New Earth-like planet could help find alien life

Astronomers have found a new Earth-like 'frozen' planet in a binary star system located 3,000 light-years away, a discovery that expands the potential locations where habitable planets can be detected.
At twice the mass of Earth, the planet orbits one of the stars in the binary system at almost exactly the same distance from which Earth orbits the Sun.
However, because the planet's host star is much dimmer than the Sun, the planet is much colder than the Earth - a little colder, in fact, than Jupiter's icy moon Europa.
The study by four international research teams, led by professor Andrew Gould of The Ohio State University, provides the first evidence that terrestrial planets can form in orbits similar to Earth's, even in a binary star system where the stars are not very far apart.

Although this planet itself is too cold to be habitable, the same planet orbiting a Sun-like star in such a binary system would be in the so-called "habitable zone" - the region where conditions might be right for life, researchers said.
"This greatly expands the potential locations to discover habitable planets in the future," said Scott Gaudi, professor of astronomy at Ohio State.

"Half the stars in the galaxy are in binary systems. We had no idea if Earth-like planets in Earth-like orbits could even form in these systems," said Gaudi.
The technique astronomers use to find such planets is called gravitational micro-lensing, and computer modelling of these events is complicated enough when only one star and its planet are acting as the lens, much less two stars.

The planet, called OGLE-2013-BLG-0341LBb, first appeared as a "dip" in the line tracing the brightness data taken by the OGLE (Optical Gravitational Lensing Experiment) telescope in April, last year.
The detailed analysis showed that the planet is twice the mass of Earth, and orbits its star from an Earth-like distance, around 90 million miles.
But its star is 400 times dimmer than our Sun, so the planet is very cold - around minus 213 Celsius.
The second star in the star system is only as far from the first star as Saturn is from our Sun. But this binary companion, too, is very dim.

Still, binary star systems composed of dim stars like these are the most common type of star system in our galaxy, the astronomers said.
So this discovery suggests that there may be many more terrestrial planets out there - some possibly warmer, and possibly harbouring life, researchers said.
The finding was published in the journal Science.