Is a 'naked singularity' lurking in our galaxy?

[Gisgangusur Profile]

Could a naked singularity, the bare core of a black hole, be sitting at the centre of our galaxy? A new study shows how astronomers could detect such a brazen object - which is so dense it would shred the known laws of physics.

Singularities exist in the heart of every black hole, according to Einstein's general theory of relativity. When matter collapses under its own gravity, it forms either a point or a ring-shaped line of infinite density. But each of these singularities is cloaked by a so-called event horizon - where light and everything else is inexorably sucked inwards. So we could never see one.

Unless, that is, there are black holes that spin at extreme speeds. A spinning black hole drags nearby space around with it, and if it spins fast enough, then light and matter could escape from right by the singularity, because they would be flung outwards by the dizzying rotation.

This gravitational tornado would have no event horizon, and the singularity would be exposed.

Its gravity would also have a telltale effect on light passing by it from background objects, say Arlie Petters of Duke University in Durham, North Carolina, US, and Marcus Werner of the University of Cambridge, UK.
Rainforest of sources

They find that a spinning naked singularity turns out to be a strong gravitational lens, magnifying the light from background stars more than an ordinary black hole and producing a distinctive pattern of images.

Astronomers could start looking for this effect in the centre of our galaxy, where some dark object 3.6 million times the mass of the Sun is lurking. It is usually assumed to be a black hole with an event horizon, but if it is instead a naked singularity, then at least one existing instrument could tell.

The CHARA interferometer is an array of six telescopes on Mount Wilson in California, US, which can produce exceptionally sharp images. Aimed at the centre of the galaxy, it would be able to distinguish the lensing effect of a black hole from that of a naked singularity.

The galactic centre is a crowded place, however, so observers will have to slog though "a rainforest of sources" to sieve out lensed images, says Petters.
Cosmic censorship

Naked singularities make many physicists uneasy. "These singularities are worrisome philosophically because they are places where the laws of physics break down," says Petters. That's because the infinite density renders all equations meaningless.

"If a naked singularity is found today, then no matter how hard we try, our current physics cannot predict the future behaviour of such objects," Petters told New Scientist.

And if a singularity follows no rules, it could leak lawlessness into the universe, destroying any concept of cause and effect.

So in 1969, Cambridge mathematician Roger Penrose coined the "cosmic censorship hypothesis" - that all singularities must be insulated from the rest of the universe behind a horizon. "When singularities are covered up by an event horizon, the problem of physics breaking down is pushed under the covers," says Petters.
Tangle of strings

But a naked singularity doesn't necessarily mean cosmic chaos. To properly describe these extreme objects, physicists need a more profound theory that can deal with strong gravity on tiny scales - a quantum theory of gravity.

A dose of quantum mechanics should blur out a singularity, so its density isn't infinite after all. One candidate for such a unified quantum gravity model is string theory, which might describe the singularity as a fuzzy tangle of tiny vibrating strings.

Depending on exactly how gravity behaves on such small scales, it is possible that a singularity would shine with its own light, or emit gravitational waves. In that case, astronomers might not have to settle for indirect evidence from lensing. One day they might be lucky enough to gaze on a singularity in all its naked splendour.

http://www.newscientist.com/article/dn12707-is-a-naked-singularity-lurking-in-our-galaxy.html

[Ghost32 Profile Website]

Light is not seen exiting the black hole because of a flaw in the human mind and not any breaking of the laws of physics.

The birth and death of the photon is the exact same instant and the light doesnt actually travel at all, but our human minds try to stretch out the exchange of energy into our human frame of referrence and we get it all wrong.

Also at the speed of light time and space stands still and thus it does not travel at all...