This column was first published in the Steamboat Today, where you can catch CMC professor Jimmy Westlake’s Celestial News column every Tuesday to learn cool skywatching and photography tips. Want to view more of Westlake’s beautiful astrophotography? Visit his website at www.jwestlake.com and purchase “Jimmy’s 2014 Cosmic Calendar.” Proceeds benefit CMC’s Sky Club.
Steamboat Springs — The best annual meteor shower of the year is in progress this week and is rising toward a spectacular peak before dawn next Saturday morning Dec. 14. It’s the Geminid meteor shower, and it could bring as many as 120 shooting stars per hour to our sky.
Geminid meteors are so named because they seem to spring from the stars of our constellation of Gemini the twins, conveniently marked this year by the dazzling planet Jupiter. Each bright streak 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.
Geminid meteors are unique for a number of reasons, foremost of which is their unusual source. Most other meteor showers are produced by fluffy little pieces of dust shed by icy comets, but Geminid meteors are tough little bits of rock, shed by an asteroid named Phaethon.
Every 17 months, Phaethon makes a close pass by the sun, and its parched surface cracks and fractures, creating a dusty tail in its wake. Earth plows through Phaethon’s dust-filled orbit in mid-December every year and, as a result, we see the Geminid meteor shower. Because the particles from Phaethon are rocky, they can penetrate deeper into the atmosphere before burning up, so Geminid meteor streaks are often long, slow and bright.\
The constellation of Gemini is above our horizon early in the evening in December, so the meteor action starts before midnight. This year, the nearly full moon will definitely put a crimp in meteor watching, but there will be plenty of bright Geminids that will shine through the moonlight. When the moon finally sets around 4:30 a.m. next Saturday, there will be an hour or two of dark sky just before dawn for the best meteor watching. A morning or two before the peak, the moon will set even earlier and allow for more dark sky observing. I plan to start watching on Friday morning around 3 a.m.
If you’d like to try to capture an image of a Geminid meteor, you’ll need a camera that you can set up on a tripod and take a brief time exposure. Set your camera’s sensitivity to about ISO 3200, aim it toward the sky and focus on infinity. Then, set the exposure for about 30 seconds and trip the shutter. Chances are, you won’t catch a falling star on your first shot, in fact, you might have to shoot 20 or 30 exposures before a bright Geminid streaks in front of your camera, but your patience might pay off.
So, bundle up against the cold, grab a thermos of your favorite warm beverage and get out there under the stars this week to watch Mother Nature’s free fireworks show.
Professor Jimmy Westlake teaches astronomy and physics at Colorado Mountain College’s Alpine Campus. His “Celestial News” column appears weekly in the Steamboat Today newspaper and his “Cosmic Moment” radio spots can be heard on local radio station KFMU.