03/16/2004: 
Technologica
It's Oort there . . . mystery of Sedna grows
from The Australian
IT'S red, round and out there. But the identity of the most distant object ever seen orbiting the Sun has astronomers baffled.
"There's absolutely nothing else like it known in the solar system," said astronomer Michael Brown, leader of the US team that discovered the mysterious world, which is three times further from the Earth than Pluto.
The distant body, reported in The Australian on Monday, is so weird it may even be a new class of astronomical object, says Michael Ashley of the University of NSW.
"It could be the first discovery of thousands of these things," Associate Professor Ashley said of the body, provisionally named Sedna for the Inuit ocean goddess.
Sedna's discovery was formally announced yesterday at the California Institute of Technology in Pasadena. Caltech's Associate Professor Brown said one thing was certain – Sedna was too small to be a planet. At a mere 1100km across, Sedna is smaller than Pluto. And at 1413km in diameter, Pluto is the tiniest member of our solar system.
Pluto's status as a planet has been hotly debated since 1992, when Brian Marsden, head of the International Astronomical Union's Minor Planet Centre, suggested it was wrongly classified.
He said Pluto was just one of thousands of rocky objects orbiting at the fringe of the solar system in a region called the Kuiper Belt, about 7 billion kilometres from Earth.
Professor Brown said Sedna's 10,500-year-long elliptical orbit took it into an even more distant, and hypothetical, territory called the Oort cloud.
What's more, Sedna may have a moon – illustrating Professor Ashley's point that the solar system "may be a much more interesting place than we thought".
Professor Brown and his colleagues at the Gemini Observatory in Hawaii and Yale University hope to look for the Sedna moon, using NASA's Hubble space telescope.
