Researchers have heated solid gold to an astonishing 19,000 kelvins (33,740°F), more than 14 times its melting point, without it melting. This unprecedented feat challenges the long-standing "entropy catastrophe" theory, which posited that solids cannot remain stable above approximately three times their melting temperature.

The study, published in Nature on July 23, 2025, marks a significant advancement in our understanding of material behavior under extreme conditions.

New method for measuring extreme temperatures

The research team, including physicists from SLAC National Accelerator Laboratory, the University of Nevada, Reno, and several international institutions, employed an innovative approach to measure temperatures in extreme conditions. They utilized ultrafast X-ray laser pulses to heat a thin gold foil to extreme temperatures.

By analyzing the vibrations of atoms within the gold using X-rays, they could directly determine the material's temperature without relying on indirect estimates. This method allowed for precise measurements in environments where traditional temperature sensors would fail due to the brevity and intensity of the heat involved.

Breaking the catastrophe barrier

The concept of the entropy catastrophe suggests that as a solid is heated, its atoms vibrate more intensely. At a certain point, these vibrations would cause the solid to become more disordered than its liquid form, leading to spontaneous melting. This threshold was believed to be around three times the melting point of the material.

However, the gold sample in this experiment withstood temperatures up to 14 times its melting point, remaining solid and crystalline. The rapid heating process, completed in just 45 femtoseconds (45 quadrillionths of a second), likely prevented the atoms from expanding and disrupting the solid structure.

This discovery has profound implications for various fields, including materials science, planetary science, and fusion energy research. Understanding how materials behave under extreme conditions is crucial for developing technologies such as nuclear fusion reactors and for studying the interiors of planets and stars. The ability to superheat materials without causing them to melt opens new avenues for creating and manipulating materials with unique properties.

Furthermore, the new measurement technique developed in this study provides a reliable method for assessing temperatures in warm dense matter, a state of matter that exists under extreme pressure and temperature conditions.

This advancement could lead to more accurate models of astrophysical phenomena and improved designs for energy systems that operate under extreme conditions.