From The New York Times:

In what amounts to a kind of holiday gift to the cosmos, astronomers from NASA’s Kepler spacecraft announced Tuesday that they had discovered a pair of planets the size of Earth orbiting a distant star. The new planets, one about as big as Earth and the other slightly smaller than Venus, are the smallest yet found beyond the solar system.

Courtesty CfA: David A. Aguilar

 The Globe has an excellent graphic and story:

Even with these two planets, the team had difficulties to overcome. (Francois Fressin, the lead author of the study and a Harvard astronomer)said the conventional method to measure the mass of a planet could not be used because these planets were so light. The team toiled to rule out other possible explanations, utilizing a supercomputer, called Pleiades, at NASA’s Ames Research Center in California. The computer, about the size of two basketball courts, ran calculations to show that it was very unlikely to be any other astrophysical phenomenon.

While these planets are inhospitable to life, (David Charbonneau, an astronomer at the Harvard-Smithsonian Center for Astrophysics and a coauthor of the paper) and his colleagues have their sights firmly on the larger goal.

“If all it was, was looking for smaller pieces of rock, I wouldn’t do it,’’ he said. “There has to be this promise, we have to eventually look for life. That has to be on the table