Frozen World Opens up the Door for Earth-like Planets

Astronomers have discovered a new frozen world in a binary star system located 3,000 light-years away. The discovery is expected to help astronomers better understand how Earth-like, or even potentially habitable, planets can form and how to find them.

The new planet, dubbed OGLE-2013-BLG-0341LBb, has twice the mass of Earth and orbits its host star at almost the same distance from which Earth orbits the Sun. But, its host star is much dimmer than the Sun, so the planet is much colder than Earth.

Although this planet itself is too cold- colder than Jupiter's icy moon Europa - 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 suitable for life.

"This greatly expands the potential locations to discover habitable planets in the future," Scott Gaudi, professor of astronomy at Ohio State, said in a statement. "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."

To find this Earth-like planet, astronomers used a technique called "gravitational microlensing," in which the gravity of a star focuses the light from a more distant star and magnifies it like a lens. To find planets using this method, astronomers look for a small dip within that magnified light signal.

According to the study, published in the journal Science, the new planet briefly disrupted one of the images formed by its host star as the system crossed in front of a more distant star 20,000 light-years away.

"Now we know that with gravitational microlensing, it's actually possible to infer the existence of a planet - and to know its mass, and its distance from a star - without directly detecting the dimming due to the planet," Gaudi explained. "We thought we could do that in principle, but now that we have empirical evidence, we can use this method to find planets in the future."