New Planet?
Nasa names new planet after Inuit goddess
By Charles Arthur, Technology Editor
16 March 2004
Nasa announced yesterday that it had discovered a new planet, the first to be found since Pluto in 1930.
There's just one problem: most astronomers don't think it's a planet - and they're pretty sure the new discovery is not going to make it into school textbooks of the future, except as a footnote. Schoolchildren will still learn that there are nine, not 10, planets in the solar system.
The new discovery, named Sedna (after the Inuit goddess who created the sea creatures of the Arctic), presently lies about 100 billion miles away from the Sun, roughly 90 times further away than the Earth. But its eccentric orbit means that sometimes it goes up to 10 times further away still. That takes it far into the "Kuiper Belt", a sort of cosmic debris collection in the outer reaches of the solar system, filled with rocks and ice. Sedna is estimated to be between 800 miles and 1,100 miles across, about three-quarters the size of Pluto, based on the light reflected from its surface detected by telescopes on Earth.
From its surface, the Sun would appear so small that "you could completely block it out with the head of a pin," said Mike Brown, an astronomer at the California Institute of Technology who led the team that found Sedna. The temperature never rises above -200C.
But the disputes about whether Sedna is really a planet began well before the announcement of its discovery last night. "If it's smaller than Pluto then it won't be classed as a planet," said Professor Iwan Williams, president of the International Astronomical Union, which has the final say on the classification of celestial objects. "The fact is that if Pluto was discovered today it wouldn't be called a planet."
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