Sedna

http://www.nasa.gov/images/content/56753main_discovery-500.jpg

What's bigger than an asteroid, smaller than a planet, red all over and far, far away? The answer -- a mysterious planet-like body orbiting our Sun -- has been discovered by NASA-funded researchers led by an astronomer at the California Institute of Technology, Pasadena, Calif.

The object is three times farther away from Earth than Pluto, making it the most distant known in the solar system.

"The Sun appears so small from that distance that you could completely block it out with the head of a pin," said Dr. Mike Brown, Caltech associate professor of planetary astronomy and leader of the research team. The object, unofficially named "Sedna," is 13 billion kilometers (8 billion miles) away from Earth.

Other notable features of Sedna include its size and reddish color; it is the second reddest object in the solar system, after Mars. At an estimated size of three-fourths the size of Pluto, it is likely the largest object found in the solar system since Pluto was discovered in 1930.

Sedna lies extremely far from the Sun, in the coldest known region of our solar system, where the temperature never rises above minus 240 degrees Celsius (minus 400 Fahrenheit).

The planetoid is usually even colder, because it approaches the Sun this closely only briefly during its 10,500 year orbit around the Sun. At its most distant, "Sedna" is 130 billion kilometers (84 billion miles) from the Sun. That is 900 times Earth's distance from the Sun.

http://www.nasa.gov/images/content/56755main_sedna-comp-330-264.jpg

http://www.nasa.gov/vision/universe/solarsystem/planet_like_body.html