In an exploding star, the shock waves generated during the explosion, known as supernova shock waves, can result in incredibly high temperatures. Depending on the energy released by the supernova and the structure of the progenitor star, the temperatures in the shock wave can vary considerably. However, it's not uncommon for atoms within the shock wave to reach temperatures ranging from tens of millions of degrees Celsius up to several hundred million degrees Celsius. These temperatures are often comparable to or exceed those found in the Sun's core.

At such extreme temperatures, atoms in the shock wave experience intense thermal energy and undergo a process called plasma formation. Electrons get stripped away from their respective atoms, leaving behind a sea of free electrons and positively charged ions. This ionized gas, or plasma, is what primarily makes up the shock wave and becomes an environment of extreme physical conditions.

For reference, the Sun's core temperature is approximately 15 million degrees Celsius, and stars like Sirius, one of the brightest in our night sky, have core temperatures of about 27 million degrees Celsius. Supernova shock waves, in comparison, can far exceed these temperatures, further highlighting their immense heat and the dynamic processes occurring during a stellar explosion.