First Exoplanet In The Habitable Zone Of A Sun-Like Star Discovered

Previously, the only two confirmed exoplanets in the habitable zone of their star (where liquid water could exist) were orbiting the same red dwarf star. Now Bill Borucki, Kepler’s chief scientist at NASA’s Ames Research Center in California, has announced the confirmation of an exoplanet 2.4 times the width of Earth which orbits in the habitable zone of a G-type star similar to our Sun. The planet, Kepler-22b, has an orbit of 290 days around a star approximately 600 light years from Earth.

Borucki told New Scientist the surface of this exoplanet is probably 22 °C [71.6 °F], although we really can’t be sure of that yet, nor can we be certain there is any water there or yet determine the type of atmosphere it has. The three separate transit observations used to confirm the exoplanet’s existence can’t pinpoint its mass, although the lack of wobbles in the host star suggests the orbiting star can’t have a mass more than 36 times that of Earth (or the gravitational pull would cause wobbling). The size, location, and maximum mass doesn’t rule out the possibility of water, but we’ll know more next summer when the planet will be easier to observe in the night sky. Phil Plait at Bad Astronomy explains why knowing the mass and atmosphere of this exoplanet is so important:

Venus and Mars are both technically inside the Sun’s habitable region, but Venus’s thick atmosphere makes it hotter than an oven, and Mars’s thin air makes it colder than a freezer (if we could swap those two, though, then things would get pretty interesting in the solar system). Kepler-22b might be a paradise, or it might be the opposite. That depends in part on the planet’s gravity, and for that you need its mass.


After the jump is SPACE‘s infographic on exoplanets which has been updated to include Kepler-22b. It took all my willpower to not photoshop a yo momma joke into it.

[Sources: New Scientist, Ars Technica, Bad Astronomy, SPACE]