Death of big stars and supernovae

Consider a massive star like Betelgeuse. This is the one star that has a large enough size and is near enough (~100 pc) to us that we can see it as a disk with the Hubble Space telescope:

Stars that start out very massive as O and B stars don't live very long. They explode, as we will discuss in some detail.

Type II supernovae

An exploding massive star (say M ~ 20 Msun) produces a very large energy release. Some of this comes in the form of visible light, so that the supernova reaches a peak luminosity of about 109 Lsun which lasts for several days and then fades away over a period of weeks. If it is in our galaxy and not obscured by dust, a supernova can be recognized as a ``new star.''

A supernova leaves behind gas expanding through space, a ``supernova remnant.''

The most famous example is a supernova in the constellation Taurus that exploded on 4 July 1054. (Actually 1054 minus the 6500 year light travel time to Earth.) Observations of this supernova were recorded by Chinese and Japanese astronomers and also (possibly) in an Anasazi rock painting in New Mexico. Europeans seem not to have paid much attention. The left over remnant is called the Crab Nebula.

The filaments are expanding. Doppler shift measurements of the rate of expansion are consistent with an explosion date around 1100 AD.

Here is a small part of another supernova remnant, the Cygnus Loop. Here is another, N123D in the Large Magellenic Cloud.

The story of the star Sanduleak -69o 202

The story of Supernova 1987A.

Importance of Supernovae

Davison E. Soper, Institute of Theoretical Science, University of Oregon, Eugene OR 97403 USA