Saturday science subject: Neighbor planets

Finding extrasolar planets is all well and good, but most are so remote that there's no way for us to ever get to them unless we somehow come up with some kind of faster-than-light transportation. However, as the New Scientist reports, there may very well be rocky, Earth-like planets right off our stellar doorstep.

The site says researchers are applying the same technique they've used to discover giant planets in very remote systems to Alpha Centauri, which lies "only" four light years away and is the closest star system to our own. This technique could uncover small, rocky planets around the two largest of Alpha Centauri's orbiting stars, something the researchers suspect is likely:

Previous computer simulations suggested terrestrial planets probably formed around one or both stars. That is borne out by the work of Javiera Guedes at the University of California, Santa Cruz (UCSC), US, and colleagues, who have gone a step further and worked out how to detect such planets. . . . "If our understanding of terrestrial planet formation is at all correct, then there should definitely be terrestrial planets orbiting both members of the Alpha Centauri binary pair," team member Greg Laughlin of UCSC told New Scientist.

What's more, any such planets might boast the conditions thought to be necessary to support life. In the team's simulations of planet formation around the smaller star, Alpha Centauri B, an Earth-like world often coalesced in or near the star's habitable zone, where liquid water could exist on the planet's surface. . . . Finding these planets could be time-consuming, but it does not require any new techniques, they say. They suggest using the "radial velocity" method, which looks for spectral signs that a star is wobbling due to gravitational tugs from an orbiting planet.

The radical velocity method has already uncovered 228 exoplanets so far, although all of them are massive, Jupiter-like ones many times the size of the Earth. The researchers expect they'll need "several years of data" to spot the faint signals of terrestrial planets, which might only cause their host star to wobble at "only about 10 centimetres per second."

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