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Monday, 15 November, 1999, 14:04 GMT
Eyes up for the Leonids
The Leonids are hard to predict
There could be a spectacular display of shooting stars in the early hours of Thursday morning, European time.

But then astronomers said the same thing last year about the Leonids and the heavenly show turned out to be something of a disappointment.

The Leonids are what we see when the Earth plunges through the dusty debris left by Comet Tempel-Tuttle, which orbits the Sun every 33 years in a direction opposite that of the planets and most other objects in the Solar System.

We have comet Tempel-Tuttle to thank for the show
Small fragments of material, mostly no larger than a grain of sand, scorch through the Earth's atmosphere at 72 km/s (150,000 mph) and burn up. This produces a streak of light in the sky. The Leonids are so-called because they appear to come out of that part of the sky that includes the constellation Leo.

Although they can be seen every year around 18 November, the Leonids tend to be at their best just after Tempel-Tuttle has paid a visit to the inner Solar System, which it did early in 1998. The comet, a ball of ice and dust, was warmed as it swept around the Sun, ejecting debris as it went.

Asia got the best of it last year
This led to the prediction that we would witness a flurry of bright fire balls that year, with Asia best placed to catch the show. In the event, the Leonids turned up 14 - 16 hours ahead of schedule to the annoyance of many skywatchers who missed them.

This year, most experts predict that the maximum rate of activity will occur between 0100 and 0400 GMT on 18 November, putting Western Europe in a prime position to see the potential meteor storm.

Records of the Leonids go back as far as 1799, and possibly 1100. The best displays have featured hundreds or even thousands of shooting stars per hour, as happened in 1866 and 1966. It is possible that 1999 could also be a great year - but you never know.

Whatever happens, and whatever the weather, astronomers will be out in force. The Leonid meteor shower is important to scientists who are trying to understand the detailed composition and dynamics of cometary debris.

Like last year, Nasa will send a mission to fly under the breaking storm.

Fifty scientists on two aircraft packed with equipment will make observations on a journey that takes them from Tel Aviv to the Azores - above the clouds.

The European Space Agency (Esa) is hoping to provide information on meteor numbers. This is useful for spacecraft operators who might want to power down satellites or turn them away from the storm to avoid sandblast damage.

Sue Nelson reports for BBC News
"High-speed shooting stars can rip through metal like a bullet"
See also:

02 Dec 98 | The Leonids 98
Into the light storm
19 Nov 98 | The Leonids 98
Hit-and-miss meteor display
19 Nov 98 | The Leonids 98
Picture gallery: Celestial fireworks
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