What is astrophysical fluid?

The fluid dynamics equations are the same (continuity, conservation of momentum, and energy). What makes peculiar the astrophysical fluids are the huge variety of dynamical conditions (from almost stationary conditions to the need of relativistic fluid dynamics), the possible presence of important magnetic fields (magnetohydrodynamics is a specialized branch of fluid dynamics), and their effects on charged fluids (plasmas), and finally, the vast difference of microscopic regimes, requiring different treatments at the macroscopic level.

Finally, the constitutive equations, providing specific information about the material the fluid is made of, are also widely varying, going from the equation of state of rarified gases to the dense neutron fluid in a neutron star.