[meteorite-list] Large Solar System Body Since Pluto Spotted
From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:31:24 2004
Largest Solar System body spotted since Pluto
February 20, 2004
The largest object to be discovered in the Solar System since Pluto was
found in 1930 was spotted by a sky survey on Tuesday.
News of the hulking object leaked out on Thursday before the researchers
at Caltech could pin down the giant's size and orbit.
Tentatively called 2004 DW, the object lies beyond Neptune in the
mysterious Kuiper Belt. This shadowy belt is a collection of primordial icy
bodies which circle our Sun and are thought to be the remnants of
Only Pluto and its moon Charon are clearly brighter than 2004 DW, but
both have icy surfaces that reflect roughly half the incident sunlight.
Typical large Kuiper Belt objects reflect only about nine percent of incident
light, says Chad Trujillo of the Gemini Observatory, who works on the
Caltech survey. Using that number, he estimates 2004 DW is 1650
kilometres in diameter - second only to Pluto at 2320 kilometres.
Brightness and distance
Several hundred Kuiper Belt objects larger than 100 kilometres have been
spotted since David Jewitt of the University of Hawaii discovered the first
in 1992, and Jewitt believes at least 70,000 exist which are larger than
100 kilometres. Larger objects are more rare, but their distribution may
illuminate their origins, and their brightness will make them easier to
study than smaller ones.
Jewitt calls the new discovery "a very nice object."
The largest previously known Kuiper Belt object - christened
Quaoar - was discovered by Tujillo, Mike Brown of Caltech and
David Rabinowitz of Yale in 2002. At 1250 kilometres Quaoar is only
slightly smaller than the 1270-kilometre Charon.
Their measurements indicate Quaoar reflects nine percent of
incident light. The group planned to study 2004 DW in detail before
announcing their discovery, as they had with Quaoar, but their
observation was posted by mistake on the website of the
Minor Planet Center at the Harvard-Smithsonian Center for
Astrophysics. Two other groups saw their report and confirmed the
finding on Wednesday.
With only two days of observations, most details remain
uncertain. The new object "is likely to be significantly larger than
Quaoar judging on its brightness and distance, but until we can
specifically measure its size, we cannot say for sure," Trujillo told New
The new discovery "tells us that there's lots more work to be done on the
Kuiper Belt, because we remain only dimly aware of even some of the
largest bodies there," says Jewitt.
Received on Fri 20 Feb 2004 11:54:32 AM PST