Scientists revise asteroid warning
4th Nov 2000
By BBC News Online
science editor Dr David Whitehouse
Astronomers say reports that the Earth could be struck
by a small asteroid in 2030 are wildly exaggerated. Less than a day
after sounding the alert about asteroid 2000SG344, a revised analysis
of the space rock's orbit shows it will in fact miss the Earth by about
five million kilometres (three million miles). However, astronomers
will continue to monitor the asteroid, which was picked up in September
and thought to be 30 - 70 metres (100-230 feet) across. Some scientists
have criticised the way the information was released to the media before
it had been thoroughly confirmed.
Asteroid 2000SG344 is the first object to have a threat
rating of greater
than zero on the 0-10 Torino scale of dangerous objects from space.
It was spotted on 29 September by astronomers David Tholen and Robert
Whiteley using the Canada-France-Hawaii 3.6-metre telescope on the island
of Hawaii. Shortly thereafter, pre-discovery observations taken in May
1999 by the Linear sky survey were also identified. On Friday, the International
Astronomical Union issued an alert saying that the object had about
a 1-in-500 chance of striking the Earth on 21 September, 2030. No object
has ever been rated with so high a chance of impact.
Were it to strike our planet, the results would be devastating, with
explosion greater than the most powerful nuclear weapon.
Sky survey data
But after the announcement, astronomers began looking
at sky survey data to see if the object had been picked up but not recognised
observations. This turned out to be the case and these past observations
allowed a more accurate calculation of the asteroid's orbit to be made.
The result: in 2030, the space rock will miss us by about five million
kilometres, or 12 times the distance from the Earth to the Moon. The
new orbit reveals a slight risk of a collision with the Earth about
2071, but it is thought that when the orbit is better known this risk
will disappear as well. Currently, asteroid 2000SG344 is about 15 million
kilometres (nine million miles) away and getting more distant.
'Premature and alarmist'
Because 2000SG344 is in a similar orbit to the Earth,
it has been suggested that it might be an old Saturn upper-stage rocket
of the type that was used in the early Apollo Moon missions. If it is
manmade and did strike Earth, the effects would be very local and limited.
Some scientists have criticised the IAU and Nasa for releasing warnings
about the asteroid only for those warnings to be rescinded less than
later. Benny Peiser of Liverpool John Moores University, UK, said it
was "extremely unwise, premature and alarmist."
Mysteries, UFOs, etc.
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