New Planet-like Discovery Casts Doubt on Pluto's Status

Astronomers have discovered a planet-like object on the outskirts of the solar system, which means that there could be one planet fewer than was thought.

This confusing conclusion, which emerged at a meeting of the American Astronomical Society in Birmingham, Alabama, was reached because the nature of the new body - named Quaoar - casts doubt on the planetary credentials of Pluto, discovered in 1930.

Pluto has been considered the outermost planet of the solar system, but Quaoar is further still from the sun, 4bn miles from earth in a region known as the Kuiper belt, home of comets. A number of astronomers believe Pluto, too, comes from the wrong side of the belt, and is not worthy of the title "planet".

"Quaoar definitely hurts the case for Pluto being a planet," said Mike Brown, associate planetary science professor at the California Institute of Technology in Pasadena. "If Pluto were discovered today, no one would even consider calling it a planet because it's clearly a Kuiper belt object."

Quaoar was hard to find. It reflects even less light than Pluto, already barely a glimmer. Dr Brown spotted it with a colleague, Chad Trujillo, on a picture taken in June using a 48-inch telescope at the Palomar Observatory in California. They searched the archives and found it again and again, enabling them to work out that its orbit was planet-like. It was named after the creation force of the Tongva tribe of the Los Angeles basin.