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Gassy Exoplanet has Earth-like Mass

  • VOA News

KOI-314c, shown in this artist's conception, is the lightest planet to have both its mass and physical size measured. (Harvard-Smithsonian Center for Astrophysics)
Astronomers have discovered what they’re saying is the first planet outside our solar system, or exoplanet, with the same mass as Earth. But although its weight is similar to Earth, the planet is 60 percent larger in diameter.

KOI-314c, which likely has a thick gaseous atmosphere, orbits a dim red dwarf star and is about 200 light-years away. The astronomers said it circles its star every 23 days and that its temperature is around 220 degrees Fahrenheit, too hot for life as we know it.



Weighing such a small planet was a challenge. Conventionally, astronomers measure the mass of an exoplanet by measuring the tiny wobbles of the parent star induced by the planet's gravity. But this method is extremely difficult for a planet with Earth's mass. The previous record holder for a planet with a measured mass (Kepler-78b) weighed 70 percent more than Earth.


Using this technique, the astronomers actually found two planets. The second planet in the system, KOI-314b, is about the same size as KOI-314c but significantly denser, weighing about 4 times as much as Earth. It orbits the star every 13 days.

The discovery was serendipitous, as the team was looking for exomoons, not exoplanets.


Kipping presented this discovery, which was based on data from NASA’s Kepler spacecraft, at the 223rd meeting of the American Astronomical Society.