Once in a lifetime meteor shower in September to shed light on dangerous comets

A rare meteor shower predicted to hit Earth on September 1 would provide astronomers the opportunity to study an ancient comets crust.

London, Aug 9 : A rare meteor shower predicted to hit Earth on September 1 would provide astronomers the opportunity to study an ancient comet's crust.

Astronomers say it could also help them develop a warning system against an otherwise insidious threat - a comet aimed at Earth from the dark fringes of the solar system.

September's shower, called the alpha Aurigids, has only been seen three times before, in 1935, 1986 and 1994. The reason for this elusiveness is the shower's unusual origin.

The Aurigids comes from a comet that takes 2000 years to orbit the Sun. With such infrequent visits, Comet Kiess can't build up a broad dust band, and only generates a narrow trail of debris each time.

"It is only a very narrow trail, and it is only once in a while that it crosses Earth's path," said Peter Jenniskens of NASA's Ames Research Center in Moffett Field, California, US.

Jenniskens is of the opinion that the gravity of Jupiter and Saturn control the path of the dust trail, waving it around like a garden hose, occasionally aiming it at Earth.

Along with his colleague J�r�mie Vaubaillon at Caltech, US, Jenniskens has calculated that the hose should be pointed at us again this year.

Now, on September 1, several teams of astronomers will be watching the shower, both from the ground and from two aircraft following the Earth's shadow.

Researches hope to see fragments of the ancient crust of Comet Kiess.

According to a report in New Scientist, for 4.5 billion years Kiess was drifting among a vast swarm of icy bodies called the Oort cloud lying far beyond the planets, before some gravitational accident nudged it towards the inner solar system.

All that time, high-energy particles called cosmic rays bombarded the comet. stronomers now suspect it created a hard crust by blasting out some of its more volatile substances.

Incidentally, only once before, have astronomers knowingly seen a shower from a long-period comet.

Alpha Monocerotids penetrated unusually far into the atmosphere, suggesting that they were made of relatively tough material, perhaps from such a cosmic-ray-produced crust.

This time, though, astronomers will be looking at the spectral signature of evaporating meteors to test this theory, the magazine reported.

"Now we are better prepared, we can do more in-depth studies to understand the properties of the material," said Jenniskens.

Jenniskens said the best view of the meteors will be from the west coast of North America, before dawn on September 1.

"Based on past showers, there should be up to 200 bright meteors visible per hour, and they may have an unusual blue-green colour. The shower probably won't return for at least 50 years. It's a once in a lifetime event," he said.

Jenniskens further said the meteor shower could also forewarn planetary peril.

At present, astronomers can only spot a long-period comet a few years before it arrives in the inner solar system, leaving little time to deflect it if it were pointed right at Earth.

But if it has visited the inner solar system before, the resulting meteor shower might be used to trace the comet's orbit and get a much earlier warning. The size and number of Aurigid meteors will tell the researchers how debris has spread along the orbit and how these showers evolve, Jenniskens said.

ANI