The Moon will be located on the opposite side of the Earth as the Sun and its face will be will be fully illuminated. This phase occurs at 17:49 UTC. This full moon was known by early Native American tribes as the Full Cold Moon because this is the time of year when the cold winter air settles in and the nights become long and dark. This moon has also been known as the Full Long Nights Moon and the Moon Before Yule.
The Ursids is a minor meteor shower producing about 5-10 meteors per hour. It is produced by dust grains left behind by comet Tuttle, which was first discovered in 1790. The shower runs annually from December 17-25. It peaks this year on the the night of the 21st and morning of the 22nd.
The December solstice occurs at 22:23 UTC. The South Pole of the earth will be tilted toward the Sun, which will have reached its southernmost position in the sky and will be directly over the Tropic of Capricorn at 23.44 degrees south latitude. This is the first day of winter (winter solstice) in the Northern Hemisphere and the first day of summer (summer solstice) in the Southern Hemisphere.
The Geminids is the king of the meteor showers. It is considered by many to be the best shower in the heavens, producing up to 120 multicolored meteors per hour at its peak. It is produced by debris left behind by an asteroid known as 3200 Phaethon, which was discovered in 1982. The shower runs annually from December 7-17. It peaks this year on the night of the 13th and morning of the 14th.
46P/Wirtanen is a small short-period comet with a current orbital period of 5.4 years. It was one of three comets discovered by astronomer Carl Wirtanen at Lick Observatory in 1948.
On Dec. 16, 2018, 8:06 a.m. EST, less than four days after making its closest approach to the sun, 46P/Wirtanen will pass very close to the Earth — just 7,199,427 miles away. That’s among the 10 closest comet approaches that have occurred since 1950 and the 20th closest approach of a comet dating as far back as the ninth century A.D.
But while that sounds great, 46P likely will not evolve into a spectacular sight.
What we are dealing with is a very small and intrinsically faint comet; ground-based observations combined with images taken with the Hubble Space Telescope in 1996 revealed the nucleus of 46P to have a diameter charitably estimated to be around seven-tenths of a miles.
Saturn’s iconic rings are clearly visible with backyard telescopes in early December—Mercury and Venus appear later in the month. Also look for Eta Cassiopeiae, a double star, with binoculars or a small telescope to discern its gold and blue hues. Finally, don’t miss the mid-December Geminid meteor shower. You could see as many as 60 colorful meteors per hour.
Find out more about what you can see from your backyard, front stoop, or local park by viewing this monthly program. “Tonight’s Sky” is produced by HubbleSite.org, online home of the Hubble Space Telescope.
Irene W. Pennington Planetarium 