The flashiest meteor shower of the year is upon us, and there is a chance to see it without the intrusion of a waxing gibbous moon.
Finding meteors from the Geminid shower will be tricky, since the moon is more than 80 percent full. But it sets a few hours before dawn, giving intrepid observers a window of opportunity if they are willing to rise early (or go to bed really, really late). The best view can be had in the dark hours before dawn on Saturday December 14, according to NASA.
"There is a 'magic hour' of good visibility just before dawn on Saturday the 14th," said Bill Cooke, lead astronomer for NASA’s Meteoroid Environment Office, in a statement. "The moon sets around 4 a.m. The dark time between 4 a.m. and sunrise is a great time for meteor watching."
Meteor showers happen all year, but they are mere previews to the showiest one, which fittingly heralds the solstice and winter holidays. The Geminids, according to NASA, are “the 900-pound gorilla of meteor showers.”
"The Geminid meteor shower is the most intense meteor shower of the year," said Cooke. "It is rich in fireballs and can be seen from almost any point on Earth. Even a bright moon won't completely spoil the show."
And they are mysterious, to boot.
"The Geminids are my favorite because they defy explanation," said Cooke, who will host an online chat and skygazing session from 11 p.m. on December 13 to 3 a.m. "Of all the debris streams Earth passes through every year, the Geminids are by far the most massive. When we add up the amount of dust in the Geminid stream, it outweighs other streams by factors of five to 500."
The difference lies in the source of Geminid meteors. While most meteor showers are generated by comet debris streams, the Geminids stem from an asteroid, “a weird rocky object,” named 3200 Phaethon. So instead of dainty dust, the debris is composed of chunks.
Rockiness aside, the fireball that exploded over Arizona on Tuesday night December 10 was in no way associated with this shower, Cooke told CNN on December 11. For one thing, its speed and trajectory were completely different than the meteors that appear to emanate from the constellation Gemini. The meteor was traveling at 45,000 miles per hour, whereas the Geminids move at 78,000, he told CNN. However it did pack a punch, weighing about 100 pounds and with a thickness of 16 inches.
Nevertheless, that meteor turned people’s attention toward the skies and the upcoming shower, which will be vibrant whether or not it’s drowned out by the moon’s luminescence. The best way to see the Geminids, astronomy websites say, is to rise a few hours before dawn on the morning of December 13, 14 or 15. The goal is to catch the sky at its darkest, between moonset and sunrise. The moon sets at 3:30 a.m. Eastern Time on the 13th and at 4:30 a.m. on the 14th, while the sun rises at 7:12 a.m. on both days. On the morning of Friday December 13th the viewing time will be longer, but the meteors will probably be faint. Saturday the 14th affords shorter, but potentially more fruitful, viewing time.
“Generally speaking, there will be about two hours of completely dark skies available on the morning of December 13,” Space.com said. “This window shrinks to only about an hour on the 14th, and to less than 10 minutes by the morning of the 15th.”
Given that, the one-hour viewing window on the 14th is the most optimal in terms of what sky gazers will see. That is when the meteors will be at their brightest, though for a shorter period than the fainter ones on the 13th. The shower has a reputation for glitz, especially in the Northern Hemisphere.
“The Geminids are a consistent and prolific shower,” Earthsky.org says. “Although the shower typically produces 50 or more meteors per hour—or an average of about one every minute—keep in mind those are the numbers you can expect on a dark, moonless night. Meteors often come in spurts and are interspersed by lulls, so give yourself at least an hour of observing time. Simply sprawl out on a reclining lawn chair, look upward and enjoy the show.”
It’s possible to see them just before the moon sets as well, if you can find something to block the light when the orb is just above the horizon.
Earthsky.org’s best advice: “Find a dark sky … on the nights of December 12-13 and 13-14, 2013. The moon will interfere, but, especially on the December 12-13, you will have a window of darkness between moonset and dawn. Plus the Geminids tend to be bright. You might catch a few in the moonlight.”