[meteorite-list] 1998 WW31 Is Revealed As Two In The Distant Kuiper Belt

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 09:50:27 2004
Message-ID: <200204172102.OAA24136_at_zagami.jpl.nasa.gov>

http://www.nature.com/nsu/020415/020415-8.html

Rocks twirl in remote two-step

One lump of rock is revealed as two in the distant Kuiper belt.

PHILIP BALL
Nature Science News
18 April 2002

The stand-offish dance of two asteroids at the outer reaches of
the Solar System is captivating astronomers. The two rocky
objects, discovered locked in mutual orbit, could tell us about
the properties of the far-flung Kuiper belt.

Christian Veillet and his team[1] studied an object called
1998 WW31 in the Kuiper belt, a sparsely populated region of space
beyond the orbit of Neptune. The object was previously thought to
be a single rock.

One is in fact two, the team found, using images obtained by the
Canada-France-Hawaii Telescope in Hawaii. And the pair follow an
unusual elongated, ellipse-shaped orbit which keeps them 20-40,000
km apart. This is considered a very distant partnership for a
'binary object'.

The circling pair, which complete a rotation every 570 days, might
offer some vital clues to the composition of rocks in the Kuiper
belt. Its extreme distance makes resident objects difficult to study.

If one of the circling bodies eclipses the other, the pair's size
could be estimated and hence their density. Understanding the
composition of material in the Kuiper belt - which is thought to
contain rubble left over from planet formation - might help to
discriminate between different explanations for the formation of
the Solar System.

Kuiper-belt binaries are hard to spot, because two small bodies can
appear as a single fuzzy blob of reflected sunlight at such long
distances. Even if two spots are seen, several images are needed to
rule out the possibility that they are two adjacent stars along our
line of sight. Veillet and his team carried out such careful analyses
before they could confidently claim that 1998 WW31 is indeed a binary.

The elliptical orbit is very different from that of the best known
partnership in the Kuiper belt: the outermost planet Pluto and its
moon Charon. The binary systems known in the asteroid belt between
Mars and Jupiter also stick closer together than 1998 WW31.

The new discovery challenges existing theories of how two
asteroid-like bodies can become bound together by their gravitational
pull. Researchers are not yet clear why the two rocks have not been
ripped apart by interactions with other bodies in the Kuiper belt.

References

    1. Veillet, C. et al The binary Kuiper-belt object 1998 WW31. Nature, 416, 711 -
      713, (2002).
Received on Wed 17 Apr 2002 05:02:55 PM PDT