The Most Earthlike World Yet
David A. Aguilar (CfA)
An artist's illustration of the strange Earth-like rocky planet Kepler-78b, which orbits a sun-like star 400 light-years from Earth. The planet is 20 percent wider and 80 percent more massive than Earth.
Also this year, researchers found the closest thing to an Earth twin in size and composition, though it's far too hot to support life as we know it.
Kepler-78b is just 20 percent wider and about 80 percent more massive than our planet, with a density nearly identical to that of Earth. The alien world, which is about 400 light-years from Earth, lies just 900,000 miles (1.5 million km) from its host star and completes one orbit every 8.5 hours. Surface temperatures on Kepler-78b likely top 3,680 degrees Fahrenheit (2,000 degrees Celsius), researchers say.