Death of small stars
Planetary nebulae
In a low mass star in its last stage, with a helium burning shell, stellar modelling suggests that the helium burning shell becomes unstable, and
burns in bursts. This causes the star to eject much of its outer layers.
The result is a ``planetary nebula'' which may last for 50,000 years before
it dissapates into space.
Here is some evidence. (Colors in general aren't exactly real in these
pictures.)
- The Egg Nebula,
where this process seems to be going on now. It appears that light gets
out near the poles of the star and is reflected from dust.
- NGC7027. The outer layers
appear to have been ejected in a spherically symmetric fashion; the inner
layers are more disorganized.
- MyCn18, The Hourglass Nebula
- NGC6543, the Cat's Eye Nebula,
a quite complex planetary nebula, possibly associated with a dying member of
a binary system.
Type I supernovae
Davison E. Soper, Institute of Theoretical Science,
University of Oregon, Eugene OR 97403 USA
soper@bovine.uoregon.edu
