Huge Mini-World Found in Outer Solar System
By Robert Roy Britt
Senior Science Writer
posted: 12:50 pm ET
19 February 2004
Updated at 5:13 p.m. ET
A newfound hunk of ice and rock beyond Neptune is larger than most and
might contend for the title of the biggest object in the solar system
besides the Sun, planets and moons.
The object is in a region of frozen, comet-like bodies called the Kuiper
Belt. The discovery was announced today by the Minor Planet Center in
Cambridge, Mass.
Preliminary observations suggest the icy rock, labeled 2004 DW, is
520-1,170 miles wide (840 to 1,880 kilometers). Physics dictates that
objects this large be generally round, like mini-worlds.
The largest known Kuiper Belt Object, or KBO, is called Quaoar (KWAH-o-ar)
and was discovered in 2002. Quaoar is roughly 780 miles (1,250 kilometers)
wide, about half as big as Pluto. It orbits the Sun every 288 years,
mostly beyond Pluto's orbit.
More observations will be needed to pin down the size of the newfound KBO.
It may turn out to be much smaller than Quaoar, or it could be bigger.
Researchers estimate the size of these objects by noting their brightness
and making assumptions about how much light they reflect. Those
assumptions assume a certain level of reflectivity for the surface
material.
The discovery was made by Caltech's Mike Brown and colleagues Chad
Trujillo and David Rabinowitz as part of the same survey that found
Quaoar two years ago.
"The object is probably about 1,600 kilometers in diameter, larger than
the 1250-kilometer Quaoar," the researchers said today in a web posting.
"If subsequent measurements verify this size estimate, this would make
2004 DW the largest minor planet known, and larger than Pluto's moon
Charon, which is about 1,300 kilometers in diameter. This still doesn't
beat Pluto, which is about 2,300 kilometers in diameter."
The finding was confirmed with observations by a team based at the
Starkenburg Observatory in Germany and other sightings from the Jet
Propulsion Laboratory's Table Mountain Observatory in southern
California.
"It wasn't moving much, so I knew it was way out there," Table
Mountain's Jim Young told SPACE.com. Researchers measure an object's
movement against the fairly stable background stars to gauge its
distance. "I went home and told my wife, '"That things gotta be big.'"
2004 DW is nearly 47 times as far from the Sun as Earth is.
Scientists expect more large objects to be found in the Kuiper Belt
now that search techniques and technology have been refined. Some
astronomers say it's possible that an object larger than Pluto might
still lurk there unfound.
Editor's Note: An earlier version of this story gave discovery credit
to NASA's Near-Earth Asteroid Tracking Program. That program had sent
the discovery data to the Minor Planet Center but was not directly
involved in the discovery.
http://space.com/scienceastronomy/new_object_040219.html |
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