WASHINGTON A team of sky-searching astronomers have become the first to discover planets believed to be smaller than Saturn -- supporting the theory that planets closer to the size of Earth and possibly harboring life may exist beyond our solar system.
The discovery brings to 34 the number of worlds discovered outside of our own planetary neighborhood. The two newly found planets are believed to be smaller than Saturn, increasing the odds that many stars harbor smaller planets, even Earth-like worlds.
The stellar duo of Geoffrey Marcy, professor of astronomy at the University of California, Berkeley and Paul Butler, staff scientist in the Department of Terrestrial Magnetism at the Carnegie Institution of Washington, announced their research findings on Wednesday at NASA headquarters. This prolific two-person team is responsible for locating two dozen worlds since 1994.
We have discovered the first Saturn-sized planets ever found outside oursolar system.
Finding Saturn-sized planets means a threshold has been crossed. A majority of extrasolar planets previously found circling sun-like stars have been Jupiter-sized or larger gas giants. Jupiter is three times as massive of Saturn.
"We have discovered the first Saturn-sized planets ever found outside our solar system," Marcy said. The planet sleuthing was done using the Keck telescope in Mauna Kea, Hawaii. "Its a marvelous machine for finding planets. We feel very lucky to have been in the right place with the right telescope," he said.
Using the facility, along with special optical hardware and computational techniques, Marcy and Butler made the discoveries. One planet is at least 80 percent the mass of Saturn and orbits the star HD 46375, 109 light-years away in the constellation Monoceros. The other planet is 70 percent of Saturn's mass, orbiting around the star 79 Ceti (also known as HD 16141), located 117 light-years away in the constellation Cetus.
Both stars are similar to our sun. The two newly found planets whirl around their parent stars every 3.02 days and 75 days, respectively.
Wobble detection
How did they detect them? Thanks to the light-gathering abilities of the Keck, the astronomers studied the stars for signs of a planets gravitational influence. As a planet circles a star, it pulls it to-and-fro, causing a slight wobble in the stars motion. This quivering motion is revealed in the spectrum of light coming from the star. Attached to the Keck telescope, the team used a spectrometer, fine-tuned for the observations by Steve Vogt of the University of California, Santa Cruz.
Their research is part of a multi-year project to look for wobbles among 1,100 stars within 300 light-years of Earth. NASA and the National Science Foundation support the work.
Butler said the two planets are "important mileposts in our exploration of planetary systems" due to their difference from the earlier extrasolar finds. "This suggests that there is going to be many, many, many more small planets than there are large planets," he said.
Planets likely lack water
Because of their elongated, eccentric orbits the planets swing far too close to their parent stars. That likely means no liquid water is present on the distant worlds, Butler said. Circular orbits characterize the nine known planets in our own solar system.
The fact that the planets found to date by the team are in eccentric orbits leads to an early sign that is "a little-bit frightening," Marcy said. "The early returns in this poll of planets suggests that our solar system is somewhat unusual," he said, although this is a preliminary thought with more research required.
Butler said that there remains a "huge looming question": What fraction of planetary systems is going to be like our own?
"Is our own solar system rare or is it common? Its a completely open question, and we hope to be able to provide preliminary answers within 10 years," Butler said.
Up next: more planets
Whats in the offing from the astronomical duo? Marcy said that they are preparing to possibly confirm another 6 to 10 new planets, perhaps within six months to a year-and-a-half. Some are Jupiter-size, with one very close to the size of Saturn, he said.
"Were proudest of the fact that of the 24 planets we have discovered, weve never made a false claim in the past four-and-a-half years," Marcy said. "It's a track record that comes from fear and concern about making mistakes."
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