Starship Asterisk*

New research has revealed that fewer than predicted planets may be capable of harbouring life because their atmospheres keep them too hot.

[img3="An artist’s impression of the exoplanetary system Kepler-444.
Credit: Tiago Campante/Peter Devine/NASA"]https://www.ras.org.uk/images/stories/p ... mage_0.jpg[/img3][hr][/hr]

When looking for planets that could harbour life, scientists look for planets in the ‘habitable zones’ around their stars – at the right distance from the stars to allow water to exist in liquid form. Traditionally, this search has focused on looking for planets orbiting stars like our Sun, in a similar way to Earth.

However, recent research has turned to small planets orbiting very close to stars called M dwarfs, or red dwarfs, which are much smaller and dimmer than the Sun. M dwarfs make up around 75 per cent of all the stars in our galaxy, and recent discoveries have suggested that many of them host planets, pushing the number of potentially habitable planets into the billions.

This month, both the TRAPPIST and Kepler planet-hunting telescopes have announced the discovery of multiple near-Earth-sized planets orbiting M dwarf stars, some within the habitable zones.

New research from Imperial College London and the Institute for Advanced Studies in Princeton has revealed that although they orbit smaller and dimmer stars, many of these planets might still be too hot to be habitable. The scientists suggest that some of the planets might still be habitable, but only those with a smaller mass than Earth, comparable to Venus or Mars. ...

• Monthly Notices of the RAS 459(4):4088 (2016 July 11) DOI: 10.1093/mnras/stw959
  arXiv.org > astro-ph > arXiv:1601.05143 > 20 Jan 2016 (v1), 20 Apr 2016 (v2)