Astronomy Picture of the Day [1]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. 2025 February 21 [2]See Explanation. Clicking on the picture will download the highest resolution version available. Hubble's Andromeda Galaxy Mosaic Image Credit: [3]NASA, [4]ESA, [5]Hubble Mission, B. F. Williams (Univ Washington), Z. Chen (Univ Washington), L. C. Johnson (Northwestern), Processing; Joseph DePasquale ([6]STScI) Explanation: The largest photomosaic ever assembled from Hubble Space Telescope image data is a panoramic view of our neighboring spiral Andromeda Galaxy. With 600 overlapping frames assembled from observations made from July 2010 to December 2022, the full [7]Hubble Andromeda Galaxy mosaic spans almost six full moons across [8]planet Earth's sky. A cropped version shown above is nearly two full moons across and partially covers Andromeda's core and inner spiral arms. Also known as M31, the [9]Andromeda Galaxy is 2.5 million light-years away. That makes it the closest large spiral galaxy to our own Milky Way. Our perspective on the spiral Milky Way is [10]anchored to the view from the [11]location of the Sun, a star found within the Milky Way's galactic disk. But Hubble's magnificent Andromeda mosaic offers an expansive view of a large spiral galaxy from the outside looking in. Hubble's comprehensive, [12]detailed [13]data set extending [14]across the Andromeda Galaxy will allow astronomers to make an unprecedented holistic exploration of the mysteries of spiral galaxy structure and evolution. Tomorrow's picture: light-weekend __________________________________________________________________ [15]< | [16]Archive | [17]Submissions | [18]Index | [19]Search | [20]Calendar | [21]RSS | [22]Education | [23]About APOD | [24]Discuss | [25]> __________________________________________________________________ Authors & editors: [26]Robert Nemiroff ([27]MTU) & [28]Jerry Bonnell ([29]UMCP) NASA Official: Amber Straughn [30]Specific rights apply. [31]NASA Web Privacy Policy and Important Notices A service of: [32]ASD at [33]NASA / [34]GSFC, [35]NASA Science Activation & [36]Michigan Tech. U. References 1. https://apod.nasa.gov/apod/archivepix.html 2. https://apod.nasa.gov/apod/image/2502/M31_HubbleMosaic1024H.jpg 3. https://www.nasa.gov/ 4. http://www.esa.int/ 5. https://www.nasa.gov/mission_pages/hubble/main/index.html 6. https://www.stsci.edu/who-we-are 7. https://hubblesite.org/contents/media/images/2025/005/01JGY8JKWBHBWJ71V3QQTKM382 8. https://apod.nasa.gov/apod/ap200925.html 9. https://en.wikipedia.org/wiki/Andromeda_Galaxy 10. https://apod.nasa.gov/apod/ap110520.html 11. https://science.nasa.gov/resource/the-milky-way-galaxy/ 12. https://ui.adsabs.harvard.edu/abs/2012ApJ...755..131R/abstract 13. https://ui.adsabs.harvard.edu/abs/2025ApJ...979...35C/abstract 14. https://science.nasa.gov/missions/hubble/nasas-hubble-traces-hidden-history-of-andromeda-galaxy/ 15. https://apod.nasa.gov/apod/ap250220.html 16. https://apod.nasa.gov/apod/archivepix.html 17. https://apod.nasa.gov/apod/lib/apsubmit2015.html 18. https://apod.nasa.gov/apod/lib/aptree.html 19. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search 20. https://apod.nasa.gov/apod/calendar/allyears.html 21. https://apod.nasa.gov/apod.rss 22. https://apod.nasa.gov/apod/lib/edlinks.html 23. https://apod.nasa.gov/apod/lib/about_apod.html 24. http://asterisk.apod.com/discuss_apod.php?date=250221 25. https://apod.nasa.gov/apod/ap250222.html 26. http://www.phy.mtu.edu/faculty/Nemiroff.html 27. http://www.phy.mtu.edu/ 28. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html 29. http://www.astro.umd.edu/ 30. https://apod.nasa.gov/apod/lib/about_apod.html#srapply 31. https://www.nasa.gov/about/highlights/HP_Privacy.html 32. https://astrophysics.gsfc.nasa.gov/ 33. https://www.nasa.gov/ 34. https://www.nasa.gov/centers/goddard/ 35. https://science.nasa.gov/learners 36. http://www.mtu.edu/