Between the smallest stars and the most massive planets, a strange class of celestial objects pervades the universe. Called brown dwarfs, or "failed stars," these liminal objects are more massive than gas giants such as Jupiter but less massive than the smallest stars.
They're also really common: Astronomers recently discovered that there could be as many as 100 billion of these faintly glowing bodies scattered throughout the Milky Way. With estimates of the Milky Way's stellar population ranging from 100 billion to 400 billion, that means brown dwarfs could be almost as common as stars themselves.
