11:00 AM | *Green "Christmas Comet" makes its closest approach to Earth…better viewing opportunities next couple of nights following numerous recent cloudy nights*
Comet 46P/Wirtanen made history on Sunday, December 16th as it entered the “top 10” list of closest comet flybys to Earth in recent history. The comet now being called the green “Christmas comet” flew past Earth at about 11.5 million km away on Sunday appearing in the constellation Taurus alongside the Pleiades cluster of stars. This is the closest the comet has come to Earth in many centuries and the closest it will come for many more centuries. The Mid-Atlantic region has been socked in thick cloud cover for the past several nights, but there is a 50/50 chance for more favorable viewing conditions tonight and even better shot tomorrow night. There is one caveat, however, and that is the fact that the waxing moon will generate quite a bit of moonlight during the next few nights and that may act to dilute somewhat the comet’s brightness.
Comet 46P/Wirtanen was discovered in 1948 by astronomer Carl Wirtanen. It whips around the sun fairly rapidly, completing an orbit of the sun every 5.4 years. Comet 46P/Wirtanen is known as the green “Christmas comet” as its gaseous atmosphere is largely made up of diatomic carbon (C2) that glows green in the near-vacuum of space. It should be fairly close to the Pleiades star cluster just before midnight which actually appears bluish because the stars themselves are actually that particular color.
Comet 46P/Wirtanen is now receding from the Earth, but it will still be nearby for days to come. The comet is unusually bright relative to its normal appearance, but it's a small comet without much of a tail. The waxing moon is going to present a challenge for viewing over the next few nights as its light will tend to dilute the comet’s brightness making it a challenge for the naked eye. Telescopes, binoculars and digital cameras should have no trouble despite the moonlight. In terms of clouds, there may be some to deal with early tonight in the I-95 corridor, but some clearing should take place late tonight and tomorrow night looks like an even better opportunity (but it’ll be quite cold).