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April 8, 2008, Cambridge, MA--The leading method of finding planets orbiting distant stars spots mostly Jupiter-sized worlds. But a laser technology being developed by scientists and engineers at the Harvard-Smithsonian Center for Astrophysics (CfA), with colleagues at the Massachusetts Institute of Technology (MIT), will enable scientists to spot Earth-sized worlds in Earth-like orbits.

Planets orbiting other stars are much too faint and far away to be seen directly and photographed. Instead, astronomers must look for the planet's effect on its star: a slight wobble. The larger the mass of the planet, the bigger the star's wobble will be, making larger planets easier to detect. At the same time, a planet in a tight, short-period orbit is easier to find than one in a wide, long-period orbit.

Current technology, although very stable and sensitive, isn't quite up to the task of finding Earths. The best instruments can only find 5-Earth-mass planets in tight, Mercury-like orbits. But a new device developed by the CfA and MIT researchers, called an astro-comb, will be able to spot Earth-mass planets in Earth-like orbits. It uses ultrashort, femtosecond pulses of laser light, linked to an atomic clock, to provide a precise standard against which light from a star can be measured.

The astro-comb can make measurements accurate to one part in a trillion. This may increase the resolution of the wobble planet-hunting technique by about 100 times, which would allow astronomers to detect Earth-sized planets. The research is published in the April 3, 2008, issue of the journal Nature.

A prototype astro-comb will be tested this summer at CfA's Mount Hopkins Observatory in Arizona. Those tests will be used to refine the design. An improved astro-comb is destined for a project being built in the Canary Islands called the New Earths Facility. The researchers expect it to be operational sometime in 2010.

For more information, visit www.cfa.harvard.edu.

Tue Apr 08 09:39:00 CDT 2008

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