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In its first four years, Kepler surveyed just .025 per cent of the sky. And for every potential planet detected, NASA estimates that 100 to 200 lurk beyond the telescope’s reach. Given a little time and some sophisticated models, scientists will use the Kepler catalogue to estimate how many stars in our galaxy could host an “Earth 2.0.”

Based on how many habitable-zone planets have already been identified, Caltech astrophysicist Courtney Dressing thinks that number could be sizable.

“I, for one, am ecstatic,” she said at a news conference Monday.

“The important thing for us is, are we alone?” added Kepler Program Scientist Mario Perez. “Kepler today tells us, indirectly … that we are probably not alone.”

This is the eighth update of the Kepler planet catalogue and the most thorough survey of the space telescope’s data to date. Of the 4,034 candidates, more than half have already been confirmed as exoplanets and not the result of miscalculations or false signals. Kepler research scientist Susan Thompson, the lead author of the catalogue study, said her team is confident about all 10 of the new “Earth-like” planets found in their stars’ habitable zones.

Several of these planets orbit G dwarfs — the same species of star as our own sun. And one, dubbed KOI 7711 (for Kepler Object of Interest), is a possible “Earth twin,” a rocky world just 30 times bigger than our own and roughly the same distance from its star.

It’s too soon to say whether KOI 7711 truly merits the label “Earth-like,” Thompson cautioned. Kepler is incapable of determining whether an exoplanet bears an atmosphere or liquid water. If aliens were observing our solar system using a similar instrument, they might think it contained three rocky, potentially habitable worlds — Venus, Earth and Mars. “But I’d only want to live on one of them,” Thompson said.