Quark-gluon plasma at the LHC

In 2012 CERN's Large Hadron Collider smashed lead nuclei together and briefly created a quark-gluon plasma, the soup of particles that normally hides inside protons and neutrons. The reading was about 5.5 trillion degrees, hundreds of thousands of times hotter than the core of the Sun. The plasma lasts only a tiny fraction of a second.

The temperature is worked out from the energies of the particles that come out, not read from a thermometer. At this scale kelvin and Celsius are effectively the same number.