Chapter 20 Between the Stars: Gas and Dust in Space
20.0 Thinking Ahead
![Image of NGC 3603 and Its Parent Cloud. The bright blue stars of the compact star cluster seen just above center in this image have blown a bubble in the gas cloud from which they formed. Part of this reddish cloud is seen in the right hand side and lower center of the frame. Irregular blue clouds and streaks are seen above and to the left of the star cluster.](https://pressbooks.bccampus.ca/practicalphysics1104/wp-content/uploads/sites/302/2017/08/OSC_Astro_20_00_NCGCluster-1.jpg)
Where do stars come from? We already know from earlier chapters that stars must die because ultimately they exhaust their nuclear fuel. We might hypothesize that new stars come into existence to replace the ones that die. In order to form new stars, however, we need the raw material to make them. It also turns out that stars eject mass throughout their lives (a kind of wind blows from their surface layers) and that material must go somewhere. What does this “raw material” of stars look like? How would you detect it, especially if it is not yet in the form of stars and cannot generate its own energy?
One of the most exciting discoveries of twentieth-century astronomy was that our Galaxy contains vast quantities of this “raw material”—atoms or molecules of gas and tiny solid dust particles found between the stars. Studying this diffuse matter between the stars helps us understand how new stars form and gives us important clues about our own origins billions of years ago.