Supermassive Diet: Black Holes Bulk-Up On Dark Matter

astroengine writes It has long been assumed that the size of a supermassive black hole in a galaxy's core is intimately related to the number of stars that galaxy contains — but it might not be that simple after all. According to new research, it may in fact be a galaxy's extensive dark matter halo that controls the evolution of the central supermassive black hole and not the total number of stars that galaxy contains. "There seems to be a mysterious link between the amount of dark matter a galaxy holds and the size of its central black hole, even though the two operate on vastly different scales," said lead author Akos Bogdan of the Harvard-Smithsonian Center for Astrophysics (CfA), Cambridge, Mass.

Comments

I always assumed

[Anonymous Coward]

it was Groblax that forgot to turn off the 3D printer before colonizing the universe. You know those game changing technologies, always changing games and collapsing into black holes under the mass of their own bounty.

If we're not careful with our 3D printers, sorry, replicators, we might face the same fate.

We would do well to heed the galactic warnings!

Might want to change your diet

[master_kaos]

After switching my diet, my blackhole no longer bulks up my dark matter.

Dark matter only interacts gravitationally?

[Mariner28]

Dark matter only interacts gravitationally with baryonic matter, right? If so, then I'd think it's pretty obvious that dark matter would be a major constituent of a galaxy's supermassive black hole. But then, according to Sheldon Cooper, I have only a Masters' Degree - in engineering, at that - so what do I know?

Re:Dark matter only interacts gravitationally?

[sexconker]

Bazinga.

Re:Dark matter only interacts gravitationally?

[rrohbeck]

Dark matter might be amassed slower than ordinary matter though because it's not slowed down by the accretion disk and similar processes that get rid of momentum. IOW, a particle has to be headed directly into the event horizon, otherwise it'll miss and continue to orbit.

Re:Dark matter only interacts gravitationally?

[Anonymous Coward]

They are so dark, so black, you can't see them at all!

Re:Dark matter only interacts gravitationally?

[stealth_finger]

The thing about space is, it's black. And the thing about black holes, their main distinguishing feature is, they're black. So how are you supposed to see 'em?

Re:Dark matter only interacts gravitationally?

[Anonymous Coward]

How would you distinguish a black hole fro ma dark matter black hole?

Re:Dark matter only interacts gravitationally?

[Bengie]

The accretion disk slows down matter consumption. It's entirely possible that a black hole may able to absorb dark matter more quickly than regular matter because of the lack of interaction with electromagnetism.

Re:Dark matter only interacts gravitationally?

[Bengie]

I forgot to mention, most of the matter in the accretion disk never even makes it into the black hole, but instead gets shot out the jets because of the strong magnetic field.

Re:Dark matter only interacts gravitationally?

[Anonymous Coward]

The question would be how would dark matter black holes form? Part of the reason matter piles up so well is electromagnetic interactions, that allow things to stick together in cold cases, or exchange energy and form a thermal distribution in hot cases (& and radiate thermal energy).

If you sprayed a bunch of particles at a spot that only interact through gravity, they would fall toward the center of mass, but then pass through each other. A spherical cloud would form, with each individual particle in either some sort of elliptical orbit. There would be no quick way for them to interact and lose momentum. The particles can individually interact via gravity, but the process would be very weak and very slow, so it would take a long time for them to form a thermal distribution (some fast, some slow), or for any cooling from particles being ejected from the system after exchanging energy with others. Models of this process is how you get halo distributions of dark matter around galaxies that is in agreement with rotation curve measurements, as opposed to a pile of dark matter just at the center of the galaxy.

With normal matter falling into a black hole though, you quickly get a thermal distribution, which starts radiating energy. You also can exchange momentum through things like the magnetic rotation instability (MRI) that allows for momentum to be removed from particles much faster than otherwise. It is that electromagnetic interaction that allows matter to fall into a black hole quickly instead of just sitting in an orbit for near forever.

Re:Dark matter only interacts gravitationally?

[Anonymous Coward]

Microlensing and occlusion, which can detect rouge planets down to possible Earth size at this point. It won't tell you exactly where every such black hole, rogue planet or brown dwarf is, but it will set an upper limit on the number that can be out there.

Jump That Gun

[sexconker]

So now we're assuming dark matter exists and we know how much of it is in any given galaxy?
And we're correlating it to the "size" (singularity? event horizon? mass?) of a black hole?

I might as well correlate the amount of Leprechauns in my ass to the "price" of Bitcoin.

Re:Jump That Gun

[Skarjak]

"Assuming?" I presume you know nothing of the abundance of research on the subject and you're talking out of your ass? Google "galaxy rotation curve" and "bullet cluster" before you embarass yourself further, please. Can't believe this trash gets modded as insightful...

Re:Jump That Gun

[Anonymous Coward]

Here is my layman's take:
There could be "dark matter", maybe matter with negative mass? There could also be a weak 5th force that is usually masked by gravity. Perhaps the inverse square law is a good approximation, but wrong. Maybe inter-galactic gravitational effects were not accounted for or underestimated.

Re:Jump That Gun

[Bengie]

We also "assume" normal matter exists using the same definition of "assume'". It is true that Dark Matter could be a collection of stuff and not a single thing, but we know for sure that it is not normal.

Re:Jump That Gun

[Bengie]

All of your points have already been extensively looked over and discarded as "not possible". "Dark Matter" is almost 100 years old. It is the longest standing scientific unknown in all of history. If you think you're smarter than 100 years of scientists, you have quite the ego.

Re:Jump That Gun

[Anonymous Coward]

I know that at least people are still working on idea #3 (MOND), so I know you are wrong about all these possibilities being discarded. I would be interested in specifically what papers were published that you think ruled out each possibility. That would be much more effective than the old "you think you're smarter than scientists... sit down" approach.

Re:Jump That Gun

[HornWumpus]

We don't know what % of dark matter is simply brown/black dwarfs. Not a fucking clue. Assumptions are made. The only data we have is the number of brown dwarfs that are observable from earth compared to the radius we can observe them. That is not a statistically significant number (too few small brown dwarfs).

Re:Jump That Gun

[Anonymous Coward]

Here are some interesting ideas. By no means mainstream, but Hyoyoung Choi claims that negative mass would be expected to be dark. He claims that matter with negative mass would have a ground state corresponding to the highest energy state. How would such matter adsorb/emit photons? I don't know, can you point out where/when this possibility was ruled out.

From the observance of the HSS team and SCP team in 1998, they gained the mass density of the negative(HSS:M = -0.38(+/-0:22), SCP: M = -0.4(+/-0:1) ), using field equations which do not have the cosmological constant. In they thought, the quantity of the mass couldn't be a negative value, so the value was discarded. We have to know that not the field equation has disposed the value, but our thought disposed that value.In the world of positive mass, ground state is a point that energy is low, but in case of negative mass, ground state is a point that energy is the highest. Accordingly, in the world of negative mass, energy level is filled from the highest to the lowest, and stable state means the highest energy state, so the catastrophe to energy level of minus infinity never happens even if negative mass spontaneously emits energy.

http://vixra.org/pdf/0907.0015vC.pdf
Hypothesis of dark matter and dark energy with negative mass
Hyoyoung Choi

Re:Jump That Gun

[Anonymous Coward]

There is a nice video (https://www.youtube.com/watch?v=MZtS7cBMIc4) showing the proposed (exotic) interactions between matter with positive and negative mass. I wonder if anyone has tried to apply this to see if it matches MOND. I know there is that odd correlation between acceleration and mass discrepancy.

The possibilities are limited. Either
  MOND is essentially correct, or
  Dark matter results in MOND-like behavior in disk galaxies.

The Mass Discrepancy-Acceleration Relation: Disk Mass and the Dark Matter Distribution. Stacy S. McGaugh.
http://arxiv.org/abs/astro-ph/0403610

I just find this negative mass explanation to be elegant if it works. In that case the existence of dark matter was predicted a priori but dismissed due some erroneous assumptions.

Re:Jump That Gun

[Anonymous Coward]

Searching a bit more I see this possibility was mentioned by Mordehai Milgrom back in 1986:

Every consequence of MOND which we have tested so far can be reproduced in the framework of the hidden mass hypothesis by assuming ad hoc the existence of the necessary distribution of hidden matter. It is thus particularly important to identify consequences of MOND which are in clear conflict with HMH.

In the present paper we show that not all the gravitational fields produced by realistic mass configurations, according to MOND, can be reproduced by Newtonian dynamics. For some fields, insistence on Newtonian dynamics with require negative masses as sources.

Can the hidden mass be negative? Milgrom, M. Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 306, July 1, 1986, p. 9-15. Research supported by the Israel Academy of Sciences and Humanities and Minerva Gesselschaft für die Forschung mbH.
http://adsabs.harvard.edu/full/1986ApJ...306....9M

Anyone know what happened with this idea?

Re:Jump That Gun

[stevelinton]

Know is a tricky word, but there is plenty of evidence that most of the dark matter is not baryonic. The proportions of light elements formed at the end of the big bang gives a contstaint on the baryon density of the universe at the time, as do the ripples in the cosmic microwave background (which reveal the balance between radiation pressure and gravity in the early universe and tell us that most of the mass did not interact with photons at all). The bullet cluster is another piece of evidence. The stars in the colliding galaxies interacted with one another and with dust and merged into one bigger galaxy, but something, detectable by its gravitational lensing of galaxies beyond it, went straight through. It's hard to see how brown dwarves would have done that.

Re:Jump That Gun

[Anonymous Coward]

No we fucking don't. Actual matter exists and can be interacted with.

There's not even agreement as to whether dark matter is a (negative?) massy thing or a new force/field or a fucking space fart. "Dark matter" is just the term used to "explain" the observed error with regards to galactic motion and mass (which is based on wild, roundabout estimates anyway). Dark matter "exists" in the sense that we know our understanding of the situation is incomplete. To relate the "size" of a black hole to an assumed quantity of an assumed definition of dark matter is ridiculous.

If you want to talk about others assuming shit, then you better back your own claims (really, the claims you support despite your not understanding them) with actual evidence NOT based on assumption.

Re:Jump That Gun

[towermac]

That mod got fixed. But don't be too smug in your theories. ;)

I been telling y'all for years. The dark matter is regular old matter that has fallen into the singularity, and is now off in one of those dimensions sting theory describes. It still 'there', it still exists, it has mass; the conservation of mass and energy will *always* be obeyed.

It's just that 'there' is kind of fuzzy, given that the singularity has no volume. It physically can't all be right there, and our measurements confirm that dark matter (we should call it dark gravity btw, because that's all we observe) does not emanate from the black hole at the center of a galaxy. The gravity we see from a black hole is mass that has not yet fallen into the singularity. And theoretically, that mass can't make it into the singularity since time approaches zero the closer you get.

I'm stuck there, on how the mass made it into the singularity in the first place, and the paradox that for a singularity to even exist, at least one bit of mass had to be compressed into a state that our known universe doesn't allow. But we do see the gravitational shadow it casts around a galaxy. Which I submit is the 'size' of that dimension.

Re:Jump That Gun

[Bengie]

They've already accounted for all forms of known types matter, including brown/black dwarfs.

Re:Jump That Gun

[Anonymous Coward]

We don't know what % of dark matter is simply brown/black dwarfs.

None based on CMB measurements. Baryonic matter has been excluded, leaving it being some more exotic form of matter, or something more fundamental like a different form of gravity (however, all proposed gravity alternatives so far don't match observations as well, despite having more fudge factors than dark matter theories). The same measurements show there is a large portion of regular matter not account for, so astronomers are already taking into consideration there is a lot of normal mass missing too.

The only data we have is the number of brown dwarfs that are observable from earth compared to the radius we can observe them.

Still have to deal with why microlensing observations are way short of matter needed to account for dark matter, which observes over distances much larger than the ~1000 light years we can directly observe brown dwarfs.

Not a fucking clue.

Succinctly describes a lot of internet posts on the subject...

Re:Jump That Gun

[Skarjak]

None of what you just wrote makes any sense... You're using word that a scientists might use, but out of their proper context. Again, google "galaxy rotation curve" and "bullet cluster". From what I gather, you seem to think we think dark matter exists because we're missing mass, but you are not taking into account the locations where we are missing mass. Black holes can't be responsible for what we're seeing. Also, dimensions are not places. Something can't be "in" a dimension. That's like saying that you got lost in a the third dimension... length! Dimensions are used to describe points in spacetime. The extra dimensions of string theory (which has yet to be proven in any way, might I add) can be thought of as extra numbers that you assign to every point of spacetime. That's all.

And just what a is a gravitational shadow?

Also the gravity that we see from black holes is from the core of the dead star that gave birth to them... Or in the case of supermassive black holes, the gas that presumably collapsed to form it. It is real matter, not twlight zone matter, and its effect is fully accounted for and routinely simulated.

Re:Jump That Gun

[Skarjak]

Bullet cluster. Google. Now.

Re:Jump That Gun

[gstoddart]

Honestly, it's hard for the lay-person to keep track, or really understand what this stuff is supposed to be.

It falls out of some math, but periodically someone says some of the assumptions might be a bit dodgy.

We can't see it, we can't measure it, we can't account for it .. but "magically" it accounts for specific ratios we take as accurate.

Many of us are just sitting on the sidelines wondering if it's a thing, or if it's a limitation in our understanding of the universe.

So, please, if you want to defend it ... dumb it down for us and don't just throw out a couple of quoted terms. We're not going to suddenly learn the massive amount of abstract maths to truly understand what the hell it's supposed to be.

It has all the hallmarks to a layman as "magic beans", because it's "special particles" which make everything taste minty, but otherwise we know fuck all about it.

It's unexplained magic, defended by math we don't understand, and articulated ... well, my smarmy wankers such as yourself who think "galaxy rotation curve" and "bullet cluster" are magical fucking statements which end all discussion.

The reality is, your average person hears dark matter and thinks "this sounds like bullshit, but I have no idea how I would know otherwise".

So, smart ass, in four sentences or less, in terms a layman can understand, and requiring zero mathematics ... what the fuck is it?

Because if you can't do that, then don't embarrass yourself further by pretending you know what it is either other than "the magical stuff we don't know what it is but falls out of the maths".

Re:Jump That Gun

[Anonymous Coward]

You're an asshole. It doesn't matter how smart you are, nobody will take you seriously if they don't like you. This is a lesson for you on slashdot and in life.

Re:Jump That Gun

[gstoddart]

Yeah, as I expected ... a google of your precious fucking bullet cluster tells me it may or may not support the notion of dark matter.

But it isn't 100% cut and dry, and there are differing interpretations.

So if all you have is "yarg, teh bullet clusters" ... well, I'm afraid you're just acting like a child.

Use your big boy words, articulate something ... we're interested, but we're not taking you on face value because you act like a loudmouth ass.

Re:Jump That Gun

[complete loony]

Or this research should point us in the other direction. Perhaps it's the size of these black holes that is the source of the extra gravity that we currently attribute to the existence of dark matter...

I've always figured there is a term missing from our formula for gravity that is only significant at large scales. Perhaps with larger black holes, this theoretical missing term is similarly larger.

Re:Jump That Gun

[Anonymous Coward]

not brown dwarves, black ninjas. that's why we can't perceive them.

Re:Jump That Gun

[Anonymous Coward]

So, please, if you want to defend it ... dumb it down for us and don't just throw out a couple of quoted terms.

Why? Why must every Slashdot and other forum post completely rewrite descriptions of things that are extensively written about already? Including volumes not using abstract math, with it dumbed down to various levels. It is one thing if something is a rather specific situation being discussed, or someone just feels like trying to write about stuff on their own anyway, but when you get to topics that are covered everywhere from Wikipedia, to pop-sci, to basic textbooks, to free intro-level course notes, and even review papers light on math.

People who can't find the basics on topics that are far from esoteric have more fundamental issues than just not understanding one particular topic. If someone posted here, "What is ethernet?" or "What is C++?", do you think it is reasonable they get indignant when someone tells them to just look it up?

Many of us are just sitting on the sidelines

No one is expecting you to go pro, but you could easily get up and play informally. Unfortunately, there are a few too many "special" people not even sitting on the sidelines, but spending their time in the bathroom or getting beers for the whole game and yet confused why they have no idea what is going on.

Re:Jump That Gun

[Anonymous Coward]

towermac is not sexconker. I never thought of - not sure if I've heard of - the "dark gravity" angle. It is interesting and could be a more apt description as the "matter" is more presumptious than the gravity. Not that I'm trying to get into a semantics debate about 'matter', but I presume closer to our understanding.

Could it be well hidden ordinary matter? I don't know and if we shouldn't rule that out (say it is compatible with string theory, perhaps), then a name change may be in order.

Re:Jump That Gun

[Anonymous Coward]

I might as well correlate the amount of Leprechauns in my ass to the "price" of Bitcoin.

Aye, laddy. What'd ye 'spect from chasing the end of me rainbow to a silicon valley parade? Buggered all, it is.

Re:Jump That Gun

[Anonymous Coward]

Basic laws of gravity from high-school physics state that a hollow shell or ring of matter would have a center-of-gravity at the geometric center point. So the singularity might just be imaginary.

Re:Jump That Gun

[Maritz]

Stars on the outskirts of a galactic disk have been observed to orbit in around the same time as the inner ones. This means there is more mass in the galaxy that we can see. Something like an order of magnitude more. Feel free to dismiss it as an assumption if you like, but I don't see your alternative explanation. Your casually ignorant arrogance is sadly really typical of this place.

Re:Jump That Gun

[Maritz]

The rotation rates of stars in the outer edge of a galactic disk is inconsistent with your theory that all the missing matter is in the black hole. The distribution is likely to be spherical and possibly larger than the galaxy in extent.

Re:Jump That Gun

[stealth_finger]

So now we're assuming dark matter exists and we know how much of it is in any given galaxy?

I'm far from an expert in the subject but as I understand it's pretty simple. Total Mass (or whatever) or a galaxy - visible/known mass = assumed dark matter mass.

If we weren't assuming it wouldn't be dark.

Re:Jump That Gun

[towermac]

You're not hearing me. The "location" of that mass is obviously not in the center of the singularity, given the rotation rates. Of course there is no such thing as a center of a singularity, it has no volume at all, so I'm not sure why people would expect gravity, which depends on mass in a 4d manifold, to emanate from it.

(But dang, flamebait, really? It's a science discussion; it can't be flamebait. What are we supposed to talk about here then? We want hundreds of posts that all simply repeat the current theory?)

Re:Jump That Gun

[Anonymous Coward]

Of course there is no such thing as a center of a singularity, it has no volume at all

Point singularities, which don't have volume, quite clearly have a location and center... it is rather straightforward to see, and you can even check by doing a center of mass calculation (even in a non-flat metric). Even removable coordinate singularities have clear locations and geometric centers can be found, for whatever reason one would want to.

why people would expect gravity, which depends on mass in a 4d manifold

GR makes no requirement that the mass have any particular distribution, and you can calculate the gravity from someone with a delta function like distribution (surprise, without charge and rotation you get the Schwarzchild metric...).

From your previous comment:

nd theoretically, that mass can't make it into the singularity since time approaches zero the closer you get.

For a distant observer seeing the mass asymptotically approach the event horizon, they would also still see the Schwarzchild metric, which doesn't care if the mass is piled up on the event horizon or at a singularity. And since the event horizon is much, much, smaller than the galaxy, there is no "fuzz" from that black hole that extends out to the outer edges, just the same effects as a point mass.

You're probably getting down modded because you have word salad. Unless you've redefined words from how they're taught in a GR and differential geometry textbooks, in which case you're making yourself horribly unclear to the point of people probably suspect you're trolling instead.

Re: Jump That Gun

[Anonymous Coward]

How does the "abundance" of research done on any subject automatically make it true? The same wrong conclusion can be made over and over again once confirmation bias sets in on the premise. Dark Matter is still theoretical, and talking about it as if we "know" it's there is just begging the question.

Re:Jump That Gun

[anarchyboy]

In the bullet cluster the stars passed right through each other as well it is only the dust clouds in the galaxies that really exchanged momentum. So extra brown dwarfs as dark matter probably isn't in conflict with the bullet cluster.

As you point out BBN and CMB measurements do suggest that dark matter in non-baryonic. Another one to add to that list is structure formation, the large structures of the universe would be very different if the dark matter was baryonic.

Re:Jump That Gun

[HornWumpus]

If we don't know how many brown dwarfs there are we don't know how much non Baryonic matter there is. Duh.

Baryonic matter has _not_ been excluded. It's unlikely to account for all of the missing matter, but certainly accounts for some.

Re:Jump That Gun

[Bengie]

All points in space have volume. The smallest anything can be is a cubic plank unit, which still has volume.

Re:Jump That Gun

[Anonymous Coward]

Reread the very first sentence of the comment you replied to. If you can't get that far, then listed and explaining other sources of evidence will be pointless, not that you couldn't find such things already written up in a lot of places online.

Re:Jump That Gun

[stevelinton]

OK. I stand corrected.

Re:Jump That Gun

[Skarjak]

The distinction here is the complete lack of humility showcased by people like you. You know that you know very little about the subject, and yet you start to make claims about how things work as if you had any authority. When you don't know much about something, you approach it with humility and try to better your reasoning before passing judgement. For example, I gave you some excellent starting points for your journey. How much time did you spend writing that post? Now, did you actually google "galaxy rotation curve" and "bullet cluster"? Cause if you didn't, I think it just shows everyone how you have zero desire to learn and only want to be argumentative for the sake of it. You lack humility. If you had approached me and asked me kindly to explain to you why dark matter must exist, I would have gladly explained this to you. But if you act like a jackass and pass judgment on something in complete ignorance of the facts, you're going to get a keyword and an invitation to google it. Dipshit.

If you can't see the difference between "Hey, I don't understand why this must be true. It makes no sense to me. Can you explain?" and "Haha! Scientists are such morons for thinking this!", you've got serious issues, and it's not my job to fix them.

Re:Jump That Gun

[Skarjak]

The only loudmouths are the people who are claiming to know better than scientists despite being completely ignorant of the facts. As I explained above, there's a difference between "I don't understand, can you explain?" and "I don't understand, this is stupid." The first will get you a helpful reply. The second will get you scorn, a keyword and an invitation to goole.

Also, I don't think you spent very long thinking about the bullet cluster. It is solid evidence for dark matter. Alternative explanations cannot explain this behaviour to the same precision, something that even a cursory search reveals. You can't just look for one discerning opinion and use that to justify your position, that's cherry picking data. The preponderance of evidence is in the direction of the existence of dark matter. I gave you a place to start, now go and educate yourself. This is slashdot, people here are supposed to be good at learning on their own.

Re:Jump That Gun

[david_thornley]

I'm not going to get into an argument about how many dimensions (in addition to the standard 3+1) the Universe has (do note that the inverse square law implies three spatial dimensions). However, saying something is "in" a dimension is stupid. You can say that most of the Universe is at one fifth-dimensional coordinate value and something else is at -20m from that (in a certain frame of reference), but that's not really saying it is in the fifth dimension, and I have no idea how you'd falsify it. If whatever strange ideas you cook up aren't potentially falsifiable, you're not talking science.

Singularities have no volume, true, but their effects do. Singularities containing enough mass to matter have event horizons big enough to matter, and you can't falsify any theory about the details of what happens inside an event horizon. (You can make calculations based on certain assumptions, and people have, but that isn't is more using the results of science than actual science.) Now, suppose you have a singularity (which you cannot see) that has mass, and you put more mass in. It goes into the singularity, duh. If you can put mass into something, there's no conceptual reason why you can't put more mass into it. You've now got a bigger black hole.

You also haven't explained galactic rotation curves, which imply distributed unseen matter, not centralized unseen matter.

Re:Jump That Gun

[david_thornley]

Last I looked, while that was a plausible theory, there was no real evidence for the Planck length being significant. It's a very plausible hypothesis, but at the moment that's all is.

Re:Jump That Gun

[david_thornley]

Dark matter is matter that does not interact using electromagnetism. Simple enough? Think something like slow, massive, neutrinos. (Three sentences.)

Re:Jump That Gun

[Skarjak]

First, thank you for phrasing your comment in a respectful way. It goes a long way to getting some good answers. I actually want to help you.

It is probably not supermassive black holes that are responsible for dark matter. That is in fact why I encouraged others to google for "galaxy rotation curves". Your orbital speed around the center of the galaxy is affected by the amount of mass inside that orbit and your distance from the point you're orbiting. Since most of the mass in the galaxy is close to the center, we should expect that a plot orbital speed vs distance would result in the orbital speed decreasing after a certain point, since there is little mass being added inside the orbit with distance. However, that is not the case. What we observe is that the orbital speed just keeps going up and up as you go further out. This relation is not just true for our galaxy. We have catalogues full of rotation curves for galaxies that obey this relation. This seems to indicate there is extra, non-luminous mass out there, further out from the center.

This means the supermassive black hole cannot be responsible for this, as its mass is located entirely in the center. The extra mass must be futher out for this to work. We quickly thought it might be objects like brown dwarfs (failed stars, essentially) that caused this, but our experiments overwhelmingly demonstrate this is not the case. That is why the commonly accepted theory is that dark matter must be particles.

Let me add that galaxy rotation curves are but one piece of a large body of evidence in favour of dark matter. The existence of dark matter is hardly a matter of debate amongst astronomers and astrophysicists. Sure, you've got some theory people trying to come up with alternate explanations cause that's their job, but by and large dark matter must exist for things to make sense. We have seen the shadow of the beast, we know it is there. Now we just have to find it.

Re:Jump That Gun

[Anonymous Coward]

Dark matter is matter that does not interact using electromagnetism.

This gets repeated a lot, but is not true in general when it comes to dark matter theories. The only requirement from observations is that it interacts with electromagnetism very weakly, not necessarily zero interaction. Several surveys looking for dark matter candidates are specifically looking for weak electromagnetic signals that would have been missed by previous observations (e.g. annihilation producing photons).

Re:Jump That Gun

[complete loony]

This seems to indicate there is extra, non-luminous mass out there

And that's the statement that I question. Sure there's an extra force, but is it due to more mass or just more gravity than we expect? Can a super-massive black hole contribute more gravitational force at greater distances than other forms of matter?

I don't have the data at my fingertips, and I suspect I'd get the maths wrong. But is this new finding inconsistent with my above poorly defined idea?

Re:Jump That Gun

[Skarjak]

As far as we know, gravity acts the same way for black holes as it does for everything else. There is no reason to believe that it could be different for supermassive black holes.

And this is the part that requires a bit of trust. People have tried alternate theories of gravity, but they always kind of single out one case and manage to do an ok job, but no one has come up with anything that explains such a large amount of observations as dark matter. Dark matter just works for a wide range of situations. This is why people are so confident in its existence. To prove this, you need to do some math, unfortunately. I can't explain the ideas to you, but ultimately what distinguishes between something that's just a neat idea and what is actually real is the cold hard math. We might dislike the idea of dark matter, but bear in mind that people really disliked quantum mechanics when it was first introduced. Our dislike for something doesn't affect how real it is. It's the experiment that makes the call.

There are many papers on the subject if you want to investigate, but it makes for quite dense reading.

Re:Jump That Gun

[Anonymous Coward]

The price of bitcoin has plummeted over the last year. Please stop eating so many fibers, you're ruining me!

Re:Jump That Gun

[Anonymous Coward]

Can a super-massive black hole contribute more gravitational force at greater distances than other forms of matter?

General relativity gives a very specific drop off with distance from a black hole, and it is the same as a similar mass, non-black hole object there too. It is not just about there being more gravity there, if that were the case the galaxy rotation curves would not have been a huge problem. The issue is the shape and rate of drop off with gravity needed for the rotation curves is wrong, which requires a distribution of mass across the galaxy under GR.

You could argue that GR is wrong, and there are several competing theories doing that. But so far the only ones to do a decent job with galaxy rotation curves, by changing gravity at a long distance, contain a couple, big arbitrary constants that have to be fit to the problem. Yet, for some reason people complain about dark matter being a fudge factor despite agreement between several different situations and kinds of measurements, while the alternative gravity models so far are just fudge factors fit to the problem (not to say something better can't exist, but so far it hasn't been found).

Re:Jump That Gun

[david_thornley]

Thank you for the correction. Dark matter is matter that does not interact electromagnetically, or does so only very weakly. Got it. Is there any reason to think it would or would not be affected by the weak force?

Re:Jump That Gun

[Anonymous Coward]

There is no exclusion of any force's interaction with it, only that it be weak enough to match upper bounds set by various measurements (e.g. both surveys of things like visible and IR light, and things like gamma ray and neutrino surveys for decays). Particular models may exclude some interactions (e.g. a form of neutrinos may have no EM and strong, but will have weak force interactions).

Just Maybe

[JimSadler]

Could it be that the black holes are turning dark matter into matter? Or maybe it is the opposite and the black holes are converting matter into dark matter. So what happens when both matter and dark matter are squeezed into a singularity? Maybe dark matter terminates the life of a black hole at a certain point.

Re:Just Maybe

[towermac]

Nice. Dark matter is the result of matter falling into the singularity.

One word...

[Anonymous Coward]

Actually, it's an acronym but anyway...
 
MoND

Supermassive Diet

[VorpalRodent]

I tried a supermassive diet, but it didn't work out so well. Turns out metabolism doesn't work that way.

Don't assume what I assume

[wonkey_monkey]

It has long been assumed that the size of a supermassive black hole in a galaxy's core is intimately related to the number of stars that galaxy contains

Not by me!

One big equation wich equals zero

[QuantumReality]

World was born from nothing and is still nothing, it's just zero. At beginning it was only zero but it evolved, at the same time it stayed 0. There are 2 sides of equation. Imagine very simple equation which is 1 - 1 = 2 + 2 - 4 , both of sides equals zero. Equation evolves with time making it more complicated, making world as it is now. Why speed of light is that number and not the other? From where those numbers that rule our universe ? From this equation. On one side you can have rules that we can measure and on the other ones we can't but they give the other side values. All comes to zero on both sides, because everything was born from nothing and is still in summary nothing. That's why you see "mysterious link" between dark matter and black holes.

Re:One big equation wich equals zero

[rogoshen1]

Where's my latte dude? get back to work.

Re:One big equation wich equals zero

[Anonymous Coward]

Is there a Time Cube in this somewhere? Otherwise, it makes no sense.

Re:One big equation wich equals zero

[QuantumReality]

Ok, ignorant i will answer on your level: Sure, just after i will take my dick from your mouth.

Re:One big equation wich equals zero

[rogoshen1]

Sorry, I didn't realize that English wasn't your first language. I take back my previous post. No bully okay?

Dark matter = Black hole excrement?

[MTEK]

Could it be that when energy/matter is ingested by a black hole it gets squeezed beyond the plank scale and into a dimension that is different than the space-time dimension we perceive; a dimension unconstrained by the black hole's gravity well -- effectively allowing the consumed energy/matter to exhaust back out into the galaxy as a different form?

Re:Dark matter = Black hole excrement?

[Anonymous Coward]

Makes sense to me. Planck length is just the minimum wavelength for electromagnetism. Dark Matter obviously isn't electromagnetic.

Re:Dark matter = Black hole excrement?

[Anonymous Coward]

Plancking is so 2014. Snow diving is the current fad.

Re:Dark matter = Black hole excrement?

[david_thornley]

So you're saying there's possibly no such thing as a supermassive black hole, since mass falling into it gets spread out on a galactic scale in some mysterious way?

Re:Dark matter = Black hole excrement?

[MTEK]

I'm thinking more of a dimension (brane) that underpins the fabric of space; one whose shape can change independently of the presence of ordinary matter/gravity in our dimension. Only a black hole would be capable of exerting an effect.

Dark matter only interacts gravitationally?

[slickwillie]

So where are all the dark matter black holes?

This comment section makes my head hurt

[Skarjak]

Why is it that people who have spent 30 seconds thinking about the problem think they know better than significantly more intelligent people who have spent decades? Especially when the (very large and convincing) amount of evidence for dark matter is easily accessible through a bit of googling. Guys, dark matter isn't just scientists throwing their arms in the air. It just works. Models with dark matter work much better than models without. And we've made multiple observations of things that point to dark matter existing. And no, it can't be black holes or brown dwarfs. That's been thought of a long time ago and it doesn't work. If you have a better idea and years of papers to support it, by all means, you can trash talk dark matter. Otherwise, please don't spread your ignorance. Science is not a democracy, and your opinion doesn't matter if it's unsupported.

Re:This comment section makes my head hurt

[Anonymous Coward]

But the current plan with dark matter seems to be add it wherever it is needed so that current assumptions/equations allow gravity to explain everything we see... This is EXACTLY like adding epicycles until the model fits the observations. There may be some mathematically equivalent and much simpler explanation that will be delayed for centuries if the current flavor gets institutionalized (which appears to be happening).

Re:This comment section makes my head hurt

[Anonymous Coward]

The new Slashdot -- 'News for Hipsters. Stuff that Confuses'

Re:This comment section makes my head hurt

[Antique Geekmeister]

Because it's the new "phogiston" or the new "ether". It solves certain observational issues, but requires an enormous leap of mathematical and physical faith to assume that it has all the necessary characteristics.

Many of the models that "work better with dark matter" neglect the existence of matter that is not emitting light, but is nevertheless normal matter. Given the observational difficulties for objects and structures billions of light years away and billions of light years old, it's presumptive in the extreme that new and nearly unobservable types of matter exist phenomena like the recent discovery of the much, much larger numbers of cold planets in interstellar space throw all the equations about galaxy size and orbital mechanics into question. And that required no exotic matter.

And let's be clear. There's no observational evidence for "dark matter" itself, only subtle gravitational effects. That's why it's been posited as an exotic form of matter, which "doesn't interact with baryonic matter".

Re:This comment section makes my head hurt

[Anonymous Coward]

Why are there so many crackpot alternative ideas?

Because dark matter and all of the special conditions around it sound like one great big crackpot idea that scientists the world over are getting in on because it keeps them funded.

The more I read about dark matter and how this special thing is related to that special thing the more I become convinced that there's something more fundamental going on that the human race has no clue on and is trying to use dark matter to explain (and failing.)

Re:This comment section makes my head hurt

[david_thornley]

And a lot of people here are adding brown dwarf stars to wherever needed so the gravity works. Same thing, except that we'd detect all those brown dwarfs.

Re:This comment section makes my head hurt

[david_thornley]

What do you have against neutrinos? (Neutrinos have a lot of the characteristics of dark matter.) Why don't you consider gravitational effects to be observational? Who cares about stuff billions of light years away when trying to explain the rotation of nearby galaxies?

Re:This comment section makes my head hurt

[Skarjak]

It's not a big leap actually. Dark matter might even be neutrinos, although I'm not entirely up to date on that area of research. We just need a particle that interacts gravitationally and perhaps weakly with baryonic matter (that's the part that most people miss, a weak interaction is allowed). We already know stuff that does that. We just aren't sure there's enough of it, so we're searching for other particles that might fit the bill. Dark matter really doesn't have to be that exotic.

And I assure you that the observational evidence for dark matter is anything but subtle. Galaxy rotation curves are a quite spectacular way to show this effect at work, as I explained above. We also have the famous bullet cluster, a merger between clusters of galaxies where gravitational lensing shows a large amount of mass is found in the non-luminous parts. Another dramatic demonstration. Anyone telling you that the effects which justify the existence of dark matter are "subtle" is not being very thruthful. I mean, there's nothing subtle about galaxies smashing into each other...

So in short, dark matter doesn't have to be all that exotic and the evidence for it is quite easy to observe. So what's the big deal? Why do peole dislike it so much? people bring up the ether example, but they tend to forget about all the other particles we predicted and then later discovered...

Re:This comment section makes my head hurt

[Anonymous Coward]

I agree. The galaxy rotation curves are not convincing once you look at it, it is just ad hoc epicycles. If anything that is the worst evidence in favor of dark matter at this point, I doubt many cosmologists still give that one to lambda-CDM rather than MOND. Then there is the CMB power spectrum, which looks impressive until you find out the fit was a posteriori and see the "no dark matter" fits that were around (they already had the location of the peaks and the first two without any dark matter, just not the amplitude of the later ones). I don't get why people love that theory so much.

Re:This comment section makes my head hurt

[Bite The Pillow]

Why is it that

Self-selected readership who, at one point in their lives, were probably complimented and/or tormented for being intelligent, thus making it a component of their personality.

Preconceived notions which survive evidential disproving, making it easy to discard any summary based on the headline, or any article based on the summary.

Also, a rotating vocal minority who read a few words and immediately have to type their thoughts, because no one could possibly understand the topic more than them - as evidenced by their grade school experiences.

Welcome to dotslash.

It is exceedingly difficult for most people to routinely consider that other people exist outside of their own experience, and the amount of personal anecdote offered here as a rebuttal of statistics is a testament to just that sort of short mindedness.

In other words, these people are human, and flawed in the same ways that humans are. They just don't realize it unless you point it out in sometimes increasingly caustic replies depending on the nature of their transgression.

Re:This comment section makes my head hurt

[Anonymous Coward]

Are you arguing epicycles are more pure than equants?

Re:This comment section makes my head hurt

[Skarjak]

I will say this though: I love that this website allows you to call people out on their idiocy and you actually get positive moderation for this. Not sure that it's actually good in the grand scheme of things, but it's kind of therapeutic. :p

Re:This comment section makes my head hurt

[Anonymous Coward]

I love that this website allows you to call people out on their idiocy and you actually get positive moderation for this

Half true. There are a few regular posters, plus various random ones, that will consistently post complete word salad or BS, get modded up, and continue to get modded up despite a dozen or more replies posting why it is wrong, including some citations. Post moderation has inertia, and it is much rarer to see that over come.

Re:This comment section makes my head hurt

[david_thornley]

I'm arguing that assuming brown epicycles and assuming dark epicycles are the same sort of thing.

I do, in fact, believe that Uranus and Neptune are planets. They were discovered by people looking at gravity not working the way they thought, and hypothesizing extra planets. (Ironically, people hypothesized Vulcan in the same way, and Mercury's aberrations were because they didn't understand all the physics.)

Re:Can't be Detected

[Anonymous Coward]

Dark matter can't be detected. Can't be seen. Doesn't act like ordinary matter, yet makes up 90+% of the universe.

Riiiigggghhhhttt.

Cosmology is so far down the rat-hole, it's incredible. Rather than re-evaluate their theories and "cosmic constants" - they come up with every more ridiculous extensions to a bad theory, all in an effort to shoe-horn the theory to match observations.

The universe MUST COMPLY with the theory, damnit!

( Rather than the theory comply with the universe )

The problem is the theory of dark matter does comply with the universe, you dumb mother fucker.

Remember:

[Cow007]

Remember we learned today that dark matter is information and when a tree falls in the forest it DOES make a sound.

Re:Remember:

[Anonymous Coward]

Sure, it says: **Timmmmbbberrrrr**

magical unicorns found at edge of universe!

[Anonymous Coward]

All I can say is, WAKE UP! This is all so farcical, it's not even funny any more.
It's all a very sad story of science gone AWOL. Restore your faith in humanity! Read up on the Electric Universe Theory. www.thunderbolts.info

In a double slit experiment the dark matter waves

[Anonymous Coward]

Dark matter has mass. Dark matter physically occupies three dimensional space. Dark matter is physically displaced by the particles of matter which exist in it and move through it.

The Milky Way's halo is not a clump of dark matter anchored to the Milky Way. The Milky Way is moving through and displacing the dark matter.

The Milky Way's halo is the state of displacement of the dark matter.

The Milky Way's halo is the deformation of spacetime.

What is referred to geometrically as the deformation of spacetime physically exists in nature as the state of displacement of the dark matter.

A moving particle has an associated dark matter displacement wave. In a double slit experiment the particle travels through a single slit and the associated wave in the dark matter passes through both.

Q. Why is the particle always detected traveling through a single slit in a double slit experiment?
A. The particle always travels through a single slit. It is the associated wave in the dark matter which passes through both.

What ripples when galaxy clusters collide is what waves in a double slit experiment; the dark matter.

Einstein's gravitational wave is de Broglie's wave of wave-particle duality; both are waves in the dark matter.

Dark matter displaced by matter relates general relativity and quantum mechanics.