EXTRASOLAR PLANETS

Can a red dwarf host a habitable planet?

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Science  24 Jun 2016:
Vol. 352, Issue 6293, pp. 1531-1532
DOI: 10.1126/science.352.6293.1531-c

A flaring red dwarf star in the nearby system DG Canum Venaticorum.

PHOTO: NASA'S GODDARD SPACE FLIGHT CENTER/S. WIESSINGER

The habitable zone is a region around a star where an Earth-mass planet with an Earth-like atmosphere would have a surface temperature of 0° to 100°C. Owen and Mohanty model planets in the habitable zone of red dwarfs, which are by far the most common type of star. These planets form with a hydrogen/helium envelope, and the greenhouse effect makes their surfaces too hot. Radiation from the star can strip away the envelope from a Venus-mass planet, causing it to fit the “habitable” criteria within a reasonable time. But the stronger gravity of an Earth-mass planet prevents it from ever losing enough of the envelope to cool down and become habitable.

Mon. Not. R. Astron. Soc. 459, 4088 (2016).

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