'Virtual Particles' Could Create Dark, Echoing Dead Stars

From Live Science.com (Mar. 17):

There might be a massive, dead star out there that bends the stuff of raw vacuum and prevents itself from collapsing into a black hole.

That's the conclusion of a new paper published in the journal Physical Review Letters in early February, which provides the first thorough theoretical framework for understanding objects called "gravastars" and "black stars." These are ultradense, collapsed stars, like the more famous black holes. But unlike black holes, gravastars and black stars don't become so dense that they form event horizons, the border beyond which light cannot escape.

That's thanks to a phenomenon known as "quantum vacuum polarization."

Here's how it works:

There's a principle in quantum mechanics, as Live Science has reported previously, that empty space isn't really empty, but instead populated with "virtual particles." These particles are artifacts of the fact, described by quantum mechanics, that physics is governed more by probabilities than fixed realities. Because of the small possibility that a particle might exist in any one empty point in space, that empty point in space acts as if the particle is sort of, kind of there.

And those virtual particles have real effects on the world. Mostly, they're pretty small and easy to ignore. But in the extreme cases described in this paper, the particles hiding inside a heavy, collapsed star would "polarize," orienting themselves in a way that keeps them from getting too close to one another. They would form a kind of scaffolding that keeps the star from crunching too small and becoming a black hole.  [read more]