                        Astronomy Picture of the Day

    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

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

   Explanation: 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 1I/ʻOumuamua in 2017 and
   the comet 2I/Borisov in 2019. Also known as 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 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 clear from its orbit, determined to
   be an eccentric, highly hyperbolic orbit that does not loop back around
   the Sun and will return 3I/ATLAS to interstellar space. Not a threat to
   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: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Amber Straughn Specific rights apply.
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                           NASA Science Activation
                             & Michigan Tech. U.

