|How would you feel if you grew almost three years older every day? If you lived on a certain exoplanet, you would. Scientists have discovered an Earth-sized planet that whips around its host star in a mere 8.5 hours.|
The exoplanet is named Kepler 78b. Located about 700 light-years away from Earth, this planet has one of the shortest orbital periods ever detected. Because it lies so close to its star, the planet has estimated surface temperatures that rise to an impressive 3,000 degrees Kelvin, or more than 5,000 degrees Fahrenheit. In this type of environment, it's likely that the planet's surface is completely melted, creating a massive, roiling ocean of superhot lava.
Actually discovering this planet wasn't easy, though. The researchers examined more than 150,000 stars that were monitored by the Kepler Telescope before they found the superheated exoplanet. Currently, scientists are pouring over Kepler data in the hopes of finding an Earth-sized planet that is, potentially, habitable. Yet the researchers were curious whether it was possible to have an Earth-sized planet with an orbital period of only a few hours.
"We've gotten used to planets having orbits of a few days," said Joshua Winn, one of the researchers, in a news release. "But we wondered, what about a few hours? Is that even possible? And sure enough, there are some out there."
The scientists detected the light given off by Kepler 78b by measuring the amount by which the overall light dimmed each time the planet passed behind the star. The researchers believe that the planet's light is possibly a combination of radiation from its heated surface and light reflected by surface materials, such as lava and atmospheric vapor.
It's likely that Kepler 78b is about 40 times closer to its star than Mercury is to our sun. In addition, the host star itself is relatively young since it rotates more than twice as fast as the sun; this indicates that not enough time has passed for it to slow down. Needless to say, Kepler 78b is not habitable.
"You'd have to really stretch your imagination to imagine living on a lava world," said Winn. "We certainly wouldn't survive there.
Currently, the researchers are searching for other short-period planets; but unlike Kepler 78b these will hopefully be habitable. Exoplanets that orbit brown dwarfs, which are cold, almost-dead stars, could hold the potential for life.
"If you're around one of those brown dwarfs, then you can get as close in as just a few days," said Winn. "It would still be habitable, at the right temperature."
The findings are published in The Astrophysical Journal.