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Black Holes

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#1
So no wimps for today I guess...

“We know that about 25% of the matter in the universe is dark matter, but we don’t know what it is,” Michael Kesden tells PhysOrg.com. “There are a number of different theories about what dark matter could be, but we think one alternative might be very small primordial black holes.”
Yeah small but darn heavy

When many of us think about black holes, we think of a huge cosmic event, sucking in everything around it. However, there is also the possibility of small black holes. “Einstein’s theory of relativity allows for black holes,” Kesden explains, “but doesn’t stipulate a size. It’s very possible that the early universe produced very small black holes. These would gravitate like massive black holes, floating through the universe and clustering.”

Kesden worked with Shravan Hanasoge, from Princeton University and the Max Planck Institute for Solar System Research, to work out method of using solar oscillations to determine whether a small, primordial black hole passed through a star. If the data can show that these small black holes formed near the beginning of the universe do exist, they might make good candidates for dark matter.
More ...

“Our approach is to consider what happens if you have dark matter made of primordial black holes passing through the sun,” Kesden says. “It’s been thought of before, but no one has actually done the calculations that we have.”
Kesden explains that the sun creates energy from the nuclear fusion at its center: “There is a balance between the outward pressure gradient due to the energy released by fusion and the inward force of gravity. If the sun, or any star, is perturbed it would shake a little.”
“A small, primordial black hole would be the size of an atom but have the mass of an asteroid,” he points out. “Its strong gravitational field, as it cut through the sun, would squeeze it, then release, and cause the sun to oscillate before ultimately settling down.”
The idea is to measure the oscillation, and determine what would cause it. “Shravan Hanasoge wrote a program to help us with a simulation to see what the sun would look like if a primordial black hole passed through. The smallest mass detectable is 10^21 grams,” Kesden continues.
They think that a tiny primordial black hole could move through the sun ....

Now that Kesden and Hanasoge know what to look for, it is possible to measure the oscillations of different stars. Since these primordial black holes are thought to be moving through the universe, it should be observable in different stars. “By inferring the total amount of dark matter in the universe, it should be able to determine how often a primordial black hole would pass through the sun – if it’s dark matter,” Kesden says. Unfortunately, dark matter would only pass through the sun every millions of years. “That’s a long time to stare at our sun, waiting for the event.”
... every millions of years. I guess I'd get bored to wait so long but ...

Instead of waiting millions of years for a primordial black hole to pass through our sun, it is possible to monitor millions of stars; one of these stars would likely encounter a primordial black hole every few years. Kesden points out that current and future space missions could collect the needed data. “It is possible to look at the data collected from asteroseismic missions for these events, now that we know what to look for. Someone could even look through data collected in the past to try to spot these oscillations.”
Would be funny if those oscillations were spotted but nobody thought it was tiny nasty black holes. But there's a hope ...

“At the Large Hadron Collider, some scientists are trying to determine if supersymmetry is dark matter,” Kesden says. “But if it isn’t found at the LHC, people will begin looking for other alternatives, and primordial black holes might be the answer to the outstanding question of what dark matter is.”
Atm it all adds only confusion.
 
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#2
I can't see dark matter being primordial black holes.
It's well established that dark matter surrounds galaxies, galactic clusters, and superclusters. This has been observed simply from inferring gravitational interactions with the visible galaxies.
It has to be WIMPS in some form or other. Primordial black holes would not survive billions of years in cosmically significant numbers to gravitationally influence galaxies without announcing themselves with gamma ray and x-ray emissions as they coalesce and merge (not gamma ray bursts, those are supernovae). Furthermore, those primordial black holes (if they were that numerous) would have merged into a lesser but still massive number of black holes with billions of solar masses, in order to gravitationally influence 'visible' baryonic matter.

I'm sure there are innumerable primordial black holes out there, but they can't account for all the mass of 'dark matter'.
 
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#3
It has to be WIMPS in some form or other. Primordial black holes would not survive billions of years in cosmically significant numbers to gravitationally influence galaxies without announcing themselves with gamma ray and x-ray emissions as they coalesce and merge (not gamma ray bursts, those are supernovae). Furthermore, those primordial black holes (if they were that numerous) would have merged into a lesser but still massive number of black holes with billions of solar masses, in order to gravitationally influence 'visible' baryonic matter. I'm sure there are innumerable primordial black holes out there, but they can't account for all the mass of 'dark matter'.
Nice. I believe in WIMPS too. I think they claim this because atom-sized black holes are just hard to detect as wimps. But I dunno what if black holes are made of wimps (or superwimps).
 
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#4
But I dunno what if black holes are made of wimps (or superwimps).
WIMPs are Weakly Interacting Massive Particles; which implies they're all floating around out there, and don't interact with normal matter or with each other much at all; so gravitationally coalescing into black holes is ruled out. Imagine large cluster spanning clouds of dark matter particles (WIMPs) gravitationally affecting the visible matter in a galaxy or cluster of galaxies.

Here's some reports on it:
http://arstechnica.com/science/news/2008/01/images-of-dark-matter-distribution-in-a-supercluster.ars

http://home.slac.stanford.edu/pressreleases/2006/20060821.htm
 
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#5
I know what wimps are. Weak is still interaction.

don't interact with normal matter or with each other much at all; so gravitationally coalescing into black holes is ruled out.
http://www.nasa.gov/mission_pages/GLAST/science/dark_matter.html

When supersymmetic neutralinos (aka wimps) interact with each other they annihilate and create secondary particles (leptons, bosons, quarks) and gamma rays. I wasn't talking about "gravitational coalescence". Just interaction. And second: I was talking about WIMP matter and a question whether black holes were made up of WIMP matter or regular matter.

http://adsabs.harvard.edu/full/2002Obs...122..199A
 
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#6
That's interesting stuff, but it's all theoretical and speculative.
I first read about WIMPs and MACHOs 25 years ago, and all that can be said, so far, is that MACHOs can possibly account for a very small percentage of what we call dark matter. The problem is that we have no way of knowing, at this point, what MACHOs really are.

Also, I have to point out that a black hole, being the remnant of a massive star, composed of baryonic matter, collapsed down to a point that is at most Planck length in diameter... that's all we can know about it. Physics can't tell us anything about what happens in there; it's just a massively compressed soup of energy, as to details... who knows? There are no particles, just energy. No dark matter in a normal black hole, just energy.

Dark matter stars and dark matter black hole analogs? Interesting but not proven.
 
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#7
That's interesting stuff, but it's all theoretical and speculative.
I first read about WIMPs and MACHOs 25 years ago, and all that can be said, so far, is that MACHOs can possibly account for a very small percentage of what we call dark matter. The problem is that we have no way of knowing, at this point, what MACHOs really are.
You're right. We don't have enough knowledge of that. All these things are so hard to detect/observe and it breeds a lot of speculations. (atm I'm reading the links you posted above). Many scientists even introduced wimp-less models (with much lighter particles than wimps, I bet you've heard about that theories). You can see it here: http://www.physorg.com/news148316483.html. They say what if there are other kinds of interactions we don't know about. Sounds so crazy. They also talk about shadow world.

Also, I have to point out that a black hole, being the remnant of a massive star, composed of baryonic matter, collapsed down to a point that is at most Planck length in diameter... that's all we can know about it. Physics can't tell us anything about what happens in there; it's just a massively compressed soup of energy, as to details... who knows? There are no particles, just energy. No dark matter in a normal black hole, just energy. Dark matter stars and dark matter black hole analogs? Interesting but not proven.
Very interesting (supersymmetry) points. This once again reminds of shadow world. Maybe at the end of the day there are other forms of interactions and many undetectable particles. In this case I think humanity will ought to re-examine all their models and knowledge. I hope quantum physics will move forward so humankind will have more knowledge about all this process.

And back to black holes. I don't like to quote wiki but however:

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

Primordial black holes may have formed shortly after the big bang when the energy density was great enough to form black holes directly from density variations, instead of from star collapse. In vast numbers they could account for the missing mass necessary to explain star motions in galaxies and gravitational lensing effects.
The other day I remember one person (as a joke) said that what if there's no missing mass in the universe, and it's just the lack/absence of anti-gravitational forces/interactions. Lol now what if it's like that for real. And now I wonder are black holes just collapsed stars or they were created in some other process. Or there are different kinds of black holes and their origins. If scientists can ever generate a black hole maybe that will explain everything.
 
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#8
The Nobel Prize for Physics was awarded this week to Adam Reiss, Saul Perlmutter and Brian P. Schmidt for their discovery of the accelerated expansion of the universe. Current theory holds that this is evidence for dark matter, though the Nobel committee was wise to award the prize for the discovery and not its inferred meaning.
Heh nice news. Congrats Adam Reiss, Saul Perlmutter and Brian P. Schmidt. I gotta read more about their work.

edit: I rather put this in the new thread

http://www.techpowerup.com/forums/showthread.php?p=2419800#post2419800
 
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#9
i dunno
the universe is too big to think about
 
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#10
I continue the topic about the dark matter. Here's some news:

NASA’s Fermi Team located 1873 new sources and 1/3 of them is a mystery. It emits gamma rays but they have no idea what is this. As always dark matter rears its head again.

 
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#11
What about "normal" black holes that are created today? Couldn't those be considered dark matter as well, then?
 
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#12
What about "normal" black holes that are created today? Couldn't those be considered dark matter as well, then?
No. "Normal" black holes aren't created in large numbers. You need a supernova explosion (or coalescing neutron stars), and there are only a handful of those every year in a galaxy the size of ours (which is a fairly large sized galaxy). So, the number of black holes 'born' every year, throughout the universe, while large, is still a miniscule amount of mass compared to the 'invisible mass' of dark matter.
Anyway, I think that estimations of total black hole mass are part of the 'visible matter' percentage totals.

Edit: Maybe a 'handful' of supernovae per year in our galaxy is a bit too much, but it's a single digit number/year.
 
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#13
Hmm....an interesting theory. Always thought that Dark matter is the product that existed outside before the big bang. Although havent read upon it a lot because i have no time do so. (will look up some papers though)
 
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#14
Birth of Famous Black Hole Unraveled

Don't wanna create a new thread so here it goes:

Using several telescopes, both ground-based and in orbit, the scientists unraveled longstanding mysteries about the object called Cygnus X-1, a famous binary-star system discovered to be strongly emitting X-rays nearly a half-century ago. The system consists of a black hole and a companion star from which the black hole is drawing material. The scientists' efforts yielded the most accurate measurements ever of the black hole's mass and spin rate.


That suckah is big. Literally.

"Because no other information can escape from a black hole, knowing its mass, spin, and electrical charge gives a complete description of it. The charge of this black hole is nearly zero, so measuring its mass and spin make our description complete.
Said Mark Reid, of the Harvard-Smithsonian Center for Astrophysics.
Just like a big big Black Box ...

Their team used Very Long Baseline Array (VLBA), a continent-wide radio-telescope system, to make a direct trigonometric measurement of the distance. VLBA observations provided a distance of 6070 light-years, while previous estimates had ranged from 5800-7800 light-years. Armed with the new, precise distance measurement, scientists using the Chandra X-Ray Observatory, the Rossi X-Ray Timing Explorer, the Advanced Satellite for Cosmology and Astrophysics, and visible-light observations made over more than two decades, calculated that the black hole in Cygnus X-1 is nearly 15 times more massive than our Sun and is spinning more than 800 times per second.
800 RPS, wow!

"We now know that Cygnus X-1 is one of the most massive stellar black holes in the Milky Way," said Jerry Orosz, of San Diego State University. "It's spinning as fast as any black hole we've ever seen," he added.
Lol that's for sure

And finally this ...

In addition to measuring the distance, the VLBA observations, made during 2009 and 2010, also measured Cygnus X-1's movement through our Galaxy. That movement, the scientists, said, is too slow for the black hole to have been produced by a supernova explosion. Such an explosion would have given the object a "kick" to a much higher speed.

"There are suggestions that this black hole could have been formed without a supernova explosion, and our results support those suggestions," Reid said.
Dark matter anyone? Anyone at all?

Anyway it's kickass and very important news.

http://www.sciencedaily.com/releases/2011/11/111117144045.htm
 
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#15
Could be dark matter born, I guess.
But it could just have been a free floater, kicked in some direction by its supernova blast, at some point, and gravitationally captured by its companion. Unlikely, but possible, considering how many stars there are out there.
OR the result of a neutron star merger that was gravitationally captured by the companion star.
OR it was made by someone or something a long long time ago.
 
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#16
Could be dark matter born, I guess.
But it could just have been a free floater, kicked in some direction by its supernova blast, at some point, and gravitationally captured by its companion. Unlikely, but possible, considering how many stars there are out there.
OR the result of a neutron star merger that was gravitationally captured by the companion star.
OR it was made by someone or something a long long time ago.
If it was a Neutron star collapsing wont there be any traces left of it. (like residual radiation or on the x-ray spectrum) ?
 
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#17
If it was a Neutron star collapsing wont there be any traces left of it. (like residual radiation or on the x-ray spectrum) ?
If it was a neutron star merger, the two neutron stars would merge, then gravitationally collapse creating a black hole, and in the process release a massive gamma ray burst that apparently would 'sterilize' the surrounding region, a few thousand light years in all directions. But after the formation of the black hole, there would be no emitted radiation we could detect (aside from the radiation emitted from the material spiraling into the black hole).

I kind of like the idea of it being a black hole formed from dark matter.
 

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#18
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...?
 
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#19
If you have read the whole article you'd know that this black hole got nothing to do with supernovae
 
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#20
There's a great series of documentaries on black holes on the science channel. Here are some interesting facts from memory.

The milky way has about 10,000 black holes in the galactic center and the largest is several million solar masses.

All galaxies have black holes at their center.

The mass of a galactic black hole is always about 1.5% of the total galactic mass.

Andromeda has a black hole that is 30 million solar masses.

M87 has one that is 1 billion solar masses.
 
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#21
Kepler (NASA satellite, launched in March 2009 to orbit the Sun) could reveal if PHB (primordial black holes) are dark matter.

Well ... the problem is scientists don't know how PHBs got formed and they don't know how massive they can be. Basically they just want to "weed out" some crap to narrow down the range of possible PHB mass. If they succeed they can say is PHB dark matter or not, if they fail they just eliminate useless factors. Let's say it's a win win situation.

PBHs are thought to have formed during the early universe from density perturbations that may have resulted from a variety of factors, such as inflation, phase transitions, and possibly even the collapse of string loops.
"Collapse of string loops" I haven't heard about this. Gotta read when I find some info about that. If anyone has a link, please post it.



Kepler's photometer could be used to detect small amounts of gravitational lensing(microlensing), which is the bending of star light as it travels through nearby space. According to general relativity, the bending is due to the gravity of an invisible mass that acts like a “lens” and lies between the light source (star) and observer (satellite). This lens could be a PBH or another type of massive compact halo object (MACHO) as well as mini halos, all of which are dark matter candidates.
As always gravity is they key. So MACHO or PHB? Let's see:

According to the scientists' calculations, Kepler could detect microlensing events caused by masses in the range between 5 x 10^-10 and 10^-4 solar masses, which means it could potentially rule out about 40% of the mass in the PBH dark matter window, if it doesn't detect anything. If it does detect microlensing events, then of course the implications would be much more exciting: PBHs could be dark matter.
However scientists ain't too optimistic about this. Sure, we still couldn't find dark matter in entire space nor in LHC, but on the bright side, Kepler's photometer with its extreme precision has a chance to detect a thing or two and maybe they can solve this 50 year old mystery. I hope :)

http://www.physorg.com/news/2011-12-nasa-satellite-reveal-primordial-black.html
 
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#22
The dark matter is no more in physicists discussion after the neutrino speed.
It is like using einstein's law to find infinitely something which you don't even know.
Either neutrino is right or wrong for the speed part, dark matter is not and has nothing to do
with einstein law's. It was found out, as something which cannot be explained.
 
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#23
The Kepler mission has a limited lifetime.
The chances of it being used to specifically look for microlensing events is small, planet hunting is sexier and has more public visibility. Especially with the news that detecting the transits of Earth analogues will require a lengthening of the mission in order to attain more statistical certainty.
Unless the dark matter researchers can use the same data sets for their analysis.
 
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#24
The Kepler mission has a limited lifetime.
The chances of it being used to specifically look for microlensing events is small, planet hunting is sexier and has more public visibility. Especially with the news that detecting the transits of Earth analogues will require a lengthening of the mission in order to attain more statistical certainty.
Unless the dark matter researchers can use the same data sets for their analysis.
I don't think that one can hinder other. Because:

Kepler's mission goal is to categorize the frequency with which stars harbor planets, especially Earth-size planets.
If dark matter plays a big part in this then it's even more important.
 
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#25
Dark matter came into existence at the moment of the Big Bang. Within its confines, galaxies formed and evolved. If you add up all the parts contained within any given galaxy you derive its mass, yet its gravitational effects can only be explained by the presence of this mysterious subatomic particle. It would be easy to believe that the larger the galaxy, the larger the amount of dark matter should be present, but new research shows that isn't so. Dwarf galaxies have even higher proportions of dark matter than their larger counterparts.
http://www.physorg.com/news/2011-12-galaxies-big-dark.html