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 can Deep MOND regime apply inside a star?

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 gravitational acceleration when acceleration ...
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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 ...
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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 ...
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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 ...
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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" ...
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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?
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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 ...
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Is the dark matter/baryonic matter ratio the same in galaxies with supermassive black holes?

My hypothesis is that if the ratio of dark matter/matter in galaxies with supermassive(weighing billions of suns) black holes are higher the black hole itself would be made of a large portion of dark ...
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Does the presence of dark matter in the Milky Way significantly distort our parallax based measurements of distance?

According to accepted astronomical wisdom, dark matter represents a large fraction of the total mass of the Milky Way. And thanks to Papa Einstein, we know that light rays can be bent when passing ...
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Which galaxies have the most well known / estimated dark matter halos?

For this I guess you need accurate circular velocity measurements of the stars in the galaxy a decent luminosity profile for the galaxy some analysis which looks at the discrepancy between the two ...
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Is there a consistent missing mass ratio for Galaxy Clusters?

The Coma Cluster is what famously lead Fritz Zwicky to the conclusion that Dark Matter exists. As the velocities of the galaxies within the cluster were too fast for them to remain within orbit of ...
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At what distance does MOND Modified Newtonian Dynamics take effect?

At what distance does MOND Modified Newtonian Dynamics take effect? I understand MOND is described in relation to very slow accelerations, which is related to distance. It is mentioned it has an ...
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In what ways does dark matter help in "binding" celestial bodies together in a Galaxy?

Earlier in history, it was said that the celestial bodies in galaxies were bound by "mutual gravity". There is still a common misconception that the gravity of supermassive black holes binds ...
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What is the estimated density of the dark matter?

What is the estimated density of the dark matter? Some clumps of dark matter might have higher density and others might have lower density. So what is the estimated density range of dark matter? Is it ...
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How does the gravitational interaction between dark a matter bulge and an ordinary matter disk affects stability over time?

From Cosmology it is known that a spherical bulge of Dark Matter, that only interacts gravitationally, surrounds the nucleus of each galaxy, that has a spinning disc component of ordinary matter. How (...
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Distribution of dark matter

Searching to understand how dark matter is distributed, I find many references like this: https://www.bbc.com/news/science-environment-57244708 Basically they state that dark matter exists wherever we ...
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Can primordial black holes comprise not only dark matter but also account for dark energy? [duplicate]

Hawking proposed primordial black holes might comprise dark matter. They certainly contribute then to dark energy via their mass and other energies; e.g. gravitational and kinetic. Does this account ...
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How did cosmic inflation even occur?

I wanted to ask this question that which inflation model shall i believe? Following below will be MY UNDERSTANDING (MAY NOT BE CORRECT) OF IT: I read "A Brief History of Time" and in chapter ...
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Is a black hole found in the centre of the low-surface-brightness and dark-matter-free galaxy AGC 114905

Per information found on Internet: AGC 114905 was discovered while observing the constellation Pisces with the VLA ground-based radio telescope. The galaxy is about 250 million light-years distant ...
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Stellar and gaseous surface mass density spiral galaxies

I have a database with more than 1000 rotation curves of spiral and lenticular galaxies (xxx-gxx notation is ESOxxx-G0xx). I am working on dark matter mass modeling and I would like to know whether ...
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Multiverse and Dark Matter [duplicate]

There are a lot of posts on dark matter, including one old one that asked the same thing, but I'm wondering if there's any more recent thoughts on this. One of the speculative theories on why gravity ...
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Can the Dark Matter / Energy problem be plausibly reframed as an ignorance of gravity problem?

I understand Dark Matter was originally proposed to explain the rotation rate of galaxies. The rate was not explained by observed matter, ergo there must be unobserved matter. An alternate explanation ...
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Are there galaxy clusters or dark matter halos in the void?

The void usually refers to the region of the Universe where the overdensity $\delta(x)$ is less than zero. What I'm curious about is whether there are virialized objects, like galaxy clusters or dark ...
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Does the density of a black hole decrease after releasing a large amount of Hawking radiation?

Is is true that the smaller a 'regular', stellar-mass black hole is, the denser it is inside of its event horizon? After all, if you look up (or calculate) the Schwarzschild radii of the Sun and the ...
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What observation methods could confirm hypothesis that primordial black holes formed from Fermi balls are the source of dark matter in the Universe?

https://arxiv.org/abs/2106.00111 What astrophysical observation methods could be used to confirm the above hypothesis that primordial black holes formed from Fermi balls are the source of the dark ...
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People Working on Dark Matter Simulations

I am interested in simulations regarding dark matter. I am looking for more details and reading material on the same. I was really hoping to get some guidance from someone working in that field. Can ...
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Could dark matter exist in the Universe in the form of sufficiently dense objects?

Albert Sneppen's publication "Divergent Reflections around the Photon Sphere of a Black Hole" provides the math related to the issue which in common language could be described as "how ...
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Would the stars look different if many primordial black holes were present?

Suppose that there are many primordial black holes. These are point masses which have a small probability to collide with stars let alone themselves. They are formed in the early universe and could ...
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Can dark matter be normal matter after all? [duplicate]

MACHO's and RAMBO's are both baryonic (and leptonic) forms of matter that can't be observed by their nature. They barely emit or reflect light. Black holes, neutron stars, or brown dwarfs (or groups ...
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Scalar field displacement from the minimum of the potential gives rise to particles/dark matter, why?

The paper Lyman-alpha Constraints on Ultralight Scalar Dark Matter by Kobayashi et al. says, at the beginning of Section 3.1: A light scalar field stays frozen at its initial field value in the early ...
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Looking for analytical expression of Cosmic Variance - Poisson distribution?

I have an expression of Matter Angular power spectrum which can be computed numerically by a simple rectangular integration method (see below). I make appear in this expression the spectroscopic ...
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Is the dark matter just regular matter out of the observable universe?

Could it be that darkmatter is actually the gravitational influence of regular matter that is situated out of the observable universe?
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How can dark matter be observed?

Look at this picture: It looks as if dark matter is observed. But what is actually observed? doesn't this picture prove MOND and emergent gravity (both assuming a different gravity tied to normal, ...
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How can the (in my eyes quite ridiculous) conjecture of Sheldrake be disproven? [closed]

In this question on the physics site, it is asked if astronomical objects can be conscious. Now, in a sense, every object has to be "conscious" somehow, as every object is composed of the ...
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Was there a formula-first hypothesis for gravity?

Being a mathematician I wonder, has there been an attempt to blindly approximate a formula for gravitational attraction that would match the data, based on "normal" matter we can see plus ...
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Could Sgr A* be a core of dark matter instead of a supermassive black hole?

A recent paper (related news) shows that Sgr A* at the center of the Milky Way galaxy could be a dark matter core, instead of a supermassive black hole, according to their calculation using the ...
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2 votes
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How to derive density and mass from the pseudo isothermal model for mapping the density profile for dark matter?

I recently read about dark matter haloes and ways to profile their density. I came across this model called the pseudo isothermal model for the halo and I wanted to know how you would model the ...
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Is there software to calculate/plot decomposed rotation curves from observational data (FITS, etc)? [closed]

I have observation data of galaxies (in FITS format). From the FITS data, I want to calculate & plot the decomposed rotation curves as pictured below. Is there a software package that will do that ...
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What consequences does a positive muon anomalous magnetic moment have for astronomy?

On April 7th, 2021, the muon $(g-2)$ collaboration published Measurement of the Positive Muon Anomalous Magnetic Moment to 0.46 ppm, a result which made it to standard news, partly under headlines ...
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What fraction of matter is not bound to the galaxies, groups and clusters that we see?

We know that most of the matter in the universe has collapsed into galaxies and galaxies into groups and clusters and that a lot of matter is presently in clusters between the galaxies. But, what ...
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How to explain tidal tails and dark matter sub-halos in simple terms?

There is the exciting news by ESA entitled Is the nearest star cluster to the Sun being destroyed? Data from ESA’s Gaia star mapping satellite have revealed tantalising evidence that the nearest ...
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Could dark matter form coherent bodies the size of stars or planets?

Is it possible that dark matter could collapse gravitationally, forming massive bodies similar to stars or planets? When I say "similar", I don't mean to imply that they would undergo ...
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How do we estimate the dimensions and mass distribution of a galaxy's dark matter halo, beyond the effective limits of its visible matter?

Current research suggests that the Milky Way's dark matter halo may extend up to about 10 - 15 times the size of the visible galaxy, and is believed to be roughly spherically symmetrical. But I don't ...
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Demo to get Matter Power Spectrum in cosmology

I would like please to demonstrate the expression of Power spectrum in Cosmology : First, I have the relative contrast: $$\delta_{i}(\vec{x}, z) \equiv \rho_{i}(\vec{x}, z) / \bar{\rho}_{i}(z)-1\quad(...
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Anatomy of a galaxy cluster: understanding the relationship between dark matter halos and subhalos and galaxies within the clusters?

In my understanding, galaxy clusters contain dark matter halos, which in turn contain subhalos, and the subhalos are what surrounds individual galaxies. I know that is a simplified picture, but I am ...
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2 votes
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In 'Modified gravity' theories like MOND, are galaxies and stars actually, slowly accelerating? In the normal sense?

In the Modified Theory of Newtonian Gravity or MOND, they say that massive objects, accelerating slowly, experience this modified gravity. But are they actually gaining in velocity, albeit very slowly?...
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New evidence against the existence of dark matter?

I've just read and heard about an article which gives new evidence for MOND - Modified Newtonian Dynamics, which is an alternative to dark matter by proposing that our gravitational law should be ...
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Why is dark matter required?

I read somewhere that the galaxy is spinning too fast (in places). Therefore, there must be dark matter. What are the equations that explain how fast the galaxy should be moving, and how are they ...
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Can there be planets, stars and galaxies made of dark matter or antimatter?

We know that the universe has more dark and anti matter as compared to normal matter. Can there be dark matter galaxies or antimatter galaxies?
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Could not slow neutrinos orbit galaxies and clusters, thus comprising a large component of even COLD dark matter?

Cold dark matter is the type of dark matter that is most eminently neutrino-free. But neutrinos themselves suffer a large survivorship detection bias (“all the neutrinos you can detect necessarily ...
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