Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2009 September 17
See Explanation.
Moving the cursor over the image will bring up an alternate version.
Clicking on the image will bring up the highest resolution version
available.

Ultraviolet Andromeda
Credit: UV - NASA/Swift/Stefan Immler (GSFC) and Erin Grand (UMCP)
Optical - Bill Schoening, Vanessa Harvey/REU program/NOAO/AURA/NSF

Explanation: Taken by a telescope onboard NASA's Swift satellite, this stunning vista represents the highest resolution image ever made of the Andromeda Galaxy (aka M31) - at ultraviolet wavelengths. The mosaic is composed of 330 individual images covering a region 200,000 light-years wide. It shows about 20,000 sources, dominated by hot, young stars and dense star clusters that radiate strongly in energetic ultraviolet light. Of course, the Andromeda Galaxy is the closest large spiral galaxy to our own Milky Way, at a distance of some 2.5 million light-years. To compare this gorgeous island universe's appearance in optical light with its ultraviolet portrait, just slide your cursor over the image.


Tomorrow's picture: pixels in space


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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
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