The Crestone Eagle • December, 2020
Skies Over Crestone: December
by Kim Malville
Mars will be high in the southern sky in the constellation of Pisces during the evenings of December. Above Mars and slightly to the right is the Great Square of Pegasus, the upside-down horse.
December 3: In the eastern skies you can see the waning gibbous moon close to Pollux. Keep that star in mind because it and its twin, Castor, will be close to the radiant of the greatest meteor shower of the year on December 13.
December 12: For you early-risers who have been admiring the beauties of Venus in the morning skies, this morning you can catch a very beautifully tiny crescent moon close to Venus about 30 minutes before sunrise.
December 13: The Geminid meteor shower should peak in the evening, becoming the major meteor shower of the year. Bundle up, get a comfortable chair, and enjoy the show.
December 14: New Moon. A total solar eclipse will occur in Chile and Argentina.
December 16: Low in the southwestern sky you should see a delicate two-day-old crescent moon below the pair of planets, Jupiter and Saturn. I hope you have noted how they have been slowly moving toward each other during the month.
December 21: The longest night of the year, December solstice, occurring at 1:02am.
December 21: A very special night! Jupiter and Saturn are in a very rare conjunction, which has not occurred in our skies for 800 years. Catch the view some 45 minutes after sunset before they disappear over the southwestern horizon. Can you separate them, only 6 minutes of arc apart? As seen in a telescope, they are separated by only 12 diameters of Jupiter.
December 30: Full Moon
Meteors from Gemini
The great event of the month will be the Geminid meteor shower on December 13, now the greatest meteor shower of them all. You shouldn’t miss it. Get yourself a comfortable chair with a good view of the sky without too many trees, bundle up, get a thermos of hot something, and allow at least 20 minutes for your eyes to become dark-adapted. These meteors tend to arrive in clumps (there may be as many as two meteors per minute) so it’s wise to set aside an hour or more. You also might take a pad of paper to record the numbers that you see.
Meteors typically occur when the Earth rushes through a stream of dust and debris left behind by a passing comet. Geminid meteors are not associated with a comet but with an asteroid with the very appropriate name of Phaethon. Most asteroids stay close to the asteroid belt between Mars and Jupiter, but Phaethon is unusual in that its highly elliptical orbit carries it close to the sun every 1.4 years, getting roasted at a temperature of 1,500°F; then it gets frozen as it moves out beyond Mars. This incessant heating and cooling breaks up its surface, releasing small rock fragments, some of which end up as meteors in our atmosphere every December 13.
In Greek mythology, Phaethon boasted that his father was the sun god, but his school mates didn’t believe him. He sought some kind of evidence from his father. He asked to drive the chariot of the sun across the sky. His father cautioned him that it was very difficult to control the horses, but Phaethon persisted. Once up in the sky, he discovered that it was even more difficult than he imagined, letting the chariot get to close to the earth, scorching it, or getting too far above the earth and freezing portions of it. People on the earth appealed to Zeus for help and he shot a thunderbolt at Phaethon, sending him blazing to his death.
Fifty years ago the Geminids were second to the famous Perseid meteors of August. But their numbers are increasing as the earth is passing through thicker portions of the cloud of particle. Now, they are number one, producing perhaps twice as many meteors per hour than the Perseids. Of course, it’s colder in December than August and the Perseid shower wins the comfort contest. But with a comfortable chair and warm clothing you should be able to enjoy the show. And this year in the dark skies of Crestone the conditions should be perfect.
How dark is our sky?
Led by Karina Danforth, the Town of Crestone is seeking designation as an International Dark Sky Community. We know the sky is beautiful at night and it seems one can reach and touch the Milky Way. But, how can one measure our darkness? One way is to purchase a Sky Quality Meter, which Colorado College is now using. Or, you can join in our dark sky project simply by using your own eyes and counting the stars in the Great Square of Pegasus. That very obvious square in the constellation of Pegasus is a large, seemingly empty region in the sky. But it contains a variety of stars, and the darker the sky, the more you can see. In well-lighted cities, that number may be zero. If you are going to watch the Geminid meteor shower, that would be a great time to join in this project. Can you get up to 13 stars; that would be superb, or even more? If you make the count please send it to me or to Karina Danforth, our Mayor of Crestone. If you wish to see a star chart containing all the stars in the Great Square (or want to know why he is upside down), please email me (email@example.com) and I’ll send you a star chart and some more information.
Limiting Magnitude Number of naked eye stars visible in the square Dark Sky
6.5 35 Exceptional
6.25 21 Excellent
6 113 Superb
5.75 9 Very good
5.5 7 Good
5.25 5 Above Average
5 4 Average
4.75 3 Below Average
4.5 1 Poor
≤ 4.00 0 Very Poor