Black Holes Going Down the Drain

Ever wonder what happens to a black hole at the end of its life, if such a thing can be said for a black hole? Does it sit there unchanging, or perhaps have a different end state? Physicist Steven Hawking put forth the idea that the fate of a black hole is essentially the same as that of a drop of water on a countertop: in both cases over time they just evaporate away.

Water evaporates because the molecules near to the surface are warmer than the other molecules on average. These warmer molecules also have higher energy and thus are able to leave the drop and escape into the air. Similarly, a black hole would also need to have matter (or equivalently light) escape.

The conundrum facing physicists is that black holes are famous for not allowing any matter or light that enters its surface to be freed back into space. This is why they are called “black,” afterall. Does this mean the story is over, and black holes cannot evaporate?

A team of researchers recently started investigating this problem using a bathtub of swirling water (to simulate the spinning black hole), and little pieces of paper confetti thrown into the water. They are finding that a ray of light bouncing off of the swirling tide pool of water (or equivalently off of the swirling tide pool of matter) can gain additional energy along the way. This process of shoplifting energy from the black hole is called "superradiance."

In this situation it is the swirling nature of the black hole that assists with the superradiance process. Over a very very long period of time, these little bits of light stolen in miniscule amounts from the black hole add up to equal the total mass of the black hole.
Superradiance processes such as this one eventually empty the black hole entirely of its contents, until the black hole just disappears from the universe.

In this way, what appears to be a grammar school science fair project is turning into some of the best evidence yet that it is possible for energy and matter to leave a black hole. And it is all made possible by the properties of matter "going down the drain."

Dr. Brenda Frye

About Dr. Brenda Frye

Brenda L. Frye is an observational cosmologist at the Department of Astronomy/Steward Observatory, University of Arizona. She earned her Ph. D. in Astrophysics from the University of California at Berkeley, assisted by a National Science Foundation Graduate Research Fellowship.

Her thesis work involved measuring the concentration of the total mass of visible plus dark matter in the fields of massive galaxy clusters, a program requiring the use of some of the largest telescopes in the world.

Moving a mile from her Ph. D. institution, she assumed a postdoctoral position with the Supernova Cosmology Project at Lawrence Berkeley National Laboratory under the direction of Professor Saul Permutter.

She then treked across the country to take a National Science Foundation Astronomy and Astrophysics Postdoctoral Fellowship and a Princeton Council on Sciences and Technology Fellowship both at Princeton University.

Moving further east, she became a Lecturer in Physics at Dublin City University in Dublin, Ireland, where a number of European collaborations were formed.

From there she crossed back across the pond to the west coast of the U. S. to become a tenure-track Assistant Professor of Physics at the University of San Francisco.

Her travels have now landed her at her Alma Mater in Tucson, where she teaches and does research. The aims of her research continue to be to use gravitational telescopes in space as 'lenses' to study the properties of dark matter and those of distant galaxies back to when the universe was <900 million years old.

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