Dark matter Definition and 919 Threads

I've been reading up a little on IC1101, the largest known galaxy and there is not a lot of info on it, but it seems to have an unusually large mass to light ratio according to this popular article (see half way down): According to this article at 20kpc it's got 12:1 mass to light, at 200kpc...

The Bullet Cluster counts as 'smoking gun' for the dark matter. But what lacks in these calculations is the super massive black holes at the center of almost every galaxy. As the most massive and most compact objects in the collision, it's expected that they are less slowed down by the collision...

if we assume each photon of light as a very very light piece of matter (by famous E = mc^2 and then: m = E / c^2) and sum up all photons that have been made from the creation time of a galaxy (also considering limitation of speed of light) and also photons that accidentally passing throw that...

A black-body absorbs and emits radiation if heated, but it does not reflect or transmit radiation.What is the temperature of dark matter?

What would be the distribution galactically, universally etc? How might distribution of DM change if involved forces, masses, energies or other fundamental components of DM occurred at different weights ie: Could there be less but stronger or perhaps "more but weaker" models of DM? What would...

Hello, could you please recommend some good introductory textbooks for studying core topics in astrophysics/cosmology, and especially dark matter? I know that 'An Introduction to Modern Astrophysics' by Caroll and Ostlie is a good book, but I 'm looking for something more concise, so to speak...

Does the diffused distribution of dark matter as halos over galaxies imply dark matter is made up of low-mass particles?

My understanding, possibly my ignorance, is that dark matter is calculated to exist from observations that there's not enough matter to fit observations if the current theory of gravity is right. Is it possible to put into a nutshell why the case for dark matter together with current...

Could dark matter consist of black holes formed shortly after the big bang? They would form the perfect development seed. If they all have Sun-like masses then they are not detectable from here (they are just 3 kilometers wide!). They have virtually no collisions with stars and could form a...

Question: How accurately does the observation of the current dark matter to baryonic matter ratio fit with its influence on the BBN? Some good references would be very helpful. Here are some references that I think might be a little helpful. (Mar 6, 2004)...

Does anyone have any good laypersons reads to get a good summary the dark matter versus modified gravity? Thanks

Could matter have formed structures in the universe, like galaxies, without the presence of dark matter?

The likelihood for dark matter appears to be lessening in direct detection and in its utility in explaining astronomical anomalies. With regard to the former, a trio of recent dark matter detection experiments (LUX 2016, PandaX II 2017 and Xenon1t 2018) have all failed to show any non-baryonic...

Summary:: I've written a song based on a lecture I attended re: the universe. I'm hoping to confirm facts re: Dark Matter, etc. discussed within the song. I have a somewhat unusual request: I have written a song based on a lecture I attended re: the universe. Before recording and releasing...

Flat rotation curve in galaxies is determined by observing neutral hydrogen which is co-distributed with dark matter. What is the rotation curve profile of neutral hydrogen in galaxies where there is less dark matter?

Hello. I'm posting here for the first time. I have a few related questions about matter, dark matter and elements for which I have not been able to find answers. Does dark matter 'hold' matter in the universe in place? Does matter 'hold' the elements of the universe in place? Does matter create...

Do we notice any significant difference in distribution and dynamics of dark matter in galaxies when n-body simulations are done with high or low-mass dark matter particles?

There are reports that our cosmological models can't explain our up to date dark matter distribution maps, and that it calls general relativity into question. https://www.bbc.com/news/science-environment-57244708 I guess the relevant publications can be found here...

Let's say that it turns out that Dark Matter is realllllly dark. And (except for gravity) none of our experiments actually result in any Matter/DM interactions at all. Not now, not for the next couple of centuries. Just based on gravity observations, are there things that we will eventually...

This paper suggests that macroscopic dark matter could leave a trail of ionized plasma as it passes through the Earth's atmosphere. If this happens during a thunderstorm it could trigger a lightning strike that follows that trail. https://journals.aps.org/prd/abstract/10.1103/PhysRevD.103.063024...

Is the Reduced Planck Constant the minimum frequently/movement/spin matter can have to exist? So if a matter were to spin lower than 1.054 571 817... x 10-34 J s, it when cease to exist? Or would matter falling below the Reduced Planck Constant by classified as Dark Matter? I heard that Higgs...

this paper, Testing the Strong Equivalence Principle: Detection of the External Field Effect in Rotationally Supported Galaxies Kyu-Hyun Chae1 , Federico Lelli2, Harry Desmond3, Stacy S. McGaugh4, Pengfei Li4, and James M. Schombert5 Published 2020 November 20 claims a 4 sigma...

I'm not sure if this paper belongs in GR or astrophysics but This articleG. O. Ludwig (2021), Galactic Rotation Curve and Dark Matter According to Gravitomagnetism, European Physical Journal C 81:186, DOI 10.1140/epjc/s10052-021-08967-3 there's no need for dark matter,as GR's Gravitomagnetism...

A new pre-print makes a sensible and convincing, in my view, argument that phenomena attributed to dark matter are not exclusively or predominantly explained by primordial black holes formed at less than the mass of a star shortly after the Big Bang, by means other than stellar collapse. This...

This post is slightly different from a previous post sent to mathematical forum : this is because I talk about here the MATLAB function "eig" with 2 arguments but this concerns actually the combination between 2 biased tracers in Cosmology context. I am looking for a common basis of...

Baryon number is, despite all guesses and searches, known to be conserved in all interactions. It is also known to be significantly nonzero, though modest, for world. Lepton number is, despite all guesses and searches, known to be conserved in all interactions. It is not known if world has any...

It looks as if ultra-light and super-heavy have become less likely. https://www.sciencedirect.com/science/article/pii/S0370269321000083

Is it possible that dark matter has Planckmass and Spin two?

Hello All There is much discussion on the existence of Dark Matter. Should we think of Dark Matter as having macro structure, ie comprising elementary particles, leading to atoms and a Dark Periodic Table? best regards ... Stef

Hey peeps, Ok, so I need some help here. I've just been watching some videos explaining the existence of dark energy and dark matter - something which has always fascinated me. These videos pose the theory that for the first 9 billion years of the universe dark matter ruled but, for the last...

This is probably a long shot but it's worth trying. My question is the following: What properties of dark matter can we derive from each of the available methods for probing the physics of dark matter? To elaborate a bit, my understanding is that the evidence for dark matter comes from its...

The speed of star on the outer of are solar system is not according to the visible mass. Change the law of gravitation F = 1/r^2 to fix this. Galaxies far away are moving away with increasing speed. Change the law of gravitation F = 1/r^2 to fix this, include a repulsive force to fix. Would this...

https://phys.org/news/2018-04-dark-interactive.html "Observations using the Hubble Space Telescope appeared to show that a galaxy in the Abell 3827 cluster - approximately 1.3 billion light years from Earth - had become separated from the dark matter surrounding it. Such an offset is predicted...

What is the shape of a typical dark matter halo around a galaxy? Does it orbit a galaxy like visible matter? It is said that dark matter does not lose angular momentum, necessary for compactification. How then does visible matter lose angular momentum?

Two Recent Papers Propose A Simply Tweak To How General Relativity (GR) Is Applied That Purports To Explain All Dark Matter Phenomena Motivated By A Version of GR and Quantum Gravity. The pair of related papers with overlapping text and common authorship (cited below) were published after peer...

In the other thread, it was noted that dark matter doesn't interact with ordinary matter. Now I tread cautiously, not knowing any of the relevant theory. In some school questions, I've come across discussion of 'dark matter halos' which are necessary to ensure the rotation curve of the galaxy...

Given the fact that our galaxy consists mostly of dark matter (accounting for roughly 70% of its mass) we know astonishingly little about the stuff. Admittedly, if I could give you a lump of dark matter, you would propably be totally underwhelmed by the "experience". First of all, you wouldn't...

The speed of the ends of the galaxies is higher than what it should be. Current solution: This could be explained by hypothetical "dark matter", which was not found up to now, or by a MOND theory (MOdified Newtonian Dynamics). Can this be explained instead with rotational frame-dragging...

I am looking for introductions and reviews (papers or books) on the possible observation and the nature of dark matter. This book seems to be a good start, but I would be grateful for any other recommendations that are accessible to people with knowledge of physics at the undergraduate level...

I understand black matter surrounds galaxies and galaxy clusters, but is it inside the galaxies themselves? Is it in interstellar space? If so, does it surround the sun and planets, and if so, could it be right here on Earth with us?

Press release arXiv ~3.5 sigma significance and it could be caused by tritium contamination - although it's unclear where the tritium would come from. If it is really new physics then solar axions or a magnetic moment of neutrinos would fit well. The key plot, figure 5 in the arXiv version...

So far as I understand it, a photon can split up and create particles with matter, even though the photon is massless, yes? So if a photon can be more places at the same time, it should be able to create multiple particles all at once? So how is this not Dark Matter?

Neil deGrasse Tyson states that "dark matter exerts gravity according to the same rules that ordinary matters follows" How do we know this? If we have no idea what dark matter is, how can we say how it behaves? How do we know that a single "molecule" of the stuff doesn't weigh as much as the...

Thoughts? Guessing it’s speculative, but is it a reasonable, testable candidate? https://scitechdaily.com/sub-atomic-particle-identified-that-could-have-formed-dark-matter/

https://www.sciencedirect.com/science/article/pii/S0370269320301040#br0210 I need to give this more thought, but the ballistics section is pretty good, and I think their basic dE/dx argument is sound: If a collision at a ballistic rate transfers about the same kinetic energy to the human body...

If there is dark matter that doesn't gravitate, do you still call it dark matter? Hossenfelder mentioned General Relativity can't be entirely correct because of quantum gravity, so this gives the possibility of dark matter that doesn't gravitate...

Is there any astronomical indication that gravitational force between dark matter might be weaker than between visible matter?

Dark matter is distributed in halos around visible galaxies, while baryon matter is distributed in spiral-shaped visible galaxies. Where does this difference come from?

Do we understand Dark Matter enough to know how it is concentrated within a galaxy. For example, would it be evenly distributed like hydrogen would be or could it be concentrated like most matter is? For example could there potentially be Dark Matter stars and Dark Matter planets within our galaxy?

Here is the Physical Review article: "Supernovae sparked by dark matter in white dwarfs" "A ball of asymmetric dark matter accumulated inside a white dwarf and collapsing under its own weight sheds enough gravitational potential energy through scattering with nuclei to spark the fusion...