With near-perfect conditions in the offing, sky-watchers should get ready for an early holiday treat. The Geminid meteor shower is upon us, and it promises to be one of the best shooting star shows of the year.
The annual shower will peak tonight and into the early morning of December 14, when viewers can expect to see dozens of meteors an hour. And in just a few days, viewers with backyard telescopes will get an extra gift: a rare glimpse of the asteroid that created the shower zipping across the sky.
Meteor showers happen when Earth plows through a cloud of debris left behind by a passing space rock. The vast majority of meteors are no bigger than grains of sand, and they burn up when they slam into the planet’s upper atmosphere, creating brilliant streaks of light.
Last year’s Geminid show peaked around the same time as a supermoon, and the intense glare from this larger-than-average full moon made it difficult to see fainter meteors. But this year, the overnight hours during the shower’s peak will be dark and almost moonless—the waning crescent moon won’t rise until 4:30 a.m. local time on December 14.
The Geminids are fun to watch because the meteors travel at slower speeds than most other annual showers, which means the streaks last longer. Moving through our atmosphere at around 20 miles a second, these meteors produce beautiful long arcs that are visible for at least a second or two.
The Geminids get their name from the Gemini constellation, because the meteors appear to radiate from that part of the sky. The best time to begin watching is when the constellation rises above the eastern horizon, which will occur after 9 p.m. local time.
Gemini will rise highest in the sky for viewers in the Northern Hemisphere, which means people in North America will see the shower really kick into gear in the darkest part of the night. Star-gazers in northern mid-latitude regions with pristine skies away from city lights can expect to see up to 120 meteors an hour. Observers stuck in light-polluted city suburbs can expect more modest numbers ranging from 20 to 60 meteors an hour.
For sky-watchers in the Southern Hemisphere, the show will be slightly less impressive, as Gemini never rises high above the local horizon. People in southern regions will still get splendid views, just with fewer meteors an hour.
Most of the annual meteor showers we see were created by passing comets, which shed dust as they get close to the sun and their ices vaporize. The Geminids are a bit different, because their debris comes from 3200 Phaethon, an odd object that astronomers have dubbed a “rock comet.” When this type of asteroid passes close to the sun, heat causes it to fracture and cough out rocky particles.
Measuring about three miles across, 3200 Phaethon’s orbit takes it closer to the sun than any other known asteroid. And on December 16, the object will make an historically close flyby of Earth, coming within 6.4 million miles of the planet. It hasn’t gotten this close to us since 1974, and it won’t come so near again until 2093.
Luckily, there’s very little chance of an impact. While the asteroid does regularly cross Earth’s orbital path, astronomers predict that it won’t come close enough to pose a threat for at least the next thousand years.
Instead, 3200 Phaethon will be a fairly easy target for sky-watchers with small telescopes. The asteroid will make its closest approach at 6 p.m. ET on the 16th, appearing as a bright ball of light streaking along at a relatively fast clip. Check out Sky and Telescope’s website for detailed charts of the asteroid’s path in the heavens.
If you miss the peak dates, there should be plenty of meteors falling a few days before and after the main event. And if clouds get in the way, you can watch online thanks to the Virtual Telescope Project, which will have live webcasts from Italy and Arizona on December 13 and 14 for the Geminds and on December 15 and 16 for 3200 Phaethon.