Earth’s new neighbor looks familiar

Planet discovered in Alpha Centauri, just a few light-years away


For exoplanets, size does matter. That’s why an Earth-sized planet just 4.4 light-years away proved to be one of the most exciting astronomical discoveries of 2012. The planet (artist’s depiction shown) circles a sunlike star in the Alpha Centauri system — the nearest stellar system to Earth and a favored target for future interstellar expeditions.

L. Calçada, Nick Risingr, ESO

Finding a rocky planet in the Alpha Centauri system settled a decades-long debate about whether the system’s three stars hosted planets. The region appeared deserted until the most powerful planet-finding instrument on Earth — the High Accuracy Radial Velocity Planet Searcher — took a four-year-long look. Now scientists are eager to confirm the finding (SN: 11/3/12, p. 5) with further observations.

Just a bit more massive than Earth, the planet, unofficially named Alpha Centauri Bb, is so close to its parent star that it completes its orbit in just over three days. That superclose orbit probably means that one side always faces the star, and that side is burnt to a 1,200° Celsius crisp. The other side of the planet could be prime real estate for landing an interstellar space probe, but is probably frigid and similarly unfriendly to life.

But don’t count Alpha Centauri out yet. Astronomers are betting there are more planets in the triple-star system, perhaps farther out and in their stars’ life-friendly zones.

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