- It's red, round and out there. But the identity of the
most distant object ever seen orbiting the Sun has astronomers baffled.
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- "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.
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- 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.
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- "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.
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- 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 ñ Sedna was too small
to be a planet. At a mere 1100 miles across, Sedna is smaller than Pluto.
And at 1413 miles in diameter, Pluto is the tiniest member of our solar
system.
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- 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.
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- 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.
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- 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.
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- What's more, Sedna may have a moon ñ illustrating
Professor Ashley's point that the solar system "may be a much more
interesting place than we thought".
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- 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.
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