獅子座流星雨
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小編： 389At its peak hour at 5 a.m. ET, the meteors could be streaming down at a rate of 70 a minute, or 4,200 an hour, says Peter Jenniskens of the SETI Institute and NASA Ames' Research Center.
Satellites, Space Station Could Be Nicked
Since the meteorites range in size from dust grains to small pebbles, they'll likely burn up completely before reaching Earth and pose no threat to people or Earth-bound objects. Satellites and the space station, however, stand a small chance of getting pelted and slightly damaged.
The meteor shower, named after the constellation Leo, from which the meteors appear to originate, is expected to be visible from all parts of North America, although Jenniskens believes those in the Northeast will have the best view.
"This could be the last opportunity for watching an impressive meteor storm in a dark sky for decades to come," said Donald Yeomans, head of NASA's Near Earth Object program office at the Jet Propulsion Laboratory in Pasadena, Calif.
Next year's Leonids could have been impressive, but they're scheduled to occur during a full moon, which will obscure their brilliance.
Some Predict More Modest Show
Although Yeomans, Jenniskens and other astronomers agree this year's Leonids show looks to be spectacular, other predictions are less grand.
For example, Robert Cooke of NASA Ames' Research Center believes the meteor shower will provide an average display of about one every 10 seconds in the United States.
"It's sort of like talking to weathermen," said Cooke, who is now in Hawaii, since his calculations show the best display will appear above that state. "You get a different answer from each one."
Astronomers form their predictions by mapping Earth's orbit with that of dust trails left behind by the comet Tempel-Tuttle. As the comet, which is made up of dirt and ice, passes near the sun every 33 years, it heats up and releases a dust trail. The last time comet Tempel-Tuttle shed a dust trail was in 1998.
Tracking Dust Trails in Space
When Earth passes close to the comet's orbit, it smacks into the comet's old dust trails. The collisions cause shooting stars as the clumps strike Earth's upper atmosphere and vaporize, creating streaks of light in the sky.
The most spectacular Leonid meteor storm in recent times was in 1966 when as many as 2,500 meteors streaked across the skies above Earth every minute.
Astronomers' various predictions reflect their different mappings of the comet's dust trails. Jenniskens based his mappings on aircraft observations that his team did in 1999 and 2000. These calculations show that collisions with the comet trail left behind in 1767 will lead to the biggest displays in the Northeast around 5 a.m. ET.
Cooke's mapping predicts the trail left behind in 1799 is poised to produce the most collisions, leading to an average show in the Northeast and a better, but still modest display of about 20 meteors a minute over Hawaii at about 3 a.m. local time.
Possible Clues About Life's Beginnings
meteor shower forecasts can disappoint. In 1998, for example, astronomers foresaw a brilliant Leonid storm, but it turned out to be less than ordinary. Jenniskens assures, however, that prediction methods have vastly improved since then due to more precise charting of the comet's dust trails.
meteor showers aren't only a treat for the eyes, science also benefits from the display. Jenniskens says he and his team plan to analyze the content of meteors as they streak by to learn what kind of organic matter they might carry and whether that matter is changed in the process.
This information could be significant since some scientists believe organic matter from comets could have planted the seeds for life on Earth billions of years ago.
"meteor showers have gone from being great anecdotes to becoming a bona fide part of astronomy," he said.At its peak hour at 5 a.m. ET, the meteors could be streaming down at a rate of 70 a minute, or 4,200 an hour, says Peter Jenniskens of the SETI Institute and NASA Ames' Research Center.
Satellites, Space Station Could Be Nicked
Since the meteorites range in size from dust grains to small pebbles, they'll likely burn up completely before reaching Earth and pose no threat to people or Earth-bound objects. Satellites and the space station, however, stand a small chance of getting pelted and slightly damaged.
The meteor shower, named after the constellation Leo, from which the meteors appear to originate, is expected to be visible from all parts of North America, although Jenniskens believes those in the Northeast will have the best view.
"This could be the last opportunity for watching an impressive meteor storm in a dark sky for decades to come," said Donald Yeomans, head of NASA's Near Earth Object program office at the Jet Propulsion Laboratory in Pasadena, Calif.
Next year's Leonids could have been impressive, but they're scheduled to occur during a full moon, which will obscure their brilliance.
Some Predict More Modest Show
Although Yeomans, Jenniskens and other astronomers agree this year's Leonids show looks to be spectacular, other predictions are less grand.
For example, Robert Cooke of NASA Ames' Research Center believes the meteor shower will provide an average display of about one every 10 seconds in the United States.
"It's sort of like talking to weathermen," said Cooke, who is now in Hawaii, since his calculations show the best display will appear above that state. "You get a different answer from each one."
Astronomers form their predictions by mapping Earth's orbit with that of dust trails left behind by the comet Tempel-Tuttle. As the comet, which is made up of dirt and ice, passes near the sun every 33 years, it heats up and releases a dust trail. The last time comet Tempel-Tuttle shed a dust trail was in 1998.
Tracking Dust Trails in Space
When Earth passes close to the comet's orbit, it smacks into the comet's old dust trails. The collisions cause shooting stars as the clumps strike Earth's upper atmosphere and vaporize, creating streaks of light in the sky.
The most spectacular Leonid meteor storm in recent times was in 1966 when as many as 2,500 meteors streaked across the skies above Earth every minute.
Astronomers' various predictions reflect their different mappings of the comet's dust trails. Jenniskens based his mappings on aircraft observations that his team did in 1999 and 2000. These calculations show that collisions with the comet trail left behind in 1767 will lead to the biggest displays in the Northeast around 5 a.m. ET.
Cooke's mapping predicts the trail left behind in 1799 is poised to produce the most collisions, leading to an average show in the Northeast and a better, but still modest display of about 20 meteors a minute over Hawaii at about 3 a.m. local time.
Possible Clues About Life's Beginnings
meteor shower forecasts can disappoint. In 1998, for example, astronomers foresaw a brilliant Leonid storm, but it turned out to be less than ordinary. Jenniskens assures, however, that prediction methods have vastly improved since then due to more precise charting of the comet's dust trails.
meteor showers aren't only a treat for the eyes, science also benefits from the display. Jenniskens says he and his team plan to analyze the content of meteors as they streak by to learn what kind of organic matter they might carry and whether that matter is changed in the process.
This information could be significant since some scientists believe organic matter from comets could have planted the seeds for life on Earth billions of years ago.
"meteor showers have gone from being great anecdotes to becoming a bona fide part of astronomy," he said.
