The Kepler mission has discovered over 2500 exoplanet candidates in the first two years of spacecraft data, with approximately 40% of them in candidate multi-planet systems. The high rate of multiplicity combined with the low rate of identified false-positives indicates that the multiplanet systems contain very few false-positive signals due to other systems not gravitationally bound to the target star (Lissauer, J. J., et al., 2012, ApJ 750, 131). False positives in the multi-planet systems are identified and removed, leaving behind a residual population of candidate multi-planet transiting systems expected to have a false-positive rate less than 1%. We present a sample of 340 planetary systems that contain 851 planets that are validated to substantially better than the 99% confidence level; the vast majority of these have not been previously verified as planets.Among these 851 planets, the ones of particular interest are the "...768 planets across 306 systems being newly validated." That is a nice collection of new new planets.
For some reason, in its press release, NASA's Jet Propulsion Laboratory announced 715 new planets around 305 star systems. But why quibble? But here is the important part:
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. One of these new habitable zone planets, called Kepler-296f, orbits a star half the size and 5 percent as bright as our sun. Kepler-296f is 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.I expect that more research on all the data acquired in the earlier Kepler mission will continue to bring forward new findings. And, as noted earlier, Kepler may still have some life left for new missions.
Image Credit: NASA/JPL-Caltech/R. Hurt (SSC-Caltech)
