[meteorite-list] Asteroid Shaves Past Earth's Atmosphere (2004 FU162)

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon Aug 23 12:51:29 2004
Message-ID: <200408231650.JAA10190_at_zagami.jpl.nasa.gov>

http://www.newscientist.com/news/news.jsp?id=ns99996307

Asteroid shaves past Earth's atmosphere
Jeff Hecht
New Scientist
August 23, 2004

The closest observed asteroid yet to skim past the Earth without hitting
the atmosphere, was reported by astronomers on Sunday.

The previously unknown object, spanning five to 10 metres across, has
been named 2004 FU162. It streaked across the sky just 6500 kilometres -
roughly the radius of the Earth - above the ground on 31 March, although
details have only now emerged.

The MIT Lincoln Laboratory's asteroid-hunting LINEAR telescope in
Socorro, New Mexico,US, observed the new object four times over a
44-minute period, several hours before its closest approach in March.

Lincoln astronomers, who have discovered over 40,000 asteroids and
comets since 1980, quickly recognised the object came exceptionally
close, and posted their findings for confirmation on a web page run by
the Minor Planet Center at the Harvard-Smithsonian Center for Astrophysics.

However, by the time it was posted the object had moved into the daytime
sky, so follow-up observations were impossible and the listing was
quickly removed. A search for prior observations yielded no results.

Dissipated harmlessly

Despite having only four positions for the object, Steven Chesley of
NASA's Jet Propulsion Laboratory was able to calculate its orbit because
it was moving rapidly across the sky.

He also calculated that the encounter with the Earth shifted the
asteroid's orbit closer towards the Sun. Previously orbiting the Sun
once a year in an orbit that ranged as far inside the Earth's orbit as
outside, 2004 FU162 now has a nine-month orbit centred closer to Venus
than the Earth. The Minor Planet Center published Chesley's results on
Sunday in its electronic circular.

"This was an extraordinarily close encounter and so the orbital change
was quite extraordinary. 2004 FU162 was deflected by about 20 degrees
because of the Earth's gravity. I've never seen anything like that
before," Chesley told New Scientist.

The previous record for the closest asteroid approach to Earth was set
on 18 March by an object called 2004 FH which missed the Earth
by about 40,000 kilometres.

That was a much larger object, around 30 metres in diameter - big enough
to produce a one-megaton explosion in the atmosphere. Although it was
likely to have exploded so high that the energy would have dissipated
harmlessly. The smaller 2004 FU162 would have burned up as a fireball
ending with a smaller explosion, had it ventured into the Earth's
atmosphere.
Received on Mon 23 Aug 2004 12:50:24 PM PDT


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