Posted on: Tuesday, June 14, 2005

'Super-Earth' planet has link to Hawai'i

By John Johnson Jr.
Los Angeles Times

Space scientists yesterday announced the discovery of what may be a rocky, Earth-like planet orbiting a star 15 light years away — a milestone in the search for a world outside the solar system that could sustain life.

The new planet, dubbed a "super-Earth" by the team that found it, is about seven times as massive as Earth and about twice the diameter. It orbits the star Gliese 876 in the constellation Aquarius.

The breakthrough that led to the discovery of the planet was the installation of a new light sensor at the W.M. Keck Observatory atop Mauna Kea on the Big Island of Hawai'i. The instrument can detect changes in star movement of one meter per second, about the speed of a mother pushing a baby carriage.

"More precision is everything," said team member Steven Vogt, a professor of astronomy and astrophysics at the University of California-Santa Cruz who designed the new instrument over the past three years.

Until now, every extra-solar planet found has been larger than Uranus, the giant ice planet at the edge of our solar system. Two other planets previously had been found orbiting Gliese 876, a small red star known as an M dwarf, the most common type of star in the galaxy, but these were Jupiter-size gas giants.

The new planet's modest size and mass suggests that it may be the first rocky planet, like Earth, that has ever been found orbiting a normal-size star. Researchers think it may resemble the inner planets of this solar system, made of nickel and iron.

"This is a big milestone, to get down to the region of rocky planets," Vogt said.

"We keep pushing the limits of what we can detect, and we're getting closer and closer to finding Earths."

Even though the new planet is the closest analog to Earth yet discovered, it could not support life as we know it. Whirling around its star in just two days, it is far too close for water to exist in liquid form. Surface temperatures range from 400 to 750 degrees Fahrenheit.

"It's not the place to go for a vacation," Vogt said.

That hardly dimmed the excitement of the team, composed of researchers from the University of California, the Carnegie Institution in Washington, D.C., and the National Aeronautics and Space Administration's Ames Research Center near Mountain View.

"Today's results are an important step toward answering one of the most profound questions that mankind can ask: Are we alone in the universe?" said Michael Turner of the National Science Foundation, which helped fund the research.

The team detected the new "extra-solar" planet by observing a tiny wobble induced in the star by the planet's gravity. The team made more than 150 observations over three years with precision-measuring instruments before announcing its findings.

"This new technology has revealed the most terrestrial planet ever found," said team leader Geoffrey Marcy, an astronomer at the University of California -Berkeley. "For the first time we are finding our planetary kin among the stars."

Pinning down the size and location of the planets is done by using a spectrometer to break down the star's light and measure tiny changes over time, indicating small movements. Until recently, the lower limit that could be measured in the movement of a star was about three meters per second, about the speed of a jogging athlete.

Although technology is not yet advanced enough to see the new planet, the research team told reporters at a news conference in Arlington, Va., that it is confident of its findings, which have been submitted to the Astrophysical Journal for publication.

There are three types of planets in our solar system: the rocky inner planets, consisting of Mercury, Venus, Earth and Mars; the gas giants, Jupiter and Saturn; and the intermediate planets like Uranus and Neptune, which are thought to be composed of rock, ice, water and other constituents. The scientific team thinks the new planet lies somewhere between the rocky inner planets and the mid-range ones.

Since scientists began hunting for extra-solar planets about a decade ago, they have found more than 150, most of them Jupiter-like giants close to their host stars, enabling them to impart a significant wobble with relative frequency.

"But there's this huge range of sizes and distances that we haven't seen yet, and with the upgrades at Keck, this team is probably going to find a large number of them," said astronomer Kevin Luhman of the Harvard-Smithsonian Center for Astrophysics.

The Washington Post contributed to this report.