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Black Holes

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#26
Astronomers have mapped dark matter on the largest scale ever observed

Good news:

An international team of researchers lead by Van Waerbeke and Heymans achieved their results by analysing images of about 10 million galaxies in four different regions of the sky. They studied the distortion of the light emitted from these galaxies, which is bent as it passes massive clumps of dark matter during its journey to Earth.
Those tiny distortions in the images of distant galaxies, called cosmic shear.

And here's Dark Matter map and the full moon to scale.



The observations show that dark matter in the Universe is distributed as a network of gigantic dense (light) and empty (dark) regions, where the largest dense regions are about the size of several Earth moons on the sky.



The densest regions of the dark matter host massive clusters of galaxies. To get these accumulated images over five years scientists used the wide field imaging camera MegaCam, a 1 degree by 1 degree field-of-view 340 Megapixel camera on the CFHT in Hawaii.

Galaxies included in the survey are typically six billion light years away. The light captured by the telescope images used in the study was emitted when the Universe was six billion years old – roughly half the age it is today.
The scientists are optimistic:

Professor Ludovic Van Waerbeke, from the University of British Columbia, said: "It is fascinating to be able to 'see' the dark matter using space-time distortion. It gives us privileged access to this mysterious mass in the Universe which cannot be observed otherwise. Knowing how dark matter is distributed is the very first step towards understanding its nature and how it fits within our current knowledge of physics."
Dr Catherine Heymans, a Lecturer in the University of Edinburgh's School of Physics and Astronomy, said: "By analysing light from the distant Universe, we can learn about what it has travelled through on its journey to reach us. We hope that by mapping more dark matter than has been studied before, we are a step closer to understanding this material and its relationship with the galaxies in our Universe."

Professor Lance Miller, from Oxford University said: "This result has been achieved through advances in our analysis techniques which we are now applying to data from the Very Large Telescope's (VLT) Survey Telescope in Chile."

Professor Koen Kuijken, from Leiden University, said: "Over the next three years we will image more than 10 times the area mapped by CFHTLenS, bringing us ever closer to our goal of understanding the mysterious dark side of the Universe."
http://www.physorg.com/news/2012-01-astronomers-universe-dark-unprecedented-scale.html

http://www.physorg.com/news/2012-01-clearest-picture-dark-energy.html

The bigger more accurate and better Dark Matter map they get the better we will understand our Universe. It will shed some light on dark energy as well.

Gravity tends to pull matter together into dense concentrations, but dark energy acts as a repulsive force that slows down the collapse. Thus the clumpiness of the dark matter maps provides a measurement of the amount of dark energy in the universe.
I just hope there will be more and more of new tools available to physicists in their study so we could get more info. :)



Teams from Fermilab and Berkeley Lab used galaxies from wide-ranging SDSS Stripe 82, a tiny detail of which is shown here, to plot new maps of dark matter based on the largest direct measurements of cosmic shear to date.
 
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#27
15 times more massive than the sun, huh? I thought black holes were created through starts hundreds or thousands of times more massive than our sun when they die in a supernova. I guess there are other ways for black holes to be made...?
There are no such stars.
The most massive star, a blue giant called R136a1 is only about 250-320 times the mass of our sun.
The biggest stars, like VV Cephei or VY Canis Majoris may be 2000 times the radius of our sun, but they have just 30-40 times the mass. These stars are literally less dense than even the uppermost part of the Earth's atmosphere.

Supermassive black holes are by necessity also primordial, and were essentially formed at the same time the universe was created. The law of conservation of angular momentum limits the speed at which matter can fall into a black hole, and essentially means the age of the universe isn't enough time for any stellar mass black hole to grow to such a size.
 

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#28
"Dark matter" is whatever is located at the center of galaxies that hold the galaxy together (much like stars hold solar systems together). For the Milky Way, it is likely Sagittarius A*.

I think a better word for it than "black hole" is a "fission star"--that is, a star composed mostly of extremely heavy metals like uranium and plutonium (but likely substantially heavier).
 
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#29
Supermassive black holes are by necessity also primordial, and were essentially formed at the same time the universe was created. The law of conservation of angular momentum limits the speed at which matter can fall into a black hole, and essentially means the age of the universe isn't enough time for any stellar mass black hole to grow to such a size.
Can you post a source for this info?
 
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#30
http://iopscience.iop.org/1538-4357/701/2/L133
Here's an interesting paper on accretion of matter into early stellar-mass blackholes, and details many of the limiting factors to black hole growth. Novel mechanisms are also explored which would account for possible growth of a stellar mass black hole into a massive entity, but not a true supermassives such as those found in galactic centers.

IMO the elephant in the room is that we have data for a lot of stellar mass black holes of up to 30 or more solar masses, and then we have supermassives but there are no intermediate mass black holes at all. If stellar mass black holes were slowly accreting matter and growing into supermassives, then we should see plenty of black holes in the 1000M range, but there aren't any. We basically go from 0-33, and then skip right into the supermassive range. This suggests a completely different method of formation for the two black hole classes.
 
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#31
http://iopscience.iop.org/1538-4357/701/2/L133
Here's an interesting paper on accretion of matter into early stellar-mass blackholes, and details many of the limiting factors to black hole growth. Novel mechanisms are also explored which would account for possible growth of a stellar mass black hole into a massive entity, but not a true supermassives such as those found in galactic centers.

Here's a quote from the abstract:
We study remnant black hole growth through accretion, including for the first time the radiation emitted due to accretion, with adaptive mesh refinement cosmological radiation-hydrodynamical simulations. The effects of photoionization and heating dramatically affect the large-scale inflow, resulting in negligible mass growth.
IMO the elephant in the room is that we have data for a lot of stellar mass black holes of up to 30 or more solar masses, and then we have supermassives but there are no intermediate mass black holes at all. If stellar mass black holes were slowly accreting matter and growing into supermassives, then we should see plenty of black holes in the 1000M range, but there aren't any. We basically go from 0-33, and then skip right into the supermassive range. This suggests a completely different method of formation for the two black hole classes.
 
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#32
I believe there are other names needed other than 'Dark Matter' for these things we see.

I personally consider dark matter to be a substance which the galaxy is kept within rather than what IS any sort of black hole.
 
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#33
I just want to say that the first person with this idea was Roger Penrose - sort of. OK, he ascribed the circular patterns in the CMBR to "leaks" from the last big crunch, but it seems that this theory lines up with his original idea.

In Nov. 2010, British physicist Roger Penrose went on the record to say that it was by his reckoning that there were patterns in the cosmic microwave background radiation (CMBR) -- the "echo" of the Big Bang. Penrose's theory is that gravitational waves -- "ripples" in spacetime -- leaked through from the pre-Big Crunch universe, imprinting the CMBR with detectable rings.

Although Penrose's idea was heavily criticized (cosmologists familiar with the CMBR said that Penrose was seeing shapes and patterns in the random temperature "anisotropies" and not seeing what he thought he was seeing), could Carr and Coley's pre-Big Bang black holes be detected?

Possibly.
 

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#34
If black holes suck every thing in including light , Then why is it that jets can come out of the center of them . I mean if the gravity is so intense as to suck in light and every thing then why are jets of hot gas and radiation allowed to escape ?
 

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#35
If black holes suck every thing in including light , Then why is it that jets can come out of the center of them . I mean if the gravity is so intense as to suck in light and every thing then why are jets of hot gas and radiation allowed to escape ?
The jets don't come out of the black hole - nothing can get out.

They're caused by the motion of the disc of gas and dust falling in and the intense gravity. I don't think that scientists have quite figured out how the jets at 90 degrees to the plane of the discs are formed though.
 
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#36
If black holes suck every thing in including light , Then why is it that jets can come out of the center of them . I mean if the gravity is so intense as to suck in light and every thing then why are jets of hot gas and radiation allowed to escape ?
qubit is right but there's also another kind of radiation:


Black holes have energy and they always emit it as photons. So Black Holes constantly lose their energy and eventually they will evaporate. It's called Hawking radiation. You ask how it happens? There's quantum tunnelling (See here: http://phys.educ.ksu.edu/vqm/html/qtunneling.html). Non-quantum (classic) objects can't escape but quantum objects (wave–particle duality of matter and the Heisenberg uncertainty principle can explain this easily) can use quantum tunnelling to break the "barriers" and escape the Black Hole. BTW quantum tunnelling also occurs in the nuclear fusion of Sun or any other star.

So Black Holes are not "some big suckers that don't ever emit". Close to event horizon of a black hole there's strong gravitational field which generates pairs of particles and anti-particles. See the pic below:



Some can escape to infinity, some can annihilate and some can get sucked in.



http://casa.colorado.edu/~ajsh/hawk.html
 
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#37
"Dark matter" is whatever is located at the center of galaxies that hold the galaxy together (much like stars hold solar systems together). For the Milky Way, it is likely Sagittarius A*.
As I understand it, if Sagittarius A* is offset slightly, but still within the small 'region' of the black hole at galactic center (as it would have to be in order for stars to appear to be orbiting it and the black hole), there is no way to know what it is without a clever astrophysicist coming up with clever mathematical inferences, based upon observations, that they would be willing to publish.

It could be a massive clump of dark matter, I suppose. But still less massive than the central black hole, which it seems to be closely orbiting.

I think it's more likely to be another black hole in close orbit, the old core of a galaxy devoured by the Milky way sometime in the distant past. Which it probably is, if the central black hole is showing a slight 'wobble'. Which would not be good for future life in our galaxy, depending on how close they are to merging.
Or, a supernova remnant (black hole or neutron star) doing its own post-death death-spiral into the massive black hole.
Or, superheated plasma in the region around the massive black hole -- which could produce radio emissions.
 

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#38
Ok so if a black hole dies what is left then ? Shouldn't there be some thing like a ball of iron ? After all it is a sun burn all them elements and making iron that leads to the end of the star then creating the black hole right ? Then once it has died shouldn't there be some thing left after the death of the black hole ?
 
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#39
^ The crust of a neutron star is made of iron. And eventually neutron stars quantum-tunnel and become black holes. Yes, there's a theory that everything in the universe after 10^1500 years (can you imagine all those zeros) will lose the energy, cool down and turn to iron because iron has the nucleus with the least binding energy. But after 10^10^26 (lol all these zeros, this is the last time I promise) years all that iron collapse into black holes. But this will happen if proton decay won't occur before this.

Some interesting thoughts here:

http://en.wikipedia.org/wiki/Future_of_an_expanding_universe

and especially here:

http://math.ucr.edu/home/baez/end.html

The end of the universe will be dark and cold, really cold (literally). But as always take this with a grain of salt. No one knows yet how the real END will look like.
 

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#40
^ The crust of a neutron star is made of iron. And eventually neutron stars quantum-tunnel and become black holes. Yes, there's a theory that everything in the universe after 10^1500 years (can you imagine all those zeros) will lose the energy, cool down and turn to iron because iron has the nucleus with the least binding energy. But after 10^10^26 (lol all these zeros, this is the last time I promise) years all that iron collapse into black holes. But this will happen if proton decay won't occur before this.

Some interesting thoughts here:

http://en.wikipedia.org/wiki/Future_of_an_expanding_universe

and especially here:

http://math.ucr.edu/home/baez/end.html

The end of the universe will be dark and cold, really cold (literally). But as always take this with a grain of salt. No one knows yet how the real END will look like.
Mind boggling !
 
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#41
Intermediate-mass black hole

Astronomers using NASA's Hubble Space Telescope have found a cluster of young, blue stars encircling the first intermediate-mass black hole ever discovered. The presence of the star cluster suggests that the black hole was once at the core of a now-disintegrated dwarf galaxy. The black hole weighs in at 20,000 solar masses and lies towards the edge of the galaxy ESO 243-49, which is 290 million light-years from Earth.


http://www.physorg.com/news/2012-02-black-hole-shredded-galaxy.html

The fate of this black hole ain't too optimistic.
 

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#42
The fate of this black hole ain't too optimistic.
Black holes are indestructible, so I'm not sure what you mean by that?
 
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#43
^

The future of the black hole is uncertain at this stage. It depends on its trajectory, which is currently unknown. It's possible the black hole may spiral in to the center of the big galaxy and eventually merge with the supermassive black hole there. Alternately, the black hole could settle into a stable orbit around the galaxy. Either way, it's likely to fade away in X-rays as it depletes its supply of gas.
And no, they are not indestructible
 

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#44
^



And no, they are not indestructible
Yes, it is. Black holes can only merge with each other to make a bigger one. All the article is saying is that it doesn't know where it's going and that it won't be detectible when the x-rays from infalling gas dry up.
 

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#46
Black holes evaporate as they lose their energy
That's splitting hairs. For anything other than a teeny tiny one, they'll take longer than the age of the universe to evaporate. And anyway, the effect is overridden because it's really really small and there's always something for a black hole to munch on and it doesn't have to be much, either, just a little gas and dust will do. :)

So, consider a black hole as existing forever for all practical purposes. And once again, the article said nothing about the black hole dying.
 
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#47
It's not. Getting "owned" by other bigger black hole is the same as dying. Because other black hole will use smaller black holes energy. The article says that it can happen. Reminds me how bigger corporations eat up smaller corporatrions.
 

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#48
It's not. Getting "owned" by other bigger black hole is the same as dying. Because other black hole will use smaller black holes energy. The article says that it can happen. Reminds me how bigger corporations eat up smaller corporatrions.
No, it's just a merge, ragardless of size - they eat each other you could say, I guess. And honestly, no one knows what happens at those singularities and we may never will. Bummer. :( I love science and I really want to know.
 
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#49
To get back to the Dark matter conversation thread:

The ESA's Planck mission which is going to be measuring the Cosmic Microwave Background radiation to higher degrees of accuracy than previously achieved, discovered something while observing the 'foreground' in order to subtract it from its main observations --- a 'haze' of microwaves in a 35 000 ly region around the core of the Milky way.

The latest announcement from the European Space Agency involves a haze of microwaves that is not yet understood. Coming from the region around galactic center, the haze appears to be synchrotron emission, produced as electrons accelerated in supernovae explosions pass through magnetic fields. So far so good, but this synchrotron emission does not fall off as rapidly at increasing energies as the synchrotron emission that can be observed elsewhere in the Milky Way.

What Planck has found is an enormous field of haze spanning some 35,000 light years. The problem: Supernovae don’t make enough electrons and positrons at high energy to fill the volume taken up by the Planck haze, according to Gregory Dobler (UC Santa Barbara):

“There are many possibilities and theories, ranging from Galactic winds to a jet generated by the black hole at the center of our Galaxy to exotic physics related to dark matter. The problem is that the picture that has emerged with the Planck data, as well as the Fermi data, challenges all of the explanations. There is no Goldilocks theory yet. None of them fit the data just right.”

The fact that early explanations for the haze are all over the map tells us how little we understand what is going on here — one theory invokes the annihilation of dark matter particles, while others involve higher supernova rates in the early universe. ESA’s Jan Tauber, project scientist for Planck, will only say that the galactic haze result is ‘interesting,’ which basically says we’re still in the dark.
There ya go, possible annihilation of dark matter particles.

http://www.centauri-dreams.org/?p=21757
 
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#50
IGR J17091 - a binary system in which a sun-like star orbits the black hole. It is found in the bulge of the Milky Way galaxy, about 28,000 light years away from Earth. Observations with Chandra have clocked the fastest wind ever seen blowing off a disk around this stellar-mass black hole at about 20 million miles per hour. The wind, which comes from a disk of gas surrounding the black hole, may be carrying away much more material than the black hole is capturing and could be variable over time.


Contrary to the popular perception of black holes pulling in all of the material that gets close, 95% of the matter in the disk around IGR J17091 is expelled by the wind. And other interesting fact is production of winds can stifle radio jets.

Astronomers believe that magnetic fields in the disks of black holes are responsible for producing both winds and jets. The geometry of the magnetic fields and rate at which material falls towards the black hole must influence whether jets or winds are produced.
They said this because jet from the black hole was not present when the ultra-fast wind was seen, although a radio jet is seen at other times. Fascinating!

http://www.physorg.com/news/2012-02-chandra-fastest-stellar-mass-black-hole.html