Last modified: Wednesday, November 7, 2001
Leonid meteor shower may be a storm this year
The annual Leonid meteor shower will peak on the night of Nov. 17-18. If the predictions of meteor specialists hold up, there will be a meteor "storm" in some locations that will be well worth staying up after midnight to see.
Several thousand meteors may streak overhead for an hour or so for observers fortunate enough to be in the right place with a clear sky. The moon will be just a few days past new and will not interfere.
According to three teams of scientists who have studied the past behavior of the Leonid meteors, there will be two periods of intense meteor activity. People watching throughout most of North and Central America should see a burst lasting perhaps two hours in the predawn hours of Nov. 18. For viewers around the western rim of the Pacific Ocean from Australia to Russia, an even bigger cascade of meteors will occur about eight hours later. Because these latter locations are west of the International Date Line, this peak will occur before dawn on Nov. 19 local time.
The Leonid meteors, so named because they appear to radiate from the constellation Leo the Lion, are caused by streams of fast-moving dust particles from Comet Tempel-Tuttle.
Meteor watchers have been anticipating the Leonids since 1999, when the Leonid shower turned out to be a meteor storm for observers in southern Europe and northern Africa. In most years the Leonids are a minor shower, but every 33 years or so, they are capable of producing a spectacular meteor storm with a thousand or more meteors per hour.
The previous Leonid storm was Nov. 17, 1966 (also not visible in most of the United States), so the meteor storm of 1999 continued the 33-year pattern. But in 1999, for the first time in history, a team of astronomers successfully predicted the exact time of the Leonid storm, missing by only a few minutes instead of by hours as previous estimates always had done. They did it by tracing specific paths of debris left behind in space during different passes of the Leonids' parent comet, Tempel-Tuttle.
Most meteor showers happen when Earth crosses the orbit of a comet. The meteors are caused by tiny particles of dust and other debris that were released from the comet's nucleus and left behind in space as the comet got closer to the sun. As Earth plows through this stream of particles, each one collides with our upper atmosphere at tremendous speed and burns up almost instantly from friction with air molecules. The resulting heat momentarily creates a streak of glowing air molecules that we see as a meteor (sometimes called a "shooting star" or "falling star").
Understanding of the Leonid meteor shower has greatly improved during the past two years, and the astronomers who so accurately predicted the 1999 Leonid storm have made new predictions for the 2001 Leonids. They have calculated that this year Earth will pass right through two trails of cometary debris left during the 1699 and 1766 passages of Comet Tempel-Tuttle, which should result in two separate bursts of meteors that could exceed even the 1999 storm. Trails of particles from the 1799, 1833 and 1866 comet passages may also contribute to the display.
Watch for meteors after midnight local time on the night of Nov. 17-18 as the constellation Leo gets higher in the east. That is when your part of the planet will be rotating into the path of the oncoming meteors. The higher Leo is above the horizon, the more meteors will appear all over the sky.
Light pollution wipes out many meteors for observers, so choose a dark site with an open view of as much of the sky as possible. Face eastward and give your eyes at least 15 minutes to adjust to the dark.
If you want to do more than just watch the meteors, you can do a scientific meteor count, yielding results that can be compared with other observations from around the world. Instructions for how to do this, including how to report your results to the International Meteor Organization for inclusion in their worldwide data base, are available at http://www.skypub.com/sights/meteors/meteorwatch.html.
A helpful background article with illustrations about the Leonid meteor shower and its history can be found at http://www.skypub.com/sights/meteors/leonids/king.html.
Mars has gradually faded over the last four months, but the red planet will still be the brightest "star" in the constellation Capricornus the Goat during November. Mars will be visible in the south as the evening sky darkens, setting five hours after the sun.
Saturn will be a brilliant yellow object in the eastern sky two hours after sunset, dominating the constellation Taurus the Bull and easily outshining its brightest star, orange Aldebaran. Next month Saturn will be as bright and large as it ever gets.
Even brighter Jupiter will follow Saturn, rising two hours later in the constellation Gemini the Twins. The bright stars Castor and Pollux will be on Jupiter's left (north), with Castor above Pollux.
Venus and Mercury will complete their rare week-long rendezvous by Nov. 7, with both planets very low in the east-southeast about 30 minutes before sunrise. The bright white star Spica will be slightly to the right (south) of the two white planets. Brilliant Venus will be easy to spot, but Mercury will be coming to the end of its best morning appearance of the year. Both planets will move quickly down into the solar glare and disappear by midmonth for most observers.
The moon will be full on Nov. 1, at third quarter on Nov. 8, new on Nov. 15, at first quarter on Nov. 22 and full again (a "blue moon") on Nov. 30.