Mauna Kea scope
spies 6 new planets

A team uses the Keck to find
them orbiting similar stars
outside Earth's solar system

By Gregg K. Kakesako
Star-Bulletin

After a three-year search, a team of astronomers using the Keck I telescope at Mauna Kea has found six new planets, increasing by more than 25 percent the number of planets discovered outside the Earth's solar system, to 28.

The six planets orbit stars that are similar in size, age and brightness to the sun and are 65 to 192 light years away from Earth.

The planets range in mass from slightly smaller to several times larger than Jupiter.

They are believed to be similar to Jupiter in their compositions, making them basically giant balls of hydrogen and helium gas, according to one of the discoverers, Steven Vogt, professor of astronomy and astrophysics at the University of California at Santa Cruz.

Vogt was part of team that surveyed 500 nearby stars for orbiting planets under a long-term project that was supported by the National Science Foundation and the National Aeronautical Science Administration.

Other team members include Geoffrey Marcy of the University of California at Berkeley; Paul Butler of the Carnegie Institution in Washington, D.C., and Kenneth Apps, a student at the University of Sussex in England.

Their findings will be published in the Astrophysical Journal.

The Keck telescope was equipped with a high-resolution spectrometer designed and built by Vogt.

Five of the six planets are in what can be considered "habitable zones" of their stars. This is the region where temperatures would allow water to exist in liquid form.

"These planets are at just the right distance," Vogt said, "with temperatures in one case around 104 degrees Fahrenheit -- like a hot day in Sacramento."

Vogt said the planets' orbits tend to be quite eccentric, tracing oval rather than circular paths.

"It is beginning to look like neatly stacked, circular orbits such as we see in our own solar system are relatively rare," he said.

The presence of a new planet around a star is revealed by the variation in the star's velocity through space as a result of the gravitational force exerted on it by an orbiting planet.

Vogt and his coworkers independently confirmed this method for detecting planets when they were able to measure the dimming of a star as a planet passed in front of it.