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 26
    [2]See Explanation. Clicking on the picture will download the highest
                        resolution version available.

                               3I/ATLAS Flyby
                Image Credit & [3]Copyright: [4]Dan Bartlett

   Explanation: [5]Attention grabbing interstellar visitor [6]3I/ATLAS
   made its not-so-close flyby of our fair planet on December 19 at a
   distance of 1.8 astronomical units. [7]That's about 900 light-seconds.
   Still, [8]this deep exposure captures the comet from another star
   system as it [9]gently swept across a faint background of stars in the
   constellation Leo about 4 days earlier, on the night of December 15.
   Though faint, colors emphasized in the image data, show off the comet's
   yellowish dust tail and bluish ion tail along with a greenish tinged
   coma. And even while [10]scrutinized by arrays of telescopes and
   spacecraft from planet Earth, 3I ATLAS is headed out of the Solar
   System. It's presently moving outward along a hyperbolic [11]trajectory
   at about 64 kilometers per second relative to the Sun, too fast to be
   bound the Sun's gravity.

                    Tomorrow's picture: Apollo's Moonship
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    Authors & editors: [23]Robert Nemiroff ([24]MTU) & [25]Jerry Bonnell
                                 ([26]UMCP)
          NASA Official: Amber Straughn [27]Specific rights apply.
            [28]NASA Web Privacy, [29]Accessibility, [30]Notices;
                A service of: [31]ASD at [32]NASA / [33]GSFC,
                         [34]NASA Science Activation
                           & [35]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/2512/3IATLAS_2025_12_15_JuneLake_DEBartlett.jpg
   3. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
   4. https://www.astrobin.com/users/h2ologg/
   5. https://science.nasa.gov/solar-system/comets/3i-atlas/3i-atlas-facts-and-faqs/
   6. https://en.wikipedia.org/wiki/3I/ATLAS
   7. https://en.wikipedia.org/wiki/Astronomical_unit
   8. https://app.astrobin.com/i/vnsgps?r=0
   9. https://app.astrobin.com/i/991zqj
  10. https://science.nasa.gov/solar-system/comets/3i-atlas/comet-3i-atlas-image-gallery/
  11. https://theskylive.com/3dsolarsystem?obj=c2025n1
  12. https://apod.nasa.gov/apod/ap251225.html
  13. https://apod.nasa.gov/apod/archivepix.html
  14. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  15. https://apod.nasa.gov/apod/lib/aptree.html
  16. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  17. https://apod.nasa.gov/apod/calendar/allyears.html
  18. https://apod.com/feed.rss
  19. https://apod.nasa.gov/apod/lib/edlinks.html
  20. https://apod.nasa.gov/apod/lib/about_apod.html
  21. https://asterisk.apod.com/discuss_apod.php?date=251226
  22. https://apod.nasa.gov/apod/ap251227.html
  23. http://www.phy.mtu.edu/faculty/Nemiroff.html
  24. http://www.phy.mtu.edu/
  25. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  26. http://www.astro.umd.edu/
  27. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  28. https://www.nasa.gov/about/highlights/HP_Privacy.html
  29. https://www.nasa.gov/general/accessibility/
  30. https://www.nasa.gov/privacy/
  31. https://astrophysics.gsfc.nasa.gov/
  32. https://www.nasa.gov/
  33. https://www.nasa.gov/centers/goddard/
  34. https://science.nasa.gov/learners
  35. http://www.mtu.edu/