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Questions tagged [stellar-dynamics]

Questions about the branch of astronomy that studies the regularities in the motions of stars in gravitational fields of stellar systems, as well as the evolution of stellar systems.

7
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1answer
174 views

What is convection overturn?

When I read some papers about MHD dynamo theory, there is always a $\tau$ that means convection overturning time. What does convection overturn mean?
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1answer
101 views

Is the three-body system “unique”?

Given a state of an ideal 3 body system (i.e., without external interference) in time $t$: the velocity $v_{i,t}$, mass $m_{i,t}$ and position $x_{i,t}$ for $i\in \{1,2,3\}$, using numerical method it ...
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4answers
960 views

Is any 3 body system known?

https://en.m.wikipedia.org/wiki/Three-body_problem Have three or more celestial bodies rotating each other in a stable manner ever been observed, or it is only a theoretical problem?
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2answers
162 views

List of Moving stars on the northern hemisphere? [Stellar kinematics]

Anyone know if there is a List of Moving stars on the northern Europe hemisphere I can search for? Like Barnard's I wish to image them [when possible] and compare their yearly movement. Thank you
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1answer
43 views

Star systems forming when large gravitational force is applied

As far as I'm concerned, most star systems in our galaxy are traveling in fairly circular paths around the black hole at the center. Hypothetically, if a large gravitational force pulled star ...
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1answer
57 views

how far away can close stars diverge with time?

Do high velocity stars decelerate if they transit at 300ly per million years? What kind of forces can decelerate them and in what kind of time frame? What about ordinary stars which travel at 70 ...
7
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3answers
956 views

Are the stars outside of the galactic plane in the galactic halo?

The majority of the stars we see in the sky, like Pollux, are outside of the galactic plane. That means that all those stars we see are not in the galactic disk, and therefore are in the galactic halo,...
2
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1answer
86 views

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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1answer
92 views

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. ...
2
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1answer
72 views

Why aren't stars like Eternally Collapsing Objects?

We know that stellar radiation pressure balances the gravitational compressive forced of a star. Are there other factors which resist such a collapse? Also, if radiation pressure balances ...
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0answers
69 views

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 $V_{max}$ ...
5
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1answer
1k views

Why is the Sun's brightness and radius increasing, but not its temperature?

On the Sun's article on Wikipedia, there is an image showing how the Sun's brightness, radius and temperature have changed over time: For the past (and next) few billion years, I see the luminosity ...
5
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3answers
363 views

If a white dwarf collides with a giant star, could it create a TZO?

Thorne–Żytkow objects (TZOs) form from collisions between neutron stars and main sequence or giant stars. Ultimately, the neutron star becomes the "core" of the giant star. However, could this also ...
5
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1answer
271 views

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 ...
6
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1answer
3k views

How do star densities work?

If we take a look at stars more massive than the Sun, their densities vary a lot. UY Scuti is an extremely low-density star that's only 8.5x more massive than the Sun, but is 1000-2000x its size. ...
4
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1answer
1k views

Does the Sun orbit the Milky way in a (kind of) flat or inclined orbit or more of a sine wave? [duplicate]

I know it can't be a perfect ellipse or smooth orbit due to all the matter in every direction, and our Sun could be affected by a gravity assist of sorts if it passes close enough to another massive ...
1
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1answer
66 views

Realistic space environments [closed]

You've seen it in all kinds of science fiction, be it books, games, movies, and such. Space is depicted all sorts of ways, with asteroids far too close together, nebula thick enough to hide in and ...
1
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1answer
55 views

Trouble understanding speed-dispersion in (elliptical) galaxies

I'm learning about LOSVDs (Line Of Sight Velocity Distributions) and I'm having a bit of trouble understanding the used terms. As I understand, the LOSVD of a given (elliptical) galaxy is the density ...
3
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1answer
153 views

Milky Way stellar number density : is the stated equation in this paper incorrect?

The paper is : http://www.astro.washington.edu/users/ivezic/Publications/tomographyI.pdf The equation is equation #23 in the paper. It's a model for the density of stars in the Milky Way's disk. It ...
12
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3answers
473 views

Metallicity of Celestial Objects: Why “Metal = Non-metal”?

Metallicity of objects refers to the amount of chemical elements present in it other than Hydrogen and Helium. Note: The other elements may or may not be actual ...
4
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3answers
325 views

Pulsation Modes of Cepheids

There are various modes of Cepheids like single modes: fundamental (F), first overtone (1O), and likewise. And then we have double modes: F/1O, 1O/2O etc. triple modes: 1O/2O/3O etc. What ...
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0answers
57 views

Triangular Asterism Trigonometry

Using the SIMBAD database for Alnitak, Saiph, and Sirius -- i.e.: Alnitak: FK5 coord. (J2000): RA = 05 40 45.527 DEC = -01 56 33.26; Saiph; FK5 coord. (J2000): RA = 05 47 45.389 DEC = -09 40 10.58; ...
3
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2answers
568 views

Hamiltonian of general three body problem

i try to extend my analysis from planar restricted three body problem to the general one. Is there anyone that can help me to find out the Hamiltonian for this prolem in cartesian coordinates? I ...
8
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1answer
104 views

How can the life time of a multiple star system, such as for example the trinary system PSR J0337+1715 be derived?

As for example explained at the beginning of this blog post, the trinary system consists of a millisecond pulsar ($1.438$ times the mass of the sun) orbited by two white dwarfs. One of the white ...
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2answers
169 views

On analogies between gas and stellar systems

Analogies between (typically) ideal gas and stellar systems are not only intuitively valid to some extent, but have been established and used in the studies of stellar clusters and galactic systems, ...
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2answers
155 views

Relativistic effects in stellar dynamical systems

I am curious, if anybody knows of any stellar dynamical systems/environments, where relativistic effects could play a dynamical role on the motion of these stellar systems? As a subquestion - are ...