Earth-like planet discovered in twin star system

Discovery opens the possibility of many planets in Earth-like orbits in star systems previously unexplored, say scientists

By Aprajita Singh
Last Updated: Saturday 04 July 2015


Scientists have found a new Earth-like planet some 3,000 light years away which belongs to a binary star system, a pair of stars that revolve around a common centre of mass. But it has a peculiar orbit. It revolves around only one of the stars (planets that orbit both members of a binary star system are relatively common).

The planet, approximately twice the mass of the Earth, orbits its star at approximately the same distance as the Earth around the sun. The only difference is both stars are much dimmer than the sun, because of which the planet is frozen.

The discovery was made by four international research teams, led by Andrew Gould of the Ohio State University, and published in the July 4 issue of the journal Science.

Initially when the planet was discovered, the scientists were unaware that it belonged to a binary system. The discovery was made using a phenomenon known as gravitational microlensing, wherein a star focuses the light from another, more distant star and magnifies it. If this magnification undergoes distortion for a short while during the process, the implication is that a planet revolves around the star. The planet, called OGLE-2013-BLG-0341LBb, was first see on April 11, 2013. While observing the new planet, the team of researchers observed an unexpected eruption of light, called a caustic eruption, and it was only then that the presence of the twin star was revealed.

Since more than half of all stars exist as binary systems, the discovery opens up new avenues in the search for habitable Earth-like planets. If the star were of the same intensity as the sun, the planet would lie in “The Goldilocks Zone”—the habitable region around a star where the conditions are just right for life.

“It is believed that all planets form in disks around stars, as the stars themselves are forming. But whether such disks would be stable enough to form planets in the presence of a second star was unknown.  Hence, this discovery opens the possibility of many planets in Earth-like orbits in star systems that were previously unexplored,” says Gould.

Scott Gaudi, professor of astronomy at Ohio State says, "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.

Three other planets were discovered orbiting binary systems, but using other techniques. None of them had Earth-like orbits or sizes comparable to that of Earth, as this one does, whose discovery was rather fortuitous.

He also pointed to the contribution of amateur contributors and collaborators  to the discovery. “This work by amateurs is extremely important, both in this planet discovery and in many previous microlensing planets. In this discovery, Ian Poritt (an amateur observer from Palmerston North, New Zealand) found the first evidence that the host to the planet was in a binary star system. Now, this binarity would have been subsequently discovered by other telescopes that were operating independently.  However, because of Mr Poritt's heads up work, we found out about the binary within minutes of the observations, and this led us to organize intensive observations of this microlensing event over its peak.”

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