                        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 August 9

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

   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 a
   comet. A teardrop-shaped cloud of dust, ejected from its icy nucleus
   warmed by increasing sunlight, is seen in this sharp image from the
   Hubble Space Telescope captured on July 21. Background stars are
   streaked in the exposure as Hubble tracked the fastest comet ever
   recorded on its journey toward the inner solar system. An analysis of
   the Hubble image indicates the solid nucleus, hidden from direct view,
   is likely less that 5.6 kilometers in diameter. This comet's
   interstellar origin is 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 inside the orbital distance of Mars.

                      Tomorrow's picture: down the road
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
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