Big Isle telescope plays
role in planet discovery

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 and capping the latest round in a frenzied hunt for other worlds like Earth.

All three of these smaller planets belong to a new class of "exoplanets" -- those that orbit stars other than our sun, the scientists said in a briefing yesterday. They define this new class by the planets' smaller mass -- roughly 14 to 18 times the size of Earth and equivalent to Neptune in our solar system.

The two planets announced yesterday were spotted by two separate teams of U.S. researchers using telescopes in Hawaii and Texas. 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 dueling announcements reflect the intensity of the race to discover exoplanets. The big prize, of course, would be to find an Earth-sized planet capable of supporting life, but today's instruments cannot detect bodies that small.

"We can't quite see the Earthlike planets yet, but we are seeing their big brothers," said planet hunter Geoffrey Marcy of the University of California-Berkeley, a leader of one of the teams.

Over 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.

Researchers don't know the composition of these new, smaller planets or what they actually look like.

In our solar system, Neptune and Uranus are of similar size and they are composed of an icy, rocky core enveloped in a thick atmosphere of hydrogen and helium. But they sit in the farthest coldest reaches of our solar system.

By contrast, both of the new planets are close to their stars, making them difficult to spot.

One of them orbits very close to the star named 55 Cancri, which is about the same size as our sun and located 41 light-years away in the constellation Cancer. The new planet was located by University of Texas-Austin astronomers using the Hobby-Eberly telescope in the Davis Mountains southeast of El Paso.

The star already had three known gas giant planets looping it in orbits that take anywhere from 14 to 4,520 days. The new planet is the innermost of the quartet, zooming around the star in 2.8 days from a distance of about 3 million miles.

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.

This Neptune-sized planet also sits 3 million miles from its star and whips around in a tight circular orbit once every 2.64 days.

It was discovered by a team led by Marcy and Paul Butler of the Carnegie Institution using one of the twin telescopes atop Mauna Kea in Hawaii.

Together, Marcy and Butler have spotted about half of the known exoplanets. They studied Gliese 436 for four years beginning in 2000.