Kepler-22b: A 2.4 Earth-radius Planet in the Habitable Zone of a Sun-like Star

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Read also: Kepler 22-b: Earth-like planet confirmed

William J. Borucki et al

Folded light curve with model fit in red. Black dots represent individual observations. Dark blue points represent 30-minute binned data, and cyan points represent residuals after fitting. Red asterisk represents the mid-transit times based on the model fit with eccentricity value allowed to float

A search of the time-series photometry from NASA’s Kepler spacecraft reveals a transiting planet candidate orbiting the 11th magnitude G5 dwarf KIC 10593626 with a period of 290 days. The characteristics of the host star are well constrained by high-resolution spectroscopy combined with an asteroseismic analysis of the Kepler photometry, leading to an estimated mass and radius of 0.970 +/- 0.060 MSun and 0.979 +/- 0.020 RSun. The depth of 492 +/- 10ppm for the three observed transits yields a radius of 2.38 +/- 0.13 REarth for the planet.
The system passes a battery of tests for false positives, including reconnaissance spectroscopy, high-resolution imaging, and centroid motion.
A full BLENDER analysis provides further validation of the planet interpretation by showing that contamination of the target by an eclipsing system would rarely mimic the observed shape of the transits.

Image of the star field near Kepler-22

The final validation of the planet is provided by 16 radial velocities obtained with HIRES on Keck 1 over a one year span.
Although the velocities do not lead to a reliable orbit and mass determination, they are able to constrain the mass to a 3{\sigma} upper limit of 124 MEarth, safely in the regime of planetary masses, thus earning the designation Kepler-22b.
The radiative equilibrium temperature is 262K for a planet in Kepler-22b’s orbit.
Although there is no evidence that Kepler-22b is a rocky planet, it is the first confirmed planet with a measured radius to orbit in the Habitable Zone of any star other than the Sun.

Characteristics of Kepler-22 and -22b

Read more: ttp://

Written by physicsgg

December 8, 2011 at 7:11 am


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