A planet about 40 light years away and twice the size of Earth is made largely out of diamond, astronomers have said. The rocky planet, called 55 Cancri e, which is in the constellation of Cancer, is orbiting a sun-like star that is visible with the naked eye. Discovered by a US-Franco research team, the planet's radius is twice that of Earth's and its mass eight times greater. Temperatures on its surface reach 3,900°F (1,648°C). "The surface of this planet is likely covered in graphite and diamond rather than water and granite," said Nikku Madhusudhan, the Yale researcher whose findings...