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 July 17
    [2]See Explanation. Clicking on the picture will download the highest
                        resolution version available.

                                  3I/ATLAS
    Image Credit: Gemini Observatory/[3]NOIRLab/NSF/AURA/K. Meech (IfA/U.
                                   Hawaii)
             Processing: Jen Miller, Mahdi Zamani (NSF/NOIRLab)

   Explanation: [4]Discovered on July 1 with the NASA-funded ATLAS
   (Asteroid Terrestrial-impact Last Alert, System) survey telescope in
   Rio Hurtado, Chile, 3I/ATLAS is so designated as the third known
   interstellar object to pass through our Solar System It follows
   [5]1I/ʻOumuamua in 2017 and the comet [6]2I/Borisov in 2019. Also known
   as [7]C/2025 N1, 3I/ATLAS is clearly a comet, its diffuse cometary
   coma, a cloud of gas and dust surrounding an icy nucleus, is easily
   seen in these images from the large [8]Gemini North telescope on
   Maunakea, Hawai‘i. The left panel tracks the comet as it moves across
   the sky against fixed background stars in successive exposures. Three
   different filters were used, shown in red, green, and blue. In the
   right panel the multiple exposures are registered and combined to form
   a single image of the comet. The comet's interstellar origin is also
   [9]clear from its orbit, determined to be an eccentric, highly
   hyperbolic orbit that does not loop back around the Sun and will return
   [10]3I/ATLAS to interstellar space. Not a threat to [11]planet Earth,
   the inbound interstellar interloper is now within the Jupiter's orbital
   distance of the Sun, while its closest approach to the Sun will bring
   it just within the orbital distance of Mars.

                     Tomorrow's picture: pixels in space
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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/2507/noirlab2522a_3i.jpg
   3. https://noirlab.edu/public/
   4. https://science.nasa.gov/blogs/planetary-defense/2025/07/02/nasa-discovers-interstellar-comet-moving-through-solar-system/
   5. https://apod.nasa.gov/apod/ap171122.html
   6. https://apod.nasa.gov/apod/ap191214.html
   7. https://minorplanetcenter.net/mpec/K25/K25N12.html
   8. https://noirlab.edu/public/news/noirlab2522/
   9. https://apod.nasa.gov/apod/ap250707.html
  10. https://en.wikipedia.org/wiki/3I/ATLAS
  11. https://science.nasa.gov/planetary-defense/
  12. https://apod.nasa.gov/apod/ap250716.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=250717
  22. https://apod.nasa.gov/apod/ap250718.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/