Astronomers of NASA’s Kepler mission announced yesterday the discovery of 715 new extrasolar planets orbiting 305 stars in our Milky Way Galaxy.
This is an artist’s impression of an exoplanet. Image credit: Ron Miller.
All of the 715 alien worlds are located in multi-planet systems. 95 percent of these planets are smaller than Neptune, which is almost four times the size of Earth.
Four of these exoplanets are less than 2.5 times the size of our planet and orbit in their habitable zones, defined as the range of distance from a star where the surface temperature of an orbiting planet may be suitable for life-giving liquid water.
One of these habitable-zone planets orbits a star half the size and 5 percent as bright as our Sun.
The planet has been dubbed Kepler-296f. It is twice the size of Earth, but the astronomers do not know whether the planet is a gaseous world or it is a water world surrounded by a deep ocean.
To verify these exoplanets, the Kepler team analyzed stars with more than one potential planet, all of which were detected in the first two years of NASA’s Kepler Space telescope’s observations – May 2009 to March 2011.
The scientists used a novel statistical technique called verification by multiplicity, which relies in part on the logic of probability.
NASA’s Kepler observed 150,000 stars and discovered a few thousand of those to have planet candidates. The mission also observed hundreds of stars that have multiple planet candidates. Through a careful study of this sample, the 715 new exoplanets were verified.
“Four years ago, Kepler began a string of announcements of first hundreds, then thousands, of planet candidates –but they were only candidate worlds,” said Dr Jack Lissauer from NASA’s Ames Research Center in Moffett Field, who is a co-author if two papers accepted for publication in the Astrophysical Journal (paper #1 and paper #2).
“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.”
Co-author Dr Jason Rowe from the SETI Institute in Mountain View said: “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.”
“The more we explore the more we find familiar traces of ourselves amongst the stars that remind us of home.”
This discovery brings the confirmed count of planets outside our solar system to nearly 1,700.
“As we continue to reach toward the stars, each discovery brings us one step closer to a more accurate understanding of our place in the galaxy,” the astronomers said.
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Jack J. Lissauer et al. 2014. Validation of Kepler’s Multiple Planet Candidates. II: Refined Statistical Framework and Descriptions of Systems of Special Interest. ApJ, accepted for publication; arXiv: 1402.6352
Jason F. Rowe et al. 2014. Validation of Kepler’s Multiple Planet Candidates. III: Light Curve Analysis & Announcement of Hundreds of New Multi-planet Systems. ApJ, accepted for publication; arXiv: 1402.6534
