Online catalogue ranks planets on suitability for life

A NEW atlas of planets and moons beyond our own solar system has been created to help scientists categorise the 700-odd ‘exoplanets’ that have been discovered by apparatus such as Nasa’s Kepler space telescope.

The online Habitable Exoplanets Catalogue rates the likelihood that planets and moons can support life by assessing characteristics such as their similarity to Earth, ability to support vegetation, and distance from their star.

It has so far found only two worlds that match the criteria for habitability: Gliese 581d and HD 85512b are both ‘earthlike’ – although only marginally.

Gliese 581d (above), a ‘warm superterran’ (a planet larger than our earth) is six times the mass of earth and has a surface temperature of -50C. HD 85512b, also a warm superterran, is only four times the mass of earth and enjoys a balmy surface temperature of 65C.

Abel Méndez, director of the Planetary Habitability Laboratory at the University of Puerto Rico and principal investigator of the project says the ranking system will help organise exoplanets from best to worst candidates for life.

“New observations with ground and orbital observatories will discover thousands of exoplanets in the coming years," says Méndez. "We expect that the analyses contained in our catalogue will help to identify, organise, and compare the life potential of these discoveries.”

Of the other entries in the catalogue, there are a further 15 or more exoplanets and 30 exomoons that are potentially habitable. Future observations with new instruments, such as Nasa’s proposed Terrestrial Planet Finder, will seek to confirm the suitability of these celestial bodies for sustaining life. ·