If you have a fuel scoop typically anything above half scoop speed will increase your heat and as the scoop rate dips below half your heat from the star will drop off. So that is a good indicator for heat if you have a fuel scoop.
If you don't have a scoop and you're in SC watch the star on the sensors, if it looks Red on sensors you are close enough to get heating from the star, fly away in SC till the star changes to blue before you Hyperspace.
If you happened to actually drop out of SC next to the star then you need to escape vector out (you may take some heat damage) just stay on the escape vector until you stop getting heated then angle for your destination.
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