December marks the beginning of winter for us in the northern hemisphere. This year that will happen at 11:28 a.m. on Thursday, Dec. 21. That signals the very moment that the sun will reach its lowest point in the sky from our perspective, which also marks our shortest day and longest night.

It can get fairly cold this month, but it will be well worth braving the elements to enjoy some of the highlights that this last month of the year has in store for us. Each month of each year is unique, and offers its share of challenges and rewards for the intrepid and curious sky watcher who is willing to stretch the boundaries of what they know.

This month’s highlights include another beautiful morning dance of two planets, along with a bright star, another occultation of Aldebaran by the moon for part of the country, two nice conjunctions of the moon with Jupiter and Mars in the morning, watching three of our five brightest planets disappear below the horizon, and not one, but two meteor showers, one of which will be the best of the whole year.

Jupiter and Mars are both getting higher and brighter, and a little closer to Earth every night now. Notice that a fairly bright star named Spica, which means “ear of wheat,” is just to the right of Mars. This is the brightest star in Virgo and the 15th-brightest star in the sky.

Spica is a very interesting double star, both of which are hotter and larger than our sun. They are whirling around each other at high speeds every four days and they are just 11 million miles apart, or almost 10 times closer than Earth is to the sun. Spica has a distinct bluish color and is located about 260 light years away. That means that the light you will see this month from this amazing multiple star system left there just before the Revolutionary War started and about 40 years before the invention of the cotton gin and the suspension bridge.

Jupiter is about 25 times brighter than Mars and is getting closer to Mars in the sky. They are 10 degrees apart now and will be much closer by the end of the year. It will be a while before they are at their best again, but stay tuned. Jupiter had its last opposition in April of this year and will next get closest to us in May of next year. Mars will reach its best opposition in over 30 years next July.

Look for the trio very low in the southwestern morning sky about half an hour before sunrise. Notice that brilliant Venus will be hugging the horizon below this pair of planets for the first 12 mornings in December until it finally sinks below the horizon after a good run in the morning sky.

The moon will occult Aldebaran, the brightest star in Taurus, on Sunday, the 3rd. However, you would have to be in the Northwest or parts of Asia to see this one. It is always educational to watch the moon cover up a planet or a star, especially if you have binoculars. You can get a good sense of the constant motion of the moon during the last minute or just before it moves in front of the more distant star or planet. A way to sense this motion more viscerally is to stand directly in the moon’s shadow as it races over you and everything in its path at around 1,500 mph, as it just did during the recent American total solar eclipse.

Two other bright planets will disappear this month: Saturn and Mercury in Scorpius. They will both sink too low to be observed by the second day of December. Then Mercury merely bounces back to the morning sky three weeks later and forms a marvelous conjunction with the orange giant star Antares in Scorpius just below Jupiter and Mars. Then our first planet continues to rise and makes one of its best appearances of the year as it attempts to catch up with Jupiter and Mars, but it will never catch them because Mercury is too close to the sun, so it always remains low on our horizon and sets shortly after sunset or rises shortly before sunrise before it fades out.

A meteor shower this month that most people don’t think about is the Ursa Minorids, emanating from Ursa Minor, also known as the Little Dipper. The moon will not interfere after it sets early in the evening on the 22nd, just after the winter solstice. These meteors are caused by Comet 8P/Tuttle, which orbits the sun every 131/2 years. It usually only produces about 10 meteors per hour, but this shower had three outbursts in the last 50 years caused by the Earth’s going through a denser part of this comet’s constant debris trail.

The more well-known meteor shower this month is the Geminids. It deserves its reputation because it is the best meteor shower each year. One of only two showers not directly caused by comets, the Geminids are caused by an asteroid named 3200 Phaethon. Its nucleus is just three miles across and it orbits the sun every 524 days. Only discovered by a satellite in 1983, 3200 Phaethon still presents a mystery as to exactly how it can have debris trail like a comet, because almost no other asteroids have them. It may be the burned-out nucleus of a former comet, which is only one explanation.

In Greek mythology, Phaethon was the son of the sun god Helios and he drove the sun chariot very recklessly until he had to be stopped by a lightning bolt from Zeus.

The Geminids can produce up to 120 meteors per hour. They will occur in bunches with longer lulls in between. They will peak on the evening of Wednesday, the 13th, into Thursday morning, the 14th. They will all appear to emanate from Gemini, which is part of the Winter Hexagon and will be high in the sky by midnight when meteor counts usually increase due to Earth’s spinning into the meteors like driving into the snow instead of looking at the snow out the back window of your car. Since they travel quite slowly and hit our atmosphere at a shallow angle, they often produce dramatic fireballs as soon as it gets dark before the shower even gets going. They also tend to be brighter than most meteors because they are created by denser particles from an asteroid rather than the usual unsubstantial comet dust.

The moon is a waning crescent then and will not rise until about 3:30 in the morning, which will make for excellent viewing this year as long as the weather also cooperates. Also look for early Geminids several days before the peak and late Geminids several days after. So bundle up and enjoy one of nature’s great spectacles.


Dec. 3: Full moon is at 10:48 a.m. This is also called the Long Night, Cold, or Moon before Yule. The moon will be close to Aldebaran in Taurus. Watch for higher tides than usual.

Dec. 7: Gerard Kuiper was born on this day in 1905. The Kuiper belt of Pluto-like objects is named after him. The New Horizons spacecraft will visit its next Kuiper belt object in another year, on Jan. 1, 2019.

Dec. 10: Last-quarter moon is at 2:53 a.m.

Dec. 13: The Geminid meteor shower peaks tonight into tomorrow morning. A waning crescent moon passes close to Mars one hour before sunrise.

Dec. 14: A slimmer crescent moon passes close to Jupiter this morning. Tycho Brahe was born on this day in 1546. He was the greatest observer of his time, before telescopes were invented.

Dec. 17: The Wright brothers’ first airplane flew a few meters today in 1903. In just 66 more years we would fly all the way to the moon.

Dec. 18: New moon at 1:32 a.m.

Dec. 21: The winter solstice is at 11:28 a.m.

Dec. 22: The Ursid meteor shower peaks tonight.

Dec. 25: Isaac Newton was born on this day in 1642.

Dec. 26: First-quarter moon is at 4:21 a.m.

Dec. 27: Johannes Kepler was born on this day in 1571.

Dec. 28: Arthur Eddington was born on this day in 1882. His photographs of a solar eclipse in May 1919 helped prove Einstein’s Theory of General Relativity correct.

Bernie Reim of Wells is co-director of the Astronomical Society of Northern New England.

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