Question

Why do stars differ in brightness?

Answer 1

star differ in brightness due to the it's age and type of reaction going in the core of that star. it can be classified into class A to class F.
star with young age are more hot and Old are less hot classified from A,B,C,D,E,F respectedly

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Answer 2

Heya,

Here is the answer:-

Stars differ widely in mass or weight, size, temperature, and brightness. The brightest stars are about a million times more powerful than the sun, while the least bright are only one hundredth as powerful red giants. The biggest stars are hundreds of times greater in size than the sun.

Thanks..