The tenth planet a/k/a 2003 UB313

The Tenth Planet - Click image to enlarge


"It's definitely bigger than Pluto," says Dr. Mike Brown of the California Institute of Technology who announced the discovery of a new planet in the outer solar system just about a year ago. Some things move fast in science. . .some, like the discovery of a dim and far distant planet, seem to move slowly. Not much new has turned up in the year since the tenth planet's discovery.

The planet, which hasn't been officially named yet (other than 2003 UB313), is nicknamed--for the moment, Xena--was found by Brown and colleagues using the Samuel Oschin Telescope at Palomar Observatory near San Diego. It has also been spotted on other and smaller telescopes. 2003 UB313 is about 97 times farther from the sun than Earth. When they discovered it last year, it was said to be 30% larger than Pluto. Since then, they have found it is about 1,490 miles in diameter. With the margin of error being about 60 miles, it may be larger or nearly exactly the same size as Pluto (which the Hubble telescope measures as 1,422 miles in diameter). Other observers/scientists say the planet is 125% the size of Pluto. Whoever you listen to 2003 UB313 is right up there!

The new planet is more or less in the Kuiper Belt, a dark realm beyond Neptune where thousands of small icy bodies orbit the sun. Its sheer size in relation to the nine known planets means that it can only be classified as a planet itself, Brown says.

Backyard astronomers with large telescopes can even see the new planet. It looks like a dim speck of light, visual magnitude 19, moving very slowly against the starry background.

"We are 100 percent confident that this is the first object bigger than Pluto ever found in the outer solar system," Brown said. "Even if it reflected 100 percent of the light reaching it, it would still be as big as Pluto," says Brown. Pluto is 1400 miles (2300 km) wide. "I'd say it's probably [about] one and a half times the size of Pluto, but we're not sure."

Rumor has it that the International Astronomical Union (IAU) has either made a decision (or will by August 2006) as to whether or not the tenth planet will really be classified as a planet or not.

The original discoverers of the tenth planet, along with astronomers at the Keck Observatory on Mauna Kea took a look at the 10th planet with a new instrument that allows them to see details as precise as those seen from the Hubble Space Telescope. The images quickly revealed that it has a faint moon in orbit around it!

The tenth planet will not be named Xena. The IAU is the group responsible for approving astronomical names and they have suggested that the name should follow in the Greco-Roman tradition that the previous planets used. The discoverers will have to come up with a more suitable name. Sheesh!
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