The shooting stars have aligned for this weekend's peak of the annual Geminid meteor shower: It's arguably the best meteor display of the year — and it reaches its height during the heart of the weekend, late Saturday night and early Sunday morning.
This year, the moon is at last quarter during the Geminids' peak. That means the meteors will have to compete with a bit of moonshine during the wee hours, but things could be worse. And the long-streaking fireballs that are characteristic of the Geminids should make an impression despite the moon.
The biggest downside to the Geminids is that they flash during a time of year that's traditionally cold and cloudy in the Northern Hemisphere. But even if it's too chilly to be out in the dark, you can still catch the show online.
Meteor showers occur when Earth passes through a trail of debris left behind by a comet or, less frequently, an asteroid that has crossed our planet's path in the past. The Geminids are spawned by the asteroid Phaethon, which is thought to be a space rock that was left behind when a comet burned itself out. It swings around the sun every 1.43 years and can cross the orbits of all the planets between Mercury and Mars — but poses no risk of collision.
Every December, our planet swings through a hail of Phaethon's grit, and those flecks create ionized trails as they burn up in the upper reaches of Earth's atmosphere. Like raindrops hitting your windshield, the meteors seem to emanate from a single point ahead of us. That point, known as the radiant, is in the constellation Gemini, which is how the Geminids get their name.
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The meteor sighting rate has been rising steadily over the past couple of nights, and early Sunday morning, astronomers expect the rate under ideal viewing conditions to rise as high as 120 sightings per hour. Most observers will see less, however, in part due to the moon's glare.
Get as far away as you can from city lights. The higher the elevation, the better. Give your eyes plenty of time to adjust to the dark.
Even though Geminid meteors are traced back to the constellation Gemini, they can pop up anywhere in the sky. The best way to watch is to look up from a lounge chair into a wide-open sky. There's no need to use a telescope or binoculars, unless you want to take in other sights in the sky.
Because the moon rises in the east around midnight, you might consider positioning yourself with a building or other obstacle that can screen out the glare.
It's not a bad idea to bring snacks and a hot drink to keep up your energy.
If you don't already have a favorite meteor-watching spot, the Clear Sky Chart can show you locales that are expected to have good viewing conditions. You can also check with your local astronomy club.
NASA's Fluxtimator applet provides predictions of the expected meteor rate, based on your locale as well as sky conditions and time of night. Make sure that your Java software and security settings are up to date, and that you enter the correct parameters into the applet.
"I'm looking forward to a good display," Cooke said in a NASA preview.
The Slooh virtual observatory will offer a webcast tracking the meteor shower from various locations, using special equipment to capture low-light video and the audio crackle of ionizing meteors. The show starts at 8 p.m. ET Saturday, and will be aired via Slooh.com and Livestream.com. Viewers can use the audio commentary as an accompaniment to their own outdoor viewing, and ask questions on Twitter by using the hashtag #sloohgeminids.
"The Geminids are very strange, because they hit Earth sideways," Slooh astronomer Bob Berman said in a preview news release. "It is the difference between being in a car and slamming head-on into somebody as opposed to someone backing into you sideways."
August's Perseids hit the atmosphere at 133,000 mph, and November's Leonids streak toward us at 144,000 mph. In contrast, the Geminids travel a mere 79,200 mph, Berman said.
Virtual Telescope Project 2.0, headquartered in Italy, will air an online show that features real-time imagery from an all-sky camera plus commentary from astrophysicist Gianluca Masi. The program starts at 9 p.m. ET Saturday (0200 GMT Sunday).