Such a world has only recently been discovered by astronomers

Sep 4, 2012 14:32 GMT  ·  By
A rendition of the Kepler-47 binary systems, with the two stars in the background and the exoplanet Kepler-47c in the foreground (left)
   A rendition of the Kepler-47 binary systems, with the two stars in the background and the exoplanet Kepler-47c in the foreground (left)

Just a week ago, astronomers announced the discovery of an extrasolar planet orbiting a binary star system. It now appears that the discovery may have been more important than first thought, since some experts argue that alien worlds like it may support life.

The planet orbits in the binary system's habitable zone, which is an area around the stars' common center of gravity where temperatures are suitable for the existence of liquid water on the surface.

The exoplanet, called Kepler-47c, orbits the two stars in this area, according to data provided by the NASA Kepler Telescope, a planet-hunter spacecraft launched into orbit back on March 7, 2009.

While the planet itself is a gas giant, and therefore unable to support life as we know it (though other lifeforms may be possible), its discovery raises hope that rocky worlds in similar orbits may one day be discovered, and that those exoplanets may have all the ingredients required to support life.

This is an extremely important finding, astronomers say, because the number of binary systems out there is staggering. One study indicates that as many as half of the 100 billion stars in the Milky Way may exist in a binary system, Space reports.

“I thought it would only be a matter of time before we found a system like Kepler-47 where a planet is in the habitable zone,” says San Diego State University astronomer and lead author, Jerome Orosz.

The Kepler-47 system lies relatively close to Earth, in astronomical terms, at a distance of 5,000 light-years, in the constellation Cygnus. It is orbited by two exoplanets, Kepler-47b and Kepler 47c.

Another remarkable aspect of this binary system is that it's the first stellar arrangement of this type known to support multiple planets in orbit. All other binaries discovered in previous studies only had one world in orbit.

“If single stars and close binary stars can host planetary systems with an equal probability – that is not at all clear at the moment – then it would follow that life could be just as common on circumbinary planets as on planets with single stars,” Orosz argues.

Kepler-47c is believed to be only a little bit larger than Uranus, and is the second planet from the stars. It takes around 303 days to complete a full orbit around the binary system's common center of gravity.

What this means – by comparison to the solar system – is that it would lie somewhere between the orbit of Earth and Venus, if it moved around the Sun.

“I expect that the transits of an Earth-sized planet will be very hard to spot by eye, so we will need to refine our automated search programs to work for binary systems. As Kepler gets more and more data, the chances go up that we can identify the smaller transits due to terrestrial planets,” Orosz concludes.