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.

                               2019 October 18

                     Interstellar Interloper 2I/Borisov
            Image Credit: NASA, ESA, and D. Jewitt (UCLA) et al.

   Explanation: After the 2017 detecton of 1I/'Oumuamua, comet 2I/Borisov
   has become the second recognized interstellar interloper. Like
   'Oumuamua, Borisov's measured hyperbolic trajectory and speed as it
   falls toward the Sun confirm that its origin is from beyond our Solar
   System. But while detailed observations indicate 'Oumuamua is a rocky
   body with differences from known Solar System objects, Borisov is
   definitely a far wandering comet. Taken on October 12, 2019 this Hubble
   Space Telescope image of Borisov reveals a familiar looking comet-like
   activity and concentration of dust around around its nucleus. Not
   resolved in the image, some estimates suggest the nucleus could be
   between 2 and 16 kilometers in diameter. At the time of the Hubble
   image, comet 2I/Borisov was about 418 million kilometers away. Borisov
   is still inbound though and will make its closest approach to the Sun
   on December 7 at a distance of about 300 million kilometers (2
   Astronomical units).

                     Tomorrow's picture: Pluto at Night
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Phillip Newman Specific rights apply.
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