Kepler space telescope's discoveries include four planets that could hold liquid surface water, believed to be key for life
Four of the newly-discovered planets were two and a half times the size of Earth.
Scientists added a record 715 more planets to the list of known worlds beyond the solar system, boosting the overall tally to nearly 1,700, astronomers said on Wednesday.
The additions include four planets about two and a half times as big as Earth that are the right distance from their parent stars for liquid surface water, which is believed to be key for life.
The discoveries were made with the National Aeronautics and Space Administration's planet-hunting Kepler space telescope before it was sidelined by a pointing system problem last year. The telescope, launched in 2009, spent four productive years staring at 160,000 target stars for signs of planets passing by, relative to the telescope's line of sight.
The tally of planets announced at a Nasa press conference on Wednesday boosted Kepler's confirmed planet count from 246 to 961.
Combined with other telescopes' results, the headcount of planets beyond the solar system, or exoplanets, now numbers nearly 1,700.
"We almost doubled, just today, the number of planets known to humanity," astronomer Douglas Hudgins, head of exoplanet exploration at Nasa headquarters in Washington, told reporters on a conference call.
The population boom is due to a new verification technique that analyses potential planets in batches rather than one at a time. The method was developed after scientists realised that most planets, like those in the solar system, have sibling worlds orbiting a common parent star.