From an interesting ScienceDaily article, I read this Before the groups of stars

Question

From an interesting ScienceDaily article, I read this

Before the groups of stars disperse, binary stars move through their birth sites and the group studied how they interact with other stars gravitationally. "In many cases the pairs are torn apart into two single stars, in the same way that a pair of dancers might be separated after colliding with another couple on a crowded dance floor," explains Michael Marks, a PhD student and member of the International Max-Planck Research School for Astronomy and Astrophysics. The population of binaries is therefore diminished before the stars spread out into the wider Galaxy.

The stellar nurseries do not all look the same and are crowded to different extents, something described by the density of the group. The more binaries form within the same space (higher density groups), the more interaction will take place between them and the more binary systems will be split up into single stars. This means that every group has a different composition of single and binary stars when the group disperses, depending on the initial density of stars.

Here's the question: what are the types of gravitational interactions that make binary systems split up into single stars?

Explanation / Answer

2-body situations alone (pairs of stars) cannot eject anything, usually. What happens a lot is that a close binary is visited by another star, or by another close binary. The outcome is hard to visualize, but sometimes it ejects one star from the group at high velocity. It could eject one of the binary components, or the visitor - all bets are off.

I used to do simulations like that, way before, and I was always amazed by the speedy rogues that were ejected from populous groups. You could do that yourself with the Universe Sandbox:

http://universesandbox.com/

If you can't setup a binary + singlet collision, just select the galaxy collision and watch the rogues spewed out.

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