What’s Inside Black Holes

Credit: Mark A. Garlick/CfA

Supermassive black holes have been thought to lie at the heart of most galaxies, but some theorists have suggested that something else exists there instead — an even stranger supermassive object that has somehow managed to avoid gravitational collapse to a singularity, or a mysterious pinpoint where the laws of physics no longer operate.

UT Austin astronomers recently devised a test to determine which idea was correct. While a singularity has no surface area, the non-collapsed object would have a hard surface. If the hard-surface theory were true, an object being pulled in would hit the surface and be destroyed. Otherwise, the object should disappear past an event horizon, an invisible boundary past which no matter or energy can escape from the immense gravity. 

“Our motive is not so much to establish that there is a hard surface, but to push the boundary of knowledge and find concrete evidence that there is an event horizon around black holes,” said Pawan Kumar, a professor of astronomy who worked with a team on the project. 

The team determined that if a star hit a hard surface of a supermassive object, its gas would envelop the object, shining for months or even years. Given the rate of stars falling onto black holes, they estimated more than ten of these events should be able to be detected over a period of 3.5 years. After searching recent archives of telescope observations, the team found none. The discovery suggests that, as predicted by Albert Einstein’s General Theory of Relativity, matter completely vanishes when pulled into black holes.