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Questions tagged [galaxy-rotation-curve]

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Are we certain of the mass we calculate for supermassive black holes?

If astronomers have concluded that the rotation speed of objects held firmly within a galaxy but far from a galactic center is too great to be explained by the visible matter of the galaxy alone, what ...
mdswartz's user avatar
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0 answers
35 views

Galaxies rotations speeds questions

We accept epic gravitational lensing effects around invisible supermassive black holes, but do we consider possible gentle lensing effects in huge galactic structures observations ? Do we take time ...
olivierlambert's user avatar
2 votes
3 answers
2k views

Is there a Dark Matter Paradox?

According to this preprint, The Importance of Being Symmetric: Flat Rotation Curves from Exact Axisymmetric Static Vacuum Spacetimes, spiral galaxies possess flat rotation curves without assuming Dark ...
timm's user avatar
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1 vote
2 answers
206 views

Is there an spherical symmetric Einstein vacuum solution which has circular orbits with flat velocities? Or a proof that it cannot exist?

The Schwarzschild solution shows decreasing velocities with larger orbits - and needs help from dark matter or MOND to explain galaxies. Apparantly no Einstein vacuum solution with flat velocities is ...
Tantal181's user avatar
-1 votes
3 answers
155 views

Mass multiplied by distance in exponential disk (galaxies)

I model an exponential disk resembling a galaxy with mass density: $\rho(r) = \rho_0 e^{(-r/h)}$ with $r$ the distance to the galatic center, $h$ the scale length of the galaxy and $\rho_0$ the ...
Manuel's user avatar
  • 476
-1 votes
1 answer
152 views

Which of Newton's shell theorems applies to a galaxy?

From this question I gathered that Newton came up with two sets of shell theorems, one for hollow spheres and one for solid. It was also said we should use the version inside a solid sphere to model ...
Livid's user avatar
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0 votes
1 answer
48 views

Galactic Rotation Curves

While researching rotation curves, I've noticed a variety of velocity behaviors in different galaxies. In some, the velocity decreases, in others, it remains relatively constant, and in some cases, it ...
mahsum's user avatar
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0 answers
117 views

Is the rotational speed of stars at the outside of galaxies larger than their Newtonian escape velocity?

Stars at the outer edge of galaxies orbit faster than expected from Newtonian gravity, if no dark matter is assumed. Does this mean that the stars orbit so rapidly that their orbital speed is even ...
KlausK's user avatar
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0 answers
31 views

Expected Rotation Curves

As you know, it is expected that the velocity of stars and gas should slow down the further they are from a galaxy's center. However, in many cases, it does not slow down as expected, and this ...
mahsum's user avatar
  • 19
0 votes
1 answer
134 views

Theoretically, is it feasible for the dark matter density to be constant and homogeneous, as dark energy is, and the two to be related?

I know that currently dark matter and dark energy are separate things, not related and one not deriving from the other. But if both are included in a generalized gravitation theory, the picture can ...
Rahim's user avatar
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1 vote
2 answers
172 views

How can I estimate the dark matter density for some specific galaxies by using the rotation curves?

I have rotation curve data (radius vs rotational velocity) for some specific galaxies. How can I estimate the dark matter density for those specific galaxies by using the rotation curves? Or is there ...
mahsum's user avatar
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2 votes
1 answer
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Is this already an established functional relationship or have I created hodgepodge?

Last winter I started toying with the galaxy gravitational rotation curve graphs. I started modifying the exponent of $r$ that in effect change the $1/r^2$ law and therefore correct the mismatch, ...
Sandman's user avatar
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1 answer
23 views

Can outer star be captured by a more distance galaxy due to dark matter?

Imagine of an outer star lies between 2 galaxy cores with identical matter & dark matter distribution. If the outer star lies closer to galaxy core 1 and farther to galaxy core 2, the dark matter ...
Hantarto's user avatar
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2 votes
1 answer
55 views

Does MOND respect linear superposition of gravitational field intensities?

Does Milgrom's MOND respect linear superposition of gravitational field intensities as Newtonian gravity does?
Manuel's user avatar
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0 answers
35 views

Gravitational field intensity in mass disk

To calculate the gravitational field intensity or acceleration in a mass disk (like a galaxy), should I do a(r)=G×Mt/r^2 or a(r)=G×M(r)/r^2 with Mt being the total mass of the disk/galaxy and M(r) the ...
Manuel's user avatar
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1 vote
1 answer
107 views

At which rate does visible matter decrease from the galatic center?

At which rate does the visible matter density in galaxies decrease when moving away from the galactic center?
Manuel's user avatar
  • 476
3 votes
2 answers
157 views

Is there dark matter in intergalactic space?

Reference: the rotation speed of galaxies in a galaxy cluster: Is the dark matter associated with each galaxy in a cluster, sufficient to explain the rotation speed of galaxies in the cluster, or ...
Angela's user avatar
  • 1,023
-1 votes
1 answer
66 views

Is dark matter present in all galaxies?

The rotation speeds of nearby galaxies like M31 or our own milky way are determined by observations. And we know there that luminous mass does not explain the rotation curve. Are there any galaxies ...
Angela's user avatar
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0 votes
1 answer
187 views

How did Zwicky discover dark matter?

According to Wikipedia Zwicky used "virial theorem" to discover the gravitational anomaly in the Coma Galaxy cluster. But I also remember reading that he used Kepler's third law. Which one ...
zeynel's user avatar
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2 votes
0 answers
35 views

Dwarf galaxy rotation speed around Andromeda/Mily way

We know that the rotation speed of stars around the center of a galaxy is roughly flat. But how fast does the dwarf galaxy rotate around the bigger galaxy, say andromeda or milky way? Do they also ...
Angela's user avatar
  • 1,023
2 votes
1 answer
239 views

Solving Poisson equation for galaxy rotation curves

Can someone point me to the numerical methods to solve the Poisson equation for the galaxy rotation curves? I've heard of some tools like PETSc or OpenFOAM. But I'm not sure if these are the right ...
Angela's user avatar
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-1 votes
1 answer
85 views

Why modifying gravity to a fixed distance cant solve dark matter? [closed]

I quote Sabine Hossenfelder: "A modification becoming important at a fixed distance however could never explain the observed rotation velocities for spiral galaxies, whose constant asymptotic ...
Manuel's user avatar
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1 vote
0 answers
56 views

Database for galaxy luminosity (or mass) distribution

I'm trying to get data on luminosity (or mass) distribution for galaxies. I came across one paper (https://arxiv.org/abs/1106.3564) which gives luminosity distribution for Andromeda. But is there any ...
Angela's user avatar
  • 1,023
2 votes
2 answers
214 views

Has MOND been tested or even confirmed for our own galaxy, the Milky Way?

MOND, based on a modifications of Newton's law for small accelerations, describes the rotation curves of stars in most galaxies, especially the outer stars. Has MOND been tested for the stars in our ...
KlausK's user avatar
  • 727
3 votes
1 answer
56 views

What are the consequences of the tidal friction on the galaxy?

In the Earth-Moon system tidal-friction slows down the rotation, so does it do the same for the galaxy? If not how come, and why it's different than on Earth? If so can this slow-down be the reason ...
zebra's user avatar
  • 131
0 votes
0 answers
60 views

Galaxy rotation curve and galaxy mass

Is there a relation between the saturation velocity of the galaxy rotation curve and the luminous mass of the galaxy? To clarify the question, if one were to plot a scatter plot with the x-axis as the ...
Angela's user avatar
  • 1,023
16 votes
4 answers
804 views

Why would GR's prediction for galaxy rotation curves differ from Newtonian gravity's in spite of prevailing intuition from dimensional analysis?

Until recently, I had assumed that the predicted (non-dark matter) galaxy rotation curves shown in plots such the one on the Wikipedia article were calculated with general relativity. However, I now ...
tomdodd4598's user avatar
1 vote
2 answers
427 views

Does loop quantum gravity explain the dark matter effect without dark matter?

Does loop quantum gravity explain the dark matter effect (the rotational curves of the galaxies, the increased velocitoes of galaxies within galaxy clusters) without using dark matter? As far as I ...
BarrierRemoval's user avatar
-1 votes
2 answers
191 views

Thought experiment on boundary condition of galaxies

A thought experiment: Let's assume that there is only one single galaxy in the whole universe. How would it look like regarding the curvature of spacetime? Would the spacetime be flat in the infinity ...
BarrierRemoval's user avatar
1 vote
2 answers
224 views

Asymptotical flatness for galaxies - Why?

During the construction of solutions for General Relativity (when leaving out Lambda), asymptotical flatness is always assumed. Why? I fully understand that it fits the solar system, as it results in ...
BarrierRemoval's user avatar
1 vote
1 answer
62 views

Why do we need hot dark matter?

Data on galaxy rotation curves suggested that not all the mass in the galaxy is accounted for and we can't observe them directly but remind me again why we need hot dark matter in the first place? ...
user6760's user avatar
  • 13k
1 vote
1 answer
83 views

Do counter rotating galaxies have dark matter?

Have counter rotating dark matter galaxies been observed? Counter rotating galaxies, you may already know, are galaxies where some stars or arms rotate in one direction and other stars or arms rotate ...
Avraam Jack Dectis's user avatar
4 votes
1 answer
841 views

Boundary condition for gravity on galaxy scale?

In general relativity, on the one hand, asymptotical flatness is assumed to derive a solution to the EFE which is a good approximation in the solar system (Schwarzschild, Kerr...) On the other hand, ...
BarrierRemoval's user avatar
1 vote
1 answer
77 views

At the other edge beyond Newton with General Relativity? #2

The Schwarzschild solution is derived by using the static, spherically symmetric solution $$ds^2=-B(r)dt^2 + A(r) dr^2 +\text{angular terms},$$ assuming a concentrated mass, therefore gaining $A=1/B$ ...
BarrierRemoval's user avatar
14 votes
3 answers
3k views

Is Dark Matter in Motion?

What is known about the motion of dark matter, especially in galaxies? It seems as though a particular distribution of dark matter might be required to cause the very flat galactic rotation curves ...
John Hunter's user avatar
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0 votes
1 answer
58 views

Derivation of gravitational potential for Einasto model

I'm following this paper to understand how the gravitational potential is derived for the Einasto model: https://www.aanda.org/articles/aa/full_html/2012/04/aa18543-11/aa18543-11.html. I got stuck ...
Andrei's user avatar
  • 15
2 votes
1 answer
168 views

Why does $10^{-31}$K change the orbits of the stars, but 2.7K does not?

Many people discussing the rotation curves of the stars in galaxies explain that the rotation curves are influenced by a cosmological acceleration of about $1.2 \cdot 10^{-10}\,\rm m/s^2$, and that ...
user avatar
4 votes
2 answers
155 views

Can Vera Rubin's findings be explained by a distribution of charge?

Vera Rubin found that the rotational velocity of galaxies is much greater than expected at greater distances from the center. Gravity from an invisible mass is assumed to account for this measurement. ...
aquagremlin's user avatar
  • 1,721
2 votes
0 answers
70 views

Does barred in spirals galaxies like ours have the same speed (spin) as the center black hole?

In the case of old galaxies (elliptical) the black hole, like one in M87 have 2 jets. This look like polarisation pushing from central BH. In barred spiral galaxies, the bar have to cross the central ...
Jean-Louis Boucher's user avatar
0 votes
0 answers
49 views

Rotation of galaxies and gravitomagnetism [duplicate]

Can we explain the bigger speed of rotation of the galaxies from gravitomagnetic field acting from the "inner layers" of the galaxy to the "outer layers" of the galaxy?
MrV's user avatar
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0 votes
1 answer
155 views

Is it true that frame-dragging (as applied to galactic rotation curves) goes as second order in $v/c$ rather than $(GM/Rc²)(v/R)$?

I have seen various people (see e.g. comments here) dismissing this article using the argument that GR frame-dragging is second order in $v/c$ and therefore insignificant because $v << c$ for ...
Kit Adams's user avatar
1 vote
1 answer
508 views

Galactic rotation curves question

I think I need to ask this question now, because it's in my mind for several years and I just can't find an answer to it. After observations of those galaxtic rotation curves, it's pretty clear, that ...
Tankbuster's user avatar
0 votes
2 answers
63 views

Forces besides gravity acting at astronomical distances?

It seems like all one reads about is gravity affecting planets and stars whereas at the atomic level there are other forces and gravity is unimportant. How do we know there are not other forces ...
releseabe's user avatar
  • 2,238
5 votes
0 answers
111 views

Fully General Relativistic treatment of Galaxy Rotation Curve

Over the years I have seen several approaches to this problem in the GR context: perturbations around a flat-spacetime, cancelation by hand of $\mathcal{O}(\partial_{\mu}\textbf{g}^{2})$ terms on the ...
Martin Nava-Callejas's user avatar
0 votes
1 answer
185 views

Is there software to calculate/plot decomposed rotation curves from observational data (FITS, etc)?

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 ...
1 vote
2 answers
51 views

How much faster are the stars on the outskirts of galaxies going than they are 'meant' to as predicted by general relativity?

this is in reference to dark matter. I've look on the internet for this but I can't find precisely what I am looking for.
Shannon T's user avatar
  • 361
1 vote
0 answers
93 views

Unruh effect on rotating galaxies?

According to the Unruh effect, an accelerating observer will experience a thermal bath. This is equivalent to Hawking radiation. If we applied this to a spinning galaxy, I wonder if this thermal bath ...
user avatar
0 votes
2 answers
106 views

How can I plot Rotation Curves of Spiral Galaxies $v$ (km/s) vs $r$ (kly)?

I have a formula about Rotation Curves of Spiral Galaxies that I have written below: $$v(r)=c [L/(2*r)+1/2\cdot c_3+ c_4\cdot\ln(r)]^{1/2}$$ that $c=3\cdot10^8m/s$ is the speed of light and $c_3=2.8\...
Alice's user avatar
  • 67
0 votes
0 answers
38 views

Are there galaxies with satellites in retrograde orbit?

If frame dragging is important for properly calculating galactic rotation curves, it seems that galactic satellites in retrograde orbit should behave as if they experience a different amount of ...
S. McGrew's user avatar
  • 24.8k
8 votes
2 answers
747 views

Has frame dragging been accounted for in galactic rotation curves?

This article explicitly takes frame dragging into account in calculating expected galactic rotation curves in the absence of dark matter, and appears to obtain very close matches to observed curves. ...
S. McGrew's user avatar
  • 24.8k