of the
Hickson 44 Group,
one of the nearer groups of galaxies to our own
Local Group of galaxies.
Pictured above, finely textured
dust lanes surround the
brightly glowing center of this picturesque
spiral.
Gravitational tidal interactions with other members of its group have likely
caused the spiral arms of
NGC 3190
to appear asymmetric around the center, while the
galactic disk also appears
warped.
NGC 3190 spans about 75,000
light years across and is visible with a small telescope toward the
constellation of the Lion (Leo).
APOD: 2010 April 13 - Unusual Spiral Galaxy M66 from Hubble
Explanation:
Why isn't spiral galaxy
M66 symmetric?
Usually
density waves of gas, dust, and newly formed stars circle a
spiral galaxy's
center and create a
nearly symmetric galaxy.
The differences between
M66's
spiral arms and the apparent displacement of its
nucleus are all likely caused by previous close interactions and the
tidal gravitational pulls
of nearby galaxy neighbors
M65 and
NGC 3628.
Spiral galaxy M66,
pictured
above, spans about 100,000
light years, lies about 35 million light years distant, and is the largest galaxy in a
group known as the
Leo Triplet.
Like many spiral galaxies, the long and intricate
dust lanes of
M66 are seen intertwined with the
bright stars and
nebulas
that light up the spiral arms.
APOD: 2010 March 30 - Unusual Starburst Galaxy NGC 1313
Explanation:
Why is this galaxy so discombobulated?
Usually, galaxies this
topsy-turvy
result from a recent collision with a neighboring galaxy.
Spiral galaxy
NGC 1313, however, appears to be alone.
Brightly lit with new and blue massive stars, star formation appears so rampant in
NGC 1313 that it has been labeled a
starburst galaxy.
Strange features of
NGC 1313 include that its
spiral arms are lopsided and its
rotational axis is not at the center of the nuclear
bar.
Pictured above,
NGC 1313 spans about 50,000
light years and lies only about 15 million light years away toward the
constellation of the
Reticle
(Reticulum).
Continued
numerical modeling
of galaxies like
NGC 1313
might shed some light on its unusual nature.
APOD: 2010 March 25 - NGC 2442: Galaxy in Volans
Explanation:
Distorted
galaxy NGC 2442
can be found in the southern constellation of the
flying fish,
(Piscis) Volans.
Located about 50 million light-years away, the galaxy's two
spiral
arms extending from a pronounced central bar have a hook-like
appearance in wide-field images.
But this mosaicked close-up,
constructed from Hubble Space Telescope
data, follows the galaxy's structure in amazing detail.
Obscuring dust lanes, young blue star clusters and
reddish star forming regions
surround a core of yellowish light from an older population of stars.
The sharp Hubble data also reveal more distant
background galaxies seen right through NGC 2442's
star clusters
and nebulae.
The image spans about 75,000 light-years at the estimated distance
of NGC 2442.
APOD: 2009 December 26 - M51 Hubble Remix
Explanation:
The 51st entry
in Charles Messier's famous catalog is perhaps the original
spiral
nebula - a large galaxy with a
well defined spiral structure also cataloged as NGC 5194.
Over 60,000 light-years across, M51's spiral arms and dust lanes
clearly sweep in front of its companion galaxy (top),
NGC 5195.
Image data from the Hubble's
Advanced Camera for Surveys has been
reprocessed to produce
this
alternative portrait of the
well-known interacting galaxy pair.
The processing has further sharpened details and enhanced color
and contrast in otherwise faint areas, bringing out
dust lanes and extended streams that cross the small companion, along
with features in the surroundings and core of M51 itself.
The pair are
about 31 million light-years distant.
Not far on the sky from the handle of the
Big
Dipper,
they officially lie within the boundaries of the small constellation
Canes Venatici.
APOD: 2009 November 27 - The Jets of NGC 1097
Explanation:
Enigmatic spiral galaxy NGC 1097 lies about
45 million light-years away in the southern constellation
Fornax.
The small companion galaxy, just below and left of center, that seems
to be wrapped in its spiral arms, is not
NGC 1097's
most peculiar feature though.
Instead, This very deep exposure shows hints of faint,
mysterious
jets, most easily seen to extend well beyond the bright arms toward
the lower right.
In fact, four faint jets are ultimately
recognized
in optical images of NGC 1097.
The jets
trace an X centered on the galaxy's nucleus, but could be
fossil trails left over from the
capture of a much smaller galaxy in the large spiral's ancient past.
A Seyfert galaxy,
NGC 1097's nucleus also harbors a
massive black
hole.
APOD: 2009 September 19 - NGC 3621: Far Beyond the Local Group
Explanation:
Far beyond
the local
group of galaxies lies
NGC 3621,
some 22 million light-years away.
Found in the multi-headed southern constellation
Hydra,
the winding spiral arms of this gorgeous
island universe are loaded with
luminous young star clusters and dark dust lanes.
Still, for earthbound astronomers NGC 3621 is not just
another
pretty face-on spiral galaxy.
Some of its
brighter
stars have been used as
standard
candles to establish important estimates of
extragalactic distances and the
scale
of the Universe.
This beautiful
image of NGC 3621 traces the loose spiral
arms far from the galaxy's brighter central regions that span some
100,000 light-years.
Spiky foreground stars in our own Milky Way Galaxy and
even more distant background galaxies are scattered across
the colorful skyscape.
APOD: 2009 May 19 - Sagittarius and the Central Milky Way
Explanation:
What does the center of our Milky Way Galaxy look like?
In visible light, no one knows!
It is not possible to see the
Galactic center in light our eyes are sensitive
to because the thick
dust in the
plane of our Galaxy obscures it.
If one
looks in the direction of
our Galaxy's center -
which is toward the
constellation of Sagittarius - many
beautiful wonders become apparent, though.
Large dust lanes and
star clouds dominate the picture.
As many as 30
Messier Objects
are
visible in the
above spectacular image mosaic, including all types of nebulas and star
clusters.
Two notable nebula include the
Lagoon Nebula (M8), a red
patch just above and to the right of center,
and slightly to its right is the red and blue
Trifid Nebula (M20).
APOD: 2009 May 10 - M31: The Andromeda Galaxy
Explanation:
Andromeda is the nearest major
galaxy to our own
Milky Way Galaxy.
Our Galaxy is thought to look much like
Andromeda.
Together these two galaxies dominate the
Local Group of galaxies.
The diffuse light from
Andromeda
is caused by the hundreds of billions of
stars that compose it.
The several distinct stars that surround
Andromeda's image
are actually stars in
our Galaxy
that are well in front of the background object.
Andromeda is
frequently referred to as M31 since it is the 31st
object on
Messier's list of diffuse sky objects.
M31 is so distant it takes
about two million years for light to reach us from there.
Although visible without aid, the
above image of M31 is a digital mosaic of
20 frames taken with a small telescope.
Much about M31
remains unknown, including how it acquired
its unusual
double-peaked center.
APOD: 2008 December 19 - The Large Cloud of Magellan
Explanation:
The 16th century Portuguese navigator
Ferdinand
Magellan and his crew had plenty of time to study the
southern sky during the first circumnavigation of planet Earth.
As a result, two fuzzy cloud-like
objects easily visible to southern hemisphere skygazers are known as the
Clouds of Magellan,
now understood to be
satellite galaxies of our much larger, spiral Milky Way galaxy.
About 160,000 light-years distant in the constellation
Dorado,
the Large
Magellanic Cloud (LMC) is seen here in a remarkably detailed,
10
frame mosaic image.
Spanning about 30,000 light-years or so, it is
the most massive of the Milky Way's
satellite
galaxies and is the site of the
closest
supernova in modern times, SN 1987A.
The prominent reddish knot near the bottom is 30 Doradus, or the
Tarantula Nebula, a giant star-forming
region in the Large Magellanic Cloud.
To identify the location of the supernova and navigate your way
around the many star clusters and nebulae of the LMC, just consult this
well-labeled view.
APOD: 2008 November 27 - Galaxies in the River
Explanation:
Large galaxies grow by eating small ones.
Even our own galaxy practices
galactic cannibalism,
absorbing small galaxies that get too close and
are captured by
the Milky Way's gravity.
In fact, the practice is common in the universe and
well
illustrated by this striking pair of interacting galaxies
from the banks of the southern constellation
Eridanus
(The River).
Located over 50 million light years away,
the large, distorted spiral NGC 1532 is seen locked in a
gravitational
struggle with dwarf galaxy NGC 1531, a struggle the smaller galaxy
will eventually lose.
Seen edge-on, spiral NGC 1532 spans about 100,000 light-years.
The NGC 1532/1531 pair is thought to be similar
to the system of face-on spiral and small companion known as M51, the
Whirlpool Galaxy.
APOD: 2008 October 10 - Irregular Galaxy NGC 55
Explanation:
Irregular galaxy NGC 55 is thought to be similar to the Large Magellanic
Cloud (LMC).
But while
the LMC is about 180,000 light-years away
and is a well known satellite of our own Milky Way Galaxy,
NGC 55 is more like 6 million light-years
distant
and is a member of the
Sculptor Galaxy Group.
Classified as an
irregular galaxy, in
deep exposures the LMC itself
resembles a barred disk galaxy.
However, spanning about 50,000 light-years, NGC 55 is
seen nearly edge-on,
presenting a flattened, narrow profile in contrast
with our face-on view of the LMC.
Just as large star forming regions create
emission nebulae
in the LMC, NGC 55 is also
seen to be
producing new stars.
This
gorgeous
galaxy portrait highlights a bright core,
telltale pinkish emission regions, and young blue star clusters
in NGC 55.
APOD: 2008 June 14 - M51 Hubble Remix
Explanation:
The 51st entry
in Charles Messier's famous catalog is perhaps the original
spiral
nebula - a large galaxy with a
well defined spiral structure also cataloged as NGC 5194.
Over 60,000 light-years across, M51's spiral arms and dust lanes
clearly sweep in front of its companion galaxy (right),
NGC 5195.
Image data from the Hubble's
Advanced Camera for Surveys has been
reprocessed to produce
this
alternative portrait of the
well-known interacting galaxy pair.
The processing has further sharpened details and enhanced color
and contrast in otherwise faint areas, bringing out
dust lanes and extended streams that cross the small companion, along
with features in the surroundings and core of M51 itself.
The pair are
about 31 million light-years distant.
Not far on the sky from the handle of the
Big Dipper,
they officially lie within the boundaries of the small constellation
Canes Venatici.
APOD: 2008 May 8 - The Dark Tower in Scorpius
Explanation:
In silhouette against a crowded star field
toward the constellation
Scorpius,
this dusty cosmic cloud evokes for some the image of an ominous
dark tower.
In fact, clumps of dust and molecular gas
collapsing
to form stars may well lurk within the dark nebula,
a structure that spans almost 40 light-years across the
gorgeous
telescopic view.
Known as a
cometary globule, the swept-back cloud,
extending from the upper right to the head (top of the tower) left and
below center, is shaped by intense ultraviolet radiation from
the OB association of very hot stars
in NGC
6231, off the left edge of the scene.
That energetic ultraviolet light also powers the globule's bordering
reddish glow of hydrogen gas.
Hot stars embedded in the dust
can be seen as small bluish
reflection nebulae.
This dark tower,
NGC 6231, and
associated nebulae are about 5,000 light-years away.
APOD: 2008 April 26 - The Tarantula Zone
Explanation:
The
Tarantula Nebula is more than 1,000 light-years in diameter --
a giant star forming region within our neighboring galaxy
the Large Magellanic Cloud (LMC).
That cosmic arachnid lies at the upper left of
this
expansive mosiac covering a part of the LMC
over 6,000 light-years across.
Within the Tarantula (NGC 2070), intense radiation, stellar winds and
supernova shocks from the central young cluster of massive
stars, cataloged as R136,
energize the nebular glow and shape the spidery filaments.
Around the Tarantula are other violent star-forming regions with
young star clusters, filaments and
bubble-shaped clouds.
The small but expanding remnant of
supernova 1987a, the closest supernova
in modern history, is located near the center of the view.
The rich field is about as wide
as four full moons on the sky, located in the southern
constellation
Dorado.
APOD: 2008 March 6 - Vela Supernova Remnant
Explanation:
The plane of our Milky Way Galaxy runs through this
complex
and beautiful skyscape.
At the northwestern edge of the constellation
Vela
(the Sails) the 16 degree wide, 30 frame mosaic is centered on the
glowing filaments of the
Vela
Supernova Remnant, the expanding debris cloud from the
death explosion of a massive star.
Light from the supernova explosion
that created the Vela remnant
reached Earth about 11,000 years ago.
In addition to the shocked filaments of glowing gas, the cosmic
catastrophe also left behind an incredibly dense,
rotating stellar core, the Vela Pulsar.
Some 800 light-years distant, the Vela remnant is likely
embedded
in a larger and older supernova remnant, the
Gum Nebula.
The broad mosaic includes
other
identified emission and reflection nebulae, star clusters,
and the remarkable
Pencil
Nebula.
APOD: 2008 January 17 - Thor's Emerald Helmet
Explanation:
This helmet-shaped cosmic cloud with
wing-like appendages is popularly called
Thor's
Helmet.
Heroically sized even for a
Norse god,
Thor's Helmet is about 30 light-years across.
In fact, the helmet is actually more like
an interstellar bubble, blown as a fast
wind from the bright, massive star near the bubble's center sweeps
through a surrounding molecular cloud.
Known as a
Wolf-Rayet star, the central star is an
extremely hot giant thought to be in a brief,
pre-supernova stage of evolution.
Cataloged as NGC 2359, the nebula is located about
15,000 light-years away in the constellation
Canis
Major.
The sharp
image captures striking details of the
nebula's filamentary structures and also
records an almost emerald color from strong emission
due to oxygen atoms in the glowing gas.
APOD: 2007 October 27 - The Great Carina Nebula
Explanation:
A jewel of the southern sky,
the Great
Carina Nebula, aka NGC 3372, spans over 300 light-years,
one of our galaxy's largest star
forming regions.
Like the smaller, more northerly
Orion Nebula, the Carina Nebula
is easily visible to the naked eye, though at a distance of
7,500 light-years it is some 5 times farther away.
This
stunning telescopic view reveals remarkable details of the
region's glowing filaments of interstellar gas and dark
cosmic dust clouds.
The Carina Nebula is home to young, extremely massive stars, including
the still enigmatic variable
Eta
Carinae, a star with well over 100 times the mass of the Sun.
Eta Carinae
is the bright star left of the central dark notch
in this field and just below the dusty Keyhole
Nebula (NGC 3324).
APOD: 2007 September 20 - Northern Cygnus
Explanation:
Bright, hot, supergiant
star Deneb lies at top center in this
gorgeous
skyscape.
The 20 frame mosaic spans an impressive 12 degrees across the northern end of
Cygnus
the Swan.
Crowded with stars and luminous gas clouds
along the plane
of our Milky Way Galaxy, Cygnus is also home to the dark,
obscuring Northern Coal Sack Nebula, extending from Deneb
toward the bottom center of the view.
The reddish glow of NGC 7000, the
North America Nebula,
and IC 5070, the Pelican Nebula,
are at the upper left, but many other
nebulae and star clusters are
identifiable
throughout the wide field.
Of course, Deneb itself is the alpha star of Cygnus and is
also known to northern hemisphere skygazers for its place in two
asterisms --
marking the top of the
Northern Cross and
a vertex of the
Summer
Triangle.
APOD: 2007 July 24 - Spiral Galaxy M83: The Southern Pinwheel
Explanation:
M83 is one of
the closest and brightest
spiral galaxies on
the sky.
Visible with binoculars in the constellation of
Hydra, majestic spiral arms
have prompted its nickname as the Southern Pinwheel.
Although discovered 250 years ago,
only
much later was it appreciated that
M83 was not a nearby gas cloud, but a
barred
spiral galaxy much like our own
Milky Way Galaxy.
M83, pictured above, is a prominent member
of a group of galaxies that includes
Centaurus A and
NGC 5253, all of which lie about 15 million
light years distant.
Several bright supernova explosions
have been recorded in M83.
An intriguing double
circumnuclear ring has been discovered
at the center of M83.
APOD: 2007 June 30 - Jumbled Galaxy Centaurus A
Explanation:
At the center of
this
sharp skyscape, Centaurus A seems to be
a fantastic jumble of old yellow stars, young blue star clusters,
and imposing dark dust lanes.
Spanning over 60,000 light-years,
the
peculiar elliptical galaxy is
apparently the result of a collision of two otherwise
normal galaxies.
The left over cosmic debris is steadily being consumed by a
black
hole with a billion times the mass of the Sun which lies
at the center of Centaurus A.
It's likely that such
black
hole central engines generate the
radio, X-ray, and gamma-ray energy radiated
by Centaurus A and other
active
galaxies.
For an active galaxy Centaurus A
is close, a mere 10 million
light-years away,
and is well-studied by
earthbound
astronomers.
APOD: 2007 February 14 - The Rosette Nebula
Explanation:
Would the
Rosette Nebula by any other
name look as
sweet?
The bland New General Catalog
designation of NGC 2237 doesn't appear to diminish the appearance of the
this flowery emission nebula.
Inside the nebula lies an
open cluster
of bright young stars designated
NGC 2244.
These stars
formed about four million years ago from the nebular
material and their
stellar winds are clearing a hole in the nebula's center,
insulated by a layer of dust and hot gas.
Ultraviolet light from the
hot cluster stars causes the surrounding nebula to glow.
The
Rosette Nebula spans about 100
light-years across, lies
about 5000 light-years away,
and can be seen with a small telescope towards the constellation of Monoceros.
APOD: 2007 February 2 - Flame Nebula Close-Up
Explanation:
Of course, the Flame Nebula is not on fire.
Also known as
NGC 2024,
the nebula's suggestive
reddish color is due to the glow
of hydrogen
atoms at the edge of the giant Orion
molecular cloud complex some 1,500 light-years away.
The hydrogen atoms have been
ionized, or stripped of their
electrons, and glow as the atoms and electrons recombine.
But what ionizes the
hydrogen atoms?
In this
close-up view,
a dark lane of absorbing interstellar dust stands out
in silhouette against the
hydrogen glow
and actually hides
the true source of the Flame Nebula's energy from optical
telescopes.
Behind the dark lane lies a cluster of hot, young stars, seen
at infrared
wavelengths through the obscuring dust.
A young, massive star in that cluster is
the likely source
of energetic ultraviolet radiation that ionizes the
hydrogen gas in the Flame Nebula.
APOD: 2007 January 6 - The Orion Deep Field
Explanation:
Adrift 1,500 light-years away in one of
the night sky's most recognizable
constellations, the glowing
Orion Nebula and the dark
Horsehead Nebula are contrasting
cosmic vistas.
But even fainter filaments of glowing gas are easily traced
throughout the region in
this
stunning composite image
that includes exposures filtered to record emission
from hydrogen atoms.
The view reveals extensive
nebulosities associated with
the giant Orion Molecular
Cloud
complex, itself hundreds of light-years across.
A magnificent emission region, the
Orion
Nebula (aka M42) lies at the
upper right of the picture.
Immediately to its left are a cluster of prominent bluish
reflection nebulae sometimes called
the Running Man.
The Horsehead
nebula appears as a dark cloud, a small silhouette
notched against the long red glow left of center.
Alnitak is the easternmost star in Orion's belt and
the brightest star to the left of the Horsehead.
Below Alnitak is the
Flame Nebula, with clouds of
bright emission and dramatic dark dust lanes.
Completing the trio of Orion's belt
stars, bluish Alnilam and Mintaka form a line with Alnitak,
extending to the upper left.
APOD: 2006 December 15 - NGC 1055 and M77
Explanation:
Large spiral galaxy NGC 1055 (top left) joins
spiral M77 in this
lovely
cosmic view toward the
constellation
Cetus.
The narrowed, dusty appearance of edge-on spiral NGC 1055
contrasts nicely with the face-on view of
M77's bright nucleus
and spiral arms.
Both over 100,000 light-years across, the pair are dominant members
of a small galaxy group about 60 million light-years away.
At that estimated distance,
M77 is one
of the most remote objects in
Charles
Messier's catalog and
is separated from fellow island universe NGC 1055 by at
least 500,000 light-years.
The mosaicked field is about the size of the full Moon
on the sky and
includes colorful foreground Milky Way stars (with diffraction
spikes)
along with more distant background galaxies.
APOD: 2006 November 26 - M31: The Andromeda Galaxy
Explanation:
Andromeda is the nearest major
galaxy to our own
Milky Way Galaxy.
Our Galaxy is thought to look much like
Andromeda.
Together these two galaxies dominate the
Local Group of galaxies.
The diffuse light from
Andromeda
is caused by the hundreds of billions of
stars that compose it.
The several distinct stars that surround
Andromeda's image
are actually stars in
our Galaxy
that are well in front of the background object.
Andromeda is
frequently referred to as M31 since it is the 31st
object on
Messier's list of diffuse sky objects.
M31 is so distant it takes
about two million years for light to reach us from there.
Although visible without aid, the
above image of M31 is a digital mosaic of
20 frames taken with a small telescope.
Much about M31
remains unknown, including how the center acquired
two nuclei.
APOD: 2006 October 15 - An Orion Deep Field
Explanation:
Adrift 1,500 light-years away in one of
the night sky's
most recognizable
constellations, the glowing
Orion Nebula and the dark
Horsehead Nebula are contrasting
cosmic vistas.
They both appear in this stunning composite digital image
assembled from over 20 hours of data that includes exposures
filtered to record emission from hydrogen
atoms.
The view reveals extensive
nebulosities associated with
the giant Orion Molecular
Cloud
complex, itself hundreds of light-years across.
The magnificent emission region, the
Orion
Nebula (aka M42), lies at the
upper right of the picture.
Immediately to its left are a cluster of
of prominent bluish
reflection nebulae sometimes called
the Running Man.
The Horsehead
nebula appears as a dark cloud, a small silhouette
notched against the long red glow at the lower left.
Alnitak is the easternmost star in Orion's belt and
is seen as the brightest star to the left of the Horsehead.
Below Alnitak is the
Flame Nebula, with clouds of
bright emission and dramatic dark dust lanes.
Fainter tendrils of glowing hydrogen gas are easily traced
throughout the region in
this
Orion deep field.
APOD: 2006 October 5 - Hidden Galaxy IC 342
Explanation:
Similar
in size to other large, bright spiral galaxies
IC 342
is a mere 7 million light-years distant in
the long-necked, northern constellation
Camelopardalis.
A sprawling island universe, IC 342
would otherwise be a
prominent galaxy in our night sky,
but it is almost hidden from view behind the veil of stars,
gas and dust clouds
in the plane of our Milky Way galaxy.
Even though IC 342's light is dimmed by
intervening cosmic
clouds, this remarkably
sharp
telescopic image
traces the galaxy's own obscuring dust, blue star clusters, and glowing
pink star forming regions along spiral arms that
wind far from the galaxy's core.
IC 342
may have undergone a recent
burst of
star formation activity and is
close enough to have gravitationally
influenced the evolution of the
local
group of galaxies and the Milky Way.
APOD: 2006 August 8 - Horse Head Shaped Reflection Nebula IC 4592
Explanation:
Do you see the horse's head?
What you are seeing is not the famous
Horsehead nebula toward Orion but
rather a fainter nebula that only takes on a familiar form with deeper imaging.
The main part of the
above imaged
molecular cloud complex is a
reflection nebula
cataloged as
IC 4592.
Reflection nebulas are actually made up of very fine
dust that normally appears dark but can
look quite blue when reflecting the light of energetic nearby stars.
In this case, the source of much of the reflected light is a star at the eye of the horse.
That star is part of
Nu Scorpii,
one of the brighter star systems toward the
constellation of Scorpius.
A second
reflection nebula
dubbed IC 4601 is visible surrounding two stars on the far right.
APOD: 2006 July 14 - The Colorful Clouds of Rho Ophiuchi
Explanation:
This
stunning mosiac of the sky around bright stars
Antares (Alpha
Scorpii)
and
Rho Ophiuchi
reveals spectacular colors in a cosmic starscape.
Near the top, Rho Ophiuchi and nearby stars
are immersed in blue reflection nebulae - dust
clouds that shine primarily by
reflected starlight.
Cool supergiant star
Antares
(lower left) is itself shedding the
material that reflects the evolved star's yellowish hue.
Characteristic of star forming regions, the telltale red
emission from hydrogen gas also
permeates the view along with dark, obscuring
dust clouds seen
in silhouette against the background stars
and brighter nebulosities.
About 500 light-years away,
the Rho Ophiuchi star clouds,
are well in front of the nearby
globular star
cluster M4, visible
just below and right of center.
The wide view spans about 6 degrees on the sky.
APOD: 2006 June 28 - The Cat's Paw Nebula
Explanation:
Nebulae are perhaps as famous for being identified with
familiar shapes as cats are for getting into trouble.
Still, no known cat could have created the vast
Cat's Paw Nebula visible in Scorpius.
At 5,500 light years distant, Cat's
Paw is an
emission nebula with a red color that
originates from an abundance of ionized
hydrogen atoms.
Alternatively known as the
Bear Claw Nebula or
NGC 6334, stars nearly ten times the mass of our
Sun have been born
there in only the past few million years.
This
deep wide-field image of the Cat's Paw nebula
was photographed from
New South Wales,
Australia.
APOD: 2006 June 1 - Reflections on NGC 6188
Explanation:
NGC 6188 is an interstellar carnival of
young blue stars,
hot red gas, and
cool dark dust.
Located 4,000 light years away in the
disk of our Galaxy,
NGC 6188 is home to the
Ara OB1 association, a group of bright young stars
whose nucleus forms the open cluster
NGC 6193.
These stars are so bright that some of their blue light reflects off of
interstellar dust
forming the diffuse blue glow surrounding the stars in the
above photograph.
Open cluster NGC 6193 formed about
three million years ago from the surrounding gas,
and appears unusually rich in close binary stars.
The red glow visible throughout the photograph arises from
hydrogen gas heated by the bright stars in Ara OB1.
The dark dust that blocks much of NGC 6188's light was likely formed in the
outer atmospheres of
cooler stars and in
supernovae ejecta.
APOD: 2006 May 20 - Elliptical Galaxy M87
Explanation:
In spiral galaxies, majestic
winding arms of young stars and
interstellar gas and dust rotate in a flat disk around a
bulging galactic nucleus.
But elliptical galaxies seem to be simpler.
Lacking gas and dust to form new stars, their
randomly swarming older stars, give them an ellipsoidal
(egg-like) shape.
Still, elliptical galaxies can be very large.
Over 120,000 light-years in diameter (larger than our own
Milky Way), elliptical galaxy M87 is the dominant
galaxy at the center
of the Virgo Galaxy Cluster, some 50 million light-years away.
M87 is likely home to a supermassive
black hole responsible
for the high-energy jet of particles emerging from the giant
galaxy's central region.
APOD: 2006 January 30 - NGC 1999: South of Orion
Explanation:
South
of the large star-forming region known as the
Orion Nebula, lies bright blue reflection nebula
NGC 1999.
The nebula is marked with a dark inverted T-shape at the
lower left in a
broad
cosmic vista that spans over 10 light-years.
The dark shape is a dense gas and dust cloud, or
Bok globule,
seen in silhouette against the bright nebula, and likely
a site of future star formation.
At the edge of the
Orion molecular
cloud complex some 1,500 light-years distant, NGC 1999's
illumination is provided by the
embedded variable star V380 Orionis.
The
region abounds with energetic young stars
producing jets and outflows that create luminous shock waves,
including HH (Herbig-Haro) 1 and 2 just below and left of NGC 1999, and
the apparent cascade
of reddish arcs and bow shocks beginning at the upper right.
The stellar jets and
outflows push through the surrounding
material at speeds of hundreds of kilometers per second.
APOD: 2006 January 9 - M45: The Pleiades Star Cluster
Explanation:
Perhaps the most famous star cluster on the sky, the
Pleiades
can be seen without binoculars from even the depths of a
light-polluted city.
Also known as the Seven Sisters and
M45,
the Pleiades
is one of the brightest and closest
open clusters.
The Pleiades
contains over 3000 stars, is about 400 light years away,
and only 13 light years across.
Quite evident in the
above
photograph are the blue reflection nebulae
that surround the brighter cluster
stars.
Low mass, faint, brown dwarfs have also
been found in
the
Pleiades.
(Editors' note: The prominent
diffraction spikes are caused by the telescope itself and may be either distracting or provide aesthetic enhancement, depending on your point of view.)
APOD: 2005 December 22 - Andromeda Island Universe
Explanation:
The most distant object easily visible to the unaided eye is
M31,
the great
Andromeda Galaxy
some two million light-years away.
But without a telescope, even this immense spiral galaxy - spanning over
200,000 light years - appears as a
faint, nebulous cloud in the
constellation
Andromeda.
In contrast, a bright yellow nucleus, dark winding dust lanes,
gorgeous blue spiral arms and star clusters are recorded in this
stunning
telescopic
digital mosaic with a cumulative exposure of over 90 hours.
While even casual
skygazers
are now inspired by the knowledge that there are
many distant galaxies like M31, astronomers
seriously debated
this fundamental concept only 80 years ago.
Were these "spiral nebulae" simply outlying components of our own
Milky Way Galaxy or were they instead "island universes" -- distant
systems of stars comparable to the Milky Way itself?
This question was central to the famous
Shapley-Curtis
debate
of 1920, which was later resolved by
observations of M31
in favor of Andromeda,
island
universe.
APOD: 2005 August 11 - Young Suns of NGC 7129
Explanation:
Young suns still lie
within dusty NGC 7129, some
3,000 light-years away toward the royal
constellation
Cepheus.
While these stars are at a relatively tender age,
only about a million years old, it is likely
that our own Sun formed in a similar stellar nursery some
five billion years ago.
Most noticeable in
the
striking image are the lovely bluish dust clouds
that reflect the youthful starlight,
but the smaller, deep
red crescent shapes are also markers of energetic,
young stellar objects.
Known as
Herbig-Haro
objects, their shape and color is
characteristic of glowing hydrogen gas
shocked by jets
streaming away from newborn stars.
Ultimately the natal gas and dust in the region
will be dispersed, the
stars
drifting apart as the loose
cluster orbits the center of the Galaxy.
NGC 7129
is about 10 light-years across.
APOD: 2005 July 8 - NGC 4565: Galaxy on the Edge
Explanation:
Magnificent spiral galaxy
NGC 4565
is viewed edge-on from planet Earth.
Also known as the Needle Galaxy
for its narrow profile, bright
NGC 4565 is a stop on many telescopic tours
of the northern sky as it lies in the faint but well-groomed
constellation Coma
Berenices.
This
sharp color image reveals the galaxy's bulging central core
dominated by light from a population of older, yellowish stars.
The core is dramatically cut by obscuring dust lanes which lace
NGC 4565's thin galactic plane.
A large island universe
similar to our own
Milky Way
Galaxy, NGC 4565 is only about 30 million
light-years distant, but over 100,000 light-years in diameter.
In fact, some consider NGC 4565 to be a prominent celestial
masterpiece Messier missed.
APOD: 2005 June 17 - The Small Cloud of Magellan
Explanation:
Portuguese navigator
Ferdinand Magellan
and his crew had plenty
of time to study the southern sky during the
first circumnavigation of planet Earth.
As a result, two celestial wonders
easily visible for southern hemisphere skygazers
are known as the Clouds of Magellan.
These cosmic clouds are now understood to be dwarf
irregular galaxies,
satellites of our larger spiral
Milky Way Galaxy.
The Small
Magellanic Cloud
pictured above actually spans 15,000 light-years or so
and contains several hundred million stars.
About 210,000 light-years distant in
the constellation
Tucana,
it is the fourth closest of the Milky Way's
known satellite galaxies, after the
Canis Major
and
Sagittarius
Dwarf galaxies and the
Large
Magellanic Cloud.
This gorgeous
view also includes two foreground globular
star clusters NGC 362 (top left) and 47 Tucanae.
Spectacular 47 Tucanae
is a mere 13,000 light-years away and seen here to the right of the
Small Magellanic Cloud.
APOD: 2005 March 24 - Simeis 147: Supernova Remnant
Explanation:
It's easy to get lost following the intricate filaments in this
detailed
image of faint
supernova remnant Simeis 147.
Seen towards the constellation
Taurus
it covers nearly 3 degrees (6
full moons) on the sky corresponding to a width of 150 light-years at
the stellar debris cloud's estimated distance of 3,000 light-years.
The color composite image includes eight hours of exposure time
with an H-alpha filter, transmiting only
the light from recombining hydrogen atoms in the expanding
nebulosity and tracing the regions of
shocked, glowing gas.
This supernova remnant has an apparent age of about 100,000
years - meaning light from the massive stellar explosion first
reached Earth 100,000 years ago - but this expanding remnant is not the only
aftermath.
The cosmic catastrophe also left behind
a spinning neutron star or pulsar,
all
that remains of the original star's core.
APOD: 2004 December 27 - Andromeda's Core
Explanation:
The center of the Andromeda galaxy is beautiful but strange.
Andromeda,
indexed as M31, is so close to our own
Milky Way Galaxy that it
gives a unique perspective into galaxy composition by
allowing us to see into its core.
Billions of stars swarm around a center that has
two nuclei and likely houses a
supermassive black hole
over 5 million times the mass of our
Sun.
M31 is about two million light years away and
visible with the unaided eye towards the constellation of Andromeda, the princess.
Pictured above, dark
knots of
dust are seen superposed on the inner 10,000
light years of M31's core.
The brighter stars are foreground stars located in our
Milky Way Galaxy.
APOD: 2004 November 4 - NGC 7023: The Iris Nebula
Explanation:
Like delicate cosmic petals, these clouds of interstellar
dust and gas have blossomed 1,300 light-years away in the fertile
star fields of the constellation Cepheus.
Sometimes called the Iris Nebula and dutifully
cataloged as NGC
7023, this is not the only nebula in the
sky to evoke the imagery of flowers.
Still, the
beautiful
digital image shows off the Iris Nebula's range of colors and
symmetries in impressive detail.
Within the Iris, dusty nebular material surrounds a massive, hot,
young star in its formative years.
Central filaments of cosmic dust glow with a reddish photoluminesence
as some dust grains
effectively
convert the star's invisible
ultraviolet
radiation to visible red light.
Yet the dominant color of the nebula is blue,
characteristic
of dust grains reflecting starlight.
Dark, obscuring clouds of dust and cold molecular gas are also
present and can lead the eye to see other
convoluted and
fantastic shapes.
Infrared observations
indicate that this nebula may contain
complex carbon molecules known as
PAHs.
As shown here, the
Iris
Nebula is about 6 light-years across.
APOD: 2004 September 9 - Sagittarius Triplet
APOD: 2004 July 18 - M31: The Andromeda Galaxy
APOD: 2004 April 10 - Facing NGC 6946
APOD: 2004 January 15 - An Orion Deep Field
APOD: 2003 December 27 - The Pleiades Star Cluster
APOD: 2003 November 24 - IC 405: The Flaming Star Nebula
APOD: 2003 September 24 - M33: Spiral Galaxy in Triangulum
APOD: 2003 July 25 - Dumbbell Nebula Halo
APOD: 2002 December 20 - Colorful Clouds of Orion
APOD: 2002 October 21 - M31: The Andromeda Galaxy
APOD: 2002 October 4 - Facing NGC 6946
APOD: 2002 August 29 - The Pelican in the Swan
APOD: 2002 June 20 - Bright Galaxy M81
APOD: 2002 May 18 - Andromeda Island Universe
APOD: 2002 February 13 - The Great Nebula in Orion
APOD: 2002 January 7 - The Mysterious Cone Nebula
APOD: 2001 December 28 - Starlight Reflections
APOD: 2001 October 23 - Emission and Reflection in NGC 6559
APOD: 2001 July 20 - The Elephant's Trunk in IC 1396
APOD: 2001 June 8 - Three Galaxies in Draco
APOD: 2001 May 10 - Spirals On Edge
APOD: 2001 February 14 - The Rosette Nebula
APOD: 2000 November 22 - The Orion Nebula in Hydrogen
APOD: 2000 September 8 - Andromeda Island Universe
APOD: 2000 August 23 - NGC 6960: The Witch's Broom Nebula
APOD: 2000 February 9 - Galaxy Wars: M81 Versus M82
APOD: 2000 January 13 - A Skygazers Full Moon
APOD: 2000 January 10 - Brown Sun Bubbling
Explanation:
These three bright nebulae are often featured in telescopic tours
of the constellation
Sagittarius and the view
toward the center
of our Milky Way galaxy.
In fact, 18th century cosmic tourist
Charles Messier
cataloged two of them; M8, the nebula above and left of center,
and colorful M20 at the lower left.
The third, NGC 6559, is at the right of M8, separated
from the the larger nebula by a dark dust lane.
All three are stellar nurseries about
five thousand light-years or so distant.
The expansive M8, over a hundred light-years across,
is also known as the Lagoon Nebula
while M20's popular moniker is
the Trifid.
In this gorgeous digital composition,
the dominant red color of the emission nebulae is due
to glowing hydrogen gas energized by the radiation of hot,
young stars.
The contrasting blue hues, most striking in the
Trifid as well as NGC 6559, are due to dust
reflected starlight.
Explanation:
Andromeda is the nearest major
galaxy to our own
Milky Way Galaxy.
Our Galaxy is thought to look much like
Andromeda.
Together these two galaxies dominate the
Local Group of galaxies.
The diffuse light from
Andromeda
is caused by the hundreds of billions of
stars that compose it.
The several distinct stars that surround
Andromeda's image
are actually stars in
our Galaxy
that are well in front of the background object.
Andromeda is
frequently referred to as M31 since it is the 31st
object on
Messier's list of diffuse sky objects.
M31 is so distant it takes
about two million years for light to reach us from there.
Although visible without aid, the
above image of M31 is a digital mosaic of
20 frames taken with a small telescope.
Much about M31
remains unknown, including how the center acquired
two nuclei.
Explanation:
From our vantage point in the
Milky
Way Galaxy, we see
NGC 6946
face-on.
The big beautiful
spiral galaxy
is located just
10 million light-years away, behind a veil of foreground stars
in the high and far-off
constellation of Cepheus.
Looking from the bright core outward along the loose, fragmented spiral
arms, the galaxy's colors show a striking change from the yellowish
light of old stars in the galaxy's center to young blue star
clusters and reddish star forming regions.
NGC 6946 is also bright in
infrared light and
rich in gas and dust, exhibiting a high star birth and
death rate.
In fact, during the 20th century, at least six supernovae, the
death explosions
of massive stars, were discovered
in NGC 6946.
In this
sharp composite color digital image, a small
barred structure
is just visible at the gorgeous galaxy's core.
Explanation:
Adrift 1,500 light-years away in one of
the night sky's
most recognizable
constellations, the glowing
Orion Nebula and the dark
Horsehead Nebula are contrasting
cosmic vistas.
They both appear in this stunning composite digital image
assembled from over 20 hours of data that includes exposures
filtered to record emission from hydrogen
atoms.
The view reveals extensive
nebulosities associated with
the giant Orion Molecular
Cloud
complex, itself hundreds of light-years across.
The magnificent emission region, the
Orion
Nebula (aka M42), lies at the
upper right of the picture.
Immediately to its left are a cluster of
of prominent bluish
reflection nebulae sometimes called
the Running Man.
The Horsehead
nebula appears as a dark cloud, a small silhouette
notched against the long red glow at the lower left.
Alnitak is the easternmost star in Orion's belt and
is seen as the brightest star to the left of the Horsehead.
Below Alnitak is the
Flame Nebula, with clouds of
bright emission and dramatic dark dust lanes.
Fainter tendrils of glowing hydrogen gas are easily traced
throughout the region in
this
Orion deep field.
Explanation:
Perhaps the most famous star cluster on the sky, the
Pleiades
can be seen without binoculars from even the depths of a
light-polluted city.
Also known as the Seven Sisters and
M45,
the Pleiades
is one of the brightest and closest
open clusters.
The Pleiades
contains over 3000 stars, is about 400 light years away,
and only 13 light years across.
Quite evident in the
above
photograph are the blue
reflection nebulae
that surround the brighter cluster
stars.
Low mass, faint, brown dwarfs have also
been found in
the
Pleiades.
(Editors' note: The prominent
diffraction spikes were added
to the image for aesthetic reasons, produced by kite string donated
by Rob Gendler's kids and placed over the telescope dew shield.)
Explanation:
Rippling dust and gas lanes give the Flaming Star Nebula its name.
The red and purple colors of the nebula are present in
different regions and are created by different processes.
The bright star AE Aurigae,
visible toward the image right, is so hot it is blue,
emitting light so energetic it knocks
electrons away from surrounding gas.
When a proton recaptures an electron,
red light is frequently emitted.
The purple region's color is a mix of this
red light and blue light emitted by AE
Aurigae but reflected to us by surrounding
dust.
The two regions are referred to as
emission nebula and
reflection nebula, respectively.
Pictured above, the Flaming Star Nebula, officially known as
IC 405, lies about 1500
light years distant, spans about 5 light years,
and is visible with a small telescope toward the constellation of
Auriga.
Explanation:
The small constellation
Triangulum
in the northern sky harbors
this magnificent face-on spiral galaxy, M33.
Its popular names include the Pinwheel Galaxy or just
the Triangulum Galaxy.
M33's diameter spans over 50,000 light-years, making it third largest in
the Local
Group of galaxies after the Andromeda Galaxy (M31), and our
own Milky Way.
About 3 million light-years from the Milky Way, M33
lies very close to the Andromeda Galaxy and
observers
in these two galaxies would likely have spectacular views of
each other's grand spiral star systems.
As for the view from planet Earth, this
sharp
27 frame mosaic of M33 nicely shows off blue star clusters
and pinkish star forming regions which trace the galaxy's
loosely wound spiral arms.
In fact, the cavernous NGC 604 is the brightest
star forming region seen here, visible
along an arm arcing above and to the right
of the galaxy center.
Like M31, M33's population of well-measured variable stars
have helped make this nearby spiral a
cosmic
yardstick for
establishing
the distance scale of the Universe.
Explanation:
In 1764, French astronomer
Charles
Messier sighted this gorgeous
cosmic cloud which
he
described as an oval nebula without stars.
Cataloged as M27,
it is now popularly known as the
Dumbbell
Nebula, not for its substandard academic performance but
for the elongated shape, like a bar with weights on each end, which
first
caught Messier's eye.
This deep image of the bright planetary
nebula does reveal the Dumbell's central star though, and
an array of foreground and background stars
toward the sly constellation
Vulpecula.
The picture is
a composite
that includes 8 hours of
exposure through a filter designed to record only the light
of hydrogen atoms, tracing the intricate details of
the nebula's faint outer halo
which spans light-years.
Thought to be an example of the
fate awaiting our own
Sun 5 billion years hence, the Dumbbell Nebula is
about 1,200 light-years away.
Explanation:
Revisiting one of the most
famous nebulae in
planet Earth's night sky,
astrophotographer
Robert Gendler has constructed this stunning,
color-enhanced mosaic
of the region surrounding the
Great
Nebula in Orion.
As seen here, the
clouds of Orion are dominated by the
reddish emission nebula M42
near the bottom of the image,
with blue reflection nebulae, including
NGC 1977, near the top.
Strewn with dust lanes and dark nebulae,
the striking cosmic apparitions
surrounding Orion's
stellar nurseries are about 1,500 light-years away and are
themselves several light-years across.
Located at the edge of a giant molecular
cloud complex
spanning hundreds of light-years, these nebulae represent only a small,
but very visible(!), fraction of this region's wealth of
interstellar
material.
Within these colorful clouds of Orion,
astronomers have also
identified what appear to be numerous
infant solar systems.
Explanation:
Andromeda is the nearest major
galaxy to our own
Milky Way Galaxy.
Our Galaxy is thought to look much like
Andromeda.
Together these two galaxies dominate the
Local Group of galaxies.
The diffuse light from
Andromeda
is caused by the hundreds of billions of
stars that compose it.
The several distinct stars that surround
Andromeda's image
are actually stars in
our Galaxy
that are well in front of the background object.
Andromeda is
frequently referred to as M31 since it is the 31st
object on
Messier's list of diffuse sky objects.
M31 is so distant it takes
about two million years for light to reach us from there.
Although visible without aid, the
above image of M31 is a digital mosaic of
20 frames taken with a small telescope.
Much about M31
remains unknown, including how the center acquired
two nuclei.
Explanation:
From our vantage point in the
Milky Way Galaxy, we see
NGC 6946
face on.
The big beautiful
spiral galaxy is located just
10 million light-years away, behind a veil of foreground stars
in the high and far-off
constellation of Cepheus.
Looking from the bright core outward along the loose, fragmented spiral
arms, the galaxy's colors show a striking change from the yellowish
light of old stars in the galaxy's center to young blue star
clusters and reddish star forming regions.
NGC 6946 is also bright in
infrared light and
rich in gas and dust, exhibiting a high star birth and
death rate.
In fact, during the 20th century, at least six supernovae, the
death explosions
of massive stars, were discovered
in NGC 6946.
In this
sharp composite color digital image, a small
barred structure
is just visible at the gorgeous galaxy's core.
Explanation:
The Pelican Nebula, also known as IC 5070, lies about 2,000 light-years
away in the high and far-off
constellation of Cygnus, the Swan.
This picture spans a portion
of the magnificent nebula about 30 light-years wide.
Fittingly, this cosmic
pelican is found
just off the east "coast" of
the North America Nebula,
another surprisingly familiar looking
emission nebula in Cygnus.
In fact, the Pelican and North America nebulae are part of the same
large star forming region.
The two glowing
nebulae appear separated from our vantage point
by a large obscuring dust cloud running across the upper
left corner in this
gorgeous
color view.
Within the
Pelican
Nebula, dark dust clouds also help define
the eye and long bill, while a
bright front of ionized gas
suggests the curved shape of the head and neck.
Even though it is almost as close as the
Orion Nebula,
the stellar nursery marked by the Pelican and North America
nebulae has
proven complex and difficult to study.
Explanation:
Big and beautiful
spiral galaxy M81,
in the northern constellation
Ursa Major,
is one of the
brightest
galaxies visible in the skies of
planet Earth.
This superbly
detailed view
reveals its bright nucleus, grand
spiral arms and sweeping cosmic dust lanes with a scale
comparable to
the Milky Way.
Hinting at a disorderly past,
a remarkable dust lane runs straight through the
disk, below and right of the galactic center,
contrary to
M81's other
prominent
spiral features.
The errant
dust lane may be the lingering result of
a close encounter between
M81 and its smaller companion galaxy, M82.
Scrutiny of variable stars in M81 (aka NGC 3031)
has yielded one of the best
determined
distances for an external galaxy -- 11.8 million light-years.
Explanation:
How far can you see?
The most distant object easily visible to the unaided eye is
M31,
the great
Andromeda Galaxy
some two million light-years away.
Without a telescope, even this immense spiral galaxy appears
as an unremarkable, faint, nebulous cloud in the
constellation
Andromeda.
But a bright yellow nucleus, dark winding dust lanes, gorgeous blue
spiral arms and star clusters are recorded in this stunning
telescopic digital
mosaic of the nearby island universe.
While even casual
skygazers
are now inspired by the knowledge that there are
many distant galaxies like M31, astronomers
seriously debated
this fundamental concept only 80 years ago.
Were these "spiral nebulae" simply outlying components of our own
Milky Way Galaxy or were they instead "island universes" -- distant
systems of stars comparable to the Milky Way itself?
This question was central to the famous
Shapley-Curtis
debate
of 1920, which was later resolved by
observations of M31
in favor of Andromeda,
island
universe.
Explanation:
Few astronomical sights excite the imagination like the
nearby stellar nursery known as the
Orion Nebula.
The Nebula's glowing gas surrounds hot young stars at
the edge of an immense interstellar
molecular cloud only 1500 light-years away.
The Great Nebula in Orion can be
found with the unaided eye just below and to the left of the
easily identifiable
belt of three stars in the popular constellation Orion.
The above image has been contrast balanced to bring out Orion's detail
in spectacular fashion.
Visible simultaneously are the bright stars of the
Trapezium in
Orion's heart, the sweeping lanes of
dark dust that cross the center,
the pervasive red glowing hydrogen gas,
and the
blue tinted dust
that reflects the light of newborn stars.
The whole Orion Nebula cloud complex, which includes the
Horsehead Nebula,
will slowly disperse over the next 100,000 years.
Explanation:
Sometimes the simplest shapes are the hardest to explain.
For example, the origin of the mysterious
cone-shaped region
seen on the far left remains a mystery.
The interstellar formation, dubbed the
Cone Nebula, is located about 2700
light years away.
Other features in the image include red
emission from diffuse
interstellar hydrogen,
wispy filaments of dark dust, and
bright star
S Monocerotis, visible on the far right.
Blue reflection nebulae surround the brighter stars.
The dark
Cone Nebula region clearly contains much
dust which blocks light from the
emission nebula and
open cluster
NGC 2264 behind it.
One hypothesis holds that the Cone Nebula is formed by
wind particles
from an energetic source blowing past the
Bok Globule at the head of the
cone.
Explanation:
Interstellar dust grains
often find themselves in a reflective "mood".
Near a bright star, clouds of these dust particles scatter
short wavelengths of visible starlight
more readily than
long wavelengths, producing lovely blue reflection nebulae.
Nine of the more spectacular examples of these dusty, blue
stellar
neighborhoods
have been assembled here by
astrophotographer
Rob Gendler.
From left to right starting with the top row are
NGC 1977 in Orion,
IC2118 (the Witch Head),
and M78 also in Orion.
Across the middle row are,
M20 (Trifid),
NGC 2264 in Monoceros,
and
IC405 (Flaming Star Nebula).
Along the bottom are
NGC 2023 (near
the Horsehead),
NGC 7023 (Iris Nebula),
and finally bright star Merope surrounded by
a veil of dust (NGC 1435).
Merope is one of the seven sisters of the Pleiades.
Explanation:
Bright gas and dark dust permeate the space
between stars in a nebula known as
NGC 6559.
The gas, primarily
hydrogen, is responsible for the diffuse red glow of the
emission nebula.
As energetic light from neighboring stars ionizes
interstellar hydrogen,
protons and
electrons recombine to emit
light of very
specific colors, including the
red hue observed.
Small dust particles
reflect blue starlight efficiently and so creates the blue
reflection nebulosity
seen near two of the bright stars.
Dust also absorbs visible light, causing the
dark clouds and
filaments visible.
NGC 6559 lies about 5000 light-years away toward the constellation of
Sagittarius.
Explanation:
Like a picture from a galactic
Just
So Story, the
Elephant's Trunk Nebula
winds through the emission nebula and young star cluster
complex
IC 1396, in the high and far off constellation
of Cepheus.
Bright swept-back ridges
compose the suggestive form, outlining pockets of interstellar dust
and gas.
Such embedded dark,
comet-shaped clouds contain the
raw material for star formation.
About 3,000
light-years distant, the relatively faint
IC
1396 complex covers a much larger region on the sky than shown
here, with an apparent width of more than 10 full moons.
This
close-up telescopic view is a delightful
color
mosaic of two digital images intended to follow
the 'satiable
curious cosmic trunk.
Explanation:
This intriguing trio of galaxies is sometimes
called the NGC 5985/Draco Group
and so (quite reasonably) is located in the northern
constellation
Draco.
From left to right are
face-on spiral NGC 5985,
elliptical galaxy NGC 5982, and
edge-on spiral NGC 5981 --
all within this single
telescopic
field of view spanning a little more than
half the width of the full moon.
While this grouping is far too small to be a
galaxy cluster
and has not been
cataloged
as a compact group,
these galaxies do lie roughly 100 million light-years from planet Earth.
On close examination with spectrographs, the bright core of the
striking face-on spiral NGC 5985 shows
prominent emission in specific wavelengths of light, prompting astronomers
to classify it as a
Seyfert, a type of active galaxy.
Not as well known as other tight
groupings of galaxies,
the contrast in
visual
appearance makes this triplet an attractive subject for
avid astrophotographers.
Explanation:
Spiral galaxies viewed face-on display a
grand design, with
graceful spiral arms traced by bright star clusters and
glowing stellar nurseries.
When seen edge-on, their appearance is very different but no less striking
as their central regions bulge and dark cosmic
dust lanes appear silhouetted against starlight from flattened galactic disks.
This masterful mosaic of
digital images
shows nine prominent edge-on
spirals arranged as follows:
top;
NGC2683,
M104,
NGC4565,
middle;
NGC891,
NGC4631,
NGC3628, and
bottom;
NGC5746,
NGC5907, and
NGC4217.
Perhaps the best known of these is
M104 (NGC4594)
whose
more descriptive moniker is the Sombrero Galaxy.
Notably, the edge-on perspective of these galaxies
allows
a measurement of their
galactic rotation speed using the
Doppler
effect.
Plotting rotation
speed versus distance from the
center determines a galaxy's gravitational mass and
historically led to premier evidence
for mysterious Dark Matter.
Explanation:
Would the
Rosette Nebula by any other
name look as
sweet?
The bland
New General Catalog
designation of
NGC 2237 doesn't appear to diminish the
appearance of the
this flowery
emission nebula.
Inside the nebula lies an
open cluster
of bright young stars designated
NGC 2244.
These stars
formed about four million years ago from the nebular
material and their
stellar winds are clearing a hole in the nebula's center,
insulated by a layer of
dust and hot gas.
Ultraviolet light from the
hot cluster stars causes the surrounding nebula to glow.
The
Rosette Nebula spans about 100
light-years across, lies
about 5000 light-years away,
and can be seen with a small telescope towards the constellation of
Monoceros.
Explanation:
The
Great Nebula in Orion can be found just below
and to the left of the easily identifiable
belt of three stars in the popular
constellation Orion.
This fuzzy patch,
visible to the unaided eye,
contains one of the closest
stellar nurseries, lying at a distance of about 1500
light years.
The
above picture highlights red light emitted
by the nebula's hydrogen gas.
Dark
dust
filaments punctuate regions of this glowing hydrogen
gas and reflect light from the
nebula's brightest stars.
Recent observations of the
Orion Nebula by the
Hubble Space Telescope
have located
solar-system sized regions that are
thought to be planet-forming circumstellar disks.
Explanation:
How far can you see?
The most distant object easily visible to the unaided eye is
M31,
the great
Andromeda Galaxy
some two million light-years away.
Without a telescope, even this immense spiral galaxy appears
as an unremarkable, faint, nebulous cloud in the
constellation
Andromeda.
But a bright yellow nucleus, dark winding dustlanes, gorgeous blue
spiral arms and star clusters are recorded in this stunning
telescopic digital
mosaic of the nearby island universe.
While even casual
skygazers
are now inspired by the knowledge that there are
many distant galaxies like M31, astronomers
seriously debated
this fundamental concept only 80 years ago.
Were these "spiral nebulae" simply outlying components of our own
Milky Way Galaxy or were they instead "island universes" -- distant
systems of stars comparable to the Milky Way itself?
This question was central to the famous
Shapley-Curtis
debate
of 1920, which was later resolved by
observations of M31
in favor of Andromeda,
island
universe.
Explanation:
Ten thousand years ago, before the dawn of recorded human history,
a new light must suddenly have appeared in the
night sky and faded after a few weeks.
Today we know this light was an exploding star and record the colorful expanding cloud as the
Veil Nebula.
Pictured above is the west end of the
Veil Nebula known technically as
NGC 6960
but less formally as the Witch's Broom Nebula.
The rampaging gas gains its colors by impacting and
exciting existing nearby gas.
The
supernova remnant lies about
1400 light-years away towards the constellation of
Cygnus.
This Witch's Broom actually spans over three times the
angular size of the full
Moon.
The bright blue star 52
Cygnus is visible with the unaided eye from
a dark location but unrelated to the ancient
supernova.
Explanation:
In the left corner, wearing a red nucleus
surrounded by blue spiral arms, is
M81.
In the right corner, sporting light stars and dark dust lanes, is
M82.
These two mammoth galaxies have been locked in
gravitational combat
for the past billion years.
The
gravity from each galaxy dramatically affects the
other during each hundred million-year pass.
Last go-round, M82's gravity likely raised circulating
density waves rippling around M81 resulting in the richness of
M81's spiral arms.
M81, though, left
M82 a messy pulp of exploded stars and
colliding gas so violent it
emits bright X-rays.
In both galaxies, colliding gas has created a recent abundance of
bright new stars.
In a few billion years only one galaxy will remain.
Explanation:
This dramatically sharp picture of the full moon was
recorded on 22 December, 1999 by astroimager
Rob Gendler.
Big, beautiful, bright, and
evocative, it was the last
full moon of the Y1.9Ks, pleasing and inspiring even
casual skygazers.
December's
moon was special for another reason, as
the full
phase
occurred on the day of the winter solstice and within hours
of lunar perigee.
The first full moon of the year 2000 will bring
a special treat
as well, presenting denizens of planet Earth with
a total lunar eclipse.
On Thursday evening, January 20, the
moon will encounter the dark edge of Earth's shadow at 10:01 PM
Eastern Time
with the total eclipse phase beginning at 11:05 PM
and lasting for 77 minutes.
This lunar eclipse will be visible from North and South America and
Western Europe (total phase begins at 4:05 AM GMT January 21).
Explanation:
Our Sun may look like all soft and fluffy, but its not.
Our Sun is an extremely large ball of
bubbling hot gas, mostly
hydrogen gas.
The
above picture was taken in a
specific color of light emitted by hydrogen gas called
Hydrogen-alpha.
Granules cover the solar
photosphere surface like shag
carpet,
interrupted by bright regions containing dark
sunspots.
Visible at the left edge is a
solar prominence.
Our Sun glows because it is hot, but it is not on fire.
Fire is the rapid acquisition of oxygen,
and there is very little
oxygen on the Sun.
The energy source of our Sun is the nuclear
fusion of hydrogen into
helium deep within its core.
Astronomers are still working to understand,
however, why so few
neutrinos are
measured from the
Sun's core.
Return to Search Page
Today's Astronomy Picture of the Day