Why are there barred spiral galaxies?
Astronomers who construct models of galaxies on supercomputers seem to think
that these galaxies arise from an instability that develops in the stellar
distribution in the nuclear regions of these galaxies. This gravitational
instability causes the orbits of the stars to get locked into a coherent
spatial 'structure' with a bar-like shape. It seems that the strength of the
bar-like instability has something to do with the mass of the nuclear region
such that galaxies with lots of stars in their nuclei are somehow immune from
this instability, while galaxies with small nuclei are prone to developing
it.
Copyright 1997 Dr. Sten Odenwald
Return to
Ask the Astronomer.