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
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    Authors & editors: [33]Robert Nemiroff ([34]MTU) & [35]Jerry Bonnell
                                 ([36]UMCP)
          NASA Official: Phillip Newman [37]Specific rights apply.
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                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/