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 December 1
   [2]A starfield is shown around a comet. The green coma of the comet is
   on the lower left. A meandering blue-tinted tail goes off to the upper
   right. A slight anti-tail is seen from the coma toward the lower left.
          Please see the explanation for more detailed information.

                  3I ATLAS: Tails of an Interstellar Comet
        Image Credit & Copyright: Victor Sabet & [3]Julien De Winter

   Explanation: How typical is our Solar System? Studying [4]3I/ATLAS, a
   comet just passing through, is providing clues. Confirmed previous
   interstellar visitors include an [5]asteroid, a [6]comet, a [7]meteor,
   and a [8]gas wind dominated by hydrogen and helium. [9]Comet 3I/ATLAS
   appears [10]relatively normal when compared to [11]Solar [12]System
   [13]comets, therefore providing more evidence that [14]our Solar System
   is a somewhat typical star system. For example, Comet 3I/ATLAS has a
   broadly similar [15]chemical composition and [16]ejected dust. The
   [17]featured image was captured last week from [18]Texas and shows a
   [19]green coma, a wandering [20]blue-tinted ion tail likely deflected
   by our [21]Sun's wind, and a slight [22]anti-tail, all typical cometary
   attributes. The comet, visible with [23]a telescope, passed its closest
   to the Sun in late October and will pass its closest to the Earth in
   mid-December, after which it will return to [24]interstellar space and
   never return.

               Explore the Universe: [25]Random APOD Generator
                      Tomorrow's picture: active galaxy
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    Authors & editors: [37]Robert Nemiroff ([38]MTU) & [39]Jerry Bonnell
                                 ([40]UMCP)
          NASA Official: Amber Straughn [41]Specific rights apply.
            [42]NASA Web Privacy, [43]Accessibility, [44]Notices;
                A service of: [45]ASD at [46]NASA / [47]GSFC,
                         [48]NASA Science Activation
                           & [49]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/2512/Comet3I_SabetWinter_4243.jpg
   3. https://www.instagram.com/dwj85
   4. https://science.nasa.gov/blogs/planetary-defense/2025/07/02/nasa-discovers-interstellar-comet-moving-through-solar-system/
   5. https://en.wikipedia.org/wiki/1I/ʻOumuamua
   6. https://apod.nasa.gov/apod/ap220305.html
   7. https://www.npr.org/2022/04/14/1092869771/interstellar-meteor-hit-earth-in-2014
   8. https://sci.esa.int/web/ulysses/-/35853-the-flow-of-interstellar-helium-in-the-solar-system
   9. https://en.wikipedia.org/wiki/3I/ATLAS
  10. https://www.skyatnightmagazine.com/news/3i-atlas-not-aliens
  11. https://apod.nasa.gov/apod/ap090207.html
  12. https://apod.nasa.gov/apod/ap200606.html
  13. https://apod.nasa.gov/apod/ap231020.html
  14. https://science.nasa.gov/solar-system/solar-system-facts/
  15. https://astrobiology.nasa.gov/nai/annual-reports/2012/uh/the-chemical-composition-of-comets/index.html
  16. https://apod.nasa.gov/apod/ap231126.html
  17. https://app.astrobin.com/i/jtmq82
  18. https://en.wikipedia.org/wiki/Texas
  19. https://www.science.org/content/article/why-do-some-comets-glow-green
  20. https://astronomy.swin.edu.au/cosmos/c/Cometary+Gas+Tail
  21. https://science.nasa.gov/sun/what-is-the-solar-wind/
  22. https://en.wikipedia.org/wiki/Comet_tail#Anti-tail
  23. https://1funny.com/wp-content/uploads/2010/12/dog-telescope.jpg
  24. https://apod.nasa.gov/apod/ap241222.html
  25. https://apod.nasa.gov/apod/random_apod.html
  26. https://apod.nasa.gov/apod/ap251130.html
  27. https://apod.nasa.gov/apod/archivepix.html
  28. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  29. https://apod.nasa.gov/apod/lib/aptree.html
  30. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  31. https://apod.nasa.gov/apod/calendar/allyears.html
  32. https://apod.com/feed.rss
  33. https://apod.nasa.gov/apod/lib/edlinks.html
  34. https://apod.nasa.gov/apod/lib/about_apod.html
  35. https://asterisk.apod.com/discuss_apod.php?date=251201
  36. https://apod.nasa.gov/apod/ap251202.html
  37. http://www.phy.mtu.edu/faculty/Nemiroff.html
  38. http://www.phy.mtu.edu/
  39. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  40. http://www.astro.umd.edu/
  41. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  42. https://www.nasa.gov/about/highlights/HP_Privacy.html
  43. https://www.nasa.gov/general/accessibility/
  44. https://www.nasa.gov/privacy/
  45. https://astrophysics.gsfc.nasa.gov/
  46. https://www.nasa.gov/
  47. https://www.nasa.gov/centers/goddard/
  48. https://science.nasa.gov/learners
  49. http://www.mtu.edu/