I was on the solar system and i decided to make the sun collide with one of the Castor starts(don't remember if it was Aa or Ba) and then i checked on neptune to see if it lost mass, i found out it did but i saw that when it lost all its hydrogen, the temperature had instantly dropped from 4700 Celsius down to -200C, then made a smaller star crash into the sun, and the same thing happened but instead it had dropped to 1100C after the hydrogen loss.
After that i made some other tests making sure i was using the same star, and the final temperature varied from 200C to -90C(With castor Ba),then i tested it with Castor Aa and it dropped down to -258C.
This (likely) means that the mass of the stars partly changes by how much the temperature drops, but part of it is also random
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Also, crashing Regulus into the sun makes the 4 gas planets insantly loose all their hydrogen even before the supernova cloud reaches them and heats them up(it didn't even need to reach jupiter), but even neptune got affected
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I always explain more than i think i should