For two decades, scientists have thought the Earth's solid core was a balmy 9,000 degrees Fahrenheit or so, based on the temperature at which iron crystallizes when under high pressure. But new research using X-rays to examine iron under huge amounts of pressure indicate the real temperature of the core is closer to 10,800 degrees—about the same as the surface of the sun, reports the BBC. The findings from the French research team are outlined in Science. (More Earth stories.)