...715 new planets... orbit 305 stars, revealing multiple-planet systems much like our own solar system. Nearly 95 percent of these planets are smaller than Neptune, which is almost four times the size of Earth. ...To verify this bounty of planets, a research team co-led by Jack Lissauer, planetary scientist at NASA's Ames Research Center in Moffett Field, Calif...used a technique called verification by multiplicity, which relies in part on the logic of probability. ...Kepler observed hundreds of stars that have multiple planet candidates. Through a careful study of this sample, these 715 new planets were verified. This method can be likened to the behavior we know of lions and lionesses. In our imaginary savannah, the lions are the Kepler stars and the lionesses are the planet candidates. The lionesses would sometimes be observed grouped together whereas lions tend to roam on their own. If you see two lions it could be a lion and a lioness or it could be two lions. But if more than two large felines are gathered, then it is very likely to be a lion and his pride. Thus, through multiplicity the lioness can be reliably identified in much the same way multiple planet candidates can be found around the same star.
"Four years ago, Kepler began a string of announcements of first hundreds, then thousands, of planet candidates --but they were only candidate worlds," said Lissauer. "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."
...Four of these new planets are less than 2.5 times the size of Earth and orbit in their sun's habitable zone, 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.
...This latest 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 findings papers will be published March 10 in The Astrophysical Journal.
Number of planets by size for all known exoplanets - In this histogram, the blue bars represent all the exoplanets known before the Kepler Planet Bonanza announcement on Feb. 26, 2014. The gold bars represent Kepler's newly-verified planets. Image Credit: NASA Ames/W Stenzel
Sciencecast about these discoveries from Science@NASA:
- Validation of Kepler's Multiple Planet Candidates. II: Refined Statistical Framework and Descriptions of Systems of Special Interest by Jack J. Lissauer, Geoffrey W. Marcy, Stephen T. Bryson, Jason F. Rowe, Daniel Jontof-Hutter, et al - http://arxiv.org/abs/1402.6352
- Validation of Kepler's Multiple Planet Candidates. III: Light Curve Analysis & Announcement of Hundreds of New Multi-planet Systems by Jason F. Rowe, Stephen T. Bryson, Geoffrey W. Marcy, Jack J. Lissauer, Daniel Jontof-Hutter, Fergal Mullally, Ronald L. Gilliland, Howard Issacson, William J. Borucki, et al. - http://arxiv.org/abs/1402.6534
Animations ...used in the Media Telecon of 2014 Feb 26:
Exoplanet Discoveries Through the Years - The histogram shows the number of planet discoveries by year for roughly the past two decades of the exoplanet search. The blue bar shows previous planet discoveries, the red bar shows previous Kepler planet discoveries, the gold bar displays the 715 new planets verified by multiplicity. Multiplicity is a statistical technique that allows for wholesale verification of multiple-planet candidate systems.
Planet System vs. Star System Stability - On the left, an animation of a gravitational simulation of a compact, multiple- planet system is shown. On the right, a gravitational simulation of a hypothetical compact multiple star system configuration is depicted. The planets in the system are shown to orbit in stable circular orbits whereas the star system is unstable. The gravitational pull of each star on one another pulls the system apart.
Kepler-296 Planetary System - The artist's animation shows the newly verified Kepler-296 system with five planets orbiting its host star. The star is half the size and five percent as bright as our sun.
Shown in green is the habitable zone of the Kepler-296 system. The habitable zone is the range of distances from a star where liquid water might persist on the surface of an orbiting planet. The outer most planet, Kepler-296f, is shown in blue and orbits within the habitable zone. Kepler-296f is twice the size of Earth and has an orbital period of 30 days.
The animation begins by viewing the system top-down. As the animation proceeds, it zooms in on the central star and the viewing angle changes to see the planetary orbits edge-on to allow the observation of the planets transiting the host star.