In the search for Earth-like planets, astronomers zeroed in Tuesday on two places that look awfully familiar to home. One is close to the right size. The other is in the right place.
European researchers said they not only found the smallest exoplanet ever, called Gliese 581 e, but realized that a neighboring planet discovered earlier, Gliese 581 d, was in the prime habitable zone for potential life.
"The Holy Grail of current exoplanet research is the detection of a rocky, Earth-like planet in the 'habitable zone,'" said Michel Mayor, an astrophysicist at Geneva University in Switzerland.
An American expert called the discovery of the tiny planet "extraordinary."
Gliese 581 e is only 1.9 times the size of Earth - while previous planets found outside our solar system are closer to the size of massive Jupiter, which NASA says could swallow more than 1,000 Earths.