CAPE CANAVERAL, FLORIDA – Scientists have found a planet out in the cosmos that is close in size and content to Earth — an astronomical first. But this rocky world is so close to its sun that it is almost certainly too hot for life, with surface temperatures of over 2,000 degrees Celsius.
Astrophysicists reported Wednesday in the journal Nature that the exoplanet Kepler-78b appears to be made of rock and iron, just like Earth, but with molten layers. They measured the planet’s mass to determine its density and content. It is actually a little bigger than Earth and nearly double its mass.
Kepler-78b is hundreds of light-years away in the constellation of Cygnus. Incredibly, it orbits its sun every 8½ hours, a mystery to astronomers, who doubt it could have formed there and wonder how it moved that close. They agree the planet will be sucked up by the sun in a few billion years.
More than 1,000 exoplanets — worlds outside our solar system — have been confirmed so far. NASA’s Kepler Space Telescope, used to discover Kepler-78b, has identified 3,500 more potential candidates. The telescope lost its precise pointing ability earlier this year, and NASA has given up trying to fix it.
The size of these planets is measured by the amount of light they block when they pass in front of their parent star, and Kepler has revealed that Earth-size planets are “abundant” in our galaxy, wrote Drake Deming of the University of Maryland’s astronomy department in a comment on the papers in Nature.