 FACT: It is stated during the super nova sequence that Johnnys  temperature of 4,000 degrees Kelvin (3,727 Celsius / 6,740  Fahrenheit) is near to the temperature of the sun and that were he  to get any hotter, he would ignite the atmosphere of the planet. In  fact, this is a discredited idea from before the earliest  atmospheric nuclear tests, and nuclear fireballs with temperatures  of tens of thousands of degrees have had no such effect.