"Astro Comb" May Boost Hunt for Earthlike Planets

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"The astro-comb is revolutionary, because it will enable astrophysical spectrographs to be much more sensitive to changes in the radial velocity of stars," Li said.

The astro-comb will also continuously adjust itself to match the atomic clock, making its astrophysical spectrographs extremely stable over long periods.

This is important, Li said, because planets in Earthlike orbits take longer to go around their host stars, so measurements need to be taken over longer time frames.

(Related news: "Potentially Habitable Planets Are Common, Study Says" [February 18, 2008].)

Li and his colleagues plan to test the astro-comb this summer at the MMT Observatory on Mount Hopkins in Arizona.

They first hope to demonstrate how the astro-comb can calibrate the facility's spectrograph to help measure the effects of dark matter on stellar motion in very old groupings of stars called globular clusters.

Then the researchers plan to use the improved technique to search the sky for small, rocky planets similar to Earth.

No Guarantee

According to the authors, the astro-comb could also be used to directly measure the expansion of the early universe.

Such measurements would typically take several decades to complete, because current technology isn't sensitive enough to detect the relatively minor wavelength changes that signal changes in cosmic acceleration.

Astro-combs, in conjunction with next-generation telescopes, could attain those results in less than ten years, the team believes.

"With the astro-comb, for the first time humans could be able to use telescopes to see changes in the large-scale structure of the universe in real-time, over the course of a few years," Li said.

Gordon Walker, a researcher from the University of British Columbia in Canada, wrote a commentary on the study for Nature but was not involved in the work.

He believes that the astro-comb could be a breakthrough in the precision of astrophysical spectroscopy, but he does foresee some challenges.

"Having the astro-comb is no guarantee that it will be possible to measure the very small wavelength shifts induced by Earthlike planets," Walker said.

"Stars are very 'noisy' targets, having hot gas boiling to their surface and rapid rotation and starspots—all of which may quite confound the search," he explained.

"It will be very interesting to see how well it works at the [MMT] telescope."

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