After locating more than 340 planets orbiting other stars, astronomers have found two that are the most similar to Earth.
The most recently discovered one is less than two times as large as Earth, making it the smallest exoplanet — for extra-solar planet — found to date. The second one was found in 2007, but new observations have shown that it is the only exoplanet to date that orbits its star in the so-called habitable zone, where water remains a liquid. Thus, it is the only exoplanet discovered that is likely to have oceans.
Intriguingly, both orbit the same star, a dwarf 20 light- years from Earth called Gliese 581, European researchers said Tuesday.
The identification of the small planet “is a remarkable discovery and bodes well for our eventual discovery of a true Earth-like, habitable planet,” astronomer Alan Boss of the Carnegie Institution of Washington said in an e-mail.
“(It) is the most exciting discovery in exoplanets so far,” wrote astronomer Geoff Marcy of the University of California at Berkeley in an e-mail. “It shows that nature makes such small planets, probably in large numbers.”
The small planet is the fourth discovered circling Gliese 581 by a team of astronomers working at the European Southern Observatory’s 3.6- meter telescope at La Silla, in Chile. They identified the planets by detecting and analyzing slight wobbles in the star’s path as the planets orbit it.
