In a press conference held at NASA's Ames Research Center, the team stated that they had identified 219 planet candidates, 10 of which are said to be rocky worlds that are in the habitable zones of stars that are similar to the Sun-which is a yellow dwarf or G dwarf.

"The Kepler data set is unique, as it is the only one containing a population of these near Earth-analogs - planets with roughly the same size and orbit as Earth", Kepler program scientist Mario Perez said in a release. Understanding how frequent planets like our own will help NASA develop the next telescope that will directly image planets like Earth.

All of these worlds were found in a patch of sky near the Cygnus constellation in our Milky Way galaxy.

NASA also announced 219 new planets.

This artist rendering provided by NASA/JPL-Caltech/T. Pyle, taken in 2015, depicts one possible appearance of the planet Kepler-452b, the first near-Earth-size world to be found in the habitable zone of a star that is similar to our sun.

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Since launching in 2009, Kepler has been watching more than 200,000 stars in one part of the sky to determine exoplanet candidates, based on the slight dimming of light emitted by stars when potential planets pass across them. But those 10 were joined by an additional 209 more garden-variety planets that are unlikely to be hospitable to life because they are too gassy, too hot, too cold or otherwise unlike the only known planet to host life: Earth. Of Kepler's list of more than 4000 likely candidates from those observations, 2335 have been verified as exoplanets with further analysis or other ground-based observations. That number includes about 50 worlds that may be about the same size and temperature as Earth. "It's incredible the things that Kepler has found, it has shown us these terrestrial worlds, and we still have all this work to do to understand how common Earths are in the galaxy". Researchers are now using the Hubble Space Telescope to determine if these planets had atmosphere. Each star will be observed for 30 days.

A follow-up study, described today by astronomer Benjamin Fulton of the University of Hawaii at Manoa in Honolulu, fine-tuned the size measurements for some 2000 Kepler planets using the Keck telescopes in Hawaii.

NASA said that the Spitzer, Hubble and Kepler will continue to conduct follow-up studies.

The James Webb Space Telescope will be able to look at targets discovered by K2 in some detail, and it will be able to focus on at least 10 exoplanets in great detail. In the mid-2020s, we have our sights on taking a picture of small planets like Earth with our Wide-Field Infrared Survey Telescope (WFIRST). A dozen of the planets that seem to be in the potentially habitable zone circle Earth-like stars, not cooler red dwarfs.

"I'm looking forward to 2030s", said Courtney Dressing, NASA Sagan Fellow.