For centuries, scientists imagined objects so heavy and dense that their gravity might be strong enough to pull anything in - including light. They would be, quite literally, a black hole in space.
But it’s only in the past few decades that astronomers have conclusively proved their existence.
Today, Hubble lets scientists measure the effects of black holes, make images of their surroundings and glean fascinating insights into the evolution of our cosmos.
You can download this episode in various formats from: http://www.spacetelescope.org/videos/hubblecast43a/