Monday, November 8, 1999 Published at 11:53 GMT
Surprise meteor shower possible
By BBC News Online Science Editor Dr David Whitehouse
Look towards the northern horizon on the night of 11 November and you might just see a meteor shower that nobody has ever seen before.
Meteors, or shooting stars, are caused by tiny grains of rock and dust lost by comets as they orbit the Sun. As they burn-up in the Earth's atmosphere due to friction, they vanish in a streak of light - a shooting star.
A comet discovered earlier this year has a small chance of producing a meteor shower on Thursday. Comet Linear was discovered by the Lincoln Near-Earth Asteroid Research (Linear) team on 12 May.
Initially identified as an asteroid, astronomers at the Klet Observatory in the Czech Republic then realised it was in fact a comet. During September and October, many astronomers observed Comet Linear brighten to just below naked-eye visibility - a small telescope or a pair of binoculars would be sufficient to pick it up.
Comet Linear may produce a meteor shower because the comet reached its closest point to the Sun on 20 September at a point just inside the Earth's orbit.
The comet is probably a long period one, taking about 63,000 years to orbit the Sun. However, calculations indicate that the comet's closest approach to the Sun, its perihelion, was at a point just 1.7 million km (1.1 million miles) from the Earth's orbit.
This means that the Earth will arrive at this point in space just 40 days later - 11 November.
The exact moment when Earth passes closest to the comet's path is at 1943 GMT on Thursday during evening darkness over Europe and regions to the east of Europe.
If it occurs the radiant, or region of the sky where the meteors will originate, will be in the Big Dipper (the Plough), the famous and prominent part of Ursa Major, the Greater Bear constellation.
Unfortunately, for UK skywatchers, the radiant will be quite low towards the northern horizon at the time that the possible shower may reach its peak.
Although meteor showers are unpredictable astronomers will be keeping an eye on this one just in case it produces some surprises.
A few days later, on 17 November, the chances are much better for a fine meteor shower. On that day, there is a possibility that the Leonids meteor stream may produce a memorable display.