Hubble Black Hole Probe
From HubbleCast. 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.
In science fiction, black holes are often portrayed as some kind of menacing threat to the safety of the whole Universe, like giant vacuum cleaners that somehow suck up all of existence. Now, in this episode, we’re going to separate the fiction from the facts and we’re going to look at the real science behind black holes and how Hubble has contributed to it.
Black holes come in different sizes. We’ve had solid evidence for the smaller ones since the 1970s. These form when a huge star explodes at the end of its life. As the outer layers are blown away, the star’s core collapses in on itself forming an incredibly dense ball. For instance, a black hole with the same mass as the Sun would have a radius of only a few kilometers.
Before Hubble was launched, astronomers had noticed that the centers of many galaxies were somehow much denser and brighter than they were expected to be. And so they speculated that there must be some kind of huge, massive objects lurking in the centers of these galaxies in order to provide the additional gravitational attraction.
Now, could these objects be supermassive black holes, that is, black holes which are millions or even billions of times more massive than the stellar ones? Or was there perhaps a simpler, less exotic explanation, like giant star clusters?
Fortunately, Hubble was on its way, along with a range of other high-tech telescopes. When the space telescope was being planned, the search for supermassive black holes was in fact one of its main objectives.