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Homing in on a home away from home.

May 31, 2006


Catching up on the implications of a two week old bit of science news. Nature reported that three new Neptune sized planets have been found circling the nearby star HD69830, 41 light years away.

This was gratifying news for three reasons. First, infrared studies had already disclosed the presence of an asteroid belt around the star. It was predicted that a pair of planets would be found, one on each side of the belt, acting as shepherds to keep the belts in place, much as the inner moons of Saturn shepherd the particles in its rings. So it was pleasant to see observation follow dynamical theory.

Second, detection of the planets was possible because of a big jump in the sensitivity of the Doppler technique for finding extrasolar planets, by observing the wobble they induce on the location of the parent star.

Third, at the new level of sensitivity, it still isn’t possible to find the holy grail of extrasolar planetary research: a rocky, earth-sized planet orbiting a sunlike star at a distance congenial to life. To do that, the sensitivity of the Doppler technique would have to be ratcheted up by another 90%.

But here’s the beauty part: most nearby stars are not sunlike. They are smaller: lighter in mass, and less bright. That makes a habitable planet easier to find on two counts. The habitable zone is closer in to the star, so that an earth-sized planet would tug harder at its sun. And the star is smaller, so that the same size tug would make it wobble further.

We’re getting close. The first planet around a different star worth a beamdown by Kirk’s crew should put in its appearance within the next three to five years.

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