As of April 26, 2013, a French research team has estimated the temperature of the Earth’s inner core at 10,800 degrees Fahrenheit. This is 1,800 degrees hotter than previous estimates. The newly hypothesized temperature approaches the measured surface temperature of the sun.
The Earth's inner core is hypothesized to be a solid iron mass despite the high temperature; this is due to extremely high pressure. It is thought that the inner core rotates within the Earth's outer core, which is composed of liquid iron and sulfur. The Earth's outer core is thought to be slightly cooler than the inner core, at a range of 7,280 to 10,340 degrees Fahrenheit.