Alpha Centauri

It is worth noting that while the radiation from Alpha Centauri B makes its neighborhood slightly worse than that of Alpha Centauri A, the third star in the system, where we have found an exoplanet, is the most hostile among the three.

At just 4.3 light years from the Sun, Alpha Centauri B is only a step away in astronomical terms.

That means that in the star system Alpha Centauri B, a just-right planet could be closer than astronomers had once imagined.

Polyphemis: An enormous planet, a gas giant almost twice the size of Jupiter, which in turn orbits the yellow sun of Alpha Centauri B. Its appearance is comparable to the eye of an angry deity leering down on Pandora.

The stars' names: Alpha Centauri A, Alpha Centauri B, and Alpha Centauri C.

Last October, astronomers announced the potential discovery of a hot Earth-mass world circling Alpha Centauri B (January issue, page 14).

"Our observations extended over more than four years using the HARPS instrument and have revealed a tiny, but real, signal from a planet orbiting Alpha Centauri B every 3.2 days," said Xavier Dumusque (Geneva Observatory, Switzerland, and Centro de Astrofisica da Universidade do Porto, Portugal), lead author of the paper.

European astronomers claim in the October 18th Nature that they have discovered an Earth-mass planet tightly orbiting Alpha Centauri B, a yellow-orange K1 star about 85% as luminous as the Sun in the closest stellar system to ours.

The rocky planet circles Alpha Centauri B, a star just a bit smaller and dimmer than the sun.

"Alpha Centauri B is overwhelmingly the best star in the sky for an intense radial-velocity campaign," says Gregory Laughlin (University of California, Santa Cruz).

Brian Wood and Jeffrey Linsky (University of Colorado) and Gary Zank and Hans Mueller (Bartol Research Institute) used the Hubble Space Telescope to analyze an ultraviolet spectral line of Alpha Centauri B, the dimmer member of the famous binary star just 4.4 light-years away.