Christmas meteors

On the night between tomorrow and Tuesday the Earth encounters the Geminid meteor stream. As many as a hundred meteors an hour can be observed provided the sky is clear and dark.

The Geminid meteor shower has always been mysterious. The first Geminid meteors appeared suddenly in the mid-1800s, unlike other showers that been observed for hundreds and even thousands of years.

After its 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.

It wasn't until 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 resembles more a rocky asteroid rather 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 on nearing the sun.

The Astronomical Society of Malta invites the public to join its members at L-Ahrax tal-Mellieha near the chapel to watch this event tomorrow from 8.30 p.m. onwards, weather permitting.

The best way to observe these 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 recently commemorated its 20th anniversary. A conference was held describing the work being done by local astronomers and the collaboration with other foreign organisations in various research fields, such as the rotational periods of asteroids, the type of sunspots on the surface of the sun and meteor observations.

The society also took part in the observation of the Venus transit last June along with thousands of people and observatories all over Europe. The need for a national observatory, considering the good climate and geographical position of Malta, was also discussed.

The Astronomical Society of Malta's Website is: www.maltastro.org.