A Newly Discovered Planet in a Binary System Points Towards Other Earths

Image credit: Cheongho Han, Chungbuk National University, Republic of Korea

A planetary discovery by four international teams of astronomers and led by Andrew Gould of the Ohio State University is leading to yet another re-examination of the number of stars which could potentially host Earth-like planets, and the number just keeps going up.

For years it has been a common assumption that planet formation, especially for smaller, Earth sized planets in binary star systems is particularly problematical.  At the same time, binary star systems constitute roughly half the systems in our galaxy, meaning that any overall change in our understanding of their planet hosting capacity has an enormous impact on the overall number of planets thought to exist.  Yet another assumption remaining to be tested was the inhospitable nature of binary systems for planets in Earth-like orbits, regardless of their size.

Meet planet  OGLE-2013-BLG-0341LBb,  a world 3,000 light years from Earth which derives its name from the Optical Gravitational Lensing Experiment telescope (OGLE) which uses the light of distant background stars to identify planets and other dim objects through the minute gravitational pull they exert on light emitted from deep space sources.

The newly discovered planet is approximately twice the size of Earth, but orbiting around a much dimmer star than our own Sol, it is a world locked in a perpetual deep freeze equivalent to that which might be found in our own outers planets.  As it was, the discovery of OGLE-2013-BLG-0341LBb, which appeared as a blip of data from the micro-lensing transit which implied its existence, might have been routine except for what came next. Astronomers were surprised when subsequent observations “lit up” with the presence of the system’s second star as it swung into view as well.  Also small and dim, and orbiting the primary star from the same distance Saturn orbits the Sun,  the arrival of the second star has profound implications for our understanding of the potential for extra-solar life.

Although the newly discovered planet, ironically sandwiched between two stars a such close proximity yet still frozen because they are both so dim, is far too cold to host life, its mere existence points the way to other, far more promising targets.

“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. ”

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