The solid iron core is actually crystalline, surrounded by liquid.
But the temperature at which that crystal can form had been a subject of long-running debate.
Experiments outlined in Science used X-rays to probe tiny samples of iron at extraordinary pressures to examine how the iron crystals form and melt.
Seismic waves captured after earthquakes around the globe can give a great deal of information as to the thickness and density of layers in the Earth, but they give no indication of temperature.
That has to be worked out either in computer models that simulate the Earth's insides, or in the laboratory. Measurements in the early 1990s of iron's "melting curves" - from which the core's temperature can be deduced - suggested a core temperature of about 5,000˚C.
"It was just the beginning of these kinds of measurements so they made a first estimate... to constrain the temperature inside the Earth," said Agnes Dewaele of the French research agency CEA and a co-author of the new research.
"Other people made other measurements and calculations with computers and nothing was in agreement. It was not good for our field that we didn't agree with each other."
The core temperature is crucial to a number of disciplines that study regions of our planet's interior that will never be accessed directly - guiding our understanding of everything from earthquakes to the Earth's magnetic field.