It’s December, and with it comes colder temperatures throughout much of the Northern Hemisphere and, in the sky, the most prolific meteor shower of the year: the Geminids.
Never heard of it? Well, that’s not a huge surprise. If you ask beginning stargazers which is the most spectacular meteor shower of the year, I’ll bet that many will cite the Perseid meteor shower in mid-August. I suspect that most would be surprised to learn that the Geminids are often brighter and more plentiful than the Perseids.
For this year’s shower — like many other things in life — there’s both good news and bad news. First, the bad news.
During this year’s Geminids shower, a bright moon will dominate the late-night sky. This can be a problem because its light can obscure many of the fainter meteors that one might otherwise see.
The good news is that the Geminids often produce brilliant fireballs that can easily outshine the moonlight. In addition, the 2019 Geminids should reach their peak activity during the evening of Friday, Dec. 13, and the predawn hours of Saturday, Dec. 14, and you may find it easier to escape town for some stargazing on the weekend.
So how many meteors (also called shooting or falling stars) can we expect to see under these bright conditions? Well, during a typical (moonless) Geminid shower, hourly numbers can reach as high as 100 or 120, so it would be significantly less than this. But if there are fireballs like those I’ve mentioned, you wouldn’t remember much else anyway!
If the Geminids are so bright and prolific, why is it that people don’t cite them as their favorite? My guess is because they occur during the wintertime when folks are generally unwilling to brave the cold to watch lights falling from the sky. That’s too bad; I’ve always felt the Geminids could easily be the best shower of the year — even under moonlight.
Geminid meteors all seem to radiate from a point in the constellation Gemini — the twins — which, during early evening hours in mid-December, appears low in the east-northeastern sky. This means that sky-watchers who can’t stay up all night can at least catch some meteor activity before retiring for the night.
Around the midnight hour, Gemini lies nearly straight overhead and showers the sky with meteors falling in all directions. If you to trace their paths backward, those associated with the shower will seem to radiate from a point (called the radiant) just west of the bright star Castor.
My recommendations for watching the Geminid meteor shower are simple. First, be sure to dress warmly and have a thermos of hot chocolate on hand to make the night even more enjoyable. Next, head out away from the city lights, where the only distraction is the moonlight. And, finally, lie back on a sleeping bag or lawn chair, and scan the entire sky with your eyes.
I promise that if you can get away and catch some great Geminid fireballs this year, you’ll definitely want to put this shower on your observing list for 2020, when moonlight will be no issue at all.
— Dennis Mammana is an astronomy writer, author, lecturer and photographer working from under the clear dark skies of the Anza-Borrego Desert in the San Diego County backcountry. Contact him at mammana@skyscapes.com and follow him on Twitter: @dennismammana. The opinions expressed are his own.