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.

                                2020 July 12

                       Comet CG Creates Its Dust Tail
                Image Credit & License: ESA, Rosetta, NAVCAM

   Explanation: Where do comet tails come from? There are no obvious
   places on the nuclei of comets from which the jets that create comet
   tails emanate. One of the best images of emerging jets is shown in the
   featured picture, taken in 2015 by ESA's robotic Rosetta spacecraft
   that orbited Comet 67P/Churyumov-Gerasimenko (Comet CG) from 2014 to
   2016. The picture shows plumes of gas and dust escaping numerous places
   from Comet CG's nucleus as it neared the Sun and heated up. The comet
   has two prominent lobes, the larger one spanning about 4 kilometers,
   and a smaller 2.5-kilometer lobe connected by a narrow neck. Analyses
   indicate that evaporation must be taking place well inside the comet's
   surface to create the jets of dust and ice that we see emitted through
   the surface. Comet CG (also known as Comet 67P) loses in jets about a
   meter of radius during each of its 6.44-year orbits around the Sun, a
   rate at which will completely destroy the comet in only thousands of
   years. In 2016, Rosetta's mission ended with a controlled impact onto
   Comet CG's surface.

    Comet NEOWISE from Around the Globe: Notable Images Submitted to APOD
                        Tomorrow's picture: NEOWISEr
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Phillip Newman Specific rights apply.
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                             & Michigan Tech. U.

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