A good analogy can help your audience to understand something strange or complicated, or both. The metaphor in the title of this post refers to an explanation by the astronomer Antony Stark of why most galaxies, including ours, have sudden periods where stars form (starbursts).
When a highly dense ring of gas is drawn toward the black hole at the center of a galaxy, its mass will exceed the ability of the black hole to consume it. Then the gas will be ejected suddenly in a starburst. Tony explains it in a newspaper story here. He is shown walking to work at his telescope located down at the South Pole in the NOVA TV program Monster of the Milky Way. Look at the beginning of Chapter 7: Fate of the Milky Way.
I recalled that analogy a week ago in describing the new Star Trek movie, which seemed to be trying to cram in way too much stuff into the story, including some black holes. By the way, Tony is my brother-in-law.