Tony Rice is a volunteer in the NASA/JPL Solar System Ambassador program and software engineer at Cisco Systems. You can follow him on twitter @rtphokie.
Earth is currently passing through a debris trail that is a bit of a mystery to scientists. Like other meteor showers, this week's Geminids meteor shower is created as Earth's orbit takes it through a stream of dust resulting in "shooting stars" in the night sky.
Named for the Gemini constellation the streaks of light appear emanate from, the Geminids are actually rock vaporizing as each enters Earth's atmosphere. However, something isn't quite right about the source.
Meteor showers like August's Persieds, October's Orionids, or April's Lyrids come from comets. As their path through the solar system takes them close to the sun, these dirty snowballs are heated, spewing a trail of meteoroids behind.
The Gemenids source is not an icy comet, but instead a 3-mile wide asteroid 3200 Phaethon, discovered in 1983 by NASA's IRAS space telescope. Phaethon is thought be the result of a collision from the much larger asteroid Pallas in the main asteroid belt between Mars and Jupiter. The problem is, asteroids normally don't have tails, comets do.
Researchers studying Phaethon noted it brightening. This led to the theory that the rock is breaking down, the result of heating by the sun, leaving a trail of dust and rock behind. This comet-like behavior, along with the very comet-like orbit, has lead to the label "rock comet" for Phaethon.
Whatever the explanation for its source, the Geminids are a favorite of skywatchers. Unlike other showers which are made up mostly of sand-sized debris, the Geminids are larger and more numerous producing more and brighter meteors. Previous years have produced more than 75 per hour. Observers in rural areas report as many as 120 per hour.
The Geminid meteor shower has been underway since this past weekend. It peeks the evening of Dec. 13. With no moon to brighten the sky, this year promises to be better than previous years. To make the show even better, a new meteor shower is also expected to peak around this time.
Bill Cooke, of NASA's Meteoroid Environment Office, points to dust coming from comet Wirtanen as the source. Those meteors appear to come from the constellation Pisces in the southern sky and are dimmer, slower and less numerous than the Geminids. But the possibility of meteors showers crossing one another in the sky has created excitement.
To experience this event for yourself, all you need is your eyes and a little patience. Look to the east, meteors will appear to come from the twin stars in the constellation Gemini. A warm coat, a blanket out on the lawn and maybe a thermos of cocoa will will help as well. The optimal time is after midnight, as Earth rotates into the path of the "rock comet".
Morehead Planetarium and Science Center will also host a special sky watching session Thursday night beginning at 8 p.m. at Jordan Lake's Ebenezer Church Recreation Area. The event is free and open to the public. Volunteers from the Chapel Hill and Raleigh astronomy clubs will also be sharing views of Jupiter and its moons.