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 August 9
    [2]See Explanation. Clicking on the picture will download the highest
                        resolution version available.

                Interstellar Interloper 3I/ATLAS from Hubble
      Image Credit: [3]NASA, [4]ESA, [5]David Jewitt ([6]UCLA) et al. -
                  Processing; Joseph DePasquale ([7]STScI)

   Explanation: [8]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
   [9]1I/ʻOumuamua in 2017 and the comet [10]2I/Borisov in 2019. Also
   known as [11]C/2025 N1, 3I/ATLAS is a comet. A teardrop-shaped cloud of
   dust, ejected from its icy nucleus warmed by increasing sunlight, is
   seen in this [12]sharp image from the Hubble Space Telescope captured
   on July 21. Background stars are streaked in the exposure as Hubble
   tracked the [13]fastest comet ever recorded on its journey toward the
   inner solar system. An [14]analysis of the Hubble image indicates the
   [15]solid nucleus, hidden from direct view, is likely less that 5.6
   kilometers in diameter. This comet's interstellar origin is [16]clear
   from its orbit, determined to be an eccentric, highly hyperbolic orbit
   that does not loop back around the Sun and will return [17]3I/ATLAS to
   interstellar space. Not a threat to [18]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
   inside the orbital distance of Mars.

                      Tomorrow's picture: down the road
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    Authors & editors: [30]Robert Nemiroff ([31]MTU) & [32]Jerry Bonnell
                                 ([33]UMCP)
          NASA Official: Amber Straughn [34]Specific rights apply.
            [35]NASA Web Privacy, [36]Accessibility, [37]Notices;
                A service of: [38]ASD at [39]NASA / [40]GSFC,
                         [41]NASA Science Activation
                           & [42]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/2508/3I_Hubble.jpg
   3. https://www.nasa.gov/
   4. https://www.spacetelescope.org/
   5. http://www2.ess.ucla.edu/~jewitt/David_Jewitt.html
   6. https://epss.ucla.edu/
   7. https://www.stsci.edu/who-we-are
   8. https://science.nasa.gov/blogs/planetary-defense/2025/07/02/nasa-discovers-interstellar-comet-moving-through-solar-system/
   9. https://apod.nasa.gov/apod/ap171122.html
  10. https://apod.nasa.gov/apod/ap191214.html
  11. https://minorplanetcenter.net/mpec/K25/K25N12.html
  12. https://science.nasa.gov/asset/hubble/comet-3i-atlas/
  13. https://www.youtube.com/watch?v=pc4A8va8NRU
  14. https://arxiv.org/abs/2508.02934
  15. https://science.nasa.gov/missions/hubble/as-nasa-missions-study-interstellar-comet-hubble-makes-size-estimate/
  16. https://apod.nasa.gov/apod/ap250707.html
  17. https://en.wikipedia.org/wiki/3I/ATLAS
  18. https://science.nasa.gov/planetary-defense/
  19. https://apod.nasa.gov/apod/ap250808.html
  20. https://apod.nasa.gov/apod/archivepix.html
  21. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  22. https://apod.nasa.gov/apod/lib/aptree.html
  23. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  24. https://apod.nasa.gov/apod/calendar/allyears.html
  25. https://apod.com/feed.rss
  26. https://apod.nasa.gov/apod/lib/edlinks.html
  27. https://apod.nasa.gov/apod/lib/about_apod.html
  28. https://asterisk.apod.com/discuss_apod.php?date=250809
  29. https://apod.nasa.gov/apod/ap250810.html
  30. http://www.phy.mtu.edu/faculty/Nemiroff.html
  31. http://www.phy.mtu.edu/
  32. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  33. http://www.astro.umd.edu/
  34. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  35. https://www.nasa.gov/about/highlights/HP_Privacy.html
  36. https://www.nasa.gov/general/accessibility/
  37. https://www.nasa.gov/privacy/
  38. https://astrophysics.gsfc.nasa.gov/
  39. https://www.nasa.gov/
  40. https://www.nasa.gov/centers/goddard/
  41. https://science.nasa.gov/learners
  42. http://www.mtu.edu/