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2 years ago in Astrophysics , Galaxy Dynamics By Mehtaab
Can someone explain stellar dynamics and how stars evolve over time?
In my galaxy formation simulations, I use codes that handle 'stellar dynamics' via N-body methods and others that use 'stellar evolution' tracks. I understand they're separate modules, but I'm fuzzy on the precise boundary. What physical processes are unique to the collective gravitational problem of many stars versus the nuclear and structural changes within an individual star?
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By Rahul S Khemnar Answered 1 year ago
This is a crucial distinction in modeling. Stellar dynamics is fundamentally a gravitational N-body problem. We model stars as point masses (or softened potentials) and solve for their orbits under mutual gravity, accounting for processes like two-body relaxation, violent relaxation after a merger, and dynamical friction. The stars themselves don't change. Stellar evolution, in contrast, is a complex initial value problem in nuclear physics, plasma physics, and fluid dynamics. We solve equations for energy generation, transport, and composition change inside a single star. In galaxy simulations, we couple them: the dynamics tells us where the stars are, and evolution libraries tell us their color, luminosity, and when they explode, feeding energy and metals back into the dynamic system.
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