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local time when the sky will look as depicted, with the comet high in the south to southeast. While comet will be in the sky most of the night, it will be highest in late evening about 10 p.m. The yellow dots mark the position of the comet at nightly intervals for late evening (10 p.m.) for North America. The path of Comet Wirtanen across the sky in December 2018. The first two weeks of December will be prime time for Wirtanen The one catch is that as it heads toward its brightest in mid-December the waxing Moon also begins to enter the sky and wash out the comet with moonlight.

However, because it is large and diffuse, in practice you need binoculars to see it Р В Р вЂ Р В РІР‚С™Р Р†Р вЂљРЎС™ now.Р В РІР‚СњР вЂ™Р’В«ut as it approaches Earth and the Sun, Wirtanen will brighten, perhaps to magnitude 3 (the brightest stars are magnitude 0 to 1), making it easier to see with the unaided eye from a dark site. (As a footnote, Comet Wirtanen was to have been the comet that the European Rosetta probe was to visit, but launch delays forced ESA to switch cometary targets.)Р В РІР‚СњР вЂ™Р’В¬omet Wirtanen is glowing at magnitude 5 to 6, technically making it visible to the naked eye. The relative position of the Sun, Earth and Comet Wirtanen on December 16, 2018.Р В РІР‚СњР вЂ™Р’В¬omet Wirtanen will be relatively bright simply by virtue of its proximity.Р В РІР‚СњР вЂ™Р’В«ut it is also an active comet, emitting a lot of gas and dust into a large Р В Р вЂ Р В РІР‚С™Р РЋРЎв„ўcoma,Р В Р вЂ Р В РІР‚С™Р РЋРЎС™ and thatР В Р вЂ Р В РІР‚С™Р Р†РІР‚С›РЎС›s what we see, not the 1-kilometre-wide icy nucleus itself which is too small and shrouded by the coma. That puts the comet Р В Р вЂ Р В РІР‚С™Р РЋРЎв„ўjustР В Р вЂ Р В РІР‚С™Р РЋРЎС™ 11,680,000 kilometres from us at its closest approach to Earth on December 16, four days after perihelion, the point when the comet is closest to the Sun. However, despite this, weР В Р вЂ Р В РІР‚С™Р Р†РІР‚С›РЎС›re expecting Р В Р вЂ Р В РІР‚С™Р Р†Р вЂљРЎС™ indeed already enjoying Р В Р вЂ Р В РІР‚С™Р Р†Р вЂљРЎС™ a good show at this return.Р В РІР‚СњР вЂ™Р’Вue to the quirk of orbital clockwork, on this return the comet reaches its closest point to the Sun just before it is also closest to Earth. (Its perihelion distance is 1.06 AU, with 1 AU, or Astronomical Unit, being the average distance from Earth to the Sun.) It isnР В Р вЂ Р В РІР‚С™Р Р†РІР‚С›РЎС›t better known because at most returns it never gets bright, and thatР В Р вЂ Р В РІР‚С™Р Р†РІР‚С›РЎС›s because it never gets closer to the Sun than a little more than the distance from the Earth to the Sun. So since it was discovered, Comet 46P (the 46th comet in the catalog of periodic comets) has been well observed. It is one of many Р В Р вЂ Р В РІР‚С™Р РЋРЎв„ўJupiter-familyР В Р вЂ Р В РІР‚С™Р РЋРЎС™ comets whose orbits have been shaped by the gravity of Jupiter and orbit the Sun about every 6 years. So unlike other recent bright comets that have visited us for the first time, Comet Wirtanen (aka 46P) is well known. By mid-December it might be bright enough to be visible to the naked eye, but only from a dark rural site.Р В РІР‚СњР вЂ™Р’Вiscovered in 1948 by Carl Wirtanen at the Lick Observatory, his namesake comet orbits the Sun every 5.4 years. A well-known comet is making its closest approach to Earth in many years and promises a good show.Р В РІР‚СњР вЂ™Р’В¬omet Wirtanen is now climbing up the late autumn and winter sky for northern hemisphere viewers, and is already a fine binocular comet.

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