A newly discovered planet in a binary star system located 3,000 light-years from Earth is expanding astronomers’ ideas of where Earth-like, potentially inhabitable, planets can form, and methods to find them.
Astronomers from Ohio State University discovered the exoplanet, which is twice the mass of Earth. The planet (known as OGLE-2013-BLG-0341LBb) orbits one of the stars in the binary system at almost exactly the same distance from which Earth orbits the sun. 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.
However, because the planet’s host star is much less intense than the sun, the planet is a lot colder than Earth: approximately -352 degrees Farheinheit.
Although this planet may be uninhabitable, binary star systems composed of dim stars like these are the most common type of star system in the Milky Way galaxy, the astronomers said, comprising a little more than half of all star systems.
This discovery suggests that there may be many more terrestrial planets out there—some possibly warmer, and possibly harboring life.
“Normally, once we see that we have a binary, we stop observing. The only reason we took such intensive observations of this binary is that we already knew there was a planet,” said Andrew Gould, astronomy professor at Ohio State University. “In the future we’ll change our strategy.”
The scientists made their discovery using a technique known as gravitational microlensing, a method that was not verified as a viable technique until this experiment.
Very rarely, the gravity of a star focuses the light from a more distant star and magnifies it like a lens. Even more rarely, the signature of a planet appears within that magnified light signal.
“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,” he said. “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.”
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