Our closest neighbor has an Earth sized planet orbiting it.
(Update – 10/20/12 – NASA issues statement about Exoplanet Discovery. See KnowledgeOrb Article – Did NASA miss an obvious place to search?)
Unfortunately the orbit of the planet is so close that it has a surface temperature of 1200 degrees Celsius. This rocky planet circles Alpha Centauri B every 3.236 days. Twin only in size to Earth this discovery is still a triumph in new methods used to find these Earth like planets around the solar systems closest to us.
Discovery team member Francesco Pepe, astronomer at the University of Geneva, Switzerland, reported the discovery online in Nature this week. He and his colleagues found the planet in an effort monitor ten of the brightest and nearest stars visible from the Southern Hemisphere. The team used the High Accuracy Radial Velocity Planet Searcher (HARPS) spectrograph on the European Southern Observatory’s 3.6-metre telescope at La Silla in Chile. The Alpha Centauri system is the fourth after the team measured. In order to make his discovery they had to make observations three times a night every night for over three years.
The planet orbits so close that there could still be an Earth like planet in another more favorable orbit around the star. So there is still hope for a habitable zone planet there. In terms of interstellar distance Alpha Centauri is our closest neighbor.