The storm was an intense instance of the annual Leonid meteor shower, which arrives every November and is named after the constellation Leo, the point in the sky from which the meteors appear to radiate. The meteors themselves are bits and pieces shed by Comet Tempel-Tuttle, pulled along in the comets wake as it orbits the sun.
The peak day this November is the 18th, at 2:51 a.m., Eastern Standard Time (07:51 GMT). But dont expect a storm. At best, it will be a drizzle. Regrettably, says astronomer John Mosley of the Griffith Observatory in Los Angeles, this years shower will be "nothing to plan a vacation around," although it should still be worth the loss of a nights sleep.
Stay tuned, though, says Mosley. Next year should be great.
He says that with some confidence. In the past, predictions of the strength and timing of a given years Leonids would often vary widely. But thanks to some very neat work by a couple of astronomers just a year ago, we now know whats coming down the celestial pike with some precision. Rob McNaught, of the Australian National University, and David Asher, of the Armagh Observatory in Northern Ireland, examined the motions of all the Tempel-Tuttle debris streams that had formed over the past millennium. They worked out where these streams of particles are now located by calculating the gravitational pull of the planets on the dust orbiting through the centuries. Then they calculated the time when Earth will be closest to the center of each stream.
"Their breakthrough," Mosley explains, "was to realize that each time the comet passed, it shed a stream that was affected differently because the planets were in different positions; prior to this, people had considered the comet to shed the same stream each time and add to it.
"So, each time the Earth comes around the Sun, we travel through different streams; its a whole graded set of streams out there." The number of meteors we see depends on the depth and density of the individual streams, which over time are stretched and thinned by gravity.
Last year a very good one Earth passed through debris that had sloughed off the comet three revolutions ago, back in 1899. The storm peaked at about 5,000 meteors per hour. This years itinerary isnt so favorable: we will be passing near, but not through, two separate streams one formed in 1733, the other in 1865. Though astronomers are leaving themselves wiggle room on this one, peak meteor rates could be around 100 an hour. To make matters worse, theres a waning Moon sitting close to Leo, obscuring the view.
But wait till next year! In 2001 the Moon will be absent, and Earth will pass through three streams, one of which from 1767 will be visible from North America, with a peak at 5:01 a.m. EST (10:01 GMT), on November 18. McNaught and Asher estimate that activity will be in the vicinity of 1,500 meteors per hour.
Dont give up on Y2000, though. Even a paltry 100 hits an hour gives you a meteor every 35 seconds or so. Get a lawn chair and a sleeping bag, and get away from city lights. Don't bring a telescope or binoculars; you want to take in as wide a view as possible. You might be surprised at what you see, and youll have to time to contemplate what was happening on Earth when those fiery particles first left their mother ship.
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