SCIENCE NEWS
March 15, 2004
A Frozen World
A cold planet-like object is discovered 8 billion miles from Earth
 An artist shows how a moon (far) may orbit Sedna (near). |
Scientists have just announced the discovery of the largest object in the solar system since Pluto was discovered in 1930. Made of ice and rock, the red planet-like object is a bit smaller than Pluto and three times farther away. It was discovered in November using NASA's new space telescope, Spitzer.
Introducing Sedna
Astronomers named the "planetoid" Sedna, after an Inuit goddess who created sea creatures of the Arctic. (The Inuits are people who live in the Arctic from northern Alaska to eastern Greenland.) Sedna is the farthest and coldest object known to orbit, or circle, the sun.
 |  An artist shows Sedna in relation to other bodies in the solar system, including Earth and its Moon; Pluto; and Quaoar. |
A Cold and Distant Object
The temperature on Sedna never rises above minus 400 degrees Fahrenheit! That makes it the coldest known body in the solar system. It is between 800 miles and 1,100 miles in diameter. Sedna is more than 8 billion miles from the sun. Traveling to Sedna would be like traveling from New York to Chicago 10,854,816 times!
What would the sun look like from Sedna? "The sun appears so small from that distance that you could completely block it out with the head of a pin," said Mike Brown, the scientist at the California Institute of Technology who led the research team.
Scientists are calling Sedna an "object" because they are not sure what to call it. Its discovery has sparked a conversation about what defines a planet. Some think that Sedna may be large enough to be called the tenth planet. Others think that it is just one of many objects in the outer reaches of the solar system.
