Read this excerpt from "Why Are They Called Black Holes?" Astronomers can observe these effects. For example, when a black hole passes through a cloud of dust, it pulls the dust inside it like a big gravity-powered vacuum cleaner. When a star passes too close to a black hole, the black hole pulls it in and breaks up the star, spewing giant flashes of high energy called gamma-ray bursts. And when scientists see light bending even though there is no visible matter nearby, they have evidence that there is an invisible black hole.

In this excerpt, the author's use of description

proves why black holes are so complicated.
details the high energy that stars have inside them.
explains how scientists know when a black hole is nearby.
describes what a black hole looks like without the use of special equipment.