[meteorite-list] Now if they can just help find my keys...

From: Darren Garrison <cynapse_at_meteoritecentral.com>
Date: Fri, 05 Oct 2007 15:59:23 -0400
Message-ID: <8o5dg39asjj2epv547k5g17aitmm2mcj2g_at_4ax.com>

http://in.news.yahoo.com/071005/139/6ll7d.html

Long-lost 'Potentially Hazardous Asteroid' re-located

By ANI
Friday October 5, 04:16 PM
Washington, Oct 5 (ANI): Astronomers have found that the recently discovered
Earth threatening asteroid 2007 RR9 is in fact the long lost object 6344 P-L
observed nearly half a century ago.

Astronomers at the Minor Planet Center of the Smithsonian Astrophysical
Observatory in Cambridge, MA have confirmed work by SETI Institute astronomer
Peter Jenniskens that the recently discovered asteroid 2007 RR9 is in fact the
long lost 6344 P-L.

The object was last seen in 1960, and ever since has had the peculiar
distinction of being the only Potentially Hazardous Asteroid (PHA) without a
formal designation.

"The object was long recognized to be dangerous, but we didn't know where it
was. Now it is no longer just out there," said Jenniskens.

A designation as Potentially Hazardous means that 2007 RR9 is one of the 886,
and not 887 known asteroids bigger than 150 m (500 ft) in diameter, which come
to within 0.05 astronomical units of Earth's orbit (roughly 7,480,000 km or
4,650,000 miles).

The size is estimated on the basis of the object's observed brightness and an
assumed reflectance of 13 percent.

Jenniskens said the object might not be even an asteroid.

"This is a now-dormant comet nucleus, a fragment of a bigger object that, after
breaking up in the not-so-distant past, may have caused the gamma Piscid shower
of slow meteors (IAU #236) that is active in mid-October and early November,"
Jenniskens said.

"2007 RR9 moves in a 4.70-year orbit, nearly all the way out to the distance of
Jupiter, and because of this elongated orbit, it has a Tisserand parameter of T
= 2.94, which defines it dynamically as a Jupiter Family Comet (T = 2.0 - 3.0),
not an asteroid (T > 3.0).

"So far, this object has not yet been seen to be even weakly active, but the now
dormant comet is still moving closer to the Sun. It is sliding rapidly toward
visibility in the southern hemisphere, and is expected to brighten to magnitude
+18.5 in mid-October," he said.

Gareth V. Williams of the Minor Planet Center said 2007 RR9 would pass Earth
around November 6 at 0.07 AU, when the minor planet is at high latitudes in
southern skies.

The original designation of P-L stands for "Palomar-Leiden," the juxtaposition
of two observatory names that reflect what was a very fruitful collaboration by
the trio of pioneer asteroid searchers Tom Gehrels of the University of Arizona,
and Ingrid van Houten-Groeneveld and her husband Cornelis Johannes van Houten of
the Netherlands.

Gehrels made a sky survey using the 48-inch Schmidt Telescope at the famed
Palomar Observatory, long before modern asteroid reconnaissance, and shipped the
photographic plates to the van Houtens at Leiden Observatory in the Netherlands.

There, Ingrid discovered 6344 P-L on four plates taken on September 24-28, 1960.

The trio are jointly credited with several thousand asteroid discoveries, but
only 6344 P-L is potentially dangerous to Earth. (ANI)
Received on Fri 05 Oct 2007 03:59:23 PM PDT