Comet Collision 'Armageddon' Unlikely

Sep 12, 2005

The chances of the Earth being hit by a comet from beyond Pluto - a la Armageddon - are much lower than previously thought, according to new research by an ANU astronomer.

Using computer simulations and data from an American military telescope, Dr Paul Francis, from the ANU Research School of Astronomy and Astrophysics at Mt Stromlo, has found there are seven times fewer comets in our solar system than previously thought.

"I calculate that small comets, capable of destroying a city, only hit the Earth once every 40 million years or so," Dr Francis said.

"Big continent-busting comets, as shown in the movies Armageddon and Deep Impact, are rarer still, only hitting once every 150 million years or so. So I don't loose sleep over it, but you're still more likely to be killed by a comet than to win the jackpot at Lotto."

Previous estimates of the number of comets were based on the work of amateur astronomers, who for hundreds of years have been scanning the skies, looking for new comets.

Previously, it was believed that these amateur astronomers were only spotting three per cent of the comets passing close to the Earth: the rest were thought to be missed because they were in the wrong part of the sky or were too faint.

But Dr Francis found that the amateurs were doing better than anyone had realised - they were actually spotting 20 per cent of comets. There are therefore far fewer undiscovered comets.

"The new data allowed us to count the number of faint and far-away comets that the amateurs had missed. And we found that they were pretty rare," Dr Francis said.

These results apply to comets coming from beyond the orbit of Pluto, which is where most comets live. The Earth is still at risk of being hit by asteroids, and by so-called short-period comets - ones that come past repeatedly, like Halley's comet.

"But asteroids and short-period comets come past again and again, so if we're clever enough we can find them all and predict which, if any, will hit the Earth," said Dr Francis. "If we find one on a collision course with the Earth, we would normally have hundreds of years warning in which to do something about it, like deflecting the asteroid.

"The comets coming from beyond Pluto, so called long-period comets, are nastier, as they are totally unpredictable, and if we see one on a collision course we'd have at best one or two years warning - not long enough to do anything."

Dr Francis' research has been accepted for publication in the Astrophysical Journal. It was based on computer simulations, published data from the Lincoln Near Earth Asteroid Research Project at White Sands Missile Range in New Mexico, and on data from amateur astronomers around the world.

Copyright 2005 by Space Daily, Distributed United Press International

Explore further: Staying warm: The hot gas in clusters of galaxies

add to favorites email to friend print save as pdf

Related Stories

New study finds oceans arrived early to Earth

Oct 30, 2014

Earth is known as the Blue Planet because of its oceans, which cover more than 70 percent of the planet's surface and are home to the world's greatest diversity of life. While water is essential for life ...

Astronomy team discovers nearby dwarf galaxy

Feb 08, 2012

(PhysOrg.com) -- A team led by UCLA research astronomer Michael Rich has used a unique telescope to discover a previously unknown companion to the nearby galaxy NGC 4449, which is some 12.5 million light years ...

Recommended for you

Orion on track at T MINUS 1 Week to first blastoff

5 hours ago

At T MINUS 1 Week on this Thanksgiving Holiday, all launch processing events remain on track for the first blast off of NASA's new Orion crew vehicle on Dec. 4, 2014 which marks the first step on the long ...

Staying warm: The hot gas in clusters of galaxies

7 hours ago

Most galaxies lie in clusters, groupings of a few to many thousands of galaxies. Our Milky Way galaxy itself is a member of the "Local Group," a band of about fifty galaxies whose other large member is the ...

Bad weather delays Japan asteroid probe lift off

11 hours ago

Bad weather will delay the launch of a Japanese space probe on a six-year mission to mine a distant asteroid, just weeks after a European spacecraft's historic landing on a comet captivated the world.

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.