Asteroid
'On Collision Course'
An
Asteroid Could Devastate Earth
By
Dr David Whitehouse
BBC News Online science editor
An asteroid discovered just weeks ago has become the most
threatening object yet detected in space. A preliminary
orbit suggests that 2002 NT7 is on an impact course with
Earth and could strike the planet on 1 February, 2019
- although the uncertainties are large.
Astronomers
have given the object a rating on the so-called Palermo
technical scale of threat of 0.06, making NT7 the first
object to be given a positive value.
From
its brightness, astronomers estimate it is about two kilometres
wide, large enough to cause continent-wide devastation
on Earth.
Many
observations
Although
astronomers say the object definitely merits attention,
they expect more observations to show it is not on an
Earth-intersecting trajectory.
This
asteroid has now become the most threatening object in
the short history of asteroid detection
Dr
Benny Peiser It was first seen on the night of 5 July,
picked up by the Linear Observatory's automated sky survey
programme in New Mexico, US.
Since
then astronomers worldwide have been paying close attention
to it, amassing almost 200 observations in a few weeks.
Could
it be deflected? Dr Benny Peiser, of Liverpool John Moores
University in the UK, told BBC News Online that "this
asteroid has now become the most threatening object in
the short history of asteroid detection".
NT7
circles the Sun every 837 days and travels in a tilted
orbit from about the distance of Mars to just within the
Earth's orbit.
Potential
devastation
Detailed
calculations of NT7's orbit suggest many occasions when
its projected path through space intersects the Earth's
orbit.
Researchers
estimate that on 1 February, 2019, its impact velocity
on the Earth would be 28 km a second - enough to wipe
out a continent and cause global climate changes.
However,
Dr Peiser was keen to point out that future observations
could change the situation.
He
said: "This unique event should not diminish the
fact that additional observations in coming weeks will
almost certainly - we hope - eliminate the current threat."
Easily
observable
According
to astronomers, NT7 will be easily observable for the
next 18 months or so, meaning there is no risk of losing
the object.
Observations
made over that period - and the fact that NT7 is bright
enough that it is bound to show up in old photographs
- mean that scientists will soon have a very precise orbit
for the object.
Dr
Donald Yeomans, of the US space agency's (Nasa) Jet Propulsion
Laboratory in California, told BBC News Online: "The
orbit of this object is rather highly inclined to the
Earth's orbit so it has been missed because until recently
observers were not looking for such objects in that region
of space."
Regarding
the possibility of an impact, Dr Yeomans said the uncertainties
were large.
"The
error in our knowledge of where NT7 will be on 1 February,
2019, is large, several tens of millions of kilometres,"
he said.
Dr
Yeomans said the world would have to get used to finding
more objects like NT7 that, on discovery, look threatening,
but then become harmless.
"This
is because the problem of Near-Earth Objects is now being
properly addressed," he said.
Source:
http://news.bbc.co.uk/go/em/fr//2/hi/science/
nature/2147879.stm
