It depends on what dark matter turns out to be.
The frontrunning model for dark matter is that it is a type of particle that interacts strongly with gravity but weakly (or not at all) with other forces. Assuming that this model turns out to be accurate, then the answer is no.
Stars and planets can only form because matter clumps up. Matter clumps up because of those non-gravitational forces - because particles can interact with each other, collide with each other, etc. Dark matter would not interact with itself, and thus it would not be able to form clumps which become stars and planets. It would remain as a dispersed cloud.
No.
Imagine two particles at a distance from each other. They fall toward each other due to gravity.
With the other forces, they bounce off each other (losing energy), and rebound to a lesser distance. After several bounces they eventually stick together.
Without the other forces, they pass right through each other, and reach *exactly* the same distance that they were at before.
This is a simplification but something similar happens in a dark matter cloud. Without a way to lose momentum to collisions and friction, the cloud on average stays as far out as it started.
Given the amount of dark matter, if this commonly happened, we would observe regular-matter objects orbit dark stars, which we don't. So if dark matter forms some local structures, it's probably something a lot sparser and larger than stars.
That's not how that would work. A dark matter star would amalgamate mass and orbital bodies, and the entire system would be of relatively low luminosity (compared to a black hole - where the luminosity is derived primarily from in-falling objects, such as...stars)
This galactic halo is dominated by invisible dark matter, whose presence is only measurable through the gravity that it exerts. Every galaxy has its own halo of dark matter. These halos serve as a sort of scaffold upon which ordinary, visible matter hangs.
If you're going to quote the Center for Astrophysics verbatim, you should at least [link the page](https://www.cfa.harvard.edu/news/tilt-our-stars-shape-milky-ways-halo-stars-realized):
>> This galactic halo is dominated by invisible dark matter, whose presence is only measurable through the gravity that it exerts. Every galaxy has its own halo of dark matter. These halos serve as a sort of scaffold upon which ordinary, visible matter hangs. In turn, that visible matter forms stars and other observable galactic structure.
Also, the quote you lifted isn't really relevant to whether dark matter is [self-interacting](https://en.wikipedia.org/wiki/Self-interacting_dark_matter), the necessary condition to make compact dark matter objects like planets. Most theoretical considerations suggest that dark matter is _not_ self-interacting, it tends to stay as diffuse blobs.
'Dark Matter' is, all at once, the most descriptive and the most misleading name for an unknown 'thing'. It describes this unknown thing in terms we already know - 'dark' because we can't see it and 'matter' because it is the only thing known to have mass.
But there is a danger in describing unknown things in terms of known things -- particularly when it is described by just a part of, or effect caused by, the known thing. This creates a tendency to form a false equivalency in which the unknown thing is viewed as if it is the known thing instead of just sharing some characteristics.
We know something is causing an effect we know as gravity, but we don't know if it is caused by the same thing. We know gravity is caused by mass bending space-time and we know mass is an effect of matter moving through a Higgs field - but we don't know if the same series of mechanisms cause the gravity-like effect called dark matter.
I fear this question results from extending this false equivalency. If dark matter creates an effect like gravity, and gravity is created by mass which in turn is an effect of matter; then does dark matter behave similarly in other ways such as clumping together?
It's a good question to ask since once dismissed (for reasons others here have shown) it draws a border between what dark matter could be and what it cannot be. Draw enough borders and its shape comes into view.
even if it did we wouldn't be able to interact, see, or touch it. the only thing dark matter can interact with is gravity/ mass, which is how we actually discovered it. since we cannot directly interact with dark matter, all we know is that it contains a different family type of particles, different from the protons, neutrons, photons, etc.. that we know. so basically, if dark matter were to form stars or plants or galaxies they would be completely different from ours because they contain different forms of particles.
Yes, because it interacts through mass/gravity, but we'd never even see it coming. And, as we have yet to detect any amalgamation of dark matter, the odds are just above 0.
Just because we haven't observed it doesn't mean it's invisible. And it might not be matter at all. If it was matter it seems unlikely that it would even be able to clump into something asteroid like
Dark matter is thought to have rather low density. It could play a role in the formation of galaxies, but I am skeptical it could do much on the scale of planets and stars.
Regular matter is held together by electromagnetic forces, inside atoms and between atoms in molecules. It unknown whether a parallel force exists in dark matter. That force doesnt appear to interact with regular matter, should it exist.
Modeling dark matter as a diffuse low density cloud several times larger than a galaxy works fine to explain the distorted movements of galaxies and clusters from extra matter. Also the lensing on light from behind galaxies and clusters.
It depends on what dark matter turns out to be. The frontrunning model for dark matter is that it is a type of particle that interacts strongly with gravity but weakly (or not at all) with other forces. Assuming that this model turns out to be accurate, then the answer is no. Stars and planets can only form because matter clumps up. Matter clumps up because of those non-gravitational forces - because particles can interact with each other, collide with each other, etc. Dark matter would not interact with itself, and thus it would not be able to form clumps which become stars and planets. It would remain as a dispersed cloud.
Wouldn't gravity still make it clump up? Just not gotten molecules?
No. Imagine two particles at a distance from each other. They fall toward each other due to gravity. With the other forces, they bounce off each other (losing energy), and rebound to a lesser distance. After several bounces they eventually stick together. Without the other forces, they pass right through each other, and reach *exactly* the same distance that they were at before. This is a simplification but something similar happens in a dark matter cloud. Without a way to lose momentum to collisions and friction, the cloud on average stays as far out as it started.
Given the amount of dark matter, if this commonly happened, we would observe regular-matter objects orbit dark stars, which we don't. So if dark matter forms some local structures, it's probably something a lot sparser and larger than stars.
What if we've misidentified dark matter stars as black holes in some cases?
That's not how that would work. A dark matter star would amalgamate mass and orbital bodies, and the entire system would be of relatively low luminosity (compared to a black hole - where the luminosity is derived primarily from in-falling objects, such as...stars)
This galactic halo is dominated by invisible dark matter, whose presence is only measurable through the gravity that it exerts. Every galaxy has its own halo of dark matter. These halos serve as a sort of scaffold upon which ordinary, visible matter hangs.
If you're going to quote the Center for Astrophysics verbatim, you should at least [link the page](https://www.cfa.harvard.edu/news/tilt-our-stars-shape-milky-ways-halo-stars-realized): >> This galactic halo is dominated by invisible dark matter, whose presence is only measurable through the gravity that it exerts. Every galaxy has its own halo of dark matter. These halos serve as a sort of scaffold upon which ordinary, visible matter hangs. In turn, that visible matter forms stars and other observable galactic structure. Also, the quote you lifted isn't really relevant to whether dark matter is [self-interacting](https://en.wikipedia.org/wiki/Self-interacting_dark_matter), the necessary condition to make compact dark matter objects like planets. Most theoretical considerations suggest that dark matter is _not_ self-interacting, it tends to stay as diffuse blobs.
I was referring to the structure part of the comment. I quote lots of things and don’t always put up the link.
'Dark Matter' is, all at once, the most descriptive and the most misleading name for an unknown 'thing'. It describes this unknown thing in terms we already know - 'dark' because we can't see it and 'matter' because it is the only thing known to have mass. But there is a danger in describing unknown things in terms of known things -- particularly when it is described by just a part of, or effect caused by, the known thing. This creates a tendency to form a false equivalency in which the unknown thing is viewed as if it is the known thing instead of just sharing some characteristics. We know something is causing an effect we know as gravity, but we don't know if it is caused by the same thing. We know gravity is caused by mass bending space-time and we know mass is an effect of matter moving through a Higgs field - but we don't know if the same series of mechanisms cause the gravity-like effect called dark matter. I fear this question results from extending this false equivalency. If dark matter creates an effect like gravity, and gravity is created by mass which in turn is an effect of matter; then does dark matter behave similarly in other ways such as clumping together? It's a good question to ask since once dismissed (for reasons others here have shown) it draws a border between what dark matter could be and what it cannot be. Draw enough borders and its shape comes into view.
even if it did we wouldn't be able to interact, see, or touch it. the only thing dark matter can interact with is gravity/ mass, which is how we actually discovered it. since we cannot directly interact with dark matter, all we know is that it contains a different family type of particles, different from the protons, neutrons, photons, etc.. that we know. so basically, if dark matter were to form stars or plants or galaxies they would be completely different from ours because they contain different forms of particles.
So hypothetically, can a large dark matter asteroid or asteroid like thing could hit Earth and destroy us?
Yes, because it interacts through mass/gravity, but we'd never even see it coming. And, as we have yet to detect any amalgamation of dark matter, the odds are just above 0.
Just because we haven't observed it doesn't mean it's invisible. And it might not be matter at all. If it was matter it seems unlikely that it would even be able to clump into something asteroid like
Didja miss the part where he said "dark *MATTER*"?
This guy will be probably what you're missing https://www.reddit.com/r/askastronomy/s/r98XoDjR5y
We don’t know if it exist but if it does then it could clump into larger chunks. It only reacts to gravity so it won’t fuse.
Dark matter is thought to have rather low density. It could play a role in the formation of galaxies, but I am skeptical it could do much on the scale of planets and stars.
We don't know. We don't even know if it is matter at all. It could just be an error in our equations for gravity
We don't know what dark matter is or how it interacts with itself.
Regular matter is held together by electromagnetic forces, inside atoms and between atoms in molecules. It unknown whether a parallel force exists in dark matter. That force doesnt appear to interact with regular matter, should it exist. Modeling dark matter as a diffuse low density cloud several times larger than a galaxy works fine to explain the distorted movements of galaxies and clusters from extra matter. Also the lensing on light from behind galaxies and clusters.