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November 10, 1998: Ready or not, here they come: the 1998
Leonid meteors. On the morning of November 17th, bits and pieces
of periodic comet Tempel-Tuttle will hurtle into Earth's atmosphere
at a head-spinning 158,000 mph. There is little danger - few
will reach the ground. Most will distintegrate and, in the process,
produce a "shooting star". Experts think that this
year's Leonids could rival any meteor storm this century, with
peak rates greater than 40 shooting stars per second. Or, it
could be another run-of-the-mill meteor shower. We won't know
for sure until next week.
Watch the Leonids on the web from sites around the world. www.LeonidsLive.com. |
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Comet Tempel-Tuttle spends most of its time far away in the outer
solar system, between the orbits of Saturn and Uranus. Occasionally
Tempel-Tuttle pays a visit to Earth when it swings by the sun
on its 33-yr elliptical orbit. The last time this happened was
just 10 months ago, in January 1998. The comet passed within
0.36 AU of Earth and was easily seen with binoculars and small
telescopes. When Tempel-Tuttle comes calling, it doesn't come alone. The comet is surrounded by a cloud of ice and dust that bubbles off the comet's nucleus as a result of solar heating. This debris orbits the sun along with the comet, forming a thin elongated stream of meteoroids. The Leonid meteor stream is several hundred million km long, but only 35,000 km wide. Earth is scheduled to pass through the meteor stream one week from today, on November 17th. It's a narrow target, but if we hit it just right a historic meteor storm could result. The last time this happened was in 1966 when as many as 100,000 shooting stars per hour were observed at some locations. |
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Since 1995, when Tempel-Tuttle began its return to the inner solar system, the November Leonids have been better than average. In 1995 observers saw about 40 shooting stars per hour. In 1996 and 1997, 80 per hour were seen, and in 1997 the shower lasted for over 12 hours. |
| Eighty shooting stars per hour is enough to excite most experienced meteor observers, but it's nothing compared to the potential 1998 Leonids. If the shower is anything like the 1966 outburst, it may be possible to see hundreds of thousands per hour. The highest rates will occur only for the brief interval while Earth is passing through the densest part of the Leonid meteor stream. The ribbon of comet debris is so narrow that Earth passes through the densest part in less than two hours. |
 Experts agree that the best
viewing sites for the Leonids are likely to be found in Japan,
China, and other parts of east Asia. The image left shows
how Earth will be presented when we pass through the orbital
plane of Tempel-Tuttle in 1998. The best estimates suggest that
the storm will occur around 1900 UT on November 17th. That's
2 p.m. on the East Coast of the US, and 11 a.m. in California. |
But what do they know?Even though the experts are predicting the storm will occur over east Asia, it's still worth looking if you're located elsewhere. The experts have been wrong before, notably in 1966. In that year the Leonids were expected to occur over Europe, but observers in North America were treated to a spectacular shower thousands of miles away. This recollection by James Young at JPL's Table Mountain Observatory in California gives a sense of what the storm was like: |
 This fireball was photographed by James Young at
JPL's Table Mountain Observatory in 1966. |
"This very noteworthy [1966] meteor shower was nearly missed altogether.... There were 2-5 meteors seen every second as we scrambled to set up the only two cameras we had, as no real preparations had been made for any observations or photography. The shower was expected to occur over the European continent. |
 Take a virtual tour of the solar system, complete with comet Tempel-Tuttle, the source of the Leonid meteors. |
NASA Wants You!For this year's Leonid meteor storm Science@NASA will be collecting observations from amateur observers, including meteor counts, pictures, and video. We plan to use your observations as the subject of a Science News Headline on November 18th or 19th. If you would like to participate simply follow the simple instructions about how to observe and keep records. Then, after the shower, return here to submit your data. |
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at a Glance
 Next week's waning crescent moon will be favorable for dark skys and good meteor observing. |
The Leonids are best viewed during the early morning hours between
about 2 am and dawn. That's when the local sky is pointing directly
into the Leonid meteor stream. Like the parent comet, Tempel-Tuttle,
the Leonid meteoroids orbit the Sun in a direction opposite to
that of Earth. As a result, we collide with the Leonids head
on at high speed, nearly 158,000 mph. These high velocities are
the reason that the Leonids usually produce more fireballs than
other showers. The constellation Leo rises about 12:30 a.m. local time. The radiant of the Leonid shower is located inside the sickle-shaped "question mark" asterism, highlighted in the sky map below. To find the constellation, go outside and face east-southeast. At 3 a.m. the question-mark pattern of stars will appear approximately 40 degrees above the horizon. The planet Mars, posing as a bright red star, is nearby. You won't need binoculars or a telescope, the naked eye is usually best for seeing meteors which often streak more than 45 degrees across the sky. The field of view of most binoculars and telescopes is simply too narrow for good meteor observations. Experienced meteor observers suggest the following viewing strategy: Dress warmly  as the autumn nights
are likely to be cold. Bring a reclining chair, or spread a thick
blanket over a flat spot of ground. Lie down and look up somewhat
toward the south. Meteors can appear in any part of the sky,
although their trails will tend to point back toward the radiant. |
The image indicates the general region of the sky from which the Leonid meteors appear to emanate (red dot). This point, called the radiant, is really an optical illusion - the meteors are moving along parallel paths, but appear to come from a single point, just as a stretch of parallel railroad tracks will appear to meet at a point on the horizon. |
| Web Links | |
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Meteor counts - submit your own meteor counts to NASA! 1998 Leonids Data Bank -- a useful summary of Leonids information from NASA Ames. The November Leonids: Will they Roar? -- from JPL Comet Tempel Tuttle image archive -- from NASA Ames Eyewitness accounts of the 1966 storm -- an Ames Research Center Archive Satellite Tracking - monitor satellites as they weather the storm NASA's Office of Space Science - press releases and other news related to NASA and astrophysics |
Related Stories: Halley's comet returns in bits and pieces -- story posted Oct 20 on the Orionid meteor shower Tune-up for the Leonids - story posted Oct 7, discusses the astronomy of the Giacobinids External Links: The Leonids -- from Gary Kronk Meteors and Comets web site Leonids: the Night of Raining Fire -- Sky &Telescope article The Leonids: King of the Meteor Showers -- Sky &Telescope article |
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return to Space Science News Home Author: Tony
Phillips |
