1. Chapter 11 The Formation of Stars

2. 11.1 Making Stars from the Interstellar Medium
Star formation/birth is ongoing in our galaxy:
e.g. sun is younger than oldest stars; short lived stars exist
How does it occur ?
youngest stars found near gas clouds
somehow: large, low-density, cold clouds of gas become
small, high density, hot stars
Gravity is Key

3. 11.1 Making stars from the interstellar medium
Shock Wave- triggers giant molecular clouds to form stars
- this is the astronomical equivalent of a sonic boom
Super nova explosions
Ignition of very hot stars ionize nearby gas
Collision of molecular clouds
Spiral pattern of Milky Way Galaxy – spiral arms are shock waves

4. Giant Molecular Clouds

5. Shocks Triggering Star Formation

6. Protostars
Still enshrouded in opaque “cocoons”of dust => barely visible in the optical, but bright in the infrared.
Protostars= pre-birth state of stars
Hydrogen to Helium fusion not yet ignited

7. ProtostellarDisks
Conservation of angular momentum leads to the formation of protostellardisks⌫birth place of planets and moons

8. Evidence of Star formation
Text pages Summarize the 4 observational types of evidence

9. 11.2 The source of stellar energy
Most stars fuse hydrogen the same way as the sun does, although main sequence stars that are more massive than 1.1. solar masses fuse hydrogen into helium using the CNO cycle.

10. CNO Cycle

11. 11. 3 Stellar Structure
Energy Transport (3 types)

13. What supports the sun? (and other similar stars)
Gravity- strong gravitational pull, pulls atoms towards the center of the sun
The pressure from inside the sun, gases that are produced, prevents the sun from shrinking, by pushing the gases outward
This gravity-pressure balance is called hydrostatic equilibrium

14. Inside Stars

15. 11. 4 The Orion Nebula Summarize star formation in the Orion Nebula
Text pages