The interstellar medium in our Galaxy.

See Chapter 20 The birth of stars, sections 20-1, 20-2, 20-4, 20-5.

The Trifid Nebula, M20

The dynamic Galaxy

If you look at the Milky Way, it seems to be static and eternal. But observations and analysis suggests that it is dynamic and changing. Gas plays a big role in this.

One part of this dynamic process is that new stars are born from clouds of cool gas. Here is a picture of a ``protoplanetary disk'' in the Orion Nebula, where, it appears, a new star has been born. This disk is about 17 times the diameter of our solar system.

Components of the interstellar medium

How do we see these?

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