Universe Today : Searching for Objects Even Stranger Than Black Holes

Written by Fraser Cain

Black holes are already plenty bizarre. Imagine all the mass of several suns compressed down into an object of potentially infinitely small size. But what if you could find an object that's even stranger: a theoretical "naked singularity"; a black hole spinning so quickly that it lacks an event horizon. A point in space where the density is infinite, yet still visible from the outside.

Here's the current thinking on black holes. They're formed when a large star collapses in on itself, lacking the outward pressure to counteract the inward pull of gravity. Once the object reaches a certain size its pull becomes so great that nothing, not even light can escape. The black hole surrounds itself in a shroud of darkness called the event horizon. Any object or radiation that passes through this event horizon is inevitably sucked down into the black hole. And that's why they're thought to be black.

But what if that's not always correct? What if there are circumstances where black holes might not be black at all? It would take some serious spinning, however.

All the black holes discovered so far are thought to be spinning, sometimes more than 1,000 times a second. But in theory, if you could get a black hole spinning ludicrously fast, so that the angular momentum of its spin overcomes the gravitational pull of its mass, it should be able to shed its event horizon. A black hole with 10 times the mass of our Sun would need to be spinning a few thousand times a second.

And here's the cool part. According to researchers from Duke University and Cambridge, an object spinning like this should be detectable by its gravitational lensing. This is where a massive object, like a black hole, acts like a natural lens to focus the light from a more distant object. If the researchers are right, astronomers should be able to see a telltale signature on the lensed light using existing instruments (or those coming soon).

Their research was published in the September 24th issue of the research journal Physical Review D.

Original Source: Duke University News Release