Life Cycle of a Star

Based on Mass of Star

All Stars – Stage 1-Nebula• Gravity main force, pulls cloud INWARD.• Temperature = INCREASES• Gravity based on MASS OF CLOUD.

Orion’s Nebula

All Stars – Stage 1 - PROTOSTAR• Size DECREASES• Mass becomes more DENSE• Temperature hot enough to give off light.

Protostar

All Stars – Stage 2 – Main Sequence• Nuclear Fusion begins in core.• Heat pushes OUTWARD• Star becomes STABLE• Now a MAIN SEQUENCE STAR

Main Sequence starOur Sun

Nuclear Fusion

• Hydrogen fuses into Helium in the Core.• 4 H 1 He Creates great heat! E = mc2

Red Giant

Medium Mass Star (Sun)-Stage 3• Red Giant– Runs out of hydrogen fuel– Fusion occurs in outer shell causing expansion– Outward pressure GREATER than inward pressure.– Sun will expand out to Mars.– Cools and turns Red.

Medium Mass Star – Final Stage• White Dwarf = Hot but Dim– Red Giant core collapses

• Inward pressure GREATER than outward pressure• Outer shell escapes into space = Planetary Nebula

White Dwarf with Planetary Nebula

Foofing

High Mass Star Stages• First stages the same but more MASSIVE!– Nebula– Protostar– Main sequence

H-R Diagram

• Where would High-Mass main sequence stars be?

High Mass Star Stages• Super Giant– Higher heat and mass allows fusion of heavier elements.

• H He C O Fe

– Outward pressure GREATER than inward pressure– Expands, runs out of fuel and cools = turns Red

Super Giant

High Mass Star – The End• Super Giant runs out of fuel = Core collapses– Inward pressure GREATER than outward pressure

• Core collapse triggers EXPLOSION!– Explosion = SUPER NOVA

Super Nova

High Mass Star – The End• Core continues to collapse– Gravitational force HUGE!– Turns into a NEUTRON STAR

• Gives off pulsing radio waves (called Pulsar)

High Mass Star – The End• Black Hole

– If massive enough:• Continues to collapse into a Black Hole• Inward pressure GREATER than outward pressure

– Gravity so great, light cannot travel fast enough to escape them. – Detected by X-rays emitted by things being pulled in.

Black Hole

Life Expectancy of a Star

• Low Mass Star– 100 Billion years

• Medium Mass Star (our Sun)– 10 Billion years

• High Mass Star– 10 Million years

The Mass of a star determines the length of it’s life. More Mass = Higher energy used = shorter life.

Solar Nebula TheoryA. NebulaB. Main sequence – accretion disk forme

dC. Collision of particles formed clumpsD. Clumps formed asteroidsE. Asteroids became planets

• https://www.youtube.com/watch?v=VW9FJb1HkDU (2:04 min)

https://www.youtube.com/watch?v=PL3YNQK960Y (3:05 min)