Questions tagged [stellar-dynamics]

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Jeans equation for a fully isotropic velocity dispersion tensor

Given a known spherically symmetric gravitational potential, $\Phi(r)$, I need to calculate the value of the velocity dispersion tensor $\sigma_{rr}$. To calculate $\sigma_{rr}$ I am using Jean's ...
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What is the rotation profile for radiative zone of Sun - Instability and convection?

I am exercising on Stellar Physics topics and in particular the questions below: 1) First of all on the rotation profile for the radiative zone: I know that unlike the convective zone, where the ...
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How does the energy of a solar flare propagate?

Does it radiate outward, spherically, or is it more directed? Is there some opening angle? Is it more complex than this?
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38 views

Population II star orbits

Ok so they are usually found in globular clusters and can consider orbits in a static spherically symmetric gravitational field. The orbits are randomly scattered. Would these be considered to be ...
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193 views

Intuition for the velocity ellipsoid

The velocity ellipsoid is a quantity that comes up in the kinematic modelling of N-body systems, e.g. stars in a galaxy. The velocity dispersion tensor describes the local distribution of velocities ...
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1answer
1k views

Do gravitational many-body systems fall apart eventually?

Imagine an $N$-body problem with lots of particles of identical mass (billions of them). I saw several simulations on the Internet, where the particles first form small clumps, then bigger clumps, ...
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198 views

What is the most commonly used density model for globular clusters?

It is possible to model a globular cluster using a number of different density models: Plummer model King model Isothermal sphere . . . They all have advantages and disadvantages, depending on ...
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2answers
394 views

Population I and II stars

I have been thinking about the formation of the galaxy. I can easily understand that old, low-metallicity stars are in the halo, but I'm missing something when it comes to the disk. If slowly-...
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1answer
220 views

What prevents stars in globular clusters from merging over time to form a black hole?

Globular clusters are apparently very very old, and the density of these clusters appears to increase as one approaches the center of a cluster. Orbits are bound to be chaotic, since there is no ...
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151 views

Could a viable solar system work with a cluster of dwarf stars in center? And would it last longer than a single stellar mass star?

So, I was watching various sci channel shows, and they touch on how extremely massive stars live only 100k years, vs the sun which lives ~10 billion years, and dwarf stars live some unspecified time ...
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255 views

Why do clusters of stars eventually dissipate?

Why don't the stars in a star cluster attract each other gravitationally, forming one big star? What causes a cluster to disperse the stars in it?
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166 views

What are the proposed models for the existence of bars in galaxies?

What are the current explanations and models for the formation of a central bar in some galaxies, and what is the difference that can produce a barred galaxy instead of a spiral one ?