Habitable Zones & Global Climate: December 2014

An MIT study finds an exoplanet, tilted on its side, could still be habitable if covered in ocean.

The quantity η⊕, the number density of planets per star per logarithmic planetary radius per logarithmic orbital period at one Earth radius and one year period, describes the occurrence of Earth-like extrasolar planets.

We calculate the pre-main-sequence HZ for stars of spectral classes F to M. The spatial distribution of liquid water and its change during the pre-main-sequence phase of protoplanetary systems is important in understanding how planets become habitable.

Among the billions and billions of stars in the sky, where should astronomers look for infant Earths where life might develop?

Determining planetary habitability is a complex matter, as the interplay between a planet's physical and atmospheric properties with stellar insolation has to be studied in a self consistent manner.

Planets orbiting close to low-mass stars - easily the most common stars in the universe - are prime targets in the search for extraterrestrial life.

Today's atmosphere likely bears little trace of its primordial self: Geochemical evidence suggests that Earth's atmosphere may have been completely obliterated at least twice since its formation more than 4 billion years ago.

Our knowledge of planets' orbital dynamics, which was based on Solar System studies, has been challenged by the diversity of exoplanetary systems.

We show that terrestrial planets in the habitable zones of M dwarfs older than ∼ 1 Gyr could have been in runaway greenhouses for several hundred Myr following their formation due to the star's extended pre-main sequence phase, provided they form with abundant surface water.