Last June, the Kepler Team announced that it had identified 706 stars with signatures of transiting exoplanets (a transit occurs when a planet passes between its host star and us, causing a dip in the observed brightness of the star). 306 of those were published and discussed, but the remaining ones – the 400 most promising and most interesting – have been under lock and key for the last six months. Yesterday, Kepler released data on these remaining planets and today announced their discoveries.
Kepler has now found 1,235 planet candidates, ranging in size from about Earth-sized to larger than Jupiter. About half of these candidates are the size of Neptune, but 68 are similar in size to the Earth. This is quite an exciting discovery, because only several of the exoplanets discovered to date have approached Earth radii. I wrote about Kepler’s discovery of one such planet, Kepler 10b, in January, but as you can see from the plot, some of the new candidates are even smaller! Even more intriguing is that 54 of the planet candidates are located in the sweet spot that is not too cold and not too hot for liquid water. (I discussed the habitable zone in a previous post; look under “Habitability of a Terrestrial Planet”). Five of these planets are Earth-sized.
Best of all, Kepler has only surveyed a tiny fraction of the sky: there are lot more planets out there than Kepler will ever find. A word of caution, however: most of the planets released by Kepler today are planet candidates. It may take years to confirm true planets and weed out false positives.
Later, I’ll be presenting a paper which has come out of this data. Anyone else excited for the future?