The correct answer is a metaphor. A metaphor is a figure of speech that uses something to refer to something else. Usually the two things are quite different things but their qualities are somewhat similar in a literal or figurative sense. In this instance "a radiant star" is just a giant conglomerate of burning gases in outer space and "love and brotherhood" are a human emotion and an ideal. However, our sun is a radiant star and it gives us warmth and life and love and brotherhood irradiate human beings with emotional warmth and life and that is why the metaphor is accurate.