It will either be the greatest show on earth or yet another dull experience standing out in the cold and dark. That's the way it goes when the Leonid meteor showers come to town.
Each November the earth's orbit takes us through the dusty waste left behind by the passing TempelTuttle comet. Being an inveterate cosmic litterbug, the comet loses dust and small bits which burn up as they get swept into the upper atmosphere. The results for viewers on the earth are shooting stars, those bright specks of light that trace a short-lived streak across the night sky.
The Leonids are so named because they appear in the sky near the constellation Leo. The showers are expected to reach peak for us just before dawn tomorrow and Saturday.
There is always rubbish out there getting burnt up in the atmosphere, and at any time of year you might see a few shooting stars an hour. Even in a bad year with few meteors the Leonids will deliver at least 10 an hour, but in a good year this figure jumps to hundreds per hour, with the chance of the odd fireball.
The displays can be better still if Tempel-Tuttle has passed recently, as it orbits the sun in its long 33year elliptical orbit. In fact the comet passed through the inner solar system in 1998, increasing the possibility of a good show.
If we happen to pass through one of the "clumps" of material given off by the comet, the meteor rate can climb past 1,000 per hour, a level that classes it as a meteor storm.
Good Leonid showers are a rare occurrence but provide a real spectacle, as they did in 1966, for example. It is a very iffy business however and astronomers are shy about promising a good show, particularly after expectations of a lively shower in 1998 delivered very little.
There are other factors working against a good display, most notably our cloudy skies. If the weather doesn't co-operate then forget about seeing anything. There is also a large bright spot obscuring the view if the night is clear - a half-moon - which will serve to wash out the light given off by the shooting stars.
The best way to view the Leonids is to sit in a comfortable chair, use either a building or tree to block out your view of the moon and then watch for the meteors' tell-tale streaks. Try to get a view that opens up the largest piece of sky possible. If the weather doesn't hold tomorrow, give it a try early Saturday morning.
Studies of particles arriving during last year's Leonid meteor showers indicate that complex organic chemicals associated with life could have penetrated the earth's atmosphere and survived intact. Reports in the journal Earth, Moon and Planets suggests that much of the organic material left in the wake of comets could reach the earth's surface despite a fiery entry.
The fingerprint of complex organic matter identical to spaceborne cometary dust was discovered in the path of a bright Leonid fireball, the researchers say. Another team also found that the incoming meteor doesn't get as hot as was thought, increasing the chance that comets could now, and probably have in the past, sprinkled the planet with substances associated with life.