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 January 17 [2]A deep image of M31, the Andromeda galaxy, shows unexpected oxygen-glowing arcs to its left. Please see the explanation for more detailed information. Unexpected Clouds Toward the Andromeda Galaxy Image Credit & Copyright: [3]Yann Sainty & [4]Marcel Drechsler Explanation: Why are there oxygen-emitting arcs near the direction of the Andromeda galaxy? No one is sure. The gas arcs, [5]shown in blue, were [6]discovered and first [7]confirmed by [8]amateur astronomers just last year. The two main origin hypotheses for the arcs are that they really are close to Andromeda ([9]M31), or that they are just coincidentally placed [10]gas filaments in our [11]Milky Way galaxy. Adding to [12]the mystery is that arcs were not seen in previous [13]deep images of M31 taken primarily in light emitted by [14]hydrogen, and that other, [15]more distant galaxies have not been generally noted as showing similar [16]oxygen-emitting structures. Dedicated amateurs using commercial telescopes made [17]this discovery because, in part, professional telescopes usually [18]investigate angularly small patches of the night sky, whereas these arcs span several times the [19]angular size of the [20]full moon. Future observations -- both in light emitted by oxygen and by [21]other elements -- are sure to follow. Tomorrow's picture: JWST lensing __________________________________________________________________ [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/2301/M31OiiiArc_Strottner_5000.jpg 3. https://www.astrobin.com/users/yann_sainty/ 4. http://www.marcel-drechsler.de/ueber_mich.html 5. https://www.astrobin.com/1d8ivk/ 6. https://youtu.be/TEMXss1Qo4E 7. https://iopscience.iop.org/article/10.3847/2515-5172/acaf7e/meta 8. https://en.wikipedia.org/wiki/Amateur_astronomy 9. https://apod.nasa.gov/apod/ap220711.html 10. https://apod.nasa.gov/apod/ap010113.html 11. https://solarsystem.nasa.gov/resources/285/the-milky-way-galaxy/ 12. https://media.gettyimages.com/id/1145793716/photo/portrait-of-a-cat-against-white-background.jpg?s=612x612&w=0&k=20&c=gxSI9GrKzLiHgaIq6M38hb5-PtzHHMctcLBJSLmiEeM= 13. https://apod.nasa.gov/apod/ap221024.html 14. https://www.nasa.gov/topics/technology/hydrogen/index.html 15. https://apod.nasa.gov/apod/ap110210.html 16. https://www.nasa.gov/centers/wstf/testing_and_analysis/oxygen_systems/index.html 17. https://www.instagram.com/p/CnMZGfwO639/ 18. https://www.scientificamerican.com/article/a-recently-discovered-gas-cloud-near-andromeda-stumps-astronomers/ 19. https://lco.global/spacebook/sky/using-angles-describe-positions-and-apparent-sizes-objects/ 20. https://apod.nasa.gov/apod/ap200322.html 21. https://apod.nasa.gov/apod/ap230108.html 22. https://apod.nasa.gov/apod/ap230116.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. http://asterisk.apod.com/discuss_apod.php?date=230117 32. https://apod.nasa.gov/apod/ap230118.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/