Close encounters between stars are very rare; only a few of the 1011 stars in a typical galaxy undergo collisions. Nonetheless, encounters between stars play a role in formation of exotic stellar systems. Below are some simple model calculations of stellar encounters.
This simulation presents a slightly off-center parabolic collision of two stars with a mass ratio of 2:1. Initially, each star was modeled as an n = 1.5 polytrope. A total of 49152 equal-mass particles were used; the calculation was run with an adaptive SPH code.
Projected View. The system is viewed along the orbital
axis. Colors indicate the value of the entropy function
a(S); blue indicates low values, while red indicates high
Meridional Slice. Only the 4096 particles nearest the
orbital plane at each instant are shown. Viewing angle and
color scheme are as above. The same slice of 4096 particles is
shown in the following animations as well.
Viscous Dissipation. Here color indicates viscous
dissipation in shocks; dark blue regions are adiabatic, while
bright red indicates the strongest shocks. A meridional slice
Density. Here color indicates gas density; dark blue
regions have the lowest densities, bright red regions have the
highest. A meridional slice is shown.
Internal Energy. Here color indicates internal energy
or temperature; blue regions are cool, red regions are hot. A
meridional slice is shown.