Four of the 715 new planets discovered by NASA's Kepler are less than 2 1/2 times the size of Earth and orbit in their sun’s 'Goldilocks' zone.
Using statistics and data from the Kepler telescope, NASA announced on Wednesday the discovery of 715 new planets, a “bonanza” likely to continue for years to come.
The newest discoveries increase the known planets outside the Milky Way to 1,700 from about 1,000.
To verify this bounty of planets, a research team co-led by planetary scientist Jack Lissauer analyzed stars with more than one potential planet.
“Four years ago, Kepler began a string of announcements of first hundreds, then thousands, of planet candidates — but they were only candidate worlds,” Lissauer said online.
“We’ve now developed a process to verify multiple planet candidates in bulk to deliver planets wholesale, and have used it to unveil a veritable bonanza of new worlds.”
The newly verified worlds orbit 305 stars, revealing multiple-planet systems much like our own solar system, NASA said.
Nearly 95 percent of these planets are smaller than Neptune, which is still almost four times the size of Earth. This discovery marks a significant increase in the number of known small-sized planets more akin to Earth than previously identified exoplanets, which are planets outside our solar system.
The research team used a technique called verification by multiplicity, which relies in part on probability. Kepler observes 150,000 stars and has found a few thousand of those to have planet candidates.
If the candidates were randomly distributed among Kepler’s stars, only a handful would have more than one planet candidate. However, Kepler observed hundreds of stars that have multiple planet candidates.
Four of the new planets are less than 2 1/2 times the size of Earth and orbit in their sun’s “Goldilocks” zone, or the distance from a star that’s “just right” for liquid water.
One of these new planets, called Kepler-296f, orbits a star half the size and five percent as bright as our sun. It’s twice the size of Earth, but scientists do not know whether the planet is a gaseous world, with a thick hydrogen-helium envelope, or it is a water world surrounded by a deep ocean.
“From this study we learn planets in these multi-systems are small, and their orbits are flat and circular — resembling pancakes —not your classical view of an atom,” said Jason Rowe, co-leader of the research.
“The more we explore the more we find familiar traces of ourselves amongst the stars that remind us of home.”
Launched in March 2009, Kepler is the first NASA mission to find potentially habitable Earth-size planets. Discoveries include more than 3,600 planet candidates, of which 961 have been verified as bona-fide worlds.
An animation of the Kepler system, AFTER THE JUMP...