﻿ 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. 2023 March 22 [2]The Andromeda Galaxy is shown in great detail. Red nebulas, blue stars, and dark dust are all seen in a swirl around the galaxy's bright center. Please see the explanation for more detailed information. M31: The Andromeda Galaxy Image Credit & Copyright: [3]Abdullah Al-Harbi Explanation: How far can you see? The most distant object easily visible to the unaided eye is M31, the great [4]Andromeda Galaxy, over two million [5]light-years away. Without a telescope, even this immense [6]spiral galaxy appears as an unremarkable, faint, [7]nebulous cloud in the [8]constellation Andromeda. But a bright white nucleus, dark winding dust lanes, luminous blue spiral arms, and bright red emission nebulas are recorded in [9]this stunning fifteen-hour telescopic digital mosaic of our [10]closest major galactic neighbor. But how do we know [11]this spiral nebula is really so far away? This question was central to the famous [12]Shapley-Curtis [13]debate [14]of 1920. M31's great distance was determined in the 1920s by [15]observations that resolved individual stars that [16]changed their brightness in a way that gave up their true distance. The result proved that [17]Andromeda is just like our [18]Milky Way Galaxy -- a conclusion making [19]the rest of the universe much [20]more vast than had ever been [21]previously imagined. Tomorrow's picture: open space __________________________________________________________________ [22]< | [23]Archive | [24]Submissions | [25]Index | [26]Search | [27]Calendar | [28]RSS | [29]Education | [30]About APOD | [31]Discuss | [32]> __________________________________________________________________ Authors & editors: [33]Robert Nemiroff ([34]MTU) & [35]Jerry Bonnell ([36]UMCP) NASA Official: Phillip Newman [37]Specific rights apply. [38]NASA Web Privacy Policy and Important Notices A service of: [39]ASD at [40]NASA / [41]GSFC, [42]NASA Science Activation & [43]Michigan Tech. U. References 1. https://apod.nasa.gov/apod/archivepix.html 2. https://apod.nasa.gov/apod/image/2303/M31_Alharbi_4822.jpg 3. https://www.instagram.com/a_alharbi97/ 4. https://en.wikipedia.org/wiki/Andromeda_Galaxy 5. https://youtu.be/MX3PIkbTQwQ 6. https://en.wikipedia.org/wiki/Spiral_galaxy 7. https://apod.nasa.gov/apod/ap160322.html 8. https://en.wikipedia.org/wiki/Andromeda_(constellation) 9. https://www.instagram.com/p/CpsrUSHMJis/ 10. https://youtu.be/TijClV4uHIk 11. https://apod.nasa.gov/apod/ap221024.html 12. https://apod.nasa.gov/debate/debate20.html 13. https://apod.nasa.gov/debate/debate.html 14. https://apod.nasa.gov/debate/debate20.html 15. https://apod.nasa.gov/apod/ap200426.html 16. https://apod.nasa.gov/apod/ap110701.html 17. https://apod.nasa.gov/apod/ap220807.html 18. https://apod.nasa.gov/apod/ap180729.html 19. https://apod.nasa.gov/apod/ap180508.html 20. https://apod.nasa.gov/apod/ap200405.html 21. https://i.pinimg.com/736x/17/e0/6c/17e06cb8ddaa2fc90b7a416c0d0349ef--pugs-on-the-beach.jpg 22. https://apod.nasa.gov/apod/ap230321.html 23. https://apod.nasa.gov/apod/archivepix.html 24. https://apod.nasa.gov/apod/lib/apsubmit2015.html 25. https://apod.nasa.gov/apod/lib/aptree.html 26. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search 27. https://apod.nasa.gov/apod/calendar/allyears.html 28. https://apod.nasa.gov/apod.rss 29. https://apod.nasa.gov/apod/lib/edlinks.html 30. https://apod.nasa.gov/apod/lib/about_apod.html 31. https://asterisk.apod.com/discuss_apod.php?date=230322 32. https://apod.nasa.gov/apod/ap230323.html 33. http://www.phy.mtu.edu/faculty/Nemiroff.html 34. http://www.phy.mtu.edu/ 35. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html 36. http://www.astro.umd.edu/ 37. https://apod.nasa.gov/apod/lib/about_apod.html#srapply 38. https://www.nasa.gov/about/highlights/HP_Privacy.html 39. https://astrophysics.gsfc.nasa.gov/ 40. https://www.nasa.gov/ 41. https://www.nasa.gov/centers/goddard/ 42. https://science.nasa.gov/learners 43. http://www.mtu.edu/