According to RealClearScience – Homepage (This article and its images were originally posted on RealClearScience – Homepage September 24, 2018 at 11:20PM.)
Stephen Hawking sadly passed away earlier this year, but his scientific legacy is well alive. The black hole information loss problem in particular still keeps physicists up at night. A new experiment might bring us a step closer to solving it.
Got any news, tips or want to contact us directly? Feel free to email us: esistme@gmail.com.
To see more posts like these; please subscribe to our newsletter. By entering a valid email, you’ll receive top trending reports delivered to your inbox.
__
This article and its images were originally posted on [RealClearScience – Homepage] September 24, 2018 at 11:20PM. Credit to the original author and RealClearScience – Homepage | ESIST.T>G>S Recommended Articles Of The Day.
Donations are appreciated and go directly to supporting ESIST.Tech. Thank you in advance for helping us to continue to be a part of your online entertainment!
According to Live Science (This article and its images were originally posted on Live Science September 26, 2018 at 07:56AM.)
(Coave Image)
Supermassive black holes blast winds outward in a spherical shape, as depicted here in this artist’s conception of a black hole.
Credit: NASA/JPL-Caltech
Very close to the very beginning, scientists think, there were black holes.
These black holes, which astronomers have never directly detected, didn’t form in the usual way: the explosive collapse of a big, dying star into its own gravity well. The matter in these black holes, researchers believe, wasn’t crushed into a singularity by the last gasps of an old star.
Indeed, back then, in the first 1 billion or so years of the universe, there were no old stars. Instead, there were huge clouds of matter, filling space, seeding the earliest galaxies. Some of that matter, researchers believe, clumped together more tightly, though, collapsing into its own gravity well just like old stars later did as the universe aged. Those collapses, researchers believe, seeded supermassive black holes that had no previous life as stars. Astronomers call these singularities “direct collapse black holes” (DCBHs).
The problem with this theory, though, is that nobody has ever found one. [The 18 Biggest Unsolved Mysteries in Physics]
But that could change. A new paper from the Georgia Institute of Technology published Sept. 10 in the journal Nature Astronomyproposes that the James Webb Space Telescope (JWST), which NASA intends to launch at some point in the next several years, should be sensitive enough to detect a galaxy containing a black hole from this ancient period of the universe’s history. And the new study proposes a set of signatures that could be used to identify a DCBH-hosting galaxy.\
And that ultrapowerful telescope might not have to search the skies for very long to find one.
Got any news, tips or want to contact us directly? Feel free to email us: esistme@gmail.com.
To see more posts like these; please subscribe to our newsletter. By entering a valid email, you’ll receive top trending reports delivered to your inbox.
__
This article and images were originally posted on [Live Science] September 26, 2018 at 07:56AM. Credit to the original author and Live Science | ESIST.T>G>S Recommended Articles Of The Day.
Donations are appreciated and go directly to supporting ESIST.Tech. Thank you in advance for helping us to continue to be a part of your online entertainment!
According to Phys.org (This article and its images were originally posted on Phys.org September 5, 2018 at 09:00AM.)
(Cover Image) Credit: CC0 Public Domain
A group of researchers led by Paula Sánchez-Sáez, a doctoral student in the Department of Astronomy of the Universidad de Chile, managed to determine that the rate of variability in the light emitted by material being swallowed by supermassive black holes in nuclei of active galaxies is determined by the accretion rate, that is, how much matter they are “eating.”
“The light emitted by the material that is falling (its brightness) changes a lot over time, without a stable pattern, so we say that they show variability. We know that it varies, but we still do not know clearly why. If one observes other objects, such as stars or galaxies without active nuclei, their brightness is constant over time, but if we look at galaxies with active nuclei their brightness rises and falls, and is completely unpredictable. We studied how the amplitude of this variation in the emitted light (or in simple words, the amplitude of the variability) is related, with the average luminosity emitted by the AGN, the mass of the super massive black hole, and the AGN accretion rate (which corresponds to how much material the black hole consumes in a year). The results of our analysis show that, contrary to what was believed, the only important physical property to explain the amplitude of the variability is the AGN accretion rate,” explains the young researcher.
Got any news, tips or want to contact us directly? Feel free to email us: esistme@gmail.com.
To see more posts like these; please subscribe to our newsletter. By entering a valid email, you’ll receive top trending reports delivered to your inbox.
__
This article and its images were originally posted on [Phys.org] September 5, 2018 at 09:00AM. All credit to both the author and Phys.org | ESIST.T>G>S Recommended Articles Of The Day.
Donations are appreciated and go directly to supporting ESIST.Tech. Thank you in advance for helping us to continue to be a part of your online entertainment!
A study on dozens of galaxies within several billion light years of our own has revealed black holes that far exceed our expectations on just how big these monsters can grow.
The discovery not only helps us better understand the evolution of our Universe’s building blocks, it leaves us with a new intriguing question – just how do black holes like these get to be so incredibly massive?
It seems like we can’t enough of these things, and there’s a good reason why.
“Galaxies are the building blocks of our Universe, and to understand their formation and evolution, we must first understand these black holes,” says physicist Julie Hlavacek-Larrondo from the Université de Montréal in Canada.
Not that the black holes make this job easy, so to get around the tricky problem of studying something that likes to keep its secrets tucked away inside an impenetrable void, astrophysicists look for shortcuts.
One is to find a relationship between a black hole’s mass and the galaxy surrounding it. If there was an easy way to match a galaxy’s size with the black hole at its core, it would save a lot of hassle.
So Hlavacek-Larrondo teamed up with other researchers from Canada, Spain, and the UK to study 72 galaxies within a radius of 3.5 billion light years to see if they could nail down some kind of formula in estimating the mass of the black hole at their centre.
To estimate the size of the black holes themselves, they analysed the spectrum of X-rays being spat out by the whirling disc of heated gas being sucked into their crazy gravity wells.
The researchers then correlated this figure with the overall luminosity of the surrounding galaxy.
It makes sense that the bigger the galaxy, the bigger the black hole – but this relationship isn’t quite as simple as they’d thought.
“We have discovered black holes that are far larger and way more massive than anticipated,” says the study’s lead author Mar Mezcua from the Institute of Space Sciences in Spain.
Rather than growing in tandem, the masses of a number of the black holes far outstripped expectations, growing faster than other stars in their neighbourhood.
In fact, around 40 percent of them weighed the equivalent of 10 billion times the mass our Sun or more.
Got any news, tips or want to contact us directly? Email esistme@gmail.com
__
This article and images were originally posted on [ScienceAlert] February 20, 2018 at 09:18PM. Credit to Author and ScienceAlert | ESIST.T>G>S Recommended Articles Of The Day
According to Phys.org – latest science and technology news stories
Passing through the outer or event horizon of a black hole would be uneventful for a massive black hole. Animation by Andrew Hamilton, based on supercomputer simulation by John Hawley.
In the real world, your past uniquely determines your future. If a physicist knows how the universe starts out, she can calculate its future for all time and all space.
But a UC Berkeley mathematician has found some types of black holes in which this law breaks down. If someone were to venture into one of these relatively benign black holes, they could survive, but their past would be obliterated and they could have an infinite number of possible futures.
Such claims have been made in the past, and physicists have invoked “strong cosmic censorship” to explain it away. That is, something catastrophic – typically a horrible death – would prevent observers from actually entering a region of spacetime where their future was not uniquely determined. This principle, first proposed 40 years ago by physicist Roger Penrose, keeps sacrosanct an idea – determinism – key to any physical theory. That is, given the past and present, the physical laws of the universe do not allow more than one possible future.
But, says UC Berkeley postdoctoral fellow Peter Hintz, mathematical calculations show that for some specific types of black holes in a universe like ours, which is expanding at an accelerating rate, it is possible to survive the passage from a deterministic world into a non-deterministic black hole.
What life would be like in a space where the future was unpredictable is unclear. But the finding does not mean that Einstein’s equations of general relativity, which so far perfectly describe the evolution of the cosmos, are wrong, said Hintz, a Clay Research Fellow.
“No physicist is going to travel into a black hole and measure it. This is a math question. But from that point of view, this makes Einstein’s equations mathematically more interesting,” he said. “This is a question one can really only study mathematically, but it has physical, almost philosophical implications, which makes it very cool.”
“This … conclusion corresponds to a severe failure of determinism in general relativity that cannot be taken lightly in view of the importance in modern cosmology” of accelerating expansion, said his colleagues at the University of Lisbon in Portugal, Vitor Cardoso, João Costa and Kyriakos Destounis, and at Utrecht University, Aron Jansen.
As quoted by Physics World, Gary Horowitz of UC Santa Barbara, who was not involved in the research, said that the study provides “the best evidence I know for a violation of strong cosmic censorship in a theory of gravity and electromagnetism.”
Hintz and his colleagues published a paper describing these unusual black holes last month in the journal Physical Review Letters.
A reasonably realistic simulation of falling into a black hole shows how space and time are distorted, and how light is blue shifted as you approach the inner or Cauchy horizon, where most physicists think you would be annihilated. However, a UC Berkeley mathematician argues that you could, in fact, survive passage through this horizon. Animation by Andrew Hamilton, based on supercomputer simulation by John Hawley.
Beyond the event horizon
Black holes are bizarre objects that get their name from the fact that nothing can escape their gravity, not even light. If you venture too close and cross the so-called event horizon, you’ll never escape.
For small black holes, you’d never survive such a close approach anyway. The tidal forces close to the event horizon are enough to spaghettify anything: that is, stretch it until it’s a string of atoms.
But for large black holes, like the supermassive objects at the cores of galaxies like the Milky Way, which weigh tens of millions if not billions of times the mass of a star, crossing the event horizon would be, well, uneventful.
Because it should be possible to survive the transition from our world to the black hole world, physicists and mathematicians have long wondered what that world would look like, and have turned to Einstein’s equations of general relativity to predict the world inside a black hole. These equations work well until an observer reaches the center or singularity, where in theoretical calculations the curvature of spacetime becomes infinite.
Even before reaching the center, however, a black hole explorer – who would never be able to communicate what she found to the outside world – could encounter some weird and deadly milestones. Hintz studies a specific type of black hole – a standard, non-rotating black hole with an electrical charge – and such an object has a so-called Cauchy horizon within the event horizon.
The Cauchy horizon is the spot where determinism breaks down, where the past no longer determines the future. Physicists, including Penrose, have argued that no observer could ever pass through the Cauchy horizon point because they would be annihilated.
As the argument goes, as an observer approaches the horizon, time slows down, since clocks tick slower in a strong gravitational field. As light, gravitational waves and anything else encountering the black hole fall inevitably toward the Cauchy horizon, an observer also falling inward would eventually see all this energy barreling in at the same time. In effect, all the energy the black hole sees over the lifetime of the universe hits the Cauchy horizon at the same time, blasting into oblivion any observer who gets that far.
A spacetime diagram of the gravitational collapse of a charged spherical star to form a charged black hole. An observer traveling across the event horizon will eventually encounter the Cauchy horizon, the boundary of the region of spacetime that can be predicted from the initial data. Hintz and his colleagues found that a region of spacetime, denoted by a question mark, cannot be predicted from the initial data in a universe with accelerating expansion, like our own. This violates the principle of strong cosmic censorship. Credit: APS/Alan Stonebraker
You can’t see forever in an expanding universe
Hintz realized, however, that this may not apply in an expanding universe that is accelerating, such as our own. Because spacetime is being increasingly pulled apart, much of the distant universe will not affect the black hole at all, since that energy can’t travel faster than the speed of light.
In fact, the energy available to fall into the black hole is only that contained within the observable horizon: the volume of the universe that the black hole can expect to see over the course of its existence. For us, for example, the observable horizon is bigger than the 13.8 billion light years we can see into the past, because it includes everything that we will see forever into the future. The accelerating expansion of the universe will prevent us from seeing beyond a horizon of about 46.5 billion light years.
In that scenario, the expansion of the universe counteracts the amplification caused by time dilation inside the black hole, and for certain situations, cancels it entirely. In those cases – specifically, smooth, non-rotating black holes with a large electrical charge, so-called Reissner-Nordström-de Sitter black holes – an observer could survive passing through the Cauchy horizon and into a non-deterministic world.
“There are some exact solutions of Einstein’s equations that are perfectly smooth, with no kinks, no tidal forces going to infinity, where everything is perfectly well behaved up to this Cauchy horizon and beyond,” he said, noting that the passage through the horizon would be painful but brief. “After that, all bets are off; in some cases, such as a Reissner-Nordström-de Sitter black hole, one can avoid the central singularity altogether and live forever in a universe unknown.”
Admittedly, he said, charged black holes are unlikely to exist, since they’d attract oppositely charged matter until they became neutral. However, the mathematical solutions for charged black holes are used as proxies for what would happen inside rotating black holes, which are probably the norm. Hintz argues that smooth, rotating black holes, called Kerr-Newman-de Sitter black holes, would behave the same way.
“That is upsetting, the idea that you could set out with an electrically charged star that undergoes collapse to a black hole, and then Alice travels inside this black hole and if the black hole parameters are sufficiently extremal, it could be that she can just cross the Cauchy horizon, survives that and reaches a region of the universe where knowing the complete initial state of the star, she will not be able to say what is going to happen,” Hintz said. “It is no longer uniquely determined by full knowledge of the initial conditions. That is why it’s very troublesome.”
He discovered these types of black holes by teaming up with Cardoso and his colleagues, who calculated how a black hole rings when struck by gravitational waves, and which of its tones and overtones lasted the longest. In some cases, even the longest surviving frequency decayed fast enough to prevent the amplification from turning the Cauchy horizon into a dead zone.
Hintz’s paper has already sparked other papers, one of which purports to show that most well-behaved black holes will not violate determinism. But Hintz insists that one instance of violation is one too many.
“People had been complacent for some 20 years, since the mid ’90s, that strong cosmological censorship is always verified,” he said. “We challenge that point of view.”
A physicist from the University of Campinas in Brazil isn’t a big fan of the idea that time started with a so-called Big Bang.
Instead, Juliano César Silva Neves imagines a collapse followed by an expansion, one that could even still carry the scars of a previous timeline.
The idea itself isn’t new, but Neves has used a fifty-year-old mathematical trick describing black holes to show how our Universe needn’t have had such a compact start to existence.
At first glance, our Universe doesn’t seem to have a lot in common with black holes. One is expanding space full of clumpy bits; the other is mass pulling at space so hard that even light has no hope of escape.
But at the heart of both lies a concept known as a singularity – a volume of energy so infinitely dense, we can’t even begin to explain what’s going on inside it.
“There are two kinds of singularity in the Universe,” says Neves.
“One is the alleged cosmological singularity, or Big Bang. The other hides behind the event horizon of a black hole.”
Taken a step further, some propose the Universe itself formed from a black hole in some other bubble of space-time.
No matter which kind we’re talking about, singularities are zones where Einstein’s general relativity goes blind and quantum mechanics struggles to take over.
Sci-fi writers might love them, but the impossible nature of singularities makes them a frustrating point of contention among physicists.
The problem is, if we rewind the expanding Universe, we get to a point where all of that mass and energy was concentrated in an infinitely dense point. And if we crunch the numbers on collapsing massive objects, we get the same kind of thing.
Singularities might break physics, but so far we haven’t been able to rule them out.
On the other hand, some physicists think there’s some wiggle room. Theoretically speaking, not all models of a black hole need a singularity to exist.
“There are no singularities in so-called regular black holes,” says Neves.
In 1968, a physicist by the name of James Bardeen came up with a solution to the singularity problem.
He devised a way of mathematically describing black holes that did away with the need for a singularity somewhere beyond its event horizon, calling them ‘regular black holes’.
The history and reasoning behind Bardeen’s model is, well, super dense; but for a tl;dr version – he assumed that the mass at the heart of a black hole needn’t be constant, but could be described using a function that depended on how far from its centre you were.
That means we can dust our hands of any stupid singularities, as mass still behaves as if it has volume. Even as it is still squeezed into a tight space.
Neves suggests we take Bardeen’s work even further and apply it to that other annoying singularity – the cosmological variety that preceded the Big Bang.
By assuming the rate of the Universe’s expansion depended not just on time, but its scale as well, he showed there was no need for a quantum leap out of a singularity into a dense, voluminous space 13.82 billion years ago.
So what happened instead?
“Eliminating the singularity or Big Bang brings back the bouncing Universe on to the theoretical stage of cosmology,” says Neves.
This ‘bouncing Universe’ is actually a century-old idea that the expanding Universe as we experience it today is space bouncing back outwards after a previous contraction.
Though it’s currently somewhat of a fringe concept in cosmology, Neves supports the view that traces of the pre-collapse Universe might have survived the Big Crunch. If so, finding those scars might help validate the hypothesis.
“This image of an eternal succession of universes with alternating expansion and contraction phases was called the cyclical Universe, which derives from bouncing cosmologies,” says Neves.
Until we have solid observations, the bouncing Universe model will no doubt stay in the ‘nice idea’ basket.
Still, anything that solves the singularity problem deserves investigating. Neves’s work is just one of a number of possible solutions that swaps around assumptions to eliminate the need for physics-breaking impossibilities.
It’s a sticking point we’ll need to solve sooner or later.
Got any news, tips or want to contact us directly? Email esistme@gmail.com
__
This article and images were originally posted on [ScienceAlert] November 29, 2017 at 01:35AM. Credit to Author and ScienceAlert | ESIST.T>G>S Recommended Articles Of The Day
Ever since LIGO (and now Virgo) started picking up gravitational waves, theorists have gone nuts. The volume of papers on exciting possibilities seems to grow faster than the disk space available to accommodate them. If I were sensible, I would probably ignore them. But I’m not, and you, dear reader, will suffer along with me.
When two black holes collide and merge, they emit gravitational waves, but we don’t expect them to emit light. But is that really true? After all, black holes decay away by emitting Hawking radiation, so maybe there is some light associated with the event.
How black are we talking?
Now, it should be pointed out that Hawking radiation, though widely accepted as an inevitable consequence of black hole physics, has never been observed. The problem is that big, long-lived black holes emit tiny amounts of Hawking radiation at very long wavelengths. The low intensity, combined with the long wavelength, makes it pretty much impossible to detect. Tiny, short-lived black holes are much brighter and might be detectable… but, I’m not sure that anyone has any idea how such a black hole might be formed in the present-day Universe. Every black hole we know about is in the large and long-lived bucket.
So, under ordinary circumstances, black holes are, for all practical purposes, black.
But, a black hole collision is anything but ordinary. And researchers are starting to wonder if there might be some glow associated with the collision. Investigating the emission of Hawking radiation during in-spiral and collision turns out to be quite tricky, though. As two black holes spiral together, they move at a respectable fraction of the speed of light. Solving the equations of general relativity for this system already requires a lot of heavy lifting with computers—and that doesn’t include adding on the bits that involve Hawking radiation.
But, as with all things, you have to start somewhere. So a group of researchers chose to examine some of the details of Hawking radiation immediately after a black hole merger. Just after the collision, the merged black hole emits a few more gravitational waves as it relaxes. In fact, the best analogy is the ringing of a bell. Our cosmic bell is the event horizon, which squeezes and expands as it absorbs and emits gravitational waves.
The researchers cobbled together a model that examines the phase and amplitude of Hawking radiation in relation to the gravitational waves that the black hole produces.
The light of ringing space
The findings can be summarized as follows: the oscillations of the black hole modulate the phase and amplitude of Hawking radiation. Essentially, at those moments in time when a gravitational wave is being absorbed, light can be emitted. Under ordinary circumstances, Hawking radiation looks like thermal radiation, which basically means it has the same properties as the light emitted from an incandescent bulb (although in a different part of the electromagnetic spectrum). That means that no two photons from a black hole share much in common: phase, amplitude, direction are all randomly selected for each photon.
But the periodic oscillations of the black hole give these photons correlations, making it unlike an incandescent bulb. In fact, the researchers show that the photons are what physicists call squeezed.
Squeezing involves the fact that the phase and amplitude of a photon are governed by the uncertainty principle; they cannot both be defined to arbitrary precision. A squeezed photon is one in which either the amplitude or phase is defined to a precision that is better than the joint minimum, while the other property is much noisier. Nothing we’re aware of naturally emits squeezed light. It usually takes highly specialized circumstances to get non-classical light sources like squeezed-photon emitters.
This means that oscillating black holes may be our first example of naturally occurring emitters of squeezed light. And, even better, the absorption of gravitational waves by the black hole amplifies the Hawking radiation.
Black holes: A sound and light show?
This all sounds pretty exciting, so should we be searching the night sky for squeezed radio waves? Well, there is some way to go yet before researchers start asking for telescope time.
The problem is that this analysis is limited to the ring-down of the black hole. The amplification of Hawking radiation is proportional to the duration of the ring-down, which lasts just a few milliseconds. Or, to put it in hard numbers: GW150914, the first merger LIGO observed, might have had a ring down that was long enough to emit one or two squeezed photons.
What makes this interesting is that, during the in-spiral before the collision, there are long-lasting oscillations. If the researchers’ analysis scales in the same way (meaning the details are different, but the general picture remains the same), then the number of photons would go up dramatically. The researchers predict that a mode that lasts on the order of 30 milliseconds might emit around 1042 photons. I put that at about 1016W of radio waves, which sounds like a lot but is still tiny compared to the Sun’s 1026W.
That last comparison is not entirely fair, though, because the researchers calculate the energy emitted by coupling to a single gravitational wave mode (radiation comes in modes that define their characteristics). During in-spiral, many modes will be excited, and the in-spiral will last somewhat longer than 30 milliseconds (although we only care about the very end, where the gravitational wave amplitude is huge). So it might not be beyond the bounds of possibility to detect these emissions.
I know that I and many others often get impatient with theoretical physicists predicting stuff that we are unlikely to measure. But we need to rein in our impatience somewhat. The cool thing about being a theoretical physicist, especially in some areas, is that your imagination is the limit. In fact, I’d say that a well-cultured imagination is a drawback.
A good theoretician’s imagination seems to be a fetid, steaming swamp, filled with the buzzing insects of quantum mechanics, the alligators of general relativity, the floating islands of Newtonian mechanics, and, yes, the occasional unidentified, half-seen scaly beast. Without theoreticians chasing down these half-seen beasts and imagining more things than are actually there, we will never know how to look for anything in the swamp, much less find anything.
So, even though I am skeptical that the radiation from colliding black holes is detectable (if it even exists), this is still a really nice result. For the first time, it seems to imply that a big black hole might emit enough Hawking radiation to be detectable, and that is worth a second look.
Through the thick fog of our own galaxy, astronomers have spotted an ultimate prize: one of the largest-known structures in the Universe.
Called the Vela supercluster, the newly discovered object is a massive group of several galaxy clusters, each one containing hundreds or thousands of galaxies.
“I could not believe such a major structure would pop up so prominently” after an observation of that region of space, said Renée Kraan-Korteweg, an astrophysicist at the University of Cape Town in South Africa, in a press release.
Kraan-Korteweg and her team published their discovery of the supercluster, named after the constellation Vela where it was found, in the Monthly Notices Letters of the Royal Astronomical Society.
But if you’re an astronomer trying to peer beyond the Milky Way and into the deeper Universe, all of this stuff is in your way:
You are here. Image: NASA; Business Insider
This is especially true of objects behind the galactic plane, which is us looking through the 100,000-light-year-wide disk of the Milky Way from the inside-out.
That cross-section of the Milky Way’s disk of stars, gas, and dust is actually what we see when we look up in the sky in a very dark place:
Flickr/Abdul Rahman
To peer through it, Kraan-Korteweg and her colleagues combined the observations of several telescopes: the newly refurbished South African Large Telescope (SALT) near Cape Town, the Anglo-Australian Telescope (AAT) near Sydney, and X-ray surveys of the galactic plane.
Using that data, they calculated how fast each galaxy they saw above and below the galactic plane was moving away from Earth. Their number-crunching soon revealed that they all seemed to be moving together – indicating a lot of galaxies couldn’t be seen.
“[I]t became obvious we were uncovering a massive network of galaxies, extending much further than we had ever expected,” Michelle Cluver, an astrophysicist at the University of the Western Cape, said in the release.
The researchers estimate that the Vela supercluster is about the same mass of the Shapley Supercluster of roughly 8,600 galaxies, which is located about 650 million light-years away. Given that the typical galaxy has about 100 billion stars, researchers estimate that Vela could contain somewhere between 1,000 and 10,000 trillion stars.
Their calculations also show Vela is about 800 million light-years distant and zooming farther and farther away from us at a speed of about 40 million mph (18,000 kilometers per second).
Despite that extra and rapidly increasing distance, however, Vela’s influence can’t be denied. The researchers estimate that Vela’s gravitational tug on the Local Group of galaxies, which includes the Milky Way, has sped them up by about 110,000 mph (50 kilometers per second).
That’s quite a pull, and could help tell the incredible story of how our Milky Way galaxy – and we – got here.
Check out our Flipboard magazineESISTIf you enjoy reading our posts. All of our handpicked articles will be delivered to the flipboard magazine every day.
Research shines startling light on star systems that host hundreds of black holes
New research by the University of Surrey published today in the journal Monthly Notices of the Royal Astronomical Society has shone light on a globular cluster of stars that could host several hundred black holes, a phenomenon that until recently was thought impossible.
Globular clusters are spherical collections of stars which orbit around a galactic centre such as our Milky-way galaxy. Using advanced computer simulations, the team at the University of Surrey were able to see the un-see-able by mapping a globular cluster known as NGC 6101, from which the existence of black holes within the system was deduced. These black holes are a few times larger than the Sun, and form in the gravitational collapse of massive stars at the end of their lives. It was previously thought that these black holes would almost all be expelled from their parent cluster due to the effects of supernova explosion, during the death of a star.
“Due to their nature, black holes are impossible to see with a telescope, because no photons can escape,” explained lead author Miklos Peuten of the University of Surrey. “In order to find them we look for their gravitational effect on their surroundings. Using observations and simulations we are able to spot the distinctive clues to their whereabouts and therefore effectively ‘see’ the un-seeable.”
It is only as recently as 2013 that astrophysicists found individual black holes in globular clusters via rare phenomena in which a companion star donates material to the black hole. This work, which was supported by the European Research Council (ERC), has shown that in NGC 6101 there could be several hundred black holes, overturning old theories as to how black holes form.
Co-author Professor Mark Gieles, University of Surrey continued, “Our work is intended to help answer fundamental questions related to dynamics of stars and black holes, and the recently observed gravitational waves. These are emitted when two black holes merge, and if our interpretation is right, the cores of some globular clusters may be where black hole mergers take place.”
Thank you in advance for helping us to continue to be a part of your online entertainment!
ESIST 