Celestial News: Geminid meteors set to dazzle
November 30, 2017
Mark your calendar. The best meteor shower of the year is heading our way for a spectacular peak on the night of Dec. 13 and 14. It's the Geminid meteor shower and, under ideal dark sky conditions, it can send as many as 120 shooting stars per hour across the sky. The Geminid meteor shower almost always makes my annual Top 10 list of celestial events, and this year is no exception.
Geminid meteors are so named because they seem to spring from the stars of our constellation of Gemini the Twins. The radiant for this shower is very near the bright star Castor; Geminid meteors will spring out in all directions from this point.
Each bright Geminid "shooting star" that you see is caused by a tiny bit of space dust entering the Earth's atmosphere at high speed and burning up, about 60 miles high. Most of the particles are so small that you could hold a thousand of them in the cupped palm of your hand.
The Geminid meteor shower is a relative newcomer to our skies. No one reported seeing any Geminid meteors before the year 1862, but every December since that year, the Geminid shower has appeared on schedule and seems to be getting stronger and better every year.
The Geminid meteors are also unique because their parent body seems to be a rocky asteroid rather than an icy comet. In 1983, the IRAS satellite spotted a small object, about 3 miles across, orbiting along the same path as the dust swarm that generates our Geminid meteor shower. Now named Phaethon, this object might well be a burned out comet disguised as an asteroid, that is, a comet that has lost all of its ice after many passes around the Sun and is now just the rocky skeleton of a once-active comet.
The trail of dust particles that follows Phaethon around the Sun could be a leftover from its comet days. Because the particles from Phaethon are rocky, they can penetrate deeper into our atmosphere before burning up, so Geminid meteor streaks are often long, slow and bright.
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This year, the waning crescent moon won't rise until nearly 4 a.m., so meteor watching can begin in dark skies as early as 8 p.m. the nights of Dec. 13 and 14, when the constellation of Gemini breaks the northeast horizon. If you are still up after the moon rises just before dawn, look for the planets Mars and Jupiter closely flanking the little crescent, Mars above, Jupiter below.
In general, you'll see more meteors in the hours after midnight as Gemini rises higher in the sky. Lesser numbers of Geminid meteors can be seen for several nights before and after the peak, too, so bundle up and take advantage of those clear, crisp December nights and see how many Geminids you can spot this year.
Jimmy Westlake's “Celestial News” column appears monthly in the Steamboat Today. Check out Jimmy's new "2018 Cosmic Calendar" of sky events on his website at jwestlake.com. It features twelve 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.