WATCH: Almost 550 Earth-like planets found in latest NASA mission

Kepler has verified the single largest finding of planets to date

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This artist's concept depicts select planetary discoveries made to date by NASA's Kepler space telescope | Image: NASA/W. Stenzel

NASA has said there could be nearly 550 planets “like Earth” in a batch of newly-validated worlds.

The Kepler mission has verified 1,284 new planets - the single largest finding of planets to date.

The announcement more than doubles the number of confirmed planets from Kepler and “gives us hope that somewhere out there, around a star much like ours, we can eventually discover another Earth,”  said Ellen Stofan, chief scientist at NASA Headquarters in Washington.

Analysis was performed on the Kepler telescope’s July 2015 planet candidate catalog, which identified 4,302 potential planets.

For 1,284 of them, the probability of being a planet is greater than 99% - the minimum required to earn the status of ‘planet’.

An additional 1,327 candidates are more likely than not to be actual planets.

And the remaining 707 are more likely to be some other astrophysical phenomena, NASA says.

Kepler captures discrete signals of distant planets: e.g. decreases in brightness that occur when planets pass in front of their stars.

NASA says that the newly-validated batch of nearly 550 planets “could be rocky planets like Earth, based on their size”.

Nine of these orbit in their sun's habitable zone, which is the distance from a star where orbiting planets can have surface temperatures that allow liquid water.

With the addition of these nine, 21 so-called exoplanets now are known to be members of this group.

The sweep of NASA Kepler mission’s search for small, habitable planets in the last six years | Image: NASA Ames/W. Stenzel

"They say not to count our chickens before they're hatched, but that's exactly what these results allow us to do based on probabilities that each egg (candidate) will hatch into a chick (bona fide planet)," said Natalie Batalha, co-author of the paper and the Kepler mission scientist at NASA's Ames Research Centre in California.

 “This work will help Kepler reach its full potential by yielding a deeper understanding of the number of stars that harbor potentially habitable, Earth-size planets - a number that's needed to design future missions to search for habitable environments and living worlds,” she added.

Of the nearly 5,000 total planet candidates found to date, more than 3,200 now have been verified and 2,325 of these were discovered by Kepler.

Launched in March 2009, Kepler is the first NASA mission to find potentially habitable Earth-size planets.