The annual Leonid meteor shower, one of the best annual meteor showers, will be reaching its peak this week although the showing is not expected to be spectacular with only 10-15 meteors per hour projected.
Space.com explained the reason for the lower count:
“The Leonid meteor shower’s parent comet, Tempel-Tuttle, orbits the sun about every 33 years. Because of the comet’s proximity to Earth from 1998 through 2002, the Leonids were producing enhanced rates ranging from a few hundred to a few thousand meteors per hour. Now, with their parent comet having retreated far back to almost the far end of its orbit, near the orbit of Uranus, the Leonid rates have returned to their more typical 10 or 15 per hour. “
This year the shower is a bit unusual with two peaks expected – one on Saturday morning (11/17/2012) and the other on Tuesday morning (11/20/2012).
Joe Rao, instructor at New York’s Hayden Planetarium explained Leonids:
“The Leonids are tiny, sand-grain- to pea-sized bits of rocky debris shed long ago by the comet Tempel-Tuttle. This comet, like all others, is slowly disintegrating. Over the centuries its crumbly remains have spread all along its orbit to form a moving river of rubble millions of miles wide and hundreds of millions of miles long. The Earth’s orbit carries us through this meteor stream every year in mid-November. The particles are traveling at 45 miles (72 kilometers) per second with respect to the Earth. When one of them strikes the Earth’s upper atmosphere, about 50 to 80 miles up, air friction vaporizes it in quick, white-hot streak.”