Novel search may have found small planet
Technique aims to find Earth-size worlds
By Richard Stenger
(CNN) -- An innovative method to find small planets around other stars has turned up a possible distant world with only one-tenth the mass of Jupiter, astronomers announced this week.
The technique could in time detect planets as small as Earth, in contrast to conventional searches that are mostly limited to gas giants, the University of Rochester researchers said.
The planet orbits Epsilon Eridani, which is about ten light-years from Earth. Among known exoplanets, the object would be one of the least massive and have perhaps the longest orbit, comparable to Pluto's path around the sun.
"We're very excited because this will open up the possibility of finding planets that we'd probably never detect just looking at the parent star," said physicist Alice Quillen, lead author of a report in the current issue of The Astrophysical Journal Letters.
Nearly all of the 100 or so known exoplanets have been identified through two means. Some have been detected as they pass in front of parent stars, dimming their light output at regular intervals.
Others have been found due to their gravitational influences on parent stars. Those with large masses and in-close orbits can sometimes tug the star enough for astronomers to detect the telltale wobble.
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Most found through that method practically hug their parent stars, some with orbits comparable to Mercury, the planet nearest the sun.
In contrast, Quillen and colleague Stephen Thorndike studied unusual dust patterns around Epsilon Eridani, a young star encircled by a dust ring, much like our sun was in its infancy.
"Not all stars have large concentrations of dust, but those that do, like Epsilon Eridani, can display certain telltale patterns in their dust fields. These patterns can betray the existence of a planet," the Rochester, New York team said in a statement.
Quillen first ran computer simulations to see how celestial objects in elliptical orbits, like Pluto, would swirl up dust around a star.
The dust clumps observed around Epsilon Eridani look like the work of a smaller planet, but she cautioned that the data is too preliminary to confirm.
"The fact that the dust around this star closely matches what we expected to see if a planet were present doesn't mean we know for sure that a planet is really there," she said.
Additional observations over several years will be necessary to pin down the planet, Quillen said.
Other planet-hunting astronomers had mixed reactions to the report.
"I have always thought that modeling the features in dusty rings was a promising way to find planets in very wide orbits," said Artie Hatzes, director of the observatory in Thueringia, Germany.
"Although it is a promising technique, I am not sure how much the results depend on the modeling since it is such an indirect technique. Any planet found in this way would have to be confirmed by other means just to be sure," he said.
Debra Fischer of the University of California, Berkeley welcomed the technique but cautioned that stars with dust disks like Epsilon Eridani are rare.
Another Berkeley astronomer, Steve Vogt, seemed less enthusiastic.
"Sounds like a long shot to me," he said. "It's quite a stretch to go from a theoretical model, which makes blobs in a map on a disk, to announcing the detection of a planet. There are no doubt many ways to make blobs in a disk, without having planets there."