There's a cool doubleheader in outer space this week: In addition to the fly-by of comet 46P/Wirtanen over the weekend, the often spectacular Geminid meteor shower will also make its annual appearance Thursday.
With hundreds of meteors streaking across the night sky, the Geminids are often the best meteor shower of the year. "The reliable Geminid shower counts as one of the year’s best, peppering the nighttime sky with 50-120 meteors per hour at its peak," noted EarthSky.org.
More good news: The crescent moon will set around 10:30 p.m., leaving the rest of the night moon-free, Astronomy.com said. Observers under a clear dark sky can expect to see an average of two per minute.
The Geminids are named for the constellation Gemini, the point from which the meteors seem to radiate. To be more specific, the meteors will appear to emanate from a spot in the sky near the bright star Castor in Gemini, Space.com's Joe Rao said.
This meteor shower is active every December, when Earth passes through a massive trail of dusty debris shed by a weird, rocky object named 3200 Phaethon, NASA said. The dust and grit burn up when they run into Earth's atmosphere in a flurry of "shooting stars."
Phaethon’s nature is debated. It’s either a near-Earth asteroid or an extinct comet, sometimes called a rock comet, according to NASA.
Geminid meteors are bright and fast (79,000 mph), and the shower is famous for producing fireballs, which are meteors brighter than magnitude -4, the same magnitude as the planet Venus.
According to Sky & Telescope, the Geminids are only behind August's Perseids when it comes to fireballs.
Meteor showers don't require binoculars or telescopes to view – just your bare eyes and some patience.
To increase the chances of seeing meteors, choose a site at least 40 miles from a major city, Astronomy.com said. "Suggested gear includes a lawn chair, lots of warm clothing, blankets, cookies or fruit, and a warm, non-alcoholic beverage. Alcohol interferes with the eye’s dark adaption as well as the visual perception of events."
The cold is always a factor with the Geminids, Rao of Space.com said. "If you are willing to brave a long lookout of possible-subfreezing temperatures, you will be amply rewarded," he said.
The best viewing weather on Thursday night is expected across the central U.S., while the eastern half of the country and the Northwest will see mostly cloudy skies, AccuWeather said.
The Geminids were first noted as a minor meteor shower back in 1862, NASA reported.
At the time of the Civil War, the shower's peak rate was about 30 meteors an hour. "Since then, the Geminids have gradually strengthened to become the strongest annual shower," NASA astronomer Bill Cooke said. "This is due to Jupiter's gravity nudging the stream closer to Earth."