Saturday, 23 December, 2000, 13:49 GMT
Asteroid misses Earth 'by whisker'

http://news.bbc.co.uk/hi/english/sci/tech/newsid_1084000/1084476.stm

Artist's impression of the asteroid poised above London

An asteroid capable of wiping out a city has missed the Earth by an astronomical whisker.
The 50-yard space rock travelled over London at more than 20 miles per second before missing the planet by just 480,000 miles - twice the distance to the moon but a near miss in astronomical terms.

If it had collided with Earth it would have left a hole three quarters of a mile across.

The asteroid, still visible through a reasonably powerful telescope in the constellation of Ophiuchus, appeared without warning above the capital at 2400GMT on Friday.

Robin Scagell, vice-president of the Society for Popular Astronomy, said astronomers can track kilometre-wide asteroids - but spotting smaller objects is much harder.

"Not long ago something like this would have been totally overlooked," he said.

"Now with the advanced image detectors available today we are beginning to realise that we're in a bit of a shooting gallery."

The asteroid, which has been given the name 2000 YA, is big enough to have devastated London, Mr Scagell added.

"An object this size would leave a crater three quarters of a mile across," he said.

Devastated London

"Imagine that in Piccadilly Circus."

"We've probably been quite lucky up to now.

"There are probably thousands of objects of this size out there."

Professor Duncan Steel, the author of Target Earth - a book about asteroids, told the BBC Radio 4's Today programme: "The last time the Earth was hit by something like this was in 1908 above Siberia.

"It released energy equivalent to about 20 megatonnes of TNT.

Prof Duncan Steel
"If it was to enter the atmosphere above London, it would take out the whole of the city out to the M25."

In September, a government task force established to assess the threat of so-called Near Earth Objects (Neos) called on ministers to seek international partners to build a new £15m telescope dedicated to sweeping the skies for threatening objects.

The three-metre (9.8 feet) survey telescope, based in the Southern Hemisphere, would be designed to detect objects down to a few hundred metres across.

Other recommendations of the official report included the setting up of an asteroid defence centre in Britain and working with the international community on ways to mitigate any future impacts.

The Liberal Democrat MP Lembit Opik, who campaigned for the task force to be set up, called for £70m ($98m) to be spent globally over 10 years on technology to track approaching asteroids.