FWD: Ice Planet extends our Solar System

Rohit Khare (khare@w3.org)
Fri, 6 Jun 1997 13:51:02 -0400 (EDT)

Icy miniplanet found in farthest reaches of solar system

Copyright =A9 1997 Nando.net
Copyright =A9 1997 The Associated Press

NEW YORK (June 4, 1997 2:25 p.m. EDT) -- Astronomers have found an icy
miniplanet that orbits the sun well beyond Pluto, providing evidence
that the solar system extends much farther than was once thought.

The little planet is about 300 miles across, which gives it a surface
area comparable to Texas. It is the brightest solar system object to be
found beyond Neptune since the discovery of Pluto's moon Charon in 1978.

At its most distant, it wanders three times farther from the sun than
Pluto, tracing a looping, oblong path into an astronomical terra

"It's the first object in a sort of no man's land, an area we never
thought we could get a glimpse of with our current technology," said
Jane Luu, an astronomer at the Harvard-Smithsonian Center for
Astrophysics in Cambridge, Mass.

And it's probably not alone. Theoretical calculations suggest that there
are millions of small, icy solar system objects well beyond the
outermost planets.

Astronomers consider their new discovery an extension of the Kuiper
belt, a collection of small, icy bodies that circle the sun beyond the
orbit of Neptune. About 40 Kuiper belt objects have been discovered
since 1992.

Before then, the only known Kuiper belt objects were the planet Pluto,
discovered in 1930, and Charon.

Luu discovered the new object, known as 1996TL66, with colleagues from
Harvard, the University of Hawaii and the University of Arizona, as well
as an amateur astronomer based in Cloudcroft, N.M. They describe the
find in Thursday's issue of the journal Nature.

"I wouldn't call this a major planet," said Brian Marsden, a Harvard
astronomer and contributer to the Nature paper. "But then I tend not to
call Pluto a major planet."

In fact, 1996TL66 is considered too minor to be named for a Roman god,
like the other planets.

Astronomers surmise that it is composed of the same material as other
outer solar system objects -- water, carbon dioxide, methane and other
materials -- all frozen solid.

The astronomers found 1996TL66 with a University of Hawaii telescope as
the object passed among the outer planets last October. They and others
followed it for several months with telescopes in Hawaii, Arizona and
New Mexico.

The object's motion over the last few months shows that it follows a
lopsided orbit unlike that of any other Kuiper belt object. It swings
through the neighborhood of the outermost planets every 800 years, then
loops far out into space before making its next pass.

Astronomers have never seen such a thing.

"It just reminds us that we really don't know what the outer solar
system holds," Luu said.

Some researchers had an inkling that the object would be out there,
however. Hal Levison, a scientist at the Southwest Research Institute in
Boulder, Colo., has been telling his colleagues for the past year that
objects such as 1996TL66 ought to exist.

The research behind that prediction, conducted with Martin Duncan of
Queen's University in Canada, is scheduled for publication in a future
issue of the journal Science.

"Though we knew that we had an interesting scientific result, it just
never occurred to me that anybody would find one," Levison said. "It's
very satisfying when someone confirms your theories."

In his Science paper, Levison describes how Uranus and Neptune probably
generated the Kuiper Belt during the formation of the solar system more
than 4 billion years ago. According to that theory, Neptune kicked a
small percentage of the Kuiper belt objects into oblong orbits such as
the one followed by 1996TL66.

Luu and her colleagues found the object at the very beginning of a
systematic search for objects at the edge of the solar system. Because
it was so easy to find, the researchers calculate that there are
hundreds, and perhaps more than 1,000, objects similar to 1996TL66.

"Unless we are improbably lucky, it is merely the first detected of a
larger population of similar bodies," the astronomers wrote.

By MATT CRENSON, The Associated Press