WASHINGTON, Aug. 19 (Xinhua) -- U.S. researchers said Monday that they have discovered an Earth-sized exoplanet that orbits its host star in the time it takes you to complete a single workday, or get a full night's sleep.
Located about 700 light-years away, the exoplanet named Kepler 78b is extremely close to its star. Its orbital radius is only about three times the radius of the star, causing it to complete an orbital year in a mere 8.5 hours, one of the shortest orbital periods ever detected.
Most importantly, researchers from the Massachusetts Institute of Technology (MIT) were able to detect light emitted by the planet,a first for an exoplanet as small as Kepler 78b. This light, once analyzed with larger telescopes, may give scientists detailed information about the planet's surface composition and reflective properties.
While it is about the size of Earth, Kepler 78b is most certainly not habitable, due to its extreme proximity to its host star, the MIT researchers wrote in the Astrophysical Journal.
They estimated that its surface temperatures may be as high as 2,760 degrees Celsius. In such a scorching environment, the top layer of the planet is likely completely melted, creating a massive, roiling ocean of lava.
"You'd have to really stretch your imagination to imagine living on a lava world," co-author Josh Winn, an associate professor of physics at the MIT, said. "We certainly wouldn't survive there."
The researchers also determined that the planet is about 40 times closer to its star than Mercury is to our Sun. The star around which Kepler 78b orbits is likely relatively young, as it rotates more than twice as fast as the Sun, a sign that the star has not had as much time to slow down.
Keplar 78b was observed by the U.S. Kepler Telescope, which has recently been retired from its planet-hunting mission after U.S. engineers failed to find a fix for its hobbled pointing system. Winn and his colleagues were tasked with looking for Earth-sized planets with very short orbital periods.
"We've gotten used to planets having orbits of a few days," said Winn. "But we wondered, what about a few hours? Is that even possible? And sure enough, there are some out there."