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. 2020 September 25 [2]See Explanation. Clicking on the picture will download the highest resolution version available. Moon over Andromeda Composite Image Credit & [3]Copyright: [4]Adam Block and [5]Tim Puckett Explanation: The Great Spiral [6]Galaxy in Andromeda (also known [7]as M31), a mere 2.5 million light-years [8]distant, is the closest large spiral to our own Milky Way. Andromeda is visible to the unaided eye as a small, faint, fuzzy patch, but because its surface brightness is so low, casual [9]skygazers can't appreciate the galaxy's impressive extent in [10]planet Earth's sky. This entertaining composite image compares the [11]angular size of the nearby galaxy to a brighter, more familiar celestial sight. In it, a [12]deep exposure of Andromeda, tracing beautiful blue star clusters in spiral arms far beyond the bright yellow core, is combined with a typical view of a nearly full Moon. Shown at the same [13]angular scale, the Moon covers about 1/2 degree on the sky, while the galaxy is clearly several times that size. The deep Andromeda exposure also includes two bright satellite galaxies, [14]M32 and [15]M110 (below and right). Tomorrow's picture: Observe the Moon __________________________________________________________________ [16]< | [17]Archive | [18]Submissions | [19]Index | [20]Search | [21]Calendar | [22]RSS | [23]Education | [24]About APOD | [25]Discuss | [26]> __________________________________________________________________ Authors & editors: [27]Robert Nemiroff ([28]MTU) & [29]Jerry Bonnell ([30]UMCP) NASA Official: Phillip Newman [31]Specific rights apply. [32]NASA Web Privacy Policy and Important Notices A service of: [33]ASD at [34]NASA / [35]GSFC & [36]Michigan Tech. U. References 1. https://apod.nasa.gov/apod/archivepix.html 2. https://apod.nasa.gov/apod/image/2009/m31abtpmoon.jpg 3. https://apod.nasa.gov/apod/lib/about_apod.html#srapply 4. http://www.caelumobservatory.com/ 5. http://www.cometwatch.com/ 6. https://apod.nasa.gov/apod/ap200430.html 7. https://www.nasa.gov/feature/goddard/2017/messier-31-the-andromeda-galaxy 8. http://arxiv.org/abs/astro-ph/0511045 9. http://www.physics.ucla.edu/~huffman/m31.html 10. https://apod.nasa.gov/apod/ap090411.html 11. https://www.astronomy.swin.edu.au/cosmos/A/Angular+Diameter 12. http://www.caelumobservatory.com/gallery/m31abtp.shtml 13. https://apod.nasa.gov/apod/ap080801.html 14. https://apod.nasa.gov/apod/ap991103.html 15. https://apod.nasa.gov/apod/ap080909.html 16. https://apod.nasa.gov/apod/ap200924.html 17. https://apod.nasa.gov/apod/archivepix.html 18. https://apod.nasa.gov/apod/lib/apsubmit2015.html 19. https://apod.nasa.gov/apod/lib/aptree.html 20. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search 21. https://apod.nasa.gov/apod/calendar/allyears.html 22. https://apod.nasa.gov/apod.rss 23. https://apod.nasa.gov/apod/lib/edlinks.html 24. https://apod.nasa.gov/apod/lib/about_apod.html 25. http://asterisk.apod.com/discuss_apod.php?date=200925 26. https://apod.nasa.gov/apod/ap200926.html 27. http://www.phy.mtu.edu/faculty/Nemiroff.html 28. http://www.phy.mtu.edu/ 29. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html 30. http://www.astro.umd.edu/ 31. https://apod.nasa.gov/apod/lib/about_apod.html#srapply 32. https://www.nasa.gov/about/highlights/HP_Privacy.html 33. https://astrophysics.gsfc.nasa.gov/ 34. https://www.nasa.gov/ 35. https://www.nasa.gov/centers/goddard/ 36. http://www.mtu.edu/