Research sheds new light on black holes

Mar 22, 2011

(PhysOrg.com) -- The quantum phenomenon which is thought to cause black holes to leak energy and ultimately explode is more common than first thought according to Victoria University researchers.

Physicist famously discovered in 1973 that are not entirely black. Instead, a subtle results in them losing energy and particles into space, causing them to shrink and, over trillions of years, disappear. Until Hawking’s discovery, black holes were considered to have such a strong gravitational field that nothing could escape.

Research led by Matt Visser, Professor of Mathematics at Victoria, has shed new light on the theory, known as , by calculating the conditions that would be needed for radiation leaks.

"We now believe there are a number of theoretically plausible objects in the universe that emit Hawking Radiation. It’s more robust and more prevalent than scientists thought."

While Hawking’s discovery is widely accepted in the scientific world, no observational astronomer has yet seen a black hole exploding. The final moments are thought to involve several hundred tonnes of matter converting itself to energy in 2 or 3 seconds, causing an explosion that would dwarf any nuclear weapon ever envisaged.

Professor Visser’s research team, which includes colleagues in Spain and Italy, has also provided new information about what happens just before a black hole disappears.

"It is the last few seconds we don’t understand. Our work has helped us to probe that period more closely and we have produced calculations that work down to the last few millionths of a second.

"It sounds good from the outside and it has added significantly to our understanding of what happens right at the end. However, a lot of unanswered questions remain."

Scientific papers on the research findings have recently been published in the Journal of High Energy Physics and in Physical Review D (the American Physical Society journal of particles, fields, gravitation & cosmology).

Professor Visser says discovering that Hawking Radiation is a more frequent occurrence helps unravel some of the mysteries of the Universe, but is not a cause for alarm.

"We’d have to be incredibly unlucky for a small black hole to wander into our solar system just before it was due to explode. It’s very very unlikely."

Another area of Professor Visser’s research is analogue spacetimes which are ways of mimicking gravity using simpler physical systems. One example is modelling acoustic black holes using sound in a moving fluid.

A former student of Professor Visser’s is setting up a laboratory in Trieste, Italy, where she hopes to construct an experiment using sound in moving fluid, to observe Hawking Radiation and test the various theories about how it works.

"We would love to have a direct experience of the Hawking effect but the most likely way we will see it is by using some kind of analogue model.

"Distance is not the issue, it’s that there are lots of sources of radiation in the Universe and what’s being emitted by a black hole, even at the end, would be dwarfed by other sources. The last few seconds of a black hole’s existence would be impressive by human standards but not by cosmological ones."

Explore further: X-ray powder diffraction beamline at NSLS-II takes first beam and first data

Provided by Victoria University

4.3 /5 (11 votes)

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User comments : 9

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randomwraith
not rated yet Mar 22, 2011
Given there are several Victoria Universities dotted around the world, it should be pointed out that Matt Visser is at Victoria University of Wellington, New Zealand.
frajo
4.5 / 5 (4) Mar 23, 2011
While Hawkings discovery is widely accepted in the scientific world, no observational astronomer has yet seen a black hole exploding.
While the latter is true, the former raises the question how to measure the "width of acceptance".
A quick glance at the Wikipedia entry on "Hawking radiation" shows at least two problems with the HR hypothesis (not: "discovery").
Objectivist
not rated yet Mar 23, 2011
@frajo
The object at the center of our galaxy is about 4 million solar masses, calculated by observing the orbits of the stars closest to it. Can you suggest any other possible type of object this massive? If not, would you consider black holes eternal? Aren't there any "problems" with that?
frajo
not rated yet Mar 23, 2011
The object at the center of our galaxy is about 4 million solar masses, calculated by observing the orbits of the stars closest to it. Can you suggest any other possible type of object this massive?
I don't suggest any other object.
If not, would you consider black holes eternal?
Eternity is a long time interval and I've not yet made up my mind whether the universe is existing eternally.
Aren't there any "problems" with that?
With the notion of "black hole"? No.
But there seems to be a huge gap between the mathematical concept of a singularity and physical reality where infinities are not possible for several reasons. This is a problem of the model. Obviously, GR cannot tell us all we want to know.
Objectivist
not rated yet Mar 24, 2011
With the notion of "black hole"? No.
Am I correct to assume that you don't believe black holes, such as micro black holes, can form out of collision?
Eternity is a long time interval and I've not yet made up my mind whether the universe is existing eternally.
Would you agree with me if I'd say that any functional system must appear eternal and infinite for any observer that is bound to only roam within it?
But there seems to be a huge gap between the mathematical concept of a singularity and physical reality where infinities are not possible for several reasons.
That may be true. Would you suggest we stop all progress in this field until the nature of black holes has been fully proven, or continue the research with the best assumption we have (and we do have some pretty solid theories)? Would you agree that ignoring obstacles for now may lead research to a point where these obstacles can more easily and at a lesser "cost" be parried?
frajo
not rated yet Mar 28, 2011
With the notion of "black hole"? No.
Am I correct to assume that you don't believe black holes, such as micro black holes, can form out of collision?
No.
Eternity is a long time interval and I've not yet made up my mind whether the universe is existing eternally.
Would you agree with me if I'd say that any functional system must appear eternal and infinite for any observer that is bound to only roam within it?
No.
But there seems to be a huge gap between the mathematical concept of a singularity and physical reality where infinities are not possible for several reasons.
That may be true. Would you suggest we stop all progress in this field until the nature of black holes has been fully proven, or continue the research with the best assumption we have (and we do have some pretty solid theories)? Would you agree that ignoring obstacles for now may lead research to a point where these obstacles can more easily and at a lesser "cost" be parried?
No.
Objectivist
not rated yet Mar 30, 2011
1) Thus you agree that black holes must evaporate in one way or another. Am I correct?

2) Can you give me one single hypothetical example of such a system? (Of course it must have functional and compatible physical laws)

3) I can only assume you answer no to both questions. If you do answer no to the latter you're implying that ignoring Newton and going straight to Einstein would have been "easier" or "cost efficient." Which only shows you don't quite understand the notion of evolution, or rather: the necessity of evolution.
frajo
not rated yet Mar 30, 2011
1) Thus you agree that black holes must evaporate in one way or another. Am I correct?
No.
2) Can you give me one single hypothetical example of such a system? (Of course it must have functional and compatible physical laws)
No.
3) I can only assume you answer no to both questions.
No.
If you do answer no to the latter you're implying that ignoring Newton and going straight to Einstein would have been "easier" or "cost efficient."
No.
Which only shows you don't quite understand the notion of evolution, or rather: the necessity of evolution.
It doesn't matter what I understand and what I don't understand. But I don't see any necessity to postulate the necessity of evolution when it's alive and kicking.
Objectivist
not rated yet Mar 30, 2011
It's like talking to a wall. I give up.

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