[meteorite-list] Hunt For Shadowy Kuiper Belt Objects All Set

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Nov 4 18:27:02 2004
Message-ID: <200411042327.PAA27472_at_zagami.jpl.nasa.gov>

http://www.newscientist.com/news/news.jsp?id=ns99996621

Hunt for shadowy Kuiper belt objects all set
Maggie McKee
New Scientist
November 4, 2004
 
An ambitious hunt for small, faint objects in the outer solar system is set
to begin in the next few weeks. The project could shed light on the
shadowy region and reveal the forces that shaped the early solar system.

The project will target the Kuiper Belt, a ring of objects beyond
Neptune left over from the formation of the planets about 4.5 billion
years ago. Most of the 1000 Kuiper Belt Objects (KBOs) discovered since
1992 orbit the Sun at a distance 30 to 50 times further than the Earth.

Based on their brightness, they appear to range from 100 to 1000
kilometres in width. Astronomers expect to see many more KBOs of smaller
size - which probably formed through collisions - but these are
difficult to detect because they reflect so little light. Only the
Hubble Space Telescope has managed to turn up any - a few objects tens
of kilometres wide.

"Progress in this area is achingly slow," says Charles Alcock, director
of the Harvard-Smithsonian Center for Astrophysics in Cambridge,
Massachusetts, US. "Most of the volume of the solar system is
inaccessible to direct surveys."

So, he and an international team of astronomers have devised an
alternative scheme to search for small KBOs. Their plan is to look not
for the objects' reflected light but for their shadows. They will use
four 50-centimetre telescopes in Taiwan to study 3000 stars
simultaneously in the hopes that one will be dimmed by the passing of an
intervening small KBO.

Perfectly aligned

This method could detect objects as small as 3 km across at distances of
100 astronomical units - one AU being the distance between the Earth and
the Sun, about 150 million km. But a KBO transit event would last less
than a second, and any detection would be dependent on the star, KBO,
and telescopes being perfectly aligned.

"It's like the shadow of a cloud - you have to be in the right place to
see it," explains Lawrence Wasserman, an astronomer at Lowell
Observatory in Flagstaff, Arizona, US and a member of another survey
team that has found about half of all known KBOs.

Alcock acknowledges that the project, called the Taiwanese American
Occultation Survey (TAOS), is likely to turn up just 10 events per year
- what he calls a "painfully low rate". And he says the automated
observation programme is vulnerable to false positives from, among other
things, birds and aircraft. "It's an act of desperation," he admits.
"One should only turn to this technique when other techniques are not
going to work."

Ground into dust

But astronomers say the project, which will start observations later in
November, will nevertheless reveal interesting science even if it does
not turn up any occultations. "If nothing happens, then we'll know there
are fewer objects than we thought," Wasserman told New Scientist.

That could mean most small KBOs have already been ground into dust by
collisions, he says. "The question is, what is the relationship between
the Kuiper Belt and the dust rings we see around other stars?"

The Kuiper Belt should also hold clues to how the solar system formed,
because its shape and size must have been determined by these processes.
"But first we've got to understand what the Kuiper Belt is now," says
Wasserman.
Received on Thu 04 Nov 2004 06:27:00 PM PST