Robin Whittle wrote:


Another such objection to quasar cores turning on and off - based on how
a core could possibly be starved of stars at all, and especially how this
starvation could change drastically in less than a million years - is
that the orbital motions of stars are generally a lot slower than this
million year timeframe. I haven't looked at current understandings of
orbital motions in spiral or elliptical galaxies, but if the Sun takes
around 240 million years to orbit our Galaxy, it is hard for me to
imagine that the orbital motions of stars in the middle of any galaxy
could all attain a black-hole avoidant state under any circumstances,
much less gain or lose that state in such a short time.


Some stars within the nuclei of galaxies have orbits only a few parsecs
or tens of parsecs in size, which means that their orbital timescales
can be as short as a few decades. Look, for example, at

http://spiff.rit.edu/classes/phys240.../mwcenter.html

and the references therein (Ghez et al., Nature, vol 407, p. 349 (2000)).

Michael Richmond