Ah -- December, the end of the year! December is often a pretty wet and/or snowy month and this might make sky gazing a real challenge. I am sure there will be the occasional clear night, a good thing for skywatchers who can become "star-starved" in the winter. Speaking of winter, the winter solstice occurs on Dec. 21 at 5:23 EST. If there are a few clear nights, December is crammed with interesting things in the sky and will repay observation.
If you are up at about dawn, you will notice very bright Venus in the east/southeast. If one has a telescope that is able to resolve it, Venus is just short of "half-Venus" and its apparent size is nearly as big as it can get. Venus is not the most interesting of planets, given it is all white and featureless, but Galileo noted that Venus had phases similar to those of the Moon, and this fact supported the Copernican view of the solar system where the Sun is the center of the solar system and the planets revolve around it.
Tiny Mercury, closest to the Sun, can be seen with the naked eye, low to the horizon below Venus, about 45 minutes before dawn around Dec. 15. It will be in the southeast. Six days later, it will be close to the gas giant Jupiter, but these two will be low to the horizon unless you have a flat or sloping away horizon unobstructed by buildings or trees. If you have a telescope of about 3 inches, you might be able to see Mercury as a ¾-lit tiny disk. This will be a real challenge.
Comet hunters haven't seen a good, bright comet for about two years. This may change in December because Comet 46P/Wirtanen will be only about 7.6 million miles away from Earth. How bright will this comet be? The majority of astronomers say this comet will reach only magnitude 7. If this is as bright as it gets, it will only be visible in large binoculars or a telescope. It will be a challenge to find if it is only this bright. However, some astronomers think it will reach magnitude 4 and this will make it visible to the naked eye under dark skies. Where could it be found? The best thing to find it would be to put the comet's name in your browser and see if there is a position map for about Dec. 16. Otherwise, this comet will be between the Pleiades star cluster and the first magnitude star Aldebaran.
This discussion of Comet 46P/Wirtanen leads me to this month's stargazing challenge. Find the Pleiades. The Pleiades is a beautiful little cluster of stars lying nearly overhead and a bit directly east in December. Some have seen it already but have not realized what it is. Some confuse it with the Little Dipper, but this is not correct. The Pleiades, sometimes called the Seven Sisters and mentioned in Scripture, is a group of several stars, bluish in color, that are all about the same age and quite inherently bright. They can be seen quite easily with the naked eye. However, in about 50mm binoculars, they are a very beautiful sight indeed! And, if you can find the Pleiades, you stand a good chance, if you use those same binoculars and a map found on your browser, of finding Comet 46P/Wirtanen.
The yearly appearance of the Geminid meteor shower peaks before dawn on Dec. 14 and there will be no Moon to compete with seeing them. Of course, it will be cold, and perhaps cloudy, but if you are into meteor showers, find a dark sight and face east about half-way down toward the horizon. The so-called center of the radiant is the constellation Gemini, The Twins, and around there you could see some nice zingers.
Saturn and Mars are still observable in the south/southwest, with Saturn's rings about as open as they get as seen from Earth.
Merry Christmas and a Happy new year! On Dec. 26, I will be 75 but still just as enthusiastic as I ever was about the night sky.
-- David Cater is a former faculty member of JBU. Email him at [email protected]. Opinions expressed are those of the author.
Editorial on 12/05/2018