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According to the discoverers from the California Institute of Technology and Yale University (Caltech) the planetoid was found as part of the same search program that discovered Quaoar in late 2002. 2004 DW and Quaoar reside within a disk of comets known as the Kuiper belt. This area lies along the plane of the solar system some 7 billion kilometres away.
The astronomers used the 48-inch Samuel Oschin Telescope at Palomar Observatory, Claifornia, and the recently installed QUEST camera built by a consortium including Yale and the University of Indiana, to systematically study different regions of the sky each night.
Unlike Quaoar, the new planetoid hasn't yet been pinpointed on old photographic plates or other images. Because its orbit is not fully understood, it cannot be given an official name. "So far we only have a one-day orbit," said Caltech Professor of planetary astronomy Mike Brown, explaining that the data covers only a tiny fraction of the orbit the objects predicted 300-year trip around the sun. "currently we know only how far away it is and how its orbit is tilted relative to the planets."
The measured tilt is an astonishingly large 20 degrees, larger even than that of Pluto, which has an orbital inclination of 17 degrees and is an anomaly among the otherwise planar planets. The size of 2004 DW is not yet certain; Brown estimates a size of about 1,400 kilometres, based on a comparison of the planetoid's luminosity with that of Quaoar. Because the distance of the object can already be calculated, its luminosity should be a good indicator of its size relative to Quaoar, provided the two objects have the same albedo, or reflectivity.
According to Brown, scientists know little about the albedos of objects this large this far away, so the true size is quite uncertain. Researchers could best make size measurements with the Hubble Space Telescope or the newer Spitzer Space Telescope.
The continued discovery of massive planetoids on the outer fringe of the solar system is further evidence that objects even farther and even larger are lurking out there. "It's now only a matter of time before something is going to be discovered out there that will change our entire view of the outer solar system," Brown says.
More info: Caltech
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