SKY GUIDE: This chart represents the sky as it appears over Maine during the month of December. The stars are shown as they appear at 9:30 p.m. early in the month, at 8:30 p.m. at midmonth and at 7:30 p.m. at month’s end. Mars is shown in its midmonth position. To use the map, hold it vertically and turn it so that the direction you are facing is at the bottom. Sky Chart prepared by George Ayers

December always marks the beginning of winter for us in the northern hemisphere. This year that will happen at exactly 5:02 a.m. on Dec. 21. That also marks the lowest point in the sky the sun will reach and the longest night of the year – over 15 hours long. Even though it will be much colder this month than our relatively warm November, this December will have far more than its usual share of exciting events, so it will be well worth braving the cold and making the effort to witness them for yourself.

The main highlight will be the closest conjunction of Jupiter and Saturn in 400 years and the closest visual conjunction of that pair in 800 years. They will be just 6 arc minutes or one-tenth of a degree apart on the winter solstice. The full moon covers five times more than that of the sky, or half a degree. Mars still shines high and bright this month. There are two new comets visible now with just a pair of binoculars, Atlas and Erasmus. There will be a total solar eclipse over Chile and Argentina, just 600 miles south of the path of another total solar eclipse that took place on July 2, 2019. There will be a daytime occultation of Venus by the crescent moon over the western part of this country. The long list ends with not one, but two meteor showers that we can see right from here. Those are the Dec. 13 Geminids and the Dec. 22 Ursids.

Jupiter and Saturn start this month only 2 degrees apart, and by Dec. 12 will be just one degree apart or twice the width of the full moon. Then Jupiter just keeps getting closer and closer to Saturn until the winter solstice when they will be just one-tenth of a degree apart, or 12 times the width of Jupiter. They will just trade places and stay within one degree of each other until Dec. 29. So our two largest planets will be visible in the same field of view in a telescope, along with all of their moons for most of this month. They were this close nearly 400 years ago, but the last observable conjunction this close was recorded in 1226, nearly 800 years ago. The pair can get fairly close every 20 years, since it takes Jupiter 12 years to orbit the sun and it takes Saturn 30 years.

The last time there was a mutual occultation when Jupiter actually passed right in front of Saturn was about 8,000 years ago. The Christmas star could have been a close conjunction of this pair in 7 BC or a triple conjunction of Venus and Jupiter in 2 and 3 BC. So this can be seen as a reenactment of this great event during this important season.

Even though Mars is getting a little fainter again each evening as we are pulling farther ahead of it in our faster orbit around the sun, the red planet still appears much brighter and closer than usual and will still offer some good views of its features in small telescopes through the rest of this year. It was at its best in 15 years just a month and a half ago in mid-October. It is moving in direct or eastward motion in Pisces now.

Venus starts the month rising two hours before sunrise and then continues to rise a little later each morning in the constellation of Scorpius. Our sister planet is getting a little more illuminated by the sun each morning even as it is getting smaller in our sky and farther ahead of Earth in its orbit around the sun. Venus remains at magnitude -3.9 all month, which is about 6 times brighter than Jupiter and 72 times brighter than Saturn. That means Jupiter is about 12 times brighter than Saturn, which will be just to the left of Jupiter all month until the King of the Planets overtakes the ringed planet on the longest night of the year.

The two comets visible this month are named Erasmus and Atlas. Atlas is an acronym for a pair of 20-inch telescopes in Hawaii. It sounds rather ominous but it is very useful. It stands for Asteroid Terrestrial-impact Last Alert System. There are several similar telescopes now that have found many asteroids and comets. In just five years of operation, Atlas has already found 536 near-earth asteroids plus 57 potentially hazardous asteroids that could hit the earth at some point, 53 comets and 7,156 supernovae in other galaxies. We are much safer with all of these telescopes working so well.

Dr. Nicolas Erasmus is an astronomer that used the same Atlas telescope to find his comet on Sept. 17. You can see it now near Venus in Virgo in the morning sky and you can see comet Atlas in Auriga near Orion in the evening sky. They are both about eighth magnitude now, or about six times fainter than anything you could see without optical aid.

This winter solstice will be one of the most remarkable ones in the past 1,000 years. You will see Jupiter and Saturn one-tenth of a degree apart, practically as one planet, comet Atlas in the evening sky, comet Erasmus in the morning sky near Venus and the Ursid meteor shower emanating from the Dippers. Nature will be providing quite a show for the longest night of the year.

The new moon on Dec. 14 will result in another total solar eclipse. It will take nearly the same path as the one last summer on July 2, just about 600 miles farther south. The moon’s shadow cone will race across the narrow countries of Chile and Argentina from the high Andes to the plateaus of Patagonia in just a few minutes at about 1,500 miles per hour. The greatest amount of time anyone can be immersed directly in the moon’s shadow this time will be only 2 minutes and 8 seconds, even a little shorter than the one I experienced over Idaho near Yellowstone three summers ago.

That was by far the most spectacular and enlightening event nature could create for earth-bound humans. Seeing all the visible planets near the sun along with many stars appear instantly after the last brilliant flash of light from the sun sears the sky as a stunning diamond ring is truly unforgettable. I could see and sense the entire precious and tenuous atmosphere of the earth at once as a 360-degree salmon-colored twilight surrounded everything in an eerie twilight and smoothly blended into the purple and black sky above us. I attained a sense of the inner workings of the solar system and the sun and the immense speed and power with which all of these objects are always moving in spite of their seemingly static nature. Ironically, the true beauty of our own day star, the sun, only blazes forth when it is completely, perfectly, and precisely covered by the moon, allowing its living, breathing, pulsing, shimmering, ethereal corona with its tremendously intricate streamers and internal structure stretching four million miles into space to become visible to humans for a few brief and precious moments every few years. Then, as suddenly as it began, it was all over with an even more brilliant flash of light stabbing the dark skies as the moon’s shadow cone lifted off our portion of the earth on a high plateau with a partial view of the Grand Tetons and everything soon returned to normal as the sun was being restored to our noontime sky, leaving nothing but an indelible memory of what is always happening.

I highly recommend that everyone should have a similar experience at least once in their lifetime. There will be one passing right over central Maine in just a few years, April 8, 2024. That one will start in Mexico and end in Canada. The weather prospects further south are much better for that event than in Maine in early April, the “cruelest of months” according to T.S. Eliot. Since far fewer people than usual will be able to travel to see this great event, there are several good websites on which is you can watch this event live including the San Francisco Exploratorium and Slooh.com. Over 50 million people from around the world were able to witness the last Great American Total Solar Eclipse on August 21, 2017, but far fewer people will see this one in person.

The best meteor shower of the year, the Geminids, will peak on Sunday night Dec. 13 into Monday morning Dec. 14, just before the eclipse in South America. This is one of only two meteor showers not caused by a comet. The Geminids are caused by an asteroid named 3200 Phaethon. It is only 3 miles wide and orbits the sun every one and a half years. The meteors travel slower than most of the showers, at only 21 miles per second, which is just a little faster than the earth is always orbiting the sun, which is 18.6 mps, 10,000 times slower than the speed of light. There will also be fewer fireballs because the tiny sand grain-sized particles of this asteroid are denser than the usual particles of comet dust that we see. You can expect up to 100 meteors per hour emanating from Gemini since there will be no moon to interfere with this great natural show.

DECEMBER HIGHLIGHTS

Dec. 7: Last quarter moon is at 7:38 p.m.

Dec. 11: Annie Jump Canon was born in 1863. She was instrumental in establishing the spectral classification system of stars along with several other women astronomers known as the “Harvard Computers.

Dec. 12: The waning crescent moon will be near Venus this morning. A daytime occultation of Venus will occur in some parts of the world and our west coast.

Dec. 13: The Geminid Meteor shower peaks tonight into Dec. 14.

Dec. 14: A total solar eclipse will occur over Chile and Argentina. Tycho Brahe was born in 1546. New moon is at 11:18 a.m.

Dec. 17: The Wright brothers performed the first powered flight in 1903. Less than 66 years later we would fly all the way to the moon.

Dec. 21: Jupiter and Saturn will be one tenth of a degree apart this evening. The winter solstice is at 5:02 a.m. First quarter moon is at 6:42 p.m.

Dec. 22: The Ursid Meteor shower peaks this morning.

Dec. 23: The moon is near Mars this evening.

Dec. 25: Isaac Newton was born in 1642.

Dec. 27: Johannes Kepler was born in 1571.

Dec. 28: Arthur Eddington was born in 1882. He took a photograph of a total solar eclipse in May of 1919 that proved Einstein’s General Theory of Relativity was precisely correct.

Dec. 29: Full moon is at 10:29 p.m. This is also known as the Long Night Moon, Moon after Yule, or Cold Moon.

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