Stars outside of the Solar System have been featured as settings in works of fiction since at least the 1600s, though this did not become commonplace until the pulp era of science fiction. Stars themselves are rarely a point of focus in fiction, their most common role being an indirect one as hosts of planetary systems. In stories where stars nevertheless do get specific attention, they play a variety of roles. Their appearance as points of light in the sky is significant in several stories where there are too many, too few, or an unexpected arrangement of them; in fantasy, they often serve as omens. Stars also appear as sources of power, be it the heat and light of their emanating radiation or superpowers. Certain stages of stellar evolution have received particular attention: supernovae, neutron stars, and black holes. Stars being depicted as sentient beings—whether portrayed as supernatural entities, personified in human form, or simply anthropomorphized as having intelligence—is a recurring theme. Real stars occasionally make appearances in science fiction, especially the nearest: the Alpha Centauri system, often portrayed as the destination of the first interstellar voyage. Tau Ceti, a relatively-nearby star regarded as a plausible candidate for harbouring habitable planets, is also popular.