For 10 years, the Hubble Space Telescope has been gathering information about Andromeda, our neighboring galaxy, situated 2.5 million light-years away from the Milky Way. The result is a 2.5 billion pixel mosaic (a pixel is the smallest unit of color information in a digital image) containing 200 million bright blue stars hotter than the Sun, with other galaxies and cosmic dust in the background. This detailed overview reveals a little more about the history of Andromeda, also known as M31. In the south of the galactic disk there are signs of a merger with smaller galaxies, such as M32, which was absorbed by Andromeda two to three billion years ago. Andromeda, a spiral galaxy like the Milky Way, can be seen with the naked eye from the Northern Hemisphere on a clear day, appearing like a gray oval with a diameter roughly six times larger than the full Moon. It is the most distant object in the Universe that can be seen without a telescope (Astrophysical Journal, January 16; Universe Today, January 20).
NASA, ESA, B. Williams (University of Washington)The most detailed picture of Andromeda, showing 200 million stars hotter than the SunNASA, ESA, B. Williams (University of Washington)
