1. The Life of a Star The Life of a Star The Life of a Star

2. Interstellar Gas Cloud
General Composition: 71% Hydrogen, 27% Helium, & 2% other
How does a cloud start forming a star?
Low temperature = low pressure (pushing out)
Leads to gravity being able to collapse the cloud into smaller, warmer, dense clumps

3. Protostar Stage Clumps to Baby star?
As the gas gets pulled in by gravity, a large flat disk with a dense core at the center starts to form
Forms in the infrared & radio
Form in groups = similar age
Protostar Stage

4. Mass Determines Temperature
More mass = more gravity = higher pressure = higher temperatures
Mass Determines Temperature

5. A star’s life is determined by how much mass it has
Low mass stars = under 10 solar masses
High mass stars = over 10 solar masses
1 solar mass = 1 sun
Mass is Key

6. Structure of High vs. Low Mass Stars
Triple Alpha Process: H He
High Mass Stars
CNO cycle: Passes the triple alpha process and moves on to heavier elements like CNO
Structure of High vs. Low Mass Stars

7. You need: 1 cup with 6 marshmallows, a napkin, and 5 pasta noodles
Fusion Demo!

8. What is that?
Nucleosynthesis: formation of heavy elements by nuclear burning process
As temperature increases in the core, heavier elements are fused forming layers of elements
Iron – 1 billion K
Nucleosynthesis

9. Pressure from the formation of new elements presses out while gravity is pushing in
Once gravity wins the star dies
Gravity is everything
Importance of Gravity

10. Once the protostar (baby star) develops H & He fuse forming a main sequence star (yellow dwarf) – like our sun
Once most of the H is fused – gravity wins – the star contracts (gets smaller), increasing the temperature, allowing the star to fuse more He – increasing the pressure – making the star expand to a much larger, cooler size – a red giant
Once that He is used – fuel runs out – star dissolves into space forming a planetary nebula
This leaves behind the bare core – a white dwarf
Low Mass Stars

11. Once the protostar (baby star) develops H, He, and heavier elements fuse forming a giant star
Once most of the elements are fused – gravity wins – the star contracts (gets smaller), increasing the temperature, allowing the star to fuse even heavier elements – increasing the pressure – making the star expand to a much larger, cooler size – a red super giant
Once that fuel runs out – gravity causes the star to collapse on its iron core causing a supernova – leaving behind either a black hole or a neutron star
High Mass Star

12. Under 10 solar masses Over 10 solar masses
Importance of Gravity
Over 10 solar masses