That Amazing Tenth Planet; Or Is It The Eleventh?

By James Donahue

August 2005

The world of astronomy has become somewhat active of late. With all of the powerful new technology allowing the star gazers to capture glimpses of our universe in more minute detail, they are seeing things we never dreamed were out there.

Within the last year they have discovered two additional bodies or globes circling our sun that exist beyond Pluto. The most recent one, so far named 2003 UB31 3, is an estimated 2,100 miles wide which makes it about one and a half times the diameter of Pluto.

It roams about three times as far from the Sun as does Pluto, making it a big surprise. Astronomers say that distance puts it right in the heart of the Kuiper Belt, a dark realm beyond Neptune where thousands of small particles orbit the sun.

Because of its sheer size, larger than one of the nine named planets, Dr. Mike Brown at the California Institute of Technology says he believes it has to be classified as a planet and eventually given a name.

Brown was among the astronomers that discovered the object using the Samuel Oschin Telescope at Palomar Observatory near San Diego.

It was discovered in 2003 but the information was kept secret until recently when a hacker got into the institute’s computer and forced an early announcement. There is still a lot more to learn about this icy ball so far out on the edge of our solar system.

Also discovered in 2003 was a smaller space body, also beyond Pluto which was given the name Sedna for an Alaskan Inuit ocean goddess. It is only 1,100 miles wide, which makes it smaller than Pluto, so there was a debate over whether to classify it as a planet.

Brian Marsden, head of the International Astronomical Union’s Minor Planet Center, has stated that he believes all of these objects, including Pluto, are among thousands of rocky particles of space debris orbiting at the fringe of the solar system in the Kuiper Belt. If he is correct, the Kuiper Belt is a very broad area of space and laced with a lot of junk.

It was Brown’s team that also found Sedna. To date, there is a lot more information known about this tiny object than there is about 2003 UB31 3.

Sedna has a 10,500-year-long elliptical orbit around the sun. It is three times farther from Earth than Pluto, or an estimated 21 billion kilometers. Thus it exists in a hypothetical territory known as the Oort cloud, a reservoir of icy comets that may extend as far as the next star.

Also Sedna is red in appearance and shines brighter than astronomers would expect in such a distant part of our solar system. And that in itself is a mystery.