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Questions tagged [dark-matter]

Questions about the source or effects of the matter that makes up 85% of the matter in the universe but appears to only interact gravitationally.

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How is dark matter distributed within our solar system?

In this episode of PBS Space Time, it's claimed that our solar system contains on the order of 1018 kg of dark matter. As a point of comparison, Mt. Everest is estimated to have roughly the same mass: ...
Tom's user avatar
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Have measurements been conducted on the position of the galactic center of mass and the orbit of the presumed black hole at the center?

Related questions have been raised before Is our central black hole actually at the CG of the galaxy? Orbiting supermassive black hole or galactic center of mass? , where explanations have been given ...
Imyaf's user avatar
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Relating virial radius to virial mass of a dark matter halo

I was studying about the definitions of virial mass and virial radius of a dark matter halo and it is basically defined as $$M_{vir}= \frac{4}{3}\pi R_{vir}^3\Delta_{c}\rho_{crit} $$n where $\rho_{...
Esanmouli Ghosh's user avatar
16 votes
9 answers
11k views

Why is it ok for people to be saying that dark matter makes up x amount of the universe when we don't know what it is?

It strikes me as contradictory that the scientific community will say that we don't know what dark matter is, but be happy to state things like "dark matter makes up about 85% of the cosmos" ...
Zinn's user avatar
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2 answers
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Light/Dark energy/Dark matter

So I have been working on my comic book project that takes place on another planet. But in my story, there will be warp gates and there will be other civs that can travel between stars. I am ...
Kul Tigin's user avatar
10 votes
1 answer
2k views

Is the amount of dark matter the same as you look back through time (further away from earth)?

In the hope that it may provide information on the development/evolution (if any) of dark matter over time, are there any differences (eg. in structure or concentration) in the dark matter at large ...
Zinn's user avatar
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How are we observing the newly discovered "dark galaxy" J0613+52, if it has no stars and is so far away from other galaxies?

I just came across a New York Times article talking about a newly found Low Surface Brightness (LSB) galaxy (also called “ultra-diffuse galaxies” or “dark galaxies”). The new galaxy, J0613+52, was ...
Curious Layman's user avatar
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Has anyone observed dark matter? What could we see?

When I was reading the Wikipedia page about dark matter, I was wondering about the nature of it and what could it be. I have a question about dark matter but first I want to list a hypothesis: We know ...
Euler-Masceroni's user avatar
-2 votes
1 answer
82 views

Does dark matter exist because as Einstein said the laws of physics should be the same inside and outside a black hole?

Spacetime is said to be time like inside a black hole ( two events can happen at the same place at different times). Spacetime is called space- like outside a black hole ( two events can happen ...
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2 votes
1 answer
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If w bosons can create dark matter neutrinos by decay, can they also create dark energy?

Dark energy is often associated with vacuum energy fluctuations. But the experimentally measured Casimir effect suggests that there is almost no vacuum energy.Because most of the vacuum energy is ...
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3 votes
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If a cluster of stars in dynamical equilibrium falls into a much larger blob of dark matter, will it get hotter and expand? Will it stop?

This question is inspired by ProfRob's inspiring answer to Are there really confined Globular Clusters? in which he invokes the concept of "virialization" where a dynamical system reaches ...
uhoh's user avatar
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What is everything wrong with this theory of dark matter?

So I had a hypothesis about why dark matter exists, but seeing as I've just barely begun studying astrophysics its most likely chock full of misconceptions and oversights. Here's a diagram of the ...
Aryaman Rtunjay's user avatar
2 votes
0 answers
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Orientation of the Dark Matter Halo in Andromeda Galaxy

In this paper: https://iopscience.iop.org/article/10.1088/0004-637X/789/1/62#apj496316t3 Refer to the Discussion and Concluding Remarks section. It says, "This result also indicates that the ...
Angela's user avatar
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How can we measure the amount of Dark Matter in the universe to the level of a percent?

Through phenomena that scientists have observed we know that dark matter is a big player in maintaining a constant speed of objects in a galaxy which means that dark matter is an active participant. ...
Shubhankar Dixit's user avatar
0 votes
2 answers
163 views

Is dark matter made from the particles that had charge but no mass in the early part of the Big Bang

It is assumed that massless charged particles acquired mass after the early phase of the Big Bang. But could most charged particles be massless now as dark matter. They wouldn't interact with photons ...
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4 votes
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369 views

Dark Matter's effect on galaxy structure

One "fun fact" that's always been, well fun. Is despite what most assume, our sun does not orbit a supermassive black hole or any object at the center of our galaxy. Recently I read an ...
Troy Dube''s user avatar
1 vote
1 answer
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Why are WIMP dark matter particles, if Majorana-like, expected to annihilate upon contact? But not neutrinos?

I have heard a lot recently about so-called 'dark stars'; stars that are formed with the help of the gravitational pull of dark matter, or perhaps entirely from self-annihilating Majorana-type dark ...
Kurt Hikes's user avatar
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Could both the high incidence of supermassive Black Holes (BH) and the expansion of the universe be consequences of vacuum entanglement energy?

The notion that spacetime may emerge from entanglement between factors comprising a Hilbert space decomposition of the vacuum has been suggested by many (for example, M. Van Raamsdonk “Building up ...
RalphW's user avatar
  • 33
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1 answer
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Why is the dark matter component of MOND important in central regions?

A lot of papers say that even the theory of MOND requires the existence of dark matter, particularly in the central regions. However this is a bit counterintuitive to me considering that rotation ...
Ambica Govind's user avatar
1 vote
0 answers
78 views

Can WIMPS be stable for a long time given that they are 60 times heavier than a proton and other particles heavier than protons decay rapidly?

WIMPS are dark matter candidates But how can they be stable for billions of years ?
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8 votes
1 answer
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Can dark matter accumulate at Lagrange points?

Interplanetary dust can accumulate at Lagrange points . "Kordylewski cloud - Wikipedia" https://en.m.wikipedia.org/wiki/Kordylewski_cloud But can dark matter accumulate at Lagrange points ...
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2 votes
1 answer
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Are vacuum fluctuations that produce dark matter correlated to fluctuations that produce baryonic matter?

When cosmic inflation began vacuum energy fluctuations created matter . But were the fluctuations that created dark matter dependent on the fluctuations that created matter ? Is the ratio of dark ...
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3 votes
0 answers
45 views

Has the missing dark matter in some galaxies been explained yet? [duplicate]

There are galaxies that should have dark matter to explain their existence but they do not. "Mystery of Galaxy's Missing Dark Matter Deepens | NASA" https://www.nasa.gov/feature/goddard/2021/...
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1 vote
1 answer
125 views

How does superfluid dark matter keep stars orbiting at high speeds in galaxies?

According to A paper on Ultra-Light Dark Matter, Superfluid dark matter is a kind of Bose-Einstein condensate. But how does it help stars keep their high or velocities in galaxies. Can somebody ...
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1 vote
1 answer
173 views

Do black holes emit dark matter as Hawking radiation?

When a star made from protons neutrons and electrons becomes a black hole that black hole can emit protons neutrons and electrons as Hawking radiation. Dark matter is unusual matter: is there any ...
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3 votes
1 answer
137 views

When two galaxies with dark matter halos merge do they provide evidence for fermionic or bosonic dark matter?

If dark matter is made from fermions these should collide and cause dark matter to become denser in some places than others Bosons wont collide in this way so there should a different effect .So is ...
user avatar
0 votes
1 answer
74 views

If a supernova explodes close to the centre of the milky way does its light get blueshifted by dark matter by the time it reaches the Earth?

Does the dark matter halo of the milky way cause most of the change in wavelength or is baryonic matter responsible?
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1 vote
0 answers
51 views

Is there any observational evidence for dark matter vortices?

The paper here "Vortices and waves in light dark matter" https://arxiv.org/abs/2004.01188 says that in dark matter halos vortices arise. In a vortex some particles move faster than others - ...
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1 vote
1 answer
63 views

Is the mass function of dark matter halos fundamental or an approximation based on experimental data?

Can the halo mass function be derived from existing physics or is it just a best fit of some data?
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1 vote
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41 views

ultra diffuse galaxies and dark matter

There are ultra diffuse galaxies (UDGs) like, NGC 1052-DF2, NGC 1052-DF4, which seem to have very little dark matter. And on the other hand UDG dragongly 44 has lots of it. How many UDGs are known to ...
Angela's user avatar
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1 vote
1 answer
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Can the CMB Cold Spot be explained by dark matter redshifting photons?

One explanation for the Cold Spot in the cosmic microwave background (CMB) is that dark matter is redshifting CMB photons; see Fermilab's article "Scientists move a step closer to understanding ...
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8 votes
1 answer
298 views

Have we discovered a Galaxy lacking in Dark matter?

This question is relevant but it was speaking about a specific discovery reported by pieter van Dokkum, and the answer then mentioned it was disputed whether the paper's conclusion is even correct. I ...
Hisham's user avatar
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13 votes
1 answer
2k views

How would "dark matter", subject only to gravity, behave?

If we were to hypothesise that the Universe contained a significant mass of "dark matter" particles subject only to gravity, presumably general relativity would give us a good idea of how ...
mikado's user avatar
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15 votes
3 answers
3k views

Is there more dark matter than we previously thought?

With the recent Nature publication showing that M dwarfs did not form in prior epochs as frequently as we had thought, what implications does this have on galaxy mass estimates and, by extension, the ...
Justin T's user avatar
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4 votes
1 answer
107 views

Proportion of dark energy, dark matter, matter

According to the article "Dark Matter" https://en.wikipedia.org/wiki/Dark_matter the current Lambda-CDM model estimates the total mass-energy content of the universe consists of 68.2% dark ...
joh5n's user avatar
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2 votes
1 answer
118 views

When did the first cold dark matter halos begin to originate?

I know that these dark matter halos should have been created in an early universe because during the formation of galaxies, the baryonic matter was too hot to form gravitationally self-bound objects ...
user9867's user avatar
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1 vote
0 answers
23 views

what does it mean to have momentum suppressed cross section

What does it mean to have momentum suppressed cross section and zero momentum transference in direct and indirect detection of dark matter
soomo56's user avatar
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4 votes
0 answers
69 views

What is the contribution of star-produced axions to the dark matter budget of the Milky Way?

I try to follow the discussion of axions since Peccei, Quinn, Wilzcek and Weinberg. What I still don't understand is how much the speculated stellar production of axions could add to the galactic dark ...
Reggie Grünenberg's user avatar
1 vote
1 answer
92 views

Could dark matter be ordinary cool matter far away? [duplicate]

We tend to think of the universe as the visible universe, but there could be large amounts of eventually hierarchically ordered, normal, matter that we can only observe at relatively close distances. ...
Lehs's user avatar
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3 votes
0 answers
177 views

How do star orbits, density wave theory and dark matter distribution work together?

I got confused while trying to combine these 3 concepts. Would love to hear some detailed explanation. Density wave theory states that spiral arms are formed by tilted elliptic orbits. Bertrand's ...
YaaZ's user avatar
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10 votes
2 answers
1k views

Could we detect dark matter by black holes gaining unexplained mass?

Dark matter is said to interact only gravitationally, so it won't commonly form black holes by itself. But if a black hole is already there, and dark matter encounters the event horizon, it should go ...
Hene's user avatar
  • 255
2 votes
1 answer
63 views

Is there any method that enables us to observe the 3D large-scale spatial distribution of the dark matter?

Can we get the three-dimensional spatial distribution of dark matter through gravitational lensing? If not, is there any other way?
Wang Yun's user avatar
  • 431
13 votes
2 answers
3k views

Is Dark Matter possible if there is dynamical friction?

If dark matter existed: wouldn't it slow down the orbital velocity of stars in galactic disks by dynamical friction more than it would accelerate them through additional mass? The original orbital ...
Reggie Grünenberg's user avatar
4 votes
1 answer
254 views

How can Deep MOND regime apply inside a star?

MY UNDERSTANDING OF THE MOND THEORY As I understand it, Milgrom's MOND model can be interpreted in one way by saying that Newton's Law of Gravitation on its own is insufficient to predict the ...
steveOw's user avatar
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21 votes
1 answer
3k views

Why doesn't dark matter clump strongly in the center of galaxies, since it doesn't feel either radiation pressure or the Pauli exclusion effect?

Dark matter is described as being spread not only throughout a galaxy, but also around it in a halo of some sort that extends far beyond the visible parts of the galaxy... In fact, dark matter haloes ...
Kurt Hikes's user avatar
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1 vote
2 answers
358 views

What is a 'square' Kelvin degree? μ$K^2$? In terms of the cosmic microwave background's (CMB's) temperature fluctuations?

From what I have read and seen, the minute temperature fluctuations in the CMB are measured in microKelvin, or μK. However, many charts and graphs show μK2, or 'microKelvin-squared'. Do they simply ...
Kurt Hikes's user avatar
  • 5,177
1 vote
2 answers
124 views

Why is the probability dP of finding an object (e.g. galaxy) in an infinitesmal volume dV equal to \overline{n}dV?

As pointed out by many cosmology lectures, such as Eq. (63) of Cosmology II-8 Structure Formation, and Eq. (3.1) of A Detailed Look at Estimators for the Two-Point Correlation Function, the ...
Wang Yun's user avatar
  • 431
3 votes
0 answers
34 views

Mass resolution in cosmological simulations [duplicate]

I've been reading papers about different cosmological simulations and they all talk about the "mass resolution" of those. Can someone please explain what does "mass resolution" ...
schrodingal's user avatar
1 vote
2 answers
128 views

Could primordial black holes explain the SMBH in the galactic centers?

If there were enough primordial black holes (with the right mass) they could explain dark matter. Could they explain the gargantuan monster holes in the center of galaxies?
Felicia's user avatar
1 vote
0 answers
103 views

Why do most astrophysicists believe the cosmic microwave background (CMB) provides the best evidence for dark matter? What, exactly, IS that evidence?

I frequently read that the cosmic microwave background contains the best overall evidence for the existence of dark matter, and conversely against alternative gravity theories like MOND. However, I ...
Kurt Hikes's user avatar
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