Quote:
Originally Posted by sjastro
Chris,
Unfortunately the "pop culture" article left more questions than answers.
The Nature paper assumes a basic knowledge of Stellar Dynamics.
In gravitational bound stellar systems such as open and globular clusters, stars interact with each other and exchange momentum and kinetic energy.
The more massive the star the less the velocity hence massive stars tend to be in lower orbits and occupy the centre of the cluster.
This is the mass segregation term mentioned in the article.
Since stars exchange kinetic energy there is a statistical tendency for the kinetic energy to equalize amongst stars.
This is the energy equipartition description in the article.
The time taken for equalization to occur is the relaxation time.
Since kinetic energy is equalized, the lower mass stars receive a larger velocity boost and can exceed the escape velocity of the cluster.
These are the familiar "star streamers" found in globular cluster images.
Other stars are pushed out into higher orbits.
The presence of a black hole at the centre changes the mass segregation and alters the velocity distribution of stars versus distance from the centre of the cluster.
The data is gathered from pulsars in the cluster.
Pulsars closer to the centre of cluster have their rotations slowed down by gravity which can measured as a Doppler shift.
From this the velocity distribution versus the distance from the centre can be determined.
Regards
Steven
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Interesting, I visualized it as a drain whirlpool in reverse. Excuse my interpretation if I have the image wrong.