Oh, heavens! Pluto is now called a plutoid

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Pluto has evolved from planet to plutoid.

The tiny body lost its status as a planet two years ago in a controversial definition change for planets by the International Astronomical Union.

Pluton was proposed as a new name for the popular ninth planet but it was rejected and a new category of dwarf planets was created for Pluto and Eris.

The IAU Executive Committee at a recent meeting in Oslo, Norway, approved plutoid as their new name.

University of Hawaii astronomer Dave Tholen said, "They just muddied the waters even more."

But Carolyn Kaichi, Bishop Museum Planetarium manager, is happy that she won't have to call Pluto a dwarf planet any more.

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Once the ninth planet in the solar system, Pluto is now a plutoid.

"It rolls off the tongue easier than dwarf planet," said Carolyn Kaichi, Bishop Museum Planetarium manager, explaining she has to say "dwarf planet" a lot in talks to planetarium visitors.

Pluto was downgraded two years ago from one of the main planets in the solar system to a dwarf planet in hotly debated action by the International Astronomical Union.

The IAU changed the definition of a planet, which kicked Pluto out of the group.

A new subcategory of "plutons" was proposed for small objects in the outer solar system but the IAU general assembly in Prague rejected that proposal in 2006.

The IAU Executive Committee approved the plutoid term at a recent meeting in Oslo, Norway.

University of Hawaii planetary scientist Dave Tholen was among more than 300 astronomers who signed a petition after the IAU meeting two years ago protesting its new definition of a planet.

The union defined a planet as an object that orbits the sun, is large enough for its own gravity to pull it into a round shape and has cleared the neighborhood around its orbit.

"We, as planetary scientists and astronomers, do not agree with the IAU's definition of a planet, nor will we use it," the petition said. "A better definition is needed."

Tholen, renowned internationally for his work on asteroids, said in an e-mail that the IAU Executive Committee apparently "decided to take matters into their own hands" since the pluton suggestion was shot down.

"As far as I'm concerned, they just muddied the waters even more," he said.

The IAU in a news release described plutoids as "celestial bodies in orbit around the sun at a distance greater than that of Neptune that have sufficient mass for their self-gravity to overcome rigid body forces so that they assume a hydrostatic equilibrium (near spherical) shape, and that have not cleared the neighborhood around their orbit."

Pluto shares the plutoid name with Eris, the largest dwarf planet, once considered the 10th planet. "It is expected that more plutoids will be named as science progresses and new discoveries are made," the IAU said.

The other dwarf planet, Ceres, isn't being called a plutoid because it's located in the asteroid belt between Mars and Jupiter, the union said.

It said Ceres is believed to be the only object of its kind. "Therefore, a separate category of Ceres-like dwarf planets will not be proposed at this time."

"I'm not crazy about the fact that they kicked Pluto out (of the planets), but I have no say in that," Kaichi said. "I personally think Pluto should have been grandfathered."

She said she has to explain to school groups and others why there are no longer nine planets in the solar system and what dwarf planets are.

It will be easier with the name "plutoid," she said. "I think it's kind of a cute name and that one might stick a little better than dwarf planet."