Source: All The Bright Places by Jennifer Niven, page 304. 

Context: “black holes are the remnants of former stars; they’re so dense that not even light can escape; they lurk inside every galaxy; they’re the most destructive force in the cosmos;”

In their words: the world or universe regarded as an orderly, harmonious system.” –https://www.dictionary.com/browse/cosmos?s=t

In my words: A complete system of the world or universe.