1. Chapter 11: The Interstellar Medium Region in the Constellation Orion named the Orion Nebula which is the closest star formation region to us. Jets and disks appear to be part of the star birth process

2. Chapter 11: The Interstellar Medium The interstellar medium is the region between the stars. It is composed of gas and dust that ultimately are the raw materials from which stars and planetary systems are made. This wide angle photograph of our milky way galaxy shows dark dust lanes cutting through the plane of our galaxy.

3. Chapter 11: The Interstellar Medium Astronomers can determine what the interstellar material is made of, its temperature, and velocity by observing the absorption lines produce when starlight passes through the clouds of material. Blue light is also scattered more easily than red so the red light makes it through better, thus objects appear reddened.

4. Chapter 11: The Interstellar Medium The clouds and dust of the interstellar medium tend to be cold and thin by our standards. Average temperature is 100 K with an average density of one atom per cm 3. On average there is one dust particle for every trillion atoms.

5. Chapter 11: The Interstellar Medium Emission Nebula

6. Chapter 11: The Interstellar Medium Dark Nebula

7. Chapter 11: The Interstellar Medium 21 centimeter radiation is produced when the spins of the electron and proton flip in a Hydrogen atom. Radio astronomers can thus map out the distribution of Hydrogen throughout the galaxy

8. Chapter 11: The Interstellar Medium Star formation take about 10 million years

9. Chapter 11: The Interstellar Medium The emission part of the star formation region is only a small part of the giant cloud.

10. Chapter 11: The Interstellar Medium The Orion Nebula

11. Chapter 11: The Interstellar Medium More Orion Individual stars forming in density fingers

12. Chapter 11: The Interstellar Medium