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rfmcdonaldThis Centauri Dreams post linked to a very interesting paper, "Near-Infrared Spectroscopy of Low-Mass Kepler Planet-Candidate Host Stars: Effective Temperatures, Metallicities, Masses and Radii" by Muirhead et al, that made a very interesting conclusion about some of the planets observed by the Kepler satellite. The authors suggest that the radii of some of the measured dimmer stars in the Kepler sample is smaller than theory predicts. What does this mean?
In other words, six of the planets found by Kepler may well be Earth-like within very specific constraints. Of course, as Centauri Dreams' Paul Gilster notes, this is both very sexy and very preliminary. "This one has struck a nerve and it’s easy to see why, as we are suddenly looking at six Earth-like planets in the habitable zone of their stars. [. . .] The authors point out, for example, that this work assumes 'the same albedo, re-radiation fraction and greenhouse effect' as are found in our own system, an assumption that may well be challenged for a terrestrial planet orbiting a red dwarf star." These worlds could very easily be greenhouse worlds akin to Venus, for instance.
But still. Wow. Miracles, meet wonders.
The effective temperatures, radii and masses of the KOIs imply different planet-candidate equilibrium temperature estimates, such that 6 planet-candidates are terrestrial-sized and have equilibrium temperatures which may permit liquid water to reside on the planet surface, assuming Earth-like albedos and re-radiation fractions. Scaling the Earth’s equilibrium temperature of 255 K by the orbital semi-major axis, stellar Teff and stellar radius of the KOIs in this letter, we find that KOIs 463.01, 1422.02, 947.01, 812.03, 448.02 and 1361.01 all have equilibrium temperatures between 217 K and 261 K: the limits of the habitable zone as described in Kasting et al. (1993).
In other words, six of the planets found by Kepler may well be Earth-like within very specific constraints. Of course, as Centauri Dreams' Paul Gilster notes, this is both very sexy and very preliminary. "This one has struck a nerve and it’s easy to see why, as we are suddenly looking at six Earth-like planets in the habitable zone of their stars. [. . .] The authors point out, for example, that this work assumes 'the same albedo, re-radiation fraction and greenhouse effect' as are found in our own system, an assumption that may well be challenged for a terrestrial planet orbiting a red dwarf star." These worlds could very easily be greenhouse worlds akin to Venus, for instance.
But still. Wow. Miracles, meet wonders.
