Earth encounters the Geminid meteor stream tonight.

The Astronomical Society of Malta said that as many as 100 meteors an hour can be observed, provided the sky is clear and dark.

The first Geminid meteors appeared suddenly in the mid-1800 unlike other showers that been observed for hundreds and even thousands of years.

After this discovery, astronomers started looking for a possible comet normally associated with a meteor shower. As a comet approaches the sun, debris from its nucleus boils off and orbits the sun along with the comet forming an elongated stream of meteoroids that we see as shooting stars when hit by the earth's atmosphere.

The society said that it was only in 1983 that Nasa's infrared astronomical satellite discovered a curious object moving in the same orbit as the Geminid meteor stream. This object, named 3200 Phaethon, orbits the sun every 1.4 years and, surprisingly, it resembles more a rocky asteroid than a comet.

From studies of the densities of observed fireballs (large meteors), it seems that Phaethon is actually an extinct comet covered by a blanket of interstellar dust grains that are released upon nearing the sun.

The society is inviting the public to join its members at L- Ahrax tal-Mellieha, near the chapel, to watch the event, from 8.30 p.m. onwards, weather permitting. The best way to observe the meteors is with the naked eye as binoculars or telescopes restrict the field of view. The ringed planet Saturn will also be visible at this time of year and telescopes will be set up for its observation. Warm clothing is essential.

The Astronomical Society has just marked 20 years since its founding in 1984.

www.maltastro.org