Skies Over Milton, December Edition

By Peter Forrester | December 6, 2018

Greetings, stargazers!

It will be an exciting month for night skywatchers.

Here are some significant events to look for this month, provided that cloudy weather doesn’t get in the way. I’m sure all you hardy ones won’t mind the cold if it means getting a look at some really important objects in the sky.

First, we have a New Moon on Friday, December 7th. This time of the lunar cycle is an ideal opportunity for stargazers because it means you can see dimmer stars without the greater light of the moon overshadowing them, so to speak. This is the point of the moon’s orbit around the Earth when it is almost directly between the Earth and the Sun, and therefore we see only its unlighted side (when it gets directly between, we get a solar eclipse, either total or partial, these only occur between 2 to 3 times a year).

Second, on Friday, December 14th, we get the peak of the Geminid meteor shower. Shooting stars will be visible each night between Friday, the 7th and Sunday, the 16th, with the largest number (up to 80 per hour) occurring on the peak night. The meteor shower occurs every year when the Earth’s orbit enters debris left by an asteroid, 3200 Phaethon. It is called “Geminid” because the origin of the shooting stars appears to be in the constellation Gemini, located just above the prominent constellation Orion. However, the shooting stars can be seen in any part of the sky. There are usually only a few shooting stars in the early evening, and the best time to see them is around 2 am for you hardcore stargazers!

Third, occurring about the same time we have the brightest comet flyby of the year. Comet 46P/Wirtanen will pass only about 7.2 million miles away, among the 10 closest approaches by comets to the Earth in modern times. It may be bright enough to see with the naked eye, especially in areas without a lot of light pollution, which I have not generally found to be a problem here in Milton. The comet will not be sharp and contained in a single point like a star, but will be more spread out. The comet will be closest to Earth, and therefore appear the largest, on Sunday, December 16th, between 9:30 and 10 pm on the East Coast. At this time it will pass very near the star cluster the Pleiades.

The comet circles out to near the planet Jupiter and back, orbiting every 5.4 years around the sun (perihelion – closest approach to the Sun is on Wednesday, December 12th), and was first discovered in 1948, by an American astronomer named Carl A Wirtanen. Don’t worry, its orbit is well known by astronomers, and there is no chance of it hitting the Earth! For more information on the campaign to observe the comet, see http://www.wirtanen.astro.umd.edu.

Fourth, we have a Full Moon on Saturday, the 22nd. For your information, the quarter moons occur on Saturday, the 15th (First Quarter), and Saturday, the 29th (Last Quarter).

There are also many events concerning when the Moon is closest to a particular star, or constellation, or when a planet is to be seen nearest to a bright star. For more information of this type, see http://skymaps.com. They publish a free monthly star chart, with 3 versions for different latitudes. I use the one for 40 degrees north of the Equator (Milton is above 43 degrees North). This chart is also useful up to 15 degrees north and south of that line. They also publish versions for the Equator, and for the Southern Hemisphere. On the second page of the sky chart is information about objects that can be seen either with the naked eye, with binoculars, or with a telescope.

Fifth, there is another meteor shower, whose peak night is also on Saturday, the 22nd. This shower has slower-moving meteors (compared to the Geminids earlier in the month) that radiate from a point in Ursa Minor (also known as the Little Dipper). It starts around Monday, the 17th and runs until the 26th of the month. The debris field causing this annual shower is associated with a comet called 8P/Tuttle. Like the other meteor shower, the best time to see it is after midnight, and due to its location it is always visible to the North.


Next in series: Skies over Milton, January Edition


References:

CBS News. (2018, December 5). Brightest comet of the year will zoom near Earth next week). By Caitlin O’Kane. Retrieved from https://www.cbsnews.com/news/brightest-comet-of-2018-46p-wirtanen-will-zoom-near-earth-next-week/

Thalassoudis, Kym. (2000-17). Skymaps. Retrieved December 6, 2018 from Skymaps.com.

Wikipedia. (2018, December 6). 46P/Wirtanen. Retrieved from https://en.wikipedia.org/wiki/46P%2FWirtanen

Wikipedia. (2018, December 6). Geminids. Retrieved from https://en.wikipedia.org/wiki/Geminids

Wikipedia. (2018, December 6). New Moon. Retrieved from https://en.wikipedia.org/wiki/New_moon.

Wikipedia. (2018, December 6). Perihelion and aphelion. Retrieved from https://en.wikipedia.org/wiki/Perihelion_and_aphelion

Wikipedia. (2018, December 6). Ursids. Retrieved from https://en.wikipedia.org/wiki/Ursids

Author: Peter Forrester

I have been interested in astronomy and stargazing for many years, and now delight to offer some of my learning to others through my weekly blog posts.

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