Questions tagged [galactic-dynamics]
Questions regarding interactions between galaxies or between major parts of a galaxy.
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Strip Brightness in a Spherical System
My question concerns the following problem, published in Galactic Dynamics by Binney and Tremaine and based on a work by Schwarzschild.
Specifically, I am having difficulties in deriving the given ...
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Do the orbits of satellite galaxies show the influence of dark matter?
I understand how galaxy rotation curves show the influence of dark matter, or something else that would produce similar behaviour, such as Modified Newtonian Dynamics (MOND). Do the orbits of ...
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Are metallicities of molecular clouds lower in the outskirts of the galaxy?
(this question was originally posted in an answer by user PSR-1937-21 to another post. I find it an interesting one, but since they don't seem to be active anymore, I'm posting it to see if somebody ...
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What does correcting for LSR mean in galactic velocities?
This is a two-part question, but both parts are related:
I'm aware that modern astronomical software can correct velocities for the local standard of rest (LSR), but what does that really mean? As in,...
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Orphaned star systems and intergalactic travel (in fictional context)
Context:
I'm looking for some authority on a particular idea that I brought up in regards to a new update brought out for a space travel sim game, Elite Dangerous
The vessels in that game can travel ...
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What's so interesting about Coma-type galaxy clusters?
When the dynamical mass of a proto-cluster of galaxies is ~(1-2)x1014 Msolar, the proto-cluster is expected to evolve into a coma-type cluster.
In almost every paper I read about the confirmation of ...
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What are Stokes parameters for galaxy shapes, how do they compare to Stokes parameters in optics?
I remember Stokes parameters as a way to completely define the polarization state of a well-defined beam of light. However several questions here refer to Stokes parameters used in characterizing the ...
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What is the characteristic time of the evaporation of the galaxies?
For a star, to leave its galaxy, it requires probably a 3-body near-collision at the edge of the galaxy. It is unlikely, but possible. And, if a star once somehow got the required velocity to escape ...
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How is the Sun tilted to its orbit around the Milky Way's center?
We know how the Sun is tilted in reference to its planets but how is it tilted to Sagittarius A or its orbit around it? Or isn't it tilted at all?
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Can the gravitational potential in a spiral galaxy be positive?
Thinking about this question I wanted to start with a rough model of the average gravitational potential of the Milky way. I ran across D. P. Cox and G. C. Gomez 2002 Analytical Expressions for Spiral ...
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How do galaxies move in space?
Kind of like a shower thought just occurred to me. We've all seen lots of animation about spiral galaxies, how they crash... in virtually all of them, I recall they move in a frisbee way, that is ...
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How do disk-shaped galaxies then form at the sites of spherical galactic halos? Do the halo stars start orbiting or just sit in place?
Phys.org's Astronomers detect large amounts of oxygen in ancient star's atmosphere mentions
"Stars like J0815+4729 are referred to as halo stars," explained UC San Diego astrophysicist Adam ...
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What is the largest cluster of merging galaxies?
Reading about the Andromeda–Milky Way collision, a galactic collision predicted to occur in about 4.5 billion years between the two galaxies, I went to the galaxy merger page and Wikipedia states that ...
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More recent data and simulations of "Milkomeda", the collision of the Milky Way and Andromeda galaxies?
The Space.com headline Hubble Telescope Spots Two Galaxies in a Doomed (but Dazzling) Dance; The galaxies will ultimately crash into each other was probably overstated as seems to be policy in some ...
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Supergalactic and Equatorial coordinates
What's the difference between Supergalactic and Equatorial coordinates?
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How do two supermassive black holes reach "the last parsec" in merging galaxies?
This answer to Why can't supermassive black holes merge? (or can they?) describes the barrier to merging that two supermassive black holes face when two galaxies are in the process of merging or have "...
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Dynamical modelling of galaxies with counter-rotating components using the Schwarzschild method
I am currently trying to understand dynamical modelling using Schwarzschild's method. I have been doing some reading the past days, but I suspect that I am getting something really wrong. According to ...
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When will the number of stars be a maximum?
There are very roughly a "mole" of stars in the universe. Wikipedia quotes an estimate of $3 \times 10^{23}$ though the number is associated with some debate and uncertainly.
I'd like to know if ...
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What has GAIA found out about the dwarf galaxy heritage of stars in the Milky Way, if anything?
I ran across the image below in the August 2000 ESA Bulletin # 103 GAIA – Unravelling the Origin and
Evolution of Our Galaxy
Figure 3. This simulation shows how a galaxy halo, like our own, may ...
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Galactic rotation speeds - questions from a non-astronomer
Are there any observations that more distant galaxies appear to rotate more slowly than closer galaxies?
What methods are used to measure the rotational speed of galaxies? (both orbital speed ...
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Population histograms and relationship between size of galactic disk and amount of dark matter
I am interested in seeing a plot of dark to baryonic matter ratios in terms of the galactic disk size (when it applies, as not all galaxies fit into disk shapes, and probably analyzing disk galaxies ...
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Is it possible to define a state of zero absolute angular momentum anywhere in the universe?
Conservation of angular momentum doesn't seem correct to me. I think this because radiation is present everywhere, no space is completely void, and no object perfect. Thus all objects will have uneven ...
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Looking for a Dwarf Galaxy < 500 L.y. in Diameter, which is not a Satellite / Companion, or is at least 500 000 L.y. away from another Galaxy
My goal is to learn about an example of a Dwarf Spheroidal or a Dwarf Irregular Galaxy which is not a Satellite / Companion Galaxy (or is at least 500 000 L.y. away from another Galaxy), and doesn't ...
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Direction of Earth’s poles relative to the Sun’s movement around the Galaxy
The plane of the solar system is at 63 degrees to the plane of the galaxy, then either the North or South Pole of Earth would be on the ‘leading edge,’ i.e. pointing roughly in the direction of ...
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Is the Milky Way Galaxy predicted to collide with a neighboring galaxy? [duplicate]
Topic
I've read several articles online that state that our galaxy will collide with a neighboring galaxy in the future, but there is no evidence about it happening.
Question(s)
After reading a ...
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Is diffuse energy distribution considered in the galaxy rotation curve explanations?
Problem number 23 in chapter 1 of Purcell's "Electricity and Magnetism" Second edition page 37 shows that 90% of the energy stored in the electrostatic field of a spherical charge distribution of ...
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Is the expected time for a star in an elliptical galaxy to collide with another star less than the average age of elliptical galaxies?
According to the Wikipedia article Elliptical galaxy, elliptical galaxies have a much lower concentration of gas between the stars than spiral galaxies. I know that until the gas is below a certain ...
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Half of the Milky Way's baryonic mass is from other galaxies - when did this happen?
The recent Phys.org article Milky Way's origins are not what they seem explains the recent MNRAS article Anglés-Alcázar et al. 2017; The cosmic baryon cycle and galaxy mass assembly in the FIRE ...
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In which direction does the Milky Way rotate?
We don't have a photo of our Milky Way the whole, all the pictures are artists' interpretations showing a bulge, a central bar, and several spiral arms. The milky way is spinning. I would like to know:...
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Does the Abell 1689 supercluster have angular momentum?
The Abell 1689 is a large group of galaxies, containing a lot of elliptical galaxies :
https://en.wikipedia.org/wiki/Abell_1689
Usually, an elliptical galaxy don't have large angular momentum around ...
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Need help on Springel model for galaxy simulation
I am working on a code for galactic dynamics simulation. Initial conditions (positions and velocities) are based on a model with a massive dark halo and a thin exponential disk.
Now, from the ...
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Star density in- versus out- of the arms of the galactic pattern?
What is the density difference in our galaxy (or in a typical spiral),
at A, B, C versus at a, b, c?
Consider the yellow track.
Do astronomers have a graph like this...
...which shows the shape of ...
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Why does the neutral hydrogen velocity have this characteristic behavior in the galactic plane?
The recently released map of galactic neutral hydrogen density and velocity is really beautiful. The work has been relased by the HI4PI collaboration (HI = neutral hydrogen, $4\pi$ = complete ...
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Examples of astrophysical objects NOT in virial equilibrium?
Astronomers always talk about astrophysical objects being in virial equilibrium (e.g., a stellar system, or a disk of gas within a galaxy, etc.). But I never hear about thermodynamical equilibrium.
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Ellipticals supported by random motions
As opposed to spiral galaxies, which are rotationally supported, elliptical galaxies are said to be supported by random motions of their stars. I don't really have an intuitive understanding of this. ...
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What (actually) is the " deprojected half-light radius" of this almost-all-dark-matter Galaxy?
The recent news of the Ultra Diffuse Galaxy (UDG) Dragonfly 44 is an excellent example of what could be termed 'observe different' thinking. The dragonfly telescope is noted not for the size of its ...
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Is a swimming pool analogy to building of black holes in the centers of galaxies valid?
In our garden, we have a little pool to enjoy our 2 children. It is 3 meters in diameter and contains some 4 m³ of water.
For cleaning-convenience every evening I go walking some 5 or 10 rounds in ...
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Why don't globular clusters flatten with a galactic disc?
Globular clusters lie in the galactic halo, outside of the disc. However, galaxies are more or less a collection of material and objects — why is it, then, that most stars form a plane due to the ...
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Virial coefficient when computing dynamical mass enclosed by a rotating galactic disk of gas
Suppose I have a large thin disk of rotating gas in a galaxy -- the disk has a maximum inclination-corrected $V_{max}$ and a maximum radial extent of $R_{max}$ corresponding to that $V_{max}$ ...
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Is our central black hole actually at the CG of the galaxy?
It seems fairly certain there is a large black hole, about 25,000 ly from Earth roughly in the center of our galaxy, in the direction of the Sag. A radio source.
• In fact, is it thought to be ...
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Stellar systems: what is the difference between virial, dynamical and thermodynamic equilibrium?
I'm currently going through Binney & Tremaine (2008) on my own to learn about stellar dynamics. I also have been perusing additional online resources such as this scholarpedia wiki.
Often when ...
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Why Milky Way and Andromeda are being drawn together if there was 'Big Bang'?
Scientists used to use following reasoning:
most galaxies are red-shifted $\implies$ there was a 'Big Bang'
Why this is being considered valid since not every galaxy has such property?
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Is the motion of the Sun around the Galaxy a result of gravitational pull?
Does the orbit of the sun (and other stars within the Milky way) around the galaxy result directly from radial gravitational force toward the objects in the center of the galaxy, or is there ...
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Why are stars more metallic closer as you move closer to the galactic bulge?
As I see it, most of the stars in the galactic bulge are Population I stars. However, as one moves farther from the galactic bulge, star metallicity decreases. In fact, halo stars are almost entirely ...
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What parameters determine whether galaxies colliding will result in a merger or a hit and run?
Colliding galaxies sometimes merge and sometimes pass through each other. Either way, there are huge changes as a result. What are the parameters that matter in determining whether a collision will ...
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Distribution of Stars in Milky Way and globular cluster analogy
Just a quick (and hopefully simple) question on the distribution of stars in the Milky Way and in globular clusters. I was wondering why it IS NOT possible to describe the distributions of stars in ...
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Is the Astronomy community still concerned about the lumpyness of matter distribution in the universe?
A decade or so ago, when I was still a science undergrad, one of the open questions in astrophysics was to explain the uneven distribution of galaxies in the observable universe. That is, why did the ...
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Has the great Andromeda Galaxy ever collided with any galaxies?
We know that the Andromeda Galaxy is moving towards the Milky Way and vice versa, so there will be a collision. Because of the vast space between them, the stars as they are defined will not ...
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What happens to galaxies when they die?
Stars explode when they die and blast heavy elements into space. Do galaxies do the same thing?
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