Although the Kepler mission has yet to fulfill one of its goals, which is determining the fraction of sun-like stars hosting Earth-like planets in our galaxy, these data will help astronomers determine that number in the next few years, the researchers said.
Between 2009 and 2013, Kepler stared at the same patch of sky in the Cygnus constellation and measured the brightness of some 200,000 stars.
NASA also announced 219 new planets.
Kepler planet candidates, plotted by size relative to Earth and length of orbit, which is a function of distance from its star.
This artist rendering provided by NASA/JPL-Caltech shows some of the 219 new planet candidates, 10 of which are near-Earth size and in the habitable zone of their star identified by NASA's Kepler space telescope. A total of 2,335 of those have been verified as exoplanets, 21 of which are Earth-sized and orbit in their star's habitable zone. "This has implications in the search for life", Fulton said.
Most exoplanets tend to have small orbital periods (less than 100 days) because it's easier to confirm a planet when you see several transits within a short period.
In comparison, our solar system looks like it has three planets in the habitable zone of the sun: Mars, Venus and Earth.
Of those, 10 are thought to be "rocky and raw" - like Earth. "I'm really excited to see what people will do with this catalog", Susan Mullally, a Kepler research scientist at the SETI Institute in Mountain View, California, told a press conference today during the Kepler & K2 Science Conference at NASA's Ames Research Center in Mountain View.
Until KOI-7711 is verified and earns an official Kepler planet name - a process that requires a different telescope (usually ground-based) to observe it transiting - this is all speculation.
Typically, exoplanets fall in one of two categories: super-Earths, which have a radius that is 1.5 times that of the Earth, rocky surfaces, and often little to no atmosphere; and those that are like mini-Neptunes, which re about twice the Earth's radius with thick atmospheres and no rocky surface.
"We like to think of this study as classifying planets in the same way that biologists identify new species of animals", said Benjamin Fulton, doctoral candidate at the University of Hawaii in Manoa, and lead author of the second study. The space administration's James Webb Space Telescope will launch in 2018, which will be able to "detect the chemical fingerprints of water, methane, oxygen, ozone, and other components of a planet's atmosphere". "Finding two distinct groups of exoplanets is like discovering mammals and lizards make up distinct branches of a family tree".