If the sun's intrinsic value is based on a human's need for it to survive, then the sun's value to a particular human is dependent on that human's valuation of his own life, yes?
Strangely enough, your argument is sound because your premise is false and your conclusion is true 1) FALSE: "the sun's intrinsic value is based on a human's need for it to survive" 2) TRUE (more or less): "the sun's value to a particular human is dependent on that human's valuation of his own life".
Your argument is valid only because every false premise logically implies every true conclusion. For example: If the sky is pink with green poke-a-dots, then dogs are mammals.
It's clear that different people value their lives different amounts. Therefore, each person values the sun different amounts. The sun's value is subjective.
Yes, the sun's value is subjective. But its value is not intrinsic.