Dark matter and supermassive black holes

In summary, the discovery of supermassive black holes at the center of every galaxy does not significantly impact the theory of dark matter, as the problem it seeks to solve lies in the outer parts of galaxies, not the center. Dark matter is called as such because it is invisible matter, and it is not possible for it to be something else as it explains not just galaxy behavior, but other phenomena as well. The amount of dark matter in a galaxy is much greater than the visible matter, which is only a small percentage of the total mass.
  • #1
Lsos
803
9
I have a rather simple question. Dark matter was first proposed because galaxies appeared to have more mass than was observable. That's fine. But then later, supermassive black holes were discovered to be at the center of every galaxy. That's billions of solar masses more in each galaxy than was observable.

Now I kind of feel like I'm out of the loop here, but it just seems obvious that the discovery of previously unseen BILLIONS of solar masses in each galaxy would have some impact on a theory that states there is lots of unseen mass in each galaxy.

And yet I never heard anything even remotely connecting these two theories. Just seems kind of strange to me. Anybody want to shed some light on this?
 
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  • #2
As big as the black holes at galaxy centres are, they make only a relatively minor contribution to the total mass of a galaxy. The problem that requires DM to exist (or something else possibly) cannot be solved by adding more mass to a galaxies centre. It is the outer parts where problems emerge, so the 'missing mass' has to reside there, not at the centre. Simulations of cosmic structure formation support this view, in that we find the central parts of galaxies are dominated by baryons (i.e. everything that isn't dark matter) while the outer parts have more dark matter.
 
  • #3
Why it is called dark matter? Does it have to be matter at all, or it can be something else that is causing such behavior of galaxies?
 
  • #4
S.Vasojevic said:
Why it is called dark matter? Does it have to be matter at all, or it can be something else that is causing such behavior of galaxies?
Because it's matter that isn't visible. Hence dark.

And no, it can't really be something else, because it's not just galaxy behavior that dark matter explains, but a whole host of other things.
 
  • #5
Post #2 is an excellent summary. You can read about Vera Rubin's work for some details of the experimental findings that led to some initial understanding of dark matter halo's/spider webs in the outer reaches of galaxies.
It's actaully pretty funny that we think we are so smart but have little idea what's inside black holes and no idea what constitutes 96% (dark matter and dark energy) of our universe (on our side of horizons)...lots to do!
 
  • #6
Ok, I guess that all makes sense. Still...BILLIONS of solar masses. Isn't there only billions of solar masses in a galaxy?
But yeah, the part where it's only at the center makes sense. Thanks everyone.
 
  • #7
Naty1 said:
It's actaully pretty funny that we think we are so smart but have little idea what's inside black holes and no idea what constitutes 96% (dark matter and dark energy) of our universe (on our side of horizons)...lots to do!
And I find that statement to be nonsensical. Especially given the observational challenge it's been to discover these things about our universe.
 
  • #8
Lsos said:
Ok, I guess that all makes sense. Still...BILLIONS of solar masses. Isn't there only billions of solar masses in a galaxy?
But yeah, the part where it's only at the center makes sense. Thanks everyone.
Try hundreds of billions of stars. The supermassive black holes are only a couple percent the total baryonic mass (if that).
 

1. What is dark matter?

Dark matter is a hypothetical type of matter that is believed to make up about 85% of the matter in the universe. It does not emit or absorb light, making it invisible to telescopes and other instruments. Its existence is inferred by the gravitational effects it has on visible matter.

2. How is dark matter related to supermassive black holes?

Supermassive black holes are believed to reside at the center of most galaxies, including our own Milky Way. They are surrounded by a region of space where the gravitational effects are so strong that even light cannot escape. Dark matter is thought to play a role in the formation and growth of these supermassive black holes, as their gravitational pull can help to attract and accumulate matter from their surroundings.

3. What evidence do we have for the existence of dark matter?

The strongest evidence for dark matter comes from observations of the rotation curves of galaxies. These curves show that the outer regions of galaxies are rotating faster than expected based on the amount of visible matter present. This suggests that there must be more matter present, and dark matter is the leading explanation for this discrepancy. Other evidence comes from the gravitational lensing of light from distant objects and the distribution of matter in galaxy clusters.

4. What is the difference between dark matter and normal matter?

The main difference between dark matter and normal matter is that dark matter does not interact with light, while normal matter does. Dark matter is also thought to be much more abundant in the universe, making up the majority of matter, whereas normal matter makes up only a small fraction. Additionally, dark matter is believed to be made up of particles that have not yet been detected, while normal matter consists of atoms and subatomic particles that we are familiar with.

5. Can we see or detect dark matter?

As of now, we have not directly observed or detected dark matter. However, scientists are conducting experiments and using various techniques to try to detect dark matter particles. Some of these include particle accelerators, underground detectors, and studying the cosmic microwave background radiation. While we have not yet found concrete evidence for dark matter, its existence is strongly supported by various observations and theories.

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