- The Washington Times - Tuesday, August 31, 2004


American astronomers say they have discovered the two smallest planets yet orbiting nearby stars, trumping a small planet discovery by European scientists five days ago.

All three of these smaller bodies belong to a new class of planets orbiting distant stars, the scientists said yesterday. The planets are roughly the size of Neptune in our solar system and are 14 to 18 times the mass of Earth.

The two new planets were spotted by two separate teams of U.S. researchers. Scientists not involved in the projects lauded both, saying their planets should be recognized as the first discoveries of planets in this class — rather than the Europeans who announced their planet last week.

The competing announcements reflect the intensity of the race to discover exoplanets, or planets orbiting stars other than our sun.

Using an Olympics analogy, Carnegie Institution planetary theorist Alan Boss said the American groups have tied for first place and should share a gold medal.

Mr. Boss noted the Americans’ findings have been accepted for publication by international science journals, while the discovery led by a pair of prominent Swiss astronomers still is being reviewed for publication.

“These two were submitted July and August, while the Swiss discovery is still in consideration,” said Mr. Boss, who did not participate in any of the discoveries.

During the past decade, astronomers have found as many as 135 planets orbiting various stars, but all of them are giant gas planets similar to Jupiter and Saturn.

One of the new planets, located by University of Texas astronomers, is orbiting very close to the star named 55 Cancri, which is about the same size as our sun and located 41 light-years away.

The star already had three known giant gas planets looping it in orbits that take anywhere from 14 to 4,520 days. The new planet is the innermost of the quartet, orbiting the star in less than three days from a distance of 3 million miles.

“This is the closest analog to our solar system,” said astronomer Barbara McArthur, who led the Texas team. “This star is the premier lab for study of the formation and evolution of planetary systems.”

The other new planet discovered by American scientists orbits a star called Gliese 436, that lies about 33 light-years from Earth in the direction of the constellation of Leo.

The Neptune-sized planet also hovers about 3 million miles from its star and whips around in its tight circular orbit once every 2.64 days.

It was discovered by premier planet hunters Geoffrey Marcy of the University of California at Berkeley and Paul Butler of the Carnegie Institution. Together, they have spotted about half of the known exoplanets.

Aside from the exoplanet’s size, what makes the discovery remarkable is that Gliese 436 is a red dwarf star that produces only 2 or 3 percent as much light as the sun. Stars in this category account for 70 percent of the stars in the our Milky Way galaxy, but until now, astronomers had not believed that such faint stars would yield new planets.

Scientists cannot yet determine the composition of the new smaller planets. They said they could be made of rock and ice.

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