Nearby “Venus Twin” Exoplanet Might Still Have Oxygen

Artist's concept of GJ 1132b with its parental star emerging from behind it. CfA/Dana Berry/Skyworks Digital

Nine months ago astronomers announced the discovery of a planet labeled a twin to Venus. A new paper raises the possibility of oxygen in its atmosphere, though its hellish temperatures rule out prospects for life.

By size and mass GJ 1132b is somewhat larger than Earth, rather than smaller like Venus, but its temperature has been estimated as somewhere between 120°C and 320°C (260°F to 620°F). Hot by our standards, but quite a bit cooler than most of the rocky planets we have detected so far, since our methods for finding planets outside the Solar System favor worlds lying close to their parental star.

GJ 1132b orbits just 2.2 million kilometers (1.4 million miles) from its star, 1.5 percent of the Earth-Sun distance. Even though its parental star, GJ 1132, is a red dwarf with a fifth of the Sun's mass, the planet is exposed to far more light than Earth receives.

Unquestionably it is very hot, but the wide estimates of its temperature reflect the possibility of a Venus-style runaway greenhouse effect.

GJ 1132b passes in front of its star often from our point of view, owing to its short orbit. At a distance of 39 light-years, tiny by astronomical standards, GJ 1132b is close enough that we have a chance of detecting the composition of its atmosphere during future transits.

Graduate student Laura Schaefer of the Harvard-Smithsonian Center for Astrophysics has already created a model to examine the chances of finding oxygen, though, and what it would mean if we do. In the Astrophysical Journal (preprint on arXiv), Schaefer has explored how the existence of an ocean of magma during GJ 1132b’s development might affect its atmosphere.

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