Black Holes

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Starburst observed 30 years ago may hide 'nearby' black hole
By Steve Connor, Science Editor
Thursday, 18 November 2010

Astronomers believe they have witnessed the birth of a nearby black hole, formed when a massive star collapsed in on itself creating a gravitational field so strong that not even light could escape. The collapsed star, which was 20 times more massive than the Sun, created a stellar explosion, or supernova, in the M100 galaxy in the Virgo cluster, 50 million light years from Earth.

The supernova, which was observed by an amateur astronomer in 1979 and called SN 1979C, has been analysed by powerful astronomical instruments including Nasa's Chandra X-ray Observatory. These have provided crucial evidence suggesting that a black hole is hidden behind the light emitted from the explosion.

Data from the Chandra observatory, Nasa's Swift satellite, the European Space Agency's XMM-Newton and the German Rosat observatory revealed a bright source of X-rays from the supernova that remained steady from 1995 to 2007, suggesting the object is a black hole perhaps being fed by material falling back into it.

"If our interpretation is correct, this is the nearest example where the birth of a black hole has been observed," said Daniel Patnaude of the Harvard-Smithsonian Centre for Astrophysics in Cambridge, Massachusetts, who led the study.

More distant black holes had been detected by analysing huge explosions called gamma-ray bursts, but SN 1979C belongs to a different class of supernovas that are not associated with gamma-ray explosions.

Scientists believe that such supernovas are in fact the most common way that black holes are created, which is why the nearby SN 1979C is so interesting, said Abraham Loeb of the Harvard-Smithsonian Centre for Astrophysics.

"This may be the first time the common way of making a black hole has been observed. However, it is very difficult to detect this type of black hole birth because decades of X-ray observations are needed to make the case," Dr Loeb said.

http://www.independent.co.uk/news/scien ... 37129.html
 

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50 million light years away isn't quite what I would call nearby...
 

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Spinning black holes 'twist light'
By Jason Palmer, Science and technology reporter, BBC News

Researchers have proposed a means to spot rotating black holes.
The idea may provide the first unique signature of black holes, which - true to their name - have never been seen.

The approach, reported in Nature Physics, relies on a property of light called its orbital angular momentum.
The roiling nature of the fabric of space-time around spinning black holes should impart a "twist" in this momentum which could be detected here on Earth, the researchers say.

Light particles known as photons carry two kinds of momentum - a kind of energy carried in motion - but only one of them is familiar.
"If we take the Earth as an example, it spins around its own axis in about 24 hours - that's its spin angular momentum, and it also moves in orbit around the Sun - that's its orbital angular momentum," explained Bo Thide, a co-author of the paper.
"Photons can carry both," he told BBC News.

The spin angular momentum of photons manifests itself in the familiar phenomenon of polarisation - an effect that some sunglasses and even 3D glasses exploit.

But orbital angular momentum is trickier, and though it was predicted by the father of electromagnetic theory James Clerk Maxwell, it took until 1992 for experimentalists to find a way to manipulate it.

Now Professor Thide, of the Swedish Institute of Space Physics, and his colleagues have shown how the unique conditions around a spinning black hole could also impart orbital angular momentum to passing light.

"Around a spining black hole, space and time behave in such an odd way; space becomes time, time becomes space, and the whole space-time is acutally dragged around the black hole, becomes twisted around the black hole," Professor Thide explained.
"If you have radiation source... it will then sense this twisting of spacetime itself. The light ray may think that 'Wahey, I'm propagating in a straight line', but if you look at it from the outside, you see it's propagating along a spiral line. That's relativity for you." [ a Geordie Swede? ;) ]

The light's "phase" would show a characteristic pattern - that astronomers have never thought to look for The idea that spinning black holes could leave their imprint on passing light was first put forward by Martin Harwit of Cornell University in 2003 in an article in the Astrophysical Journal.
Professor Harwit presumed the light would be coming from some point beyond the black hole and simply passing nearby, and his calculations showed the effect would be minimal.

Professor Thide's team have now shown that the light emission from the swirling disc of material hypothesised to be around black holes, which emits intense light, would show the imprint more profoundly - enough to be spotted by the biggest telescopes on Earth, if their operators knew what they were looking for.

The great masses that sit at the centres of galaxies including our own Milky Way are by consensus presumed to be black holes, and if they are, are likely to be spinning. So a signature of light that can reveal spinning black holes is a potentially powerful tool in discovering how our galaxy is put together.

"While this effect has been known to theorists for some time, it has been regarded as obscure and of no practical importance," said Saul Teukolsky, an astrophysicist and black hole expert at Cornell University in Ithaca, US.
"What is exciting here is the prospect it might be used to measure the spin of the black hole at the center of our galaxy - the measurement will be difficult, though," he told BBC News.

In fact, to put the method into practice, only the very largest telescope arrays can be used. Professor Thide said that the Very Large Array in New Mexico, and the coming Square Kilometer Array and Atacama Large Millimetre Array telescopes could be the proving grounds for the idea.

"You would have to modify (the telescope arrays) slightly - probably only through software, and then you combine the signals in a way that's never been done before," he explained.
"If we are lucky, we should see the twisted light stand out, and then we open a bottle of champagne or two." 8)

http://www.bbc.co.uk/news/science-environment-12434007
 

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Supermassive black hole will 'eat' gas cloud

Researchers have spotted a giant gas cloud spiralling into the supermassive black hole at our galaxy's centre.
Though it is known that black holes draw in everything nearby, it will be the first chance to see one consume such a cloud.
As it is torn apart, the turbulent area around the black hole will become unusually bright, giving astronomers a chance to learn more about it.
The cloud, which is described in Nature, should meet its end in 2013.

Researchers using the European Southern Observatory's Very Large Telescope estimate that despite its size, the cloud has a total mass of only about three times that of Earth.
They have plotted the cloud's squashed, oval-shaped path and estimate it has doubled its speed in the last seven years - to 2,350km per second.
It should spiral in to within about 40 billion kilometres of the black hole in the middle of 2013.

Our local supermassive black hole, dubbed Sagittarius A*, lies about 27,000 light-years away, and has a mass about four million times that of our Sun.
As the name implies, beyond a certain threshold point - the event horizon - nothing can escape its pull, not even light itself.
But outside that regime is a swirling mass of material, not unlike water circling a drain. In astronomical terms, is a relatively quiet zone about which little is known.
That looks set to change, though, as the gas cloud approaches.

It does not comprise enough matter to hold itself together under its own gravity, as a star might, so the cloud will begin to elongate as it meets its doom.
"The idea of an astronaut close to a black hole being stretched out to resemble spaghetti is familiar from science fiction," said lead author of the study Stefan Gillessen, from Max Planck Institute for Extraterrestrial Physics in Germany.
"But we can now see this happening for real to the newly discovered cloud. It is not going to survive the experience."

It is likely that about half of the cloud will be swallowed up, with the remainder flung back out into space.
But this violent process will literally shed light on the closest example we have of an enigmatic celestial object.
The acceleration of the cloud's constituent material will create a shower of X-rays that will help astronomers learn more about our local black hole.

As astronomer Mark Morris of the University of California Los Angeles put it in an accompanying article in Nature, "many telescopes are likely to be watching".

http://www.bbc.co.uk/news/science-environment-16178112
 

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Giant black hole in tiny galaxy confounds astronomers

Astronomers have spotted an enormous black hole - the second-heaviest ever seen - but it resides in a tiny galaxy.
The galaxy NGC 1277, just a quarter the size of our own Milky Way, hosts a black hole 4,000 times larger than the one at the Milky Way's centre.
It has a mass some 17 billion times that of our Sun.

The surprise finding is hard to reconcile with existing models of black hole growth, which hold that they evolve in tandem with host galaxies.
Getting to grips with just how large black holes are is a tricky business - after all, since they swallow light in their vicinities, they cannot be seen.

Instead, astronomers measure the black holes' "sphere of influence" - the gravitational effects they have on surrounding gas and stars.
In the Milky Way, it is possible to observe individual stars as they orbit Sagittarius A, our own local black hole, to guess its mass.
But for the 100 or so far more distant black holes whose masses have been estimated, astronomers have made average measurements of associated stars' speeds - their "velocity dispersion".

On a hunt for the Universe's largest black holes, astronomers using the Hobby-Eberly Telescope in the US state of Texas undertook a survey that brought in a haul of nearly 900 host galaxies.

But Remco van den Bosch, then at the University of Texas at Austin, and his colleagues were surprised to find that some of the largest black holes were to be found in small galaxies.
Among them was NGC 1277, 220 million light years away in the constellation Perseus, which happens to appear also in a high-resolution Hubble Space Telescope image, helping the researchers to refine their computer models.

"We make a model of the galaxy and compute all the possible stellar orbits," Dr Van den Bosch explained to BBC News. "Like a big jigsaw, we try to put those orbits together to reproduce that galaxy so it has the same stellar velocities we measure. "

What the team found was that the NGC 1277 black hole was enormous - as large as our Solar System, and comprising some 14% of the entire galaxy's mass.
"The only way to you can actually make those high dispersions in the centre is by having that really big black hole, there's really no other way around it," Dr Van den Bosch said.

What is more, the team have five other small-galaxy candidates that, with the help of more data, could disprove the rule that big black holes only happen in big galaxies.
But NGC 1277 is stranger still, and could help advance our theories of how black holes evolve in the first place.

"This galaxy seems to be very old," Dr Van den Bosch said. "So somehow this black hole grew very quickly a long time ago, but since then that galaxy has been sitting there not forming any new stars or anything else.
"We're trying to figure out how this happens, and we don't have an answer for that yet. But that's why it's cool."

http://www.bbc.co.uk/news/science-environment-20528137
 

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27 February 2013 Last updated at 18:38

First glimpse of a black hole's spin

Astronomers have measured the rate of spin of a supermassive black hole for the first time - and it is big.
Measurements undertaken with two space-based X-ray telescopes imaged the black hole at the centre of galaxy NGC 1365.
The spin measurement, published in Nature, gives precious clues as to how the black hole grew and achieved supermassive status.
That growth influences the evolution of galaxies, so this simple number stands to teach scientists a great deal.

Black holes are notoriously difficult to study, since so much in astronomy depends on the detection of light - and beyond a certain distance, even that cannot escape.
Black holes are known to draw in material - gas and even stars - and stretch the very fabric of space-time at their edges. As matter goes in and gathers into what is called an accretion disk, it heats up and emits X-rays.

Previous attempts to quantify black holes' spins have attempted to analyse these X-rays - accounting for the violent processes within that can stretch and distort the X-rays' energies.
Those studies have until now focused on a fairly low-energy X-ray range. But those lower-energy X-rays can be further distorted by layers of gas between the black hole and the Earth, and previous spin observations have been contentious.

Now Guido Risaliti of the Harvard-Smithsonian Center for Astrophysics and colleagues have looked at markedly higher energies - less subject to absorption in those gas layers - using Europe's XMM-Newton telescope and the recently launched Nustar telescope.
Nustar is unprecedented in its ability to focus in on distant parts of the cosmos in these high-energy X-rays.

The results suggest a black hole more than 3 million km across, whose outermost edge is moving at a speed near that of light. :shock:
But as Dr Risaliti explained, "the black hole's spin is a memory, a record, of the past history of the galaxy as a whole".
Had the black hole grown in a series of small "feeds" of gas or stars from random directions, its spin would be low. The results instead suggest that the black hole grew in one or a series of large absorptions of matter, taking on the momentum in one or a few events.

And as Christopher Reynolds of the University of Maryland explains in an accompanying article in Nature, understanding the evolution of such supermassive black holes at galaxies' centres is crucial to our understanding of how galaxies themselves grow.
"The energy released by a growing supermassive black hole can be so powerful that it disrupts the normal growth of the host galaxy," Prof Reynolds wrote.
"In extreme cases, (it) can terminate all subsequent growth of the galaxy."

However, the measurement is that of just one galaxy, and Prof Reynolds notes that even more advanced X-ray observatories will be needed to unravel the riddle with so few clues.

http://www.bbc.co.uk/news/science-environment-21607945
 

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Black hole bonanza possible as immense gas cloud passes
By Jason Palmer, Science and technology reporter, BBC News

A vast and hidden field of small black holes predicted to be near the centre of our galaxy could be revealed as a giant gas cloud passes by.
The G2 cloud is as large as our Solar System, and bound for a "supermassive" black hole at the Milky Way's core.
On the way, it should encounter many black holes just tens of km across.

A report in Physical Review Letters suggests they will spin and heat the gas, which will emit a spray of X-ray light that telescopes could see.

The cloud of gas - three times larger than Pluto's orbit but with a total mass just three times that of the Earth - was first spotted on its course toward the galaxy's centre in 2011.
Researchers have been gearing up for the cloud's approach to the galaxy's enormous central black hole, with its closest approach in September.

But Imre Bartos of Columbia University in New York, US, and colleagues hit on the idea of using the cloud's passage for another purpose.
"We know that there is a very massive black hole in the centre of the galaxy, many millions of times heavier than our Sun, and we also suspect that there are thousands and thousands much smaller - a few times the mass of the Sun," explained Dr Bartos.

"When I first saw this G2 cloud going toward the centre, we thought that this may be the first opportunity to hopefully say something directly, to see these black holes near the centre," he told BBC News.

The idea is that as the cloud speeds past these small black holes - some slightly more massive than our Sun but just a few tens of km across - gas will spiral around them faster and faster, heating up to millions of degrees and emitting X-ray light.

It is a bit like allowing a giant sink to empty through thousands of tiny drains and looking for any evidence of swirling water.

The team estimates - based on guesses about just how much gas is in the cloud - that as G2 makes its pass around the central black hole, X-ray space telescopes such as Chandra or NuStar should be able to glimpse about 16 interactions with its smaller cousins.

Keeping an eye out for these X-rays may also confirm the existence of what are called "intermediate mass" black holes - a few thousand times the mass of our Sun.
Here again, theory predicts their existence - particularly near the centres of galaxies - but none has ever been definitively confirmed.

"I think it's a good idea," said Stefan Gillessen of the Max Planck Institute for Extraterrestrial Physics, co-author of the 2012 paper in Nature on the G2 cloud's discovery.
"We didn't think of that when we did the original paper - I think it's something worth following up," he told BBC News.
"But the big uncertainty, as always in this game, is what is the density of the gas which comes in."

The less dense the gas is, the less likely that enough light will be produced that our telescopes can see it. But as Dr Bartos points out, it is the first real chance to get a look at what may be thousands of smaller black holes hidden between us and the galactic core.

"It's a very special opportunity, and it's also lucky that we've now got the capacity to observe these things with X-ray telescopes on satellites," he said.

http://www.bbc.co.uk/news/science-environment-22694229
 

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Black hole caught napping after meal

A black hole 11 million light-years away has gone dormant, a decade after being spotted consuming cosmic debris.
The black hole lies at the centre of the Sculptor galaxy, a so-called starburst galaxy where stars are being born at a prodigious rate.
But the X-ray light corresponding to a black hole's snack has dimmed markedly.
The find, to appear in Astrophysical Journal, has mystified astronomers because star formation and black hole activity tend to go hand-in-hand.

The Sculptor galaxy - also known as NGC 253 - hosts a central black hole with a mass some five million times that of our Sun - a quarter again as plump as the black hole at the centre of our own Milky Way galaxy.
In 2003, researchers using the Chandra space telescope caught sight of the X-rays that correspond to matter spiralling down into the black hole and heating up to millions of degrees.

But as of mid-2012, the X-ray sky has a new observer: a space telescope called the Nuclear Spectroscopic Telescope Array or Nustar, already a successful black-hole hunter.

Nustar can spot even higher-energy X-rays than Chandra, and in late 2012, both telescopes were trained on NGC 253 - with the surprise finding that the X-ray emission seems to have stopped.

"Black holes feed off surrounding accretion disks of material. When they run out of this fuel, they go dormant," said Ann Hornschemeier of Nasa's Goddard Space Flight Center, a co-author on the new study.
"NGC 253 is somewhat unusual because the giant black hole is asleep in the midst of tremendous star-forming activity all around it."

The subtle interplay between black hole activity and the birth rate of new stars remains somewhat mysterious, but Bret Lehmer of Nasa's Goddard Space Flight Center, lead author on the paper, said that the Sculptor galaxy could shed new light on these dark galactic corners.
"Periodic observations with both Chandra and Nustar should tell us unambiguously if the black hole wakes up again. If this happens in the next few years, we hope to be watching," he said.

http://www.bbc.co.uk/news/science-environment-22874192
 

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Horizon - 2012-2013 - 15. Swallowed by a Black Hole

This summer, the black hole at the centre of the Milky Way is getting ready to feast.

A gas cloud three times the size of our planet has strayed within the gravitational reach of our nearest supermassive black hole. And across the globe, telescopes are being trained on the heart of our Milky Way galaxy, some 27,000 light years from Earth, in the expectation of observing this unique cosmic spectacle.

For cosmic detectives across the Earth, it is a unique opportunity. For the first time in the history of science, they hope to observe in action the awesome spectacle of a feeding supermassive black hole.

http://www.bbc.co.uk/iplayer/episode/b0 ... lack_Hole/

Available until
9:59PM Wed, 17 Jul 2013

Bon Appetit!
 

The late Pete Younger

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I hate the way these programs are presented as if we are all children who need to be entertained with special effects and flashy graphics, it was never like this on the sky at night.
 

rynner2

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Ronson8 said:
I hate the way these programs are presented as if we are all children who need to be entertained with special effects and flashy graphics, it was never like this on the sky at night.
Yes, this one was poor in that respect. Basically, enough info for a half-hour programme was padded to make it one-hour.
 

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Black hole set to 'eat a gas cloud'
9 January 2014 Last updated at 22:27 GMT

A gas cloud is being sucked towards the "supermassive" black hole at the heart of our galaxy, and astronomers are anxious to see what will happen.
If the black hole devours the cloud, called G2, X-rays will flare out - giving scientists a rare glimpse of the mysterious, dark core of the Milky Way.

The first moment of collision is predicted in Spring of this year. Scientists say it could be the black hole's "biggest meal in hundreds of years".

http://www.bbc.co.uk/news/science-environment-25663620

Video: The computer simulation of the event is rather lovely! 8)


More details here:
http://www.bbc.co.uk/news/world-middle-east-25678737
 

rynner2

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rynner2 said:
Black hole set to 'eat a gas cloud'
9 January 2014 Last updated at 22:27 GMT

A gas cloud is being sucked towards the "supermassive" black hole at the heart of our galaxy, and astronomers are anxious to see what will happen.
...
http://www.bbc.co.uk/news/science-environment-25663620
And on to today: science in the making as experts disagree:

Mystery over monster cosmic cloud
By Paul Rincon, Science editor, BBC News website

Observations of a cosmic confrontation between a huge gas cloud and the black hole at the centre of our galaxy have sparked debate among astronomers.
Celestial fireworks were thought to be a possibility as the gas was torn apart by the black hole.
But their absence so far has rekindled suggestions that it may not be a pure gas cloud after all.

One study suggests the cloud, named G2, is in fact a pair of stars that have merged into a much bigger one.
This conclusion has been prompted by observations that G2 survived its closest approach to the Milky Way's black hole, known as Sagittarius A* (Sgr A*).
"A gas cloud would not do that," said Prof Andrea Ghez, from the University of California, Los Angeles (UCLA), who co-authored the research in Astrophysical Journal Letters.

But other astronomers are not as sure, and suggest that a more compact gas cloud should still fit the data.
Beyond a certain threshold point - the event horizon - nothing can escape the pull of a black hole, not even light itself. But outside that is a swirling mass of material, not unlike water circling a drain.

Astronomers had already seen G2 being stretched out like a string of spaghetti by the black hole's extreme gravitational field.
Over an extended period of time, it was expected that about half of the cloud would be swallowed up, with the remainder flung out into space by Sgr A*.

The acceleration of the matter in the cloud would set off a shower of X-rays - the much-awaited celestial fireworks - that would help astronomers learn more about our local supermassive black hole.
But Prof Ghez explained that the cloud was "completely unaffected by the black hole; no fireworks".

The team has proposed an alternative explanation for G2 based on their detailed study of the cloud with the huge optical and infrared telescopes at the Keck Observatory in Hawaii.
In their view, the object is in fact best explained by a pair of stars - a binary system - that had been orbiting the black hole in tandem. The stars then merged to form an extremely large star cloaked in gas and dust.

But Dr Stefan Gillessen, who was not involved in the recent study, maintains that the original interpretation of G2 stands. Dr Gillessen led the team that detected the red cloud approaching Sgr A*, reporting their discovery in Nature journal in 2012.

"The observational facts are clear, I guess: There is gas, which shows a beautiful tidal evolution, as witnessed in the radial velocities. And there is dust emission, which appears to be compact," Dr Gillessen, from the Max Planck Institute for Extraterrestrial Physics in Garching, Germany, told BBC News.
"I personally am sceptical about the new proposed model: While I trust the observations, I don't think it is very likely that we can catch an object in the transitional stage of merging."

Prof Ghez and colleagues suggest that the newly formed object will eventually look like the massive young stars that are tightly clustered around the Milky Way's black hole - the so-called S-stars.
They also propose that the gravitational influence of the black hole could make mergers of binary stars more likely by increasing the eccentricity of their orbits.

But Dr Gillessen explained: "I think we are far from excluding any model."
He added: "My guess is still: it is an unlucky clump of gas on an almost plunge orbit. The new observations show, that it might be more compact by some moderate factor than what we thought."

Dr Gillessen suggested there was a very low chance - perhaps lower than 10% - that the observations could be explained by a recently merged binary star. And he added that mathematical models of the object as a gas cloud could be tweaked to enable them to match the new data.
He added that the UCLA team did not detect any emission from the surface of the star.

Of the absence of fireworks, he said: "This is factually correct, but no models actually predicted increased accretion in 2014 - that would come later only. So the absence now is not telling much, I fear.

"On the other hand, it was estimated that the shock front of G2 rushing through the ambient gas might be observable. That has not been observed, which in turn means that G2 is more compact, or the ambient gas is thinner than assumed in these calculations.
"But G2 does not need to be as small as a star for that."

The debate is likely to continue, but in the meantime, astronomers will be keeping their eyes glued on the centre of our galaxy.

http://www.bbc.co.uk/news/science-environment-29934458
 

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[Video]

Supermassive black hole discovery made by Southampton astrophysicists

Astrophysicists at the University of Southampton say they have made a fundamental discovery about supermassive black holes.
The scientists, led by Sebastian Hoenig, worked out that these largest types of black hole are much further away and 40% bigger than first thought.

Dr Hoenig was studying a supermassive black hole called the Eye of Sauron with a colleague in Denmark and said he realised there was a way to measure its distance away no-one had thought of before.

He said: "The key point is that black holes are very mystical. They are a billion times the mass of the sun, and they are essentially in all centres of galaxies."

The discovery has been published in the scientific journal Nature.

http://www.bbc.co.uk/news/uk-england-hampshire-30241884
 

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That really doesn't tell us anything, like how this information reconciles with distances established by red shift?
 

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OneWingedBird said:
That really doesn't tell us anything, like how this information reconciles with distances established by red shift?
You probably need to read the paper for the nitty-gritty.

But such paradigm shifts happen frequently in science - just when you think you've got it all pinned down, someone takes a second look and finds it all has to be recalibrated!

In fact, the same thing happened to the Hubble constant itself:

"Hubble was able to plot a trend line from the 46 galaxies he studied and obtain a value for the Hubble constant of 500 km/s/Mpc (much higher than the currently accepted value due to errors in his distance calibrations)."

http://en.wikipedia.org/wiki/Hubble%27s ... asurements
 

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Now that I get into thinking about that, if I've got this right then apparent brightness is the inverse square of the distance, so if the black hole was twice as far away as expected it would need to be 400% the actual brightness to appear the same.

So a 40% increase probably doesn't change the distance much.
 

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The new technique does not rely on measuring the brightness of the accretion disk around the black hole, but measurement of the size of the disk. The energy from a flare close to the black hole is tracked in infrared over time crossing the disk. This establishes the adjacent distance and the team used trig to calculate absolute distance.

Previous estimated distances to NGC 4151 ranged from 4 to 29Mpc - which is more or less saying 'it's over there somewhere'. The team are confident the current measurement 'pins' the distance at 19Mpc, give or take 10%.

NGC 4151 is a disrupted galaxy with a clear view of it's particularly active core, but I suppose this technique will be refined and used to make more accurate maps. Unless it's wrong...

But such paradigm shifts happen frequently in science - just when you think you've got it all pinned down, someone takes a second look and finds it all has to be recalibrated!
Astronomy is currently undergoing a revolution. Telescopes and sensors have followed their own version of "Moore's law" and lot's of seemingly reasonable assumptions about everything from planetary formation to the large scale structure of the universe are being replaced with very interesting new data.

More black hole oddness:
http://www.sciencedaily.com/releases/2014/11/141119084506.htm
 

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The reporting there is quite misleading as it does imply the object is a lot more distant, interesting stuff though.

My first thought was whether this tied in with allegedly anomalous quasar redshift, though clearly not now.
 

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I hadn't seen the BBC report, just the teams press release. As always, the TV report was light on facts, figures and any science really.

Very interested to see how this technique will impact distances derived from redshift (is there a emoticon for understatement?).
 

Schwadevivre

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A long but fascinating article on the Phys Org site about a new hypothesis regarding the effect of Planck scale indeterminacy on the black hole information loss problem. Despite the title of the article it has more to do with the existence of the event horizon rather than the actual black hole - I think, but I could be wrong after giving it some more thought ...

Anyway here's the link to the article
 

Ermintruder

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I need to re-read this at least a couple of times, but if the word 'information' here means (in the context of black holes) measurable physical parameters (yes? Or No?)

A paradox in this scenario is that Hawking radiation originates from the mass of objects that fell into the black hole, but (in theory) the radiation does not carry complete information about these objects as it radiates away from the black hole. Eventually this radiation is expected to cause the black hole to evaporate completely. So the question then arises: where does the information about the objects go?

In everyday life, shredding or burning paper documents may be common practice to destroy information, but according to quantum theory, information can never be completely destroyed. In principle, the initial state of a system can always be determined by using information about its final state....
My understanding of cosmology is poor, but, I get the impression (and please do not be offended by this statement) if I wait a while, with the constantly-changing definitions that attempt to define it, my misunderstood interpretations of it will maybe become in itself, correct. But not within any widely-shared reference frame...

There is an Emperor's New Mind aspect to vast amounts of what is called theoretical physics (in itself, a terminological paradox). Hawking has attracted much recent superficial interest with his apparent postulation that black holes don't actually exist. When of course we all know that they do...and don't.

If people can infinitely theorise about the nature of time and space, until the end of time, tell me with absolute conviction in what way is this science any different from religion in terms of faith and indeterminacy? In what way is a professorial chair of astrophysics different from that of divinity?

I'm sorry, this reads like a rant....but, as a science junkie, I always hoped for absolutes. Or closest-to...

And on a related note, I wonder if this part is intended to sound quite as doubly-odd as it sounds:

the energy of a particle cannot get as large as possible, but that there is a maximum energy that any particle can reach. This restriction can be easily combined with Einstein's special theory of relativity, and the resultant theory is called the doubly special theory of relativity, or DSR."

As the physicists explain, it is possible to generalize DSR to include gravity, and this theory is called gravity's rainbow.
ps Something I've always wondered...do astrophysicists and exobiologists hold each-other in the same level of mutual disdain as their more prosaic earth-dwelling vocationally-focussed cousins appear to? If so, this would mean that there would be a particular (may I say DSR) animosity between, say, photo-optics physicists and Martian lander exobiologists. And between cosmologists & say microbiologists.
 

Schwadevivre

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The way I read it was that, on a quantum level, the event horizon (and thus the black hole) is not a discrete boundary but rather it is smeared out allowing information to be carried out of the black hole.

TBH I really posted it because of the Ted Logan "Whooaah!" factor
 

rynner2

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I need to re-read this at least a couple of times, but if the word 'information' here means (in the context of black holes) measurable physical parameters (yes? Or No?)

If people can infinitely theorise about the nature of time and space, until the end of time, tell me with absolute conviction in what way is this science any different from religion in terms of faith and indeterminacy? In what way is a professorial chair of astrophysics different from that of divinity?
Astrophysics uses much more high level maths!

(About the only maths in Divinity is counting the generations in those long lists of who begat whom!)
 

rynner2

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Event horizon snapshot due in 2017
By Jonathan Webb Science reporter, BBC News, Kissimmee, Florida

Long article: highlights:-

A network of nine radio telescopes, dotted around the globe, is set to take the first ever picture of a black hole's event horizon in 2017.
The project, called the Event Horizon Telescope, has completed most of its technical preparations as well as extensive theoretical calculations.
It will focus on Sagittarius A*, the black hole at the Milky Way's centre.
...

Supermassive though it may be, the heart of the Milky Way's black hole is not as big as you might think; the event horizon of Sagittarius A* is just 24 million km across - 17 times bigger than the Sun.
At 25,000 light years away, that makes it a pinprick. From the surface of the Earth, Prof Ozel explained, it takes up about as much of the sky as a CD sitting on the moon.

And surrounding this mysterious, spherical frontier are roiling clouds of gas and dust, which blaze with energy as they are sucked and squeezed furiously towards it.
These clouds are trouble for the EHT astronomers, who want to peer closer than ever before at this fringe of the observable universe.
...

"We've run upwards of a million simulations, for many different configurations of what that gas might look like. And in all cases, we think that the 1.3mm wavelength is the right choice to see down to the event horizon."
It was an "incredibly lucky coincidence", she added, that any wavelength at all was feasible.
Because as well as penetrating the black hole's dust cloud, Prof Ozel and her colleagues need the hot gas right at the event horizon to shine brightly in this colour - which they believe it does.
Finally, the light has to travel easily through the Earth's own atmosphere into the dishes of the waiting telescopes; 1.3mm fortunately fits that bill in every case.

The nine stations enlisted to stare at SagA* include the big dishes in Antarctica, Chile, Hawaii, Spain, Mexico and Arizona.
Altogether this makes what the team calls a "virtual telescope the size of the Earth".

So what will this mammoth eye actually see?
"Hopefully it will look like a crescent - it won't look like a ring," Prof Ozel said.
This is because the glowing gas is spinning around the black hole, and a dramatic Doppler effect should make the stuff moving towards the Earth appear much brighter.
"The rest of the ring will also emit, but what you will brightly pick up is a crescent."

In fact, the picture that emerges from the EHT next year will put general relativity on the line.
Einstein's theory states that a mass - especially one as big as a black hole - bends space-time. And that curvature can be calculated mathematically.
So the size of the shadow cast by SagA* will either match what is predicted by general relativity, or it won't.
"We know exactly what GR predicts for that size," Prof Ozel said - making this observation what scientists call a "null hypothesis test" of the theory.
Astronomers rely on general relativity all the time, making use of the way masses bend the path of light. But it has never been tested on this scale before.

etc...

http://www.bbc.co.uk/news/science-environment-35258378
 

rynner2

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Stephen Hawking’s Reith Lecture: Annotated transcript
By David Shukman Science editor

My talk is on black holes. It is said that fact is sometimes stranger than fiction, and nowhere is that more true than in the case of black holes.

Black holes are stranger than anything dreamed up by science fiction writers, but they are firmly matters of science fact. The scientific community was slow to realize that massive stars could collapse in on themselves, under their own gravity, and how the object left behind would behave.

Albert Einstein even wrote a paper in 1939, claiming stars could not collapse under gravity, because matter could not be compressed beyond a certain point. Many scientists shared Einstein's gut feeling.

etc...

http://www.bbc.co.uk/news/science-environment-35354313
 

hunck

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I read an article just a few days ago which said there are estimated to be around 300 million smaller black holes in the Milky Way as well as the super massive one at the centre. I was a bit amazed by this & now can't find the article...
 

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Well, a respectable fraction of the largest stars in the galaxy will explode as supernovas then collapse into a black hole or a neutron star, so I would expect there to be large numbers of these remnants out there. Some of these smaller black holes are visible, because they are in a binary relationship with another star; these binaries tend to have large, highly luminous accretion disks around them formed from material dragged from the companion star.

Some black-hole binary stars here
 

rynner2

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The Sky at Night - Stephen Hawking on Black Holes

The programme looks at the latest understanding of black holes, featuring an interview with Stephen Hawking. Black holes are one of the greatest mysteries in the universe. They behave in a way that is contrary to laws of physics and one has never actually been seen. However, the recent detection of gravitational waves, as predicted by Einstein, proves that black holes exist and provides a way to investigate their remarkable behaviour and properties.

http://www.bbc.co.uk/iplayer/episode/b077ryr3/the-sky-at-night-stephen-hawking-on-black-holes
 
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