                        Astronomy Picture of the Day

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                    written by a professional astronomer.

                               2022 October 8

                        Two Comets in Southern Skies
           Image Credit & Copyright: Jose J. Chambo (Cometografia)

   Explanation: Heading for its closest approach to the Sun or perihelion
   on December 20, comet C/2017 K2 (PanSTARRS) remains a sight for
   telescopic observers as it sweeps through planet Earth's southern
   hemisphere skies. First time visitor from the remote Oort cloud this
   comet PanSTARRS sports a greenish coma and whitish dust tail about half
   a degree long at the upper left in a deep image from September 21. It
   also shares the starry field of view toward the constellation Scorpius
   with another comet, 73P/Schwassmann-Wachmann 3, seen about 1 degree
   below and right of PanSTARRS. Astronomers estimate that first time
   visitor comet C/2017 K2 (PanSTARRS) has been inbound from the Oort
   cloud for some 3 million years along a hyperbolic orbit.
   Schwassmann-Wachmann 3 is more familiar though. The periodic comet
   loops through its own elliptical orbit, from just beyond the orbit of
   Jupiter to the vicinity of Earth's orbit, once every 5.4 years. Just
   passing in the night, this comet PanSTARRS is about 20 light-minutes
   from Earth in the September 21 image. Seen to be disintegrating since
   1995, Schwassmann-Wachmann 3 was about 7.8 light-minutes away.

                   Tomorrow's picture: northern skylights
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
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