Friday, April 8, 2011

Geminid meteor shower promises to be year's best, despite mysterious origins, 12.10.10

The Geminids meteor shower has long been considered by astronomers to be the best meteor shower to see. Taking place just a few days before the winter solstice, the cold weather is usually accompanied by high pressure fronts and clear, high-visibility skies. The Geminids themselves usually bring well over 100 meteoroids per hour, and can be seen from any point on the planet. The Geminids are puzzling astronomers though; “they defy explanation,” says NASA’s Bill Cooke.

The problem, he says, is that most meteor showers’ point of origin is a comet. No matter how they do the math on the Geminids, though, the trajectories all point to an object that simply should not be putting off that volume of material: 3200 Phaethon, a “weird rocky object.”

This poses a problem because 3200 Phaethon is currently not shedding much debris at all. The way meteor showers usually work is that earth passes through a dust or debris field left by comets, and the debris is burnt up in our atmosphere as we pass causing streaks or “shooting stars” in the night sky. According to NASA Science, the Geminids are the “900-lb gorilla of meteor showers,” yet “3200 Phaethon is more of a 98-lb weakling.” It simply does not add up.

NASA discovered 3200 Phaethon in 1983 using its IRAS satellite and, according to NASA, “promptly classified it as an asteroid.” Astronomers believe the Geminids originate from debris that is left over from an orbital point when 3200 Phaethon was close to the sun. Astronomers believe the heat from the sun may have caused some dust and debris to have been blown off the side, and this is what causes the Geminids every year. This hypothesis was further strengthened last year during 3200 Phaethon’s observation by NASA’s twin STEREO spacecraft. While extremely close to the sun, “3200 Phaethon unexpectedly brightened by a factor of two,” the only explanation being that it was ejecting material in response to a surface breakdown and reactions within its crust of possible moisture to the intense solar heat waves. Quite simply, it got too close to the sun and started to blow up (or blow off, really).

The best time for observing the Geminids this year is probably between 12-7AM on December 14th. Gemini should be directly overhead as a good starting place to look. Thronateeska’s Jim Friese recommends going outside the city to a rural area with less atmospheric light pollution and an open sky view. Thronateeska Heritage Center wishes you happy hunting, and be sure to bundle up!

Credit: NASA Science.

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