Exoplanet Kepler-78b's earth-like mass suggests more such out there

An earth-sized planet far beyond our solar system has been found to have a similar mass to our planet, said researchers engaged in the hunt for other habitable worlds.

While Kepler-78b is not a hospitable place, with surface temperatures exceeding 2,000 degrees Celsius, confirmation of its mass and density was hailed as a good omen for the discovery of other earth-like planets.

In separate papers in the journal Nature, two groups of scientists said they had independently measured Kepler-78b's mass - one team put it at 1.69 times that of earth and the other at 1.86 times.

Their calculations of the exoplanet's density were 5.3 and 5.57 grams per cubic centimetre respectively - also similar to earth's 5.5 grams and implying a composition of rock and iron.

This made Kepler-78, which orbits its star every 8.5 hours, the exoplanet most similar to earth for which the mass, radius and density has been determined.

"Its existence bodes well for the discovery and characterisation of habitable planets," Drake Deming of the University of Maryland's astronomy department wrote in a comment on the papers, also carried by the journal Nature.