VOA慢速英语:研究人员：银河系中心的许多黑洞

galaxy – n. any one of the very large groups of stars that make up the universe

stellar – adj. of or relating to the stars

x-ray – n. powerful invisible rays that can pass through various objects and that make it possible to see inside things, such as the human body

spiral – n. a circular curving line that goes around a central point while getting closer to or farther away from it

layer – n. an amount of something that is spread over an area