In US2, when you change the temperature of a star (colder or hotter), there is no impact in temperature of the orbiting bodies (e.g. planets).
This use to work in (original) Universe Sandbox, where the changing of a star's temperature did impact the temperature of the orbiting bodies.
NEW- as pointed out in the below post (thanks Lord DC), changing the Luminosity of a Star (changes the temperature) and thus changes the temperature of the orbiting bodies. However, since Temperature and Luminosity are related, changes in temperature should also change luminosity, thus changing the temperature of the surrounding orbiting bodies.
So the bug Subject has now been modified to the "Changing the temp of a Star, doesn't change Luminosity"