The search for a far-off twin of Earth has turned up two of the most intriguing candidates yet. Planet Kepler-62e and Planet Kepler-62f
Scientists say these new worlds are the right size and distance from their parent star, so that you might expect to find liquid water on their surface. With water comes the possibility bacteria and Alien life forms.
“They are the best candidates found to date for habitable planets,” stated Bill Borucki, who leads the team working on the US space agency Nasa’s orbiting Kepler telescope.
The prolific observatory has so far confirmed the existence of more than 100 new worlds beyond our Solar System since its launch in 2009. The two now being highlighted were actually found in a group of five planets circling a star that is slightly smaller, cooler and older than our own Sun. Called Kepler-62, this star is located in the Constellation Lyra.
They are what one might term “super-Earths” because their dimensions are somewhat larger than our home planet – about one-and-a-half-times the Earth’s diameter. Nonetheless, their size, the researchers say, still suggests that they are either rocky, like Earth, or composed mostly of ice. Certainly, they would appear to be too small to be gaseous worlds, like a Neptune or a Jupiter.
Given the right kind of atmosphere, it is therefore reasonable to speculate, says the team, that they might be able to sustain water in a liquid state – a generally accepted precondition for life.
“Statements about a planet’s habitability always depend on assumptions,” said Lisa Kaltenegger, an expert on the likely atmospheres of “exoplanets” and a member of the discovery group.
Dr Suzanne Aigrain is a lecturer in astrophysics at the University of Oxford.
She said ground-based experiments and space missions planned in the next few years would give more detailed information on distant planets like those announced by the Kepler team. Astronomers would like to pin down the masses of the planets (information difficult to acquire with Kepler), as well as getting that data on atmospheric composition.
Dr Aigrain told BBC News: “What we do next is we try to find more systems like these; we try to measure the frequency of these systems; and we try to characterise individual systems and individual planets in more detail.
“That involves measuring their masses and their radii, and if possible getting an idea of what’s in their atmospheres. But this is a very challenging task.”Kepler meanwhile will just keep counting planets beyond our Solar System.
The hunt continues…