While December's supermoon will wash out the peak of this year's Geminid meteor shower, you can still expect to see several bright shooting stars in the sky. There will just be fewer of them during the North American peak on the night of Dec. 13 and morning of Dec. 14.
"It's usually the best meteor shower of the year," NASA meteor expert Bill Cooke told Space.com. Typical rates are about 120 meteors an hour under dark skies, but this year, because of the simultaneous full moon, it will look more like 40 meteors an hour. People living in light-polluted areas can expect to see even fewer shooting stars.
The supermoon occurs when the moon is full and at its closest point to Earth in its orbit. December's will be the third supermoon in the last three months of 2016. During a supermoon, the moon appears slightly bigger in the sky and is thus slightly brighter than usual, which washes out shooting stars. (In fact, any full moon hurts meteor-viewing conditions; they are seen best with a crescent or new moon, or after the moon has set.) [Geminid Meteor Shower Awes Skywatchers Worldwide (Photos)]
The Geminid meteor shower itself is nearly 200 years old, according to known records, and is still going strong — in fact, it's growing stronger. The first recorded observation was in 1833 from a riverboat on the Mississippi River, Cooke said. "They've been gaining strength ever since," he added, because Jupiter's gravity has tugged the stream of particles from the shower's source ― the asteroid 3200 Phaethon ― closer to Earth over the centuries.
When to see them
The full moon is up all night, so there is no way to avoid it. That said, the meteors tend to peak about 2 a.m. local time, so that will be the best time for people in North America to see it, Cooke said. "Bundle up and keep warm," he advised.
The Geminids, as their name implies, appear to emanate from the bright constellation Gemini (the twins). To find Gemini, look in the northeastern sky for the constellation Orion, which is easy to spot by the three stars in the hunter's "belt." Then look just up and to the right of Orion to see Gemini, high in the northeastern sky.
Although the meteors will appear to stream away from Gemini, they can appear all across the sky. For best results, you should look slightly away from Gemini so that you can see meteors with longer "tails" as they streak by; staring directly at Gemini will just show you meteors that don't travel very far.
Where do they come from?
The Geminids are associated with the near-Earth object 3200 Phaethon, an asteroid that may have undergone a collision with another object in the distant past to produce the stream of particles that Earth runs into — creating the meteor shower.
The asteroid orbits the sun every 1.4 years. It occasionally comes close to Earth (at a safe distance) and also passes very close to the sun, inside of Mercury's orbit and only 0.15 astronomical units from the sun. (An astronomical unit is the distance between the sun and the Earth.)
"The NASA STEREO spacecraft has observed weak activity in this object, which occasionally sheds material," Cooke said. "The activity is not enough to account for the meteor shower, though."
Rocks in space that are about to collide with Earth's atmosphere are called meteoroids. Those that streak through the atmosphere are called meteors, and if they reach the ground (which won't happen with the Geminids, as the particles are too small to survive the trip) the rocks are called meteorites.
How to get the best view
Meteor showers don't require binoculars or telescopes to view — just your bare eyes. Find a comfortable spot to lie on the ground, far away from lights and ideally in a dark-sky area. Bring a blanket and dress warmly if you're in cold weather. Give your eyes about 20-30 minutes to adjust to the dark, then sit back and enjoy the show.