NASA in telephonic conference just announced, Kepler space telescope has found two new Earth-sized planets orbiting a distant sun-like star, and the researchers who made the find say these two are the size of Earth or smaller. That’s a first in the search for extraterrestrial life.

If the discovery holds up under scrutiny by other scientists, it could be a very big deal. Earth-sized planets are considered critical in the search for life elsewhere in the universe, but until now, scientists said their instruments were not sensitive enough to detect them.

“Theoretical considerations imply that these planets are rocky, with a composition of iron and silicate,” wrote Francois Fressin of the Harvard-Smithsonian Center for Astrophysics, the leader of the team that made the discovery. “The outer planet could have developed a thick water vapour atmosphere.”

The team is publishing its report today online in the journal Nature.

The two newly-found planets, called Kepler-20e and Kepler-20f, are much too far away to be seen directly. They circle a star about 950 light-years away. Scientists measured the miniscule dimming of their host star as they passed in front of it, and then did the math to figure out how large they are likely to be and in what orbits they move.

Just two weeks ago scientists reported a planet orbiting a different star, right in the middle of its so-called habitable zone. That planet was believed to be much larger (10 times as massive as Earth), but its temperature was estimated at an average of 72 degrees Fahrenheit — perfect for liquid water, considered essential for life as we know it.

Put the two finds together, say scientists, and chances are good that some day soon we will find a planet of just the right size and temperature to have at least a chance of being a lively place.