Ginormous HIDDEN BLACK HOLES flood the universe – boffins NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) X-Ray telescope has observed a cluster of massive black holes that were hidden from Earth's view by interstellar dust clouds. Crucially, the findings indicate that there many more holes dotted around the universe than first thought. The black hole spotted by Durham …
Genuine questions*: Might this account for some of the so called "missing mass" of the universe, lessening the need to rely on more exotic theories like dark matter? OR has this been presumed all along and already factored into the universe's total mass?
* because I am NOT trying to be snarky, sarcastic, or pedantic. I truly wish to learn.
It's no different to measuring the mass of any other object. It's not special just because it is a black hole. The obvious way is to measure the orbital period of orbiting objects.
The other way of looking at is if you can walk away from a car you can walk away from a black hole with the mass of a car.
This unfortunate fact along with Hawking radiation scuppered my invention of the black hole vacuum cleaner.
You take measurements of the fingers holding it open, extrapolate the approximate density of the person who owns said fingers based on their chubbiness, and then you can get the mass of the black hole.
What? You're not talking about goatse, but about the cosmological phenomenon? Sorry, no idea.
No. Even the most massive black holes are just a tiny fraction (<<1%) of the total (visible) mass of the galaxies in which they have been found. For dark matter, we're looking for something that's 4-5x the total visible mass. Massive compact halo objects (MACHOs) - stellar mass black holes, brown dwarfs, etc. - have been pretty much eliminated as a possible explanation for the 'missing' dark matter; the search is on for Weakly Interacting Massive Particles (WIMPs) - it's hoped that CERN may turn up a candidate particle now it's running close to its full power rating.
The other possibility is Modified Newtonian Dynamics (MOND), changing the inverse square law of gravity in a way that would be undetectable at the scale of the solar system, but could account for the dynamics of galaxies. But the smart money is still on WIMPs (unless CERN turns up empty?)
I thought that discovery of the bullet galaxy had rather damaged the chances for MOND. It's two clusters of galaxies that have collided head-on. The normal matter has been slowed down by that collision. The weakly-interacting dark matter has continued at pretty much unchanged velocity, and it is now possible to deduce from observations (of gravitational lensing) that it is displaced with respect to the original galaxies.
It's not entirely clear-cut, though.
https://en.wikipedia.org/wiki/Bullet_Cluster
Missing Mass: As it turns out, information has mass.
Strangely, misinformation has 2π the mass density per bit as compares to correct information. So the missing mass of the Universe can be explained by the widespread existence in the Universe of bad ideas and idiotic concepts. As we humans inexorably move along this axis of daft, the mass of the Earth slowly increases, and Leap Seconds will need to be inserted to compensate.
This very post has increased the mass of the Universe by 3.8 g.
That was my first thought as well. I've always suspected that the phenomena ascribed "dark mass" may actually be caused by clusters of black holes. I think it is pretty difficult to distinguish the effects of a cloud of dark mass from a group of black holes, and they are both pretty difficult to see.
But then, I discount my own ideas as well, as it is difficult to believe that I would have thought of something that the "professional" astrophysicists hadn't thought of, and it seems rather arrogant to suggest that I did.
1) Everyone suspected every galaxy had a supermassive black hole at its center, we just couldn't directly observe many of them
2) The behavior of galaxies indicates that the missing mass (assuming Newtonian gravity, not MOND) is not concentrated at the center, but far away from it. Unless the big bang created a huge huge huge amount of tiny black holes they can't be responsible for the missing mass.
Personally my money's on theories needing to be revisited. Not necessarily MOND, but something that indicates our calculations are off. Given that we not only have dark matter but also dark energy as fudge factors now, and can't identify either. Or maybe that's just what I hope, because I don't want Einstein's theories and the standard model to be it, with only quantum gravity as the last unknown. I want Douglas Adams to be right, and once we figure out the universe it is replaced by something even stranger. Bring on supersymmetry, hidden dimensions, hell at this point I'd even take Electric Universe just so things don't get boring!
Personally my money's on theories needing to be revisited. Not necessarily MOND
Pretty much guarantee it's not MOND. That's been almost completely ruled out by now. I don't think you'll get much disagreement that the standard model needs revisiting, but the question remains by how much. Supersymmetry is a candidate that would require almost no revisiting.
The big one is going to be explaining the matter/anti-matter imbalance while also explaining the extra mass (and dark energy). Preferably without getting into too many additional dimensions. (Damn you, string theory!)
I also used to get chin-rub doubtful about dark matter but recently read a very good summary of the evidence for its existence as something like WIMPs existing in halos in and around galaxies and clusters of galaxies, which I found persuasive.
Dark energy, on the other hand, is where even the tip-top cosmological boffins get all shruggy shouldered, and it seems our current theory set just doesn't explain the apparent accelerating expansion at all.
Icon: Another slapped wrist for El Reg for once again failing to state what is an artists impression and what is an actual observational image.
There's quote a lot of unanswered physics questions that aren't particularly answered and are likely to have some significant bearing on the "missing matter" and "missing energy" problems.
For example C is assumed to be a constant therefore the obvious questions are such as why should it be a constant, why should it have the value it has and how to definitively explain why this is a set velocity regardless of the emitter's velocity and if there is such a set velocity, should there not also be a set lack of velocity, e.g. absolute zero velocity. While absolute zero may never be achievable by standard matter in the same way we can't accellerate an atom to C (just very close) but some particles / waves may achieve it in the same manner that EM manages to propogate at C.
Then there's the rather interesting question as to what gravity exactly is and how it's effect is propogated. Similar questions apply to the other fundamental forces which while they've been isolated and identified their mechanisms, or how and why they work, are rather less so.
But then I'm not a physicist... :)
So all we've done is established what state some of the matter is in. These are black holes in other galaxies - we already knew the mass of the galaxies. A black hole in the galaxy doesn't change our understanding of the mass of the galaxy.
Dark matter makes up around 85% of the matter in the universe, and that's before we even consider dark energy.
No, this doesn't account for the missing mass. Black holes are (sort of) baryonic in nature, and we long ago predicted how many there would have to be. We have a rough handle on how much baryonic matter there is in the universe. The "missing mass" of dark matter is non-baryonic mass, and we don't know what that might be. (Though some have ideas. See: WIMPs as a great place to start learning.)
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