Originally posted by Magnon
Heat (energy) should be distinguished from temperature.
You're right.
Originally posted by Magnon
The energy emitted by a star over its lifetime is ca. 10^44 Joules, therefore the heat of "ten billion suns" equals 10^54 Joules.
Where did you get the Sun's lifetime from? Because Superman was only exposed to the heat for a brief instance, not 10 billion years.
The sun has a total effect of 4×10²⁶ J/s, suppose that Superman is exposed to the blast for a second, that's 4×10²⁶ J. And that's still a generous assumption because because it assumes we're dealing with the total effect (and not just part of it which would usually be the case), and because we're assuming a 100% absorption.
Originally posted by Magnon
If we assume the heat capacity of CAS is 5*10^6 J/K (a rough order-of-magnitude estimate) then the heat of "ten billion suns" would increase his temperature by 2*10^47 K. That's way more than the Planck temperature.
The issue isn't whether or not it reaches Planck temperature, but moreso because it's finite.