Celestial News: Geminid meteor shower peaks this week
For Steamboat Pilot & Today
Let’s end the year with a celestial bang — the Geminid meteor shower. In spite of the cold December nights, the annual Geminid meteor shower is my favorite shower of the year. Their numbers equal or even surpass the popular August Perseids, and the bright stars of Orion form a wonderful winter backdrop.
The Geminid meteor shower is a relative newcomer to our skies. There are no reports of Geminid meteors before the year 1862, and the shower seems to be increasing in strength every year.
The Geminid meteor shower is unique among our annual meteor showers, because it is the only one whose source is an asteroid, not a comet. While comets are icy bodies orbiting the sun, asteroids are rocky bodies. The parent body and source of the Geminid meteors is an asteroid named 3200 Phaethon.
Once every 1.4 years, Phaethon passes uncomfortably close to the sun’s hot surface. This bakes and cracks the asteroid’s surface and releases millions of tiny particles that trail behind it. Every December, when Earth crosses Phaethon’s orbit, these particles create our Geminid meteors.
While in space, these tiny particles are called meteoroids. Geminid meteoroids zip through space at the breakneck speed of 22 miles per second.
Think about that for a moment. In space, moving that fast isn’t a problem because space is empty, but when a speeding meteoroid enters the Earth’s atmosphere, it smacks into air molecules and generates heat as it slows down. It is this heat that incinerates the meteoroid and creates the bright streak of light that we call a meteor. Most meteors burn out about 60 miles above Earth’s surface.
Every year, on the night of Dec. 13, Earth plows head-on into the dusty meteoroid river created by 3200 Phaethon. You’ll see a few Geminid meteors shooting across the sky as early as Dec. 4 and as late as Dec. 17, but the meteor action reaches a crescendo on the night of the peak, Dec. 13 and 14.
During the peak and under ideal dark sky conditions, a single observer can expect to see between 90 and 120 Geminid meteors per hour. The meteors seem to shoot out of the sky from a point near the twin stars of Castor and Pollux in the constellation of Gemini, the Twins. Because meteor showers are named for the constellation from which they appear to radiate, this is the Geminid meteor shower.
In general, you will see more meteors after midnight than before midnight. That’s because before midnight, we are looking out of the Earth’s rear windshield. After midnight, Earth rotates us around to where we are looking out of the front windshield, in the direction Earth is moving. That’s when the meteor action peaks.
This year, the moon will be three days past full on the night of Dec. 13 and 14 and will be sitting smack in the middle of the constellation Gemini — far from ideal conditions. But even so, with the bright moonlight at your back, there will still be plenty of bright Geminids to enjoy.
So, bundle up against the cold and wander out under the starry December sky this week. You’ll be rewarded with some beautiful Geminid shooting stars.
Jimmy Westlake’s “Celestial News” column appears monthly in the Steamboat Pilot & Today. Check out Jimmy’s new “2020 Cosmic Calendar” of sky events on his website at http://www.jwestlake.com. It features 12 of his best astro-photos and a day-by-day listing of cool celestial events that you and your family can enjoy watching all year.
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