When you heat up an asteroid, rocky planets or gas giant to temperatures which are over 1000 degrees Celsius, there should be a habitable zone forming around the hot object. Currently developers did not bother making habitable zones for hot objects other than stars.
There is a need for habitable zones on hot asteroids, rocky planets and gas giants, because when they are heated up manually by editing the temperature or heated by collisions, automatically a new habitable zone is created in the space around the object.
For example, if I put Earth into a new simulation and heat it up to 1000+ degrees Celsius, a habitable zone should begin to appear.
However small or big a rocky or gas planet is, it is suppose to have zones around it. The distance of the temperature zones depends on how much heat the object is ejecting into the occupying space around its body.
Please add temperature zones around hot asteroids, rocky planets and gas giants.