"Button up your overcoat...
Get to bed by three...."
With apologies to Helen Kane, who made those song lyrics famous in 1929, you may want to stay up late tonight or get up early Friday morning, even as winter approaches. The Geminid meteor shower peaks tonight -- usually one of the best of the year, and early indications are that it's already putting on a good show.
Earth is passing through the orbit of an asteroid called 3200 Phaethon, and astronomers think we're seeing its debris -- shooting stars, more than 50 per hour, many of them no larger than grains of sand, burning up as they plow into the atmosphere.
Scientists think the Geminids could have some extra punch this year. There is a comet called 46P/Wirtanen, discovered in 1948, and we could pass through the trail of debris from its orbit tonight as well. It would be the first time on record -- two meteor showers at once.
"Dust from this comet hitting Earth's atmosphere could produce as many as 30 meteors per hour," said Bill Cooke of NASA's Meteoroid Environment Office on the NASA Science News page.
A little quick arithmetic -- 50 plus 30 per hour -- means it could be a lively night in the sky.
Astronomers say it's worth watching after 9 or 10 p.m. local time, and the seeing gets better after midnight, since the morning side of the Earth is the one that faces forward as we travel around the sun. Conveniently, there's a new moon -- nothing bright in the night sky to blind you to the sometimes-faint shooting stars.
The Geminids, which happen this time of year like clockwork, are an oddity. Most major meteor showers -- the Perseids in August, the Leonids in November -- have occurred for thousands of years, caused as Earth passes through clouds of debris left by passing comets.
But the Geminids only appeared in the 1860s. Not until 1983 did astronomers find 3200 Phaethon, in a lopsided orbit that crosses our own and also brings it close to the sun -- close enough, they theorize, that the sun's heat cracks it and kicks up dust, which, over time, has spread out along the asteroid's path.
How to Watch
The worst thing for sky watchers about the Geminids is that the air is often cold and crisp -- but the best thing for sky watchers about the Geminids is that the air is often cold and crisp. You may have to bundle up, but if the sky is clear, it's very clear.
Be alert; most meteors streak by in a second or less, sometimes in clusters. They could appear anywhere in the sky, though they'll appear to come from the constellation Gemini the twins. Gemini is just north and to the left of the familiar stars of Orion, and will be highest in the sky around 2 a.m.
(If you want to stay indoors, NASA said it will stream video from an astronomy camera in Huntsville, Ala. from 11 p.m. to 3 a.m. EST. More information HERE.)
The best way to see meteors is to find a nice, dark place with no street lights and as few trees as possible, and look up. You may be happiest in a lawn chair or a sleeping bag; something hot to drink may be nice, too.
No other equipment is needed. A telescope or binoculars will just narrow your view. While the shower actually peaks tonight, meteors are often spotted several nights before and after. Friday night may be almost as good as Thursday.
So if the weather is clear and you don't have something urgent in the morning, you may want to, er, button up your overcoat and stay up. Past three if you like.