New Evidence Confirms New Planets

April 3 -- They're up to 13 times the mass of our biggest planet, Jupiter, and they roam at will — unattached to any star.

For over a year, the 13 mysterious bodies discovered around the Orion Nebula have befuddled scientists, but today two astronomers claimed they can confirm they are, in fact, planets. The evidence? Water vapor.

The puzzling planet-like bodies were discovered inside the Orion nebula Trapezium star cluster, a collection of gas and dust 1,500 light-years away from Earth.

"If they were stars, they'd be too warm to host water vapor," reasons Patrick Roche, an astrophysicist at the University of Cambridge, England, who teamed with Phil Lucas at the University of Hertfordshire in Hatfield, England, to detect the signature markings of water vapor around the bodies. The pair made their observations in infrared light, using the United Kingdom infrared telescope at Mauna Kea Observatory in Hawaii.

Since a star would burn off any nearby water vapor rather than absorb it, Roche and Lucas concluded the large, free-floating bodies must be planets. While some astronomers embrace the observations as new evidence the bodies are planets, others remain unconvinced.

And, if they are planets, they are strange ones.

Rule-Defying Planets

As astronomers have understood in the past, planets are objects no larger than about three to 10 times the size of Jupiter. And, as in our solar system, planets normally orbit around a star.

These newly discovered bodies, which range between six and 13 times the size of Jupiter, break both those rules.

"It's like anything in life," says Alan Stern, an astrophysicist at the Southwest Research Institute in Boulder, Colo., about the discovery of the perplexing bodies. "It's like studying Roman history and then going there and finding out there's an order of magnitude of more detail to learn."

In the face of newly discovered complexity, Stern and other astrophysicists say the definition of a planet should remain simple.