The Naked Singularity Recipe: Spin a Black Hole, Add Mass

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The event horizon of a black hole is the point of no return. If anything, even light, strays within the bounds of this gravitational trap, it will never escape. The event horizon is what makes a black hole black.

But say if there was a way to remove the event horizon, leaving just the black hole’s singularity to be “seen” by the rest of the universe? What if there is a special condition that would allow this infinitely small, yet massive point to become naked?

Generally physicists agree that this is a physical impossibility, but the mathematics says otherwise; a naked singularity could be possible.

Previously on Astroengine, one “special condition” was investigated when an extreme black hole collision was simulated by a Caltech researcher. In this case, the black hole pair was smashed together, head-on, at a velocity close to the speed of light. The gravitational waves travelling away from the collision were then modelled and characterized. It turns out that after this insanely energetic impact, 14% of the total mass was converted into gravitational wave energy and both black holes merged as one.

While this might not be very realistic, it proved to be a very useful diagnostic tool to understand the conditions after the collision of two black holes. As an interesting observation, the Caltech researchers found that although the collision was extreme, and there was a huge amount of mass-energy conversion going on (plus, I’d imagine, a rather big explosion), neither black hole lost their event horizons.

Case closed, wouldn’t you think?

Actually, another theory as to how a black hole could be stripped naked has been knocking around for some time; what if you added mass to a black hole spinning at its maximum possible rate? Could the black hole be disrupted enough to shed its event horizon?

It turns out there’s a natural braking system that prevents this from happening. As soon as mass is dropped into the black hole, it is flung out of the event horizon by the black hole’s huge centrifugal force, preventing it from coming close to the singularity.

However, Ted Jacobson and Thomas Sotiriou at the University of Maryland at College Park have now improved upon this idea, sending mass in the same direction as the spinning black hole. Only this time, the black hole isn’t spinning at its fastest possible rate, the simulation lets the orbiting matter fall into the event horizon, speeding up its spin. The result? It appears to disrupt the black hole enough to strip away the event horizon, exposing the singularity.

The most interesting thing to come of this research is that swirling matter is falling into black holes all over the universe, speeding up their spin. Jacobson and Sotiriou may have stumbled on a viable mechanism that actually allows naked singularities in the cosmos. Unless nature has found another way to prevent the cosmic censorship hypothesis from being violated that is…

Source: New Scientist

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Would You Like a Slice of Moon with that Solar Observation?

The Hinode view of the eclipse (JPL/NASA).

The Hinode view of the eclipse (JPL/NASA).

On July 22nd, Asia witnessed the longest solar eclipse of the century. I saw the pictures, it looked like fun. I’ve only seen a partial solar eclipse in the past, so when I heard about last week’s eclipse lasting nearly 7 minutes, I was more than a little envious.

So another eclipse, another momentous event if you could witness it, but if you couldn’t, at least you had some nice pictures to look at. However, there seems to be one forgotten spectator who had the best seat in the house to watch the moon pass in front of our Sun: the Hinode solar observatory.

Hinode (meaning “Sunrise”) is a space-based observatory launched by the Japanese space agency JAXA in 2006, and since then it has changed our perception of the inner dynamics of the solar corona. It can image the fine-scale magnetic structure of coronal loops and track plasma features with astounding precision.

On Wednesday however, Hinode caught an entirely different feature in its lens.

Actually, I’m a little surprised there’s not much of a fuss about the eclipse from space. Admittedly, the lunar transit across the solar disk didn’t attain totality, but it sure looks amazing!

For more of the Hinode eclipse, have a look at the Flickr gallery

The Event Horizon Telescope: Are We Close to Imaging a Black Hole?

A modelled black hole shadow (left) and two simulated observations using a 7-telescope and 13-telescope array (Fish & Doeleman)

A modelled black hole shadow (left) and two simulated observations of Sgr A* using a 7-telescope and 13-telescope array (Fish & Doeleman)

All the evidence suggests there is a supermassive black hole lurking in the centre of our galaxy. We’ve known as much for quite some time, but it wasn’t until recently that we’ve been able to confirm it. As it turns out, most galactic nuclei are predicted to contain supermassive black holes in their cores.

The Milky Way’s supermassive black hole is called Sagittarius A*, a well-known compact radio source used by radio astronomers as an instrumental calibration target. The black hole driving this emission has been calculated to weigh in at a whopping 4×106 solar masses.

So, we’re certain Sgr A* is a supermassive black hole, how can we use it?

Using our Sun as an example, stellar physicists use the Sun as an up-close laboratory so they can better understand stars located many light years away. It is an up-close star that we can study in great detail, gleaning all kinds of information, helping us learn more about how stars work in general.

What if Sgr A* could be used in a similar way, not in the study of stellar physics, but in the pursuit to understand the dynamics of black holes throughout the Universe?

This is exactly the question Vincent Fish and Sheperd Doeleman from the MIT Haystack Observatory ponder in a recent publication. The researchers make an important point early in their paper:

Due to its proximity at ~ 8 kpc [26,000 ly], Sgr A* has the largest apparent event horizon of any known black hole candidate.

The centre of our galaxy as imaged by Spitzer (NASA)

The centre of our galaxy as imaged by Spitzer (NASA)

In other words, the supermassive black hole in the centre of the galaxy is the largest observable black hole in the sky. As Sgr A* is so massive, its event horizon is therefore bigger, providing a sizeable target for Earth-based observatories to resolve.

Although the black hole is quite a distance from us, the size of its event horizon more than makes up for its location, it even trumps closer, less massive stellar black holes. Sgr A* could therefore be our own personal black hole laboratory that we can study from Earth.

But there’s a catch: How do you directly observe a black hole that’s 26,000 light years away? Firstly, you need an array of telescopes, and the array of telescopes need to have very large baselines (i.e. the ‘scopes need to be spread apart as wide as possible). This means you would need an international array of collaborating observatories to make this happen.

The authors model some possible results using many observatories as part of a long baseline interferometry (VLBI) campaign. As Sgr A*’s emissions peak in the millimetre wavelengths, a VLBI system observing in millimetre wavelengths could spot a resolved black hole shadow in the heart of Sg. A*. They also say that existing millimetre observations of Sgr A* show emission emanating from a compact region offset from the centre of the black hole, indicating there is some kind of structure surrounding the black hole.

The results of their models are striking. As can be seen in the three images at the top of this post, a definite black hole shadow could be observed with just 7 observatories working together. With 13 observatories, the resolution improves vastly.

Could we be on the verge of tracking real-time flaring events occurring near the black hole? Perhaps we’ll soon be able to observe the rotation of the supermassive black hole as well as accretion disk dynamics. If this is the case, we may be able to also witness the extreme relativistic effects predicted to be acting on the volume of space surrounding Sgr A*.

The best news is that technological advancements are already in progress, possibly heralding the start of the construction of the world’s first “Event Horizon Telescope.”

Source: Observing a Black Hole Event Horizon: (Sub)Millimeter VLBI of Sgr A*, Vincent L. Fish, Sheperd S. Doeleman, 2009. arXiv:0906.4040v1 [astro-ph.GA]

Astroengine Live CANCELLED… Until Next Week

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Apologies for the break in Astroengine Live service. Due to some uber-technical problems, I’m going to have to re-launch the show this time next week. Stay tuned for updates.

For now, check out my Astroengine Live archives and enjoy!

***

Earlier post:

It’s been a while, but Astroengine Live is back on the air, TODAY! It’s been a fascinating few weeks, so I want to share some of the stuff I’ve come across. I especially want to go into the current Wide Angle over at Discovery Space, “Surfing Spacetime”.

So tune in to the Badlands Radio feed at 4pm PST/7pm EST and all the timezones in between and far away

I’ll also be tweeting throughout the broadcast, so feel free to interrupt me on @astroengine.

Are Wormholes Quantum Vacuum Cleaners?

The wormhole could form shortcuts in space-time (www.designboom.com)

General relativity and quantum dynamics don’t get along too well.

If you had to compare the two it would be like evaluating the differences between a Mac and a PC; both are well-honed examples of modern computing, but both are hopelessly incompatible. In computing, this isn’t too much of a problem, you either use a PC or a Mac, or you buy both for their individual strengths (and then complain about Microsoft regardless). But in physics, when you’re trying to find a unified theory, the fact that gravity has been outcast from the Standard Model club, tough questions need to be asked. Although there is some hope being generated by superstring theory, quantum gravity has a long way to go before it can be proven (although high energy particle accelerators such as the LHC will be able to help out in that department).

As pointed out by KFC at the Physics ArXiv Blog, “physicists have spent little time bothering to find out” how quantum mechanics operates in a curved space-time as predicted by Einstein’s general relativity. But now, a physicist has done the legwork and imagined what a quantum particle would do when faced with one of the most famous loopholes in space-time; the mouth of a wormhole. And what popped out of the equations? Another curious force called the “quantum anticentrifugal force.”

So, what’s that all about?

Rossen Dandolo from the Universite de Cergy-Pontoise, France, decided to focus on the wormhole as this is the most extreme example of curved space-time there is. Wormholes are used over and over in sci-fi storylines because they are theorized to link two locations in space-time (thereby forming a shortcut), or even two different universes. As this is space-time we’re talking about, there’s also some possibility of using wormholes as passages through time. Although wormholes sound like a whole lot of fun, in practical terms, they won’t be of much use without some exotic energy to hold the throat of the wormhole open.

Dandolo, however, isn’t too interested in traversing these holes in space-time, he is interested in finding out how a particle acts when in the locality of the mouth of a wormhole.

Beginning with some bedrock quantum theory, Dandolo uses the Heisenberg Uncertainty Principal that stipulates that you cannot know a particle’s momentum and location at the same time. So far, so good. Now, looking at a prediction of general relativity, the wormhole will warp space-time to the extreme, stretching the space around the hole. This space-time stretching causes an increase in uncertainty in the location of the particle. As uncertainty in location increases, the uncertainty in momentum decreases. Therefore, the closer you get to the mouth of the wormhole, the momentum, and therefore particle energy, will decrease.

This interaction between the stretching of space-time and quantum properties of the particle has some amazing ramifications. If the particle’s energy deceases the closer it gets to falling into the wormhole, the wormhole is acting as a potential well; particles will move to a location with less energy. Therefore, a new force — combining both quantum dynamics and general relativity — is acting on particles that stray close to the wormhole: an anticentrifugal force.

This makes wormholes particle vacuum cleaners, exerting a space-time curvature effect on the quantum qualities of matter.

General relativity and quantum dynamics might have some stronger ties than we think…

Source: Wormholes Generate New Kind of Quantum Anticentrifugal Force, by KFC on the ArXiv Blog.

Warp Drives and… Black Holes?

Could warp drives be a bad thing for Earth?

Why do all roads seem to lead to black holes? Man made black holes are supposedly going to be produced by the Large Hadron Collider, swallowing Earth (or, at least, a large fraction of Europe), so it seems only logical that something like a warp drive — a technology of the uber-future requiring uber-energies — would also generate a black hole, right?

Yes, we are talking about a vastly theoretical technology, but according to Italian researchers, the spaceship propulsion device popularized by Star Trek could have grave consequences for Planet Earth.

Over the past week, I’ve been deep inside the science behind faster-than-light-speed propulsion and time travel as a part of the Discovery Space Wide Angle: Surfing Spacetime, and I feel well versed in the astounding physics that could make warp speed a possibility in the future. All this started when interviewing one of the leading authorities on warp drive propulsion, Dr Richard Obousy, who is not only upbeat about the possibilities of the futuristic warpship, he’s done the math to prove that a sufficiently advanced civilization could “surf” on a spacetime wave.

However, there’s a catch. Well, two.

Firstly, we need to develop an understanding for dark energy. And second, we need a gargantuan energy source.

Dark energy is a cosmological theory that explains the continued expansion of the universe. This energy pervades all of the cosmos, explaining everything from the grouping of galactic clusters to the faster-than-light-speed inflationary period immediately after the Big Bang. There’s a lot of indirect observation of dark energy and its effects on spacetime. It’s out there, but it’s a tough proposition to think we might be able to harness it someday. But then again, we said that about electricity once, who knows what technological revolutions await us in the decades and centuries ahead.

Assuming we find a way of harnessing dark energy, how can we use it? This is where visionary physicists like Dr Obousy come in. Skipping over the superstring small-print of extra-dimensional theory, we basically need a huge amount of energy to manipulate the universal dark energy, thereby shrinking and expanding vanishingly small dimensions beyond our three dimensional universe.

So how much energy is needed warp spacetime, allowing a futuristic spaceship to zip through space? “Some back of the envelope calculations I performed last year indicated approximately the mass energy contained within the planet Jupiter,” Richard told me.

This sounds like a lot of energy! However, there’s a trend, the rest mass energy of Jupiter is actually an improvement on previous warp drive calculations. “The very early warp drive calculations indicated that one would need more mass energy than was available within the entire universe… that’s TRILLIONS of Jupiters!

This improvement is down to recent developments in superstring theory and quantum dynamics. It would appear that the energy requirements for a warp drive improves with developments in physics. If this trend continues, we may find other energy saving ways to make a warpship a reality.

However, there are some practical issues putting the breaks on travelling at warp speed. Only recently, I reported on a study focusing on quantum fluctuations as the warp “bubble” (containing our warpship) blasts through the light speed barrier: the occupants could get roasted by Hawking Radiation.

Today, another problem has surfaced from the extreme warp equations: black holes (who would have guessed?). Italian physicist Stefano Finazzi of Italy’s International School for Advanced Studies has crunched the numbers and wondered about what would happen when the energy runs out. It’s all very well generating a Jupiter’s rest mass-worth of energy, but how will it be sustained by the warp drive? What will happen when all the energy is depleted?

Eventually the energy would run out. The [warp] bubble would rupture, with catastrophic effects. Inside the bubble the temperature would rise to about 1032 degrees Kelvin, destroying almost anything on the bubble.Eric Bland, Discovery News

It gets better, Finazzi also predicts a fair amount of doom outside the warp bubble, too. “We know that the warp drive will be destabilized,” he added. “But we do not know if it will in the end explode or collapse to a black hole.”

Don’t go running out of gas any where near Earth is all I say

Although these implications of doom and gloom should have given Jean Luc Picard a panic attack whenever he said “engage!” or “make it so Number One…”, we have to remind ourselves warp drive propulsion isn’t even close to being a reality. Dr Obousy and warp scientists before him are only just beginning to assemble a theoretical framework around the sci-fi notion of warping spacetime, so to already be predicting warp speed fail seems a little premature in my opinion.

In response to the Hawking Radiation problem, Dr Obousy pointed out that if we get to the point of generating vast quantities of energy, harnessing the spacetime warping power of dark energy, we should be able to at least have a stab at finding solutions to these potential warp drive problems.

Objections are good, but usually we find smart ways of circumventing problems. Humans are good at that,” he said.

I agree.

Solar Cycle Prediction: “None of Our Models Were Totally Correct”

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Predicting space weather is not for the faint-hearted. Although the Sun appears to have a predictable and regular cycle of activity, the details are a lot more complex. So complex in fact, that the world’s greatest research institutions have to use the most powerful supercomputers on the planet to simulate the most basic of solar dynamics. Once we have a handle on how the Sun’s interior is driven, we can start making predictions about how the solar surface may look and act in the future. Space weather prediction requires a sophisticated understanding of the Sun, but even the best models are flawed.

Today, another solar cycle prediction has been released by the guys that brought us the “$2 trillion-worth of global damage if a solar storm hits us” valuation earlier this month. According to NOAA scientists sponsored by NASA, Solar Cycle 24 will peak in May 2013 with a below-average number of sunspots.

If our prediction is correct, Solar Cycle 24 will have a peak sunspot number of 90, the lowest of any cycle since 1928 when Solar Cycle 16 peaked at 78,” says Doug Biesecker of the NOAA Space Weather Prediction Center.

Although this may be considered to be a “weak” solar maximum, the Sun still has the potential to generate some impressive flares and coronal mass ejections (CMEs). Although I doubt we’ll see the record-breaking flares we saw in 2003 (pictured top), we might be hit by some impressive solar storms and auroral activity will certainly increase in Polar Regions. But just because the Sun will be more active, it doesn’t mean we will be struck by any big CMEs; space is a big place, we’d be (un)lucky to be staring directly down the solar flare barrel.

So, we have a new prediction and the solar models have been modified accordingly, but it is hard to understand why such tight constraints are being put on the time of solar maximum peak (one month in 2013) and the number of sunspots expected (90, or thereabouts). Yes, sunspot activity is increasing, but we are still seeing high-latitude sunspots from the previous cycle (Solar Cycle 23) pop up every now and again. This is normal, an overlap in cycles do occur, yet it surprises me that any definitive figures are being placed on a solar maximum that may or may not peak four years from now.

Ah, I see, it's obvious Solar Cycle 24 will look like that... is it really? (NOAA/NASA)

Tenuous link: Are you really happy with that prediction? (NOAA/NASA)

We are able to look at the history of sunspot number and we can see the cycles wax and wane, and we can pick out a cycle that most resembles the one we are going through now, but that doesn’t mean that particular cycle will happen this time around. Statistically-speaking, there’s a higher chance of a similar-looking cycle from the past happening in this 24th cycle, but predictions based on this premise are iffy to say the least.

Also, solar models are far from being complete, and many aspects of the physics behind the Sun’s internal dynamics are a mystery. The Sun really is acting strange, which is fascinating for solar physicists.

It turns out that none of our models were totally correct,” says Dean Pesnell of the Goddard Space Flight Center, NASA’s lead representative on the panel. “The sun is behaving in an unexpected and very interesting way.”

Personally, I think we should concentrate less on predicting when or how the next solar maximum presents itself. Solar models are not going to suddenly predict the nature of the solar cycle any more than we can predict terrestrial weather systems more than a few days in advance.

Using the atmospheric weather analogy, we know the seasons cycle as the year goes on, but there is no way we can say with any degree of certainty when the hottest day of the year is going to be, or which week will yield the most rain.

The same goes for our Sun. It is vastly complex and chaotic, a system we are only just beginning to understand. We need more observatories and more solar missions with advanced optics and spectrometers (and therefore a huge injection of funding, something solar physicists have always struggled without). Even then, I strongly doubt we’ll be able to predict exactly when the peak of the solar cycle is going to occur.

That said, space weather prediction is a very important science, but long-term forecasts don’t seem to be working, why keep on releasing new forecasts when the old one was based on the same physics anyway? Predicting an inactive, active or mediocre solar maximum only seems to cause alarm (although it is a great means to keep solar physics in the headlines, which is no bad thing in my books).

I suppose if you make enough predictions, eventually one will be correct in four years time. Perhaps there will be a peak of 90 sunspots by May 2013, who knows?

If you’re blindfolded, spun around and armed with an infinite supply of darts, you’ll eventually hit the board. Hell, you’ll probably even hit the bullseye

Source: NASA, special thanks to Jamie Rich for bringing this subject to my attention!