Meteors to light night sky
Late Monday night and early Tuesday morning, the Earth’s orbit will carry it through the orbital planes of two dust streams the comet Tempel-Tuttle left in our solar system hundreds of years ago.
One of the streams was left when the comet passed through the solar system in 1767. In 1866, the comet deposited the other, said Geoff Chester, an astronomer at the U.S. Naval Observatory.
When dust particles hit the Earth’s atmosphere, they burn up, causing meteor showers, Chester said.
“Basically what happens is, it’s kind of a slow-motion cosmic traffic accident. There are comets which are in orbit around the sun and as they go through the inner solar system, basically the ice melts and liberates dust particles, which get strewn along the orbital path of the comet,” said Chester, the observatory’s public affairs officer.
The Tempel-Tuttle comet passes through our solar system every 33 years and deposits dust each time. Occasionally, the Earth’s orbit intersects with those of the dust streams.
To the earthbound, the glowing particles look as if they originate in the middle of the constellation Leo as they enter the atmosphere and burn up. Scientists call the particles the “Leonids.”
This year’s display, Chester said, should be particularly lively and is probably the last Earthlings will see of the Leonids for some time.
The geometry won’t be in our favor again for maybe a century since the comet is “periodically perturbed” in its orbit, Chester said.
“It comes by every 33 years and each time it comes by, its orbital path is slightly different because it gets tugged around by Jupiter and Saturn and stuff,” Chester said.
The dust streams orbit the sun as well and are similarly affected, Chester said.
Sometimes the Earth and space dust have close encounters and sometimes they don’t.
“Each of these streams of material is in a slightly different place,” Chester said. “We have in the last couple of years been in a favorable position to see spectacular displays from this particular shower.”
But the heavenly bodies will not properly align again soon.
“This basically is the last shot we have at seeing a really good display from this particular meteor shower for perhaps ninety or more years,” he said.
Fortunately or unfortunately, depending on your schedule, our best meteor- shower viewing time will be between 5:30 and 5:40 a.m. Tuesday, Chester said.
Europe will be better positioned to watch the results of passing through the dust left by the comet during its 1767 return to the solar system, Chester said.
That shower will occur for us between 11 and 11:30 p.m. Monday.
North America’s best viewing chance will come later.
“Around 5:30 (a.m.) on Tuesday is when we cross the stream from the 1866 comet,” Chester said.
To continue the allusion to cosmic traffic, Chester explained why the later meteor shower will look better to us.
“The analogy is like when you’re driving down the road in a snowstorm with your high beams on, the snowflakes seem to be coming from a point directly in front of you,” he said
“When you stop the car it becomes apparent that they’re raining down on you from above, but because of the motion of the car through the stream, they appear to be coming at you from this point somewhere in space … somewhere in space in front of you. Exactly the same thing happens as the Earth plows into these streams,” Chester said.
On Monday night, Chester said, North America won’t be facing the best direction.
“We’re going to be the side windows at 11 o’clock. At 5:30, we’re the windshield,” Chester said.
“The peak time would be between about 5:30 and 5:40 in the morning,” the astronomer said.
While we are the “windshield,” the meteors will enter the Earth’s atmosphere in what scientists call a “radiant,” Chester said.
The radiant will look to us as if it originates in Leo’s head, which can also be seen as a backward question mark, halfway up, in the southeast quadrant of the sky.
But Chester said it’s not really necessary to know the celestial location of Leo or even be able to find the southeast quadrant of the night sky.
“Basically all you have to do is look up,” he said. “If this pans out the way we think it’s going to, it will not take you long to figure out where they’re coming from and where to look.”
Unfortunately the moon will be full that night, so many of the smaller shooting stars will not be visible, Chester said.
Luckily there will be plenty coming down, and since the moon’s light will obscure many of the meteors, it won’t be necessary to seek exceptionally dark places to watch the show.
Chester said scientists predict that 2,000 to 3,000 meteors per hour will enter the earth’s atmosphere during peak times.
“Moonlight will eliminate half of those,” he said.
Even so, Chester said, plenty of the meteors will be visible
“We’re still talking about the possibility of seeing one or two every couple of seconds,” he said.
For viewing the showers, Chester recommends that people find an open area that is away from street lights.
For more information, visit http://www.skyandtelescope.com or find the Naval Observatory Web Site at http://www.usno.mil.