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Kepler today released an updated catalog of candidate exoplanets observed during the space telescope’s first sixteen months of observations. In this release, they list more than a thousand new exoplanet candidates, almost two hundred of which are Earth-sized. Among the new exoplanet candidates, twenty-five are in the habitable zone!
Now for some details.
First, they have a found lot of new candidate exoplanets.
The metrics and procedures described above … yield 1091 new planet candidates, representing a gain of 88% over the B11 catalog. Eight of the new candidates are single-transit events. … After removing the single-transit based candidates, the remaining candidates range in size from one-third the size of Earth to three times the size of Jupiter. … Of the new candidates, 196 are Earth-size (RP < 1.25R⊕), 416 super-Earth-size (1.25R⊕ ≤ RP < 2R⊕), 421 Neptune-size (2R⊕ ≤ RP < 6R⊕ ), and 41 Jupiter-size (6R⊕ ≤ RP < 15R⊕ ), respectively. An additional 17 candidates are included in the catalog that are larger than 15R⊕ , a small number of which are larger than three times the size of Jupiter and unlikely to be consistent with the planet interpretation. [pages 25-26, emphasis mine]
Second, of these, three hundred of these thousand exoplanets are part of multiple planet systems.
Third, twenty-five of these exoplanets are in the habitable zone:
With each successive catalog, we see clear progress toward the Earth-size planets in the Habitable Zone. … Twenty-five of the new candidates are located in the range 185 K < Teq < 303 K, and one, KOI-2124.01, is near Earth-size and at the hot end of this temperature range.
To put it in plain English, these twenty-five planets experience temperatures ranging from -125 to 85 degrees Fahrenheit. One planet, KOI-2124.01, is about the same size as the Earth and sits in the high end of that temperature range.
Finally, they are finding more small rocky planets than their computer simulations had predicted.
The distribution in both size and orbital period of the new candidates is qualitatively similar to that of the previously published candidates, although smaller planets are more prevalent. More than 91% of the new planet candidates are smaller than Neptune (compared to 73% for the B11 catalog). The largest relative gains are seen not only for the smaller planets but also for those at longer orbital periods.
In other words, the longer they look, the more rocky Earthlike planets they find, in longer orbits. Why they are finding more of these rocky Earthlike planets than predicted is as yet unclear. It could be that solar systems naturally produce more of these rocky planets, or that their sample is simply not large enough yet.
While the scientists caution that many of these candidates might be false positives, they are also appear confident that most are real.
Either way, expect to hear a lot more about exoplanet KOI-2124.01 in the coming years. It appears it could be the first exoEarth so far discovered that humans could actually live on.