Fundamental Astronomy by Hannu Karttunen

Fundamental Astronomy by Hannu Karttunen

Author:Hannu Karttunen
Language: eng
Format: epub
Publisher: Springer Berlin Heidelberg


(12.3)

where is the constant of gravity and the stellar radius. For the Sun the thermal time scale is about 20 million years or of the nuclear time scale.

The Dynamical Time Scale

The third and shortest time scale is the time it would take a star to collapse if the pressure supporting it against gravity were suddenly removed. It can be estimated from the time it would take for a particle to fall freely from the stellar surface to the centre. This is half of the period given by Kepler’s third law, where the semimajor axis of the orbit corresponds to half the stellar radius :



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