Stars- Evolution

Question 1

Star Evolution Order

Answer 1

1. Main Sequence
2. Red Giant
3. Horizontal Branch Star
4. Asymptotic Giant Branch
5. White Dwarf

Question 2

Main Sequence Star Evolution Stage (5)

Answer 2

• Majority of Star’s Lifetime
• H -> He fusion in core
• Core Temperature increases, Luminosity increases
• Temperature increases through contraction
• T ∝ M/R

Question 3

Red Giant Evolution Stage (5)

Answer 3

• Hydrogen runs out in core
• H fusion in shells around core
• Helium core
• Shells thin out as mass increases
• Core contracts, envelope expands

Question 4

Horizontal Branch Star Evolution Stage (5)

Answer 4

• Helium core contracts and becomes hotter
• He fusion into carbon in core (10^8 K)
• Helium fusion is heat sensitive ~T^40
• Fusion heats up and core inflates
• Envelope contracts, star shrinks and becomes hotter

Question 5

Asymptotic Giant Branch Evolution Stage (6)

Answer 5

• Process repeats until helium runs out
• C/O core
• He/H fusion in outer shells
• Mass is lost as planetary nebula
• Core contracts and gains mass
• Envelope expands once more

Question 6

White Dwarf Evolution Stage (4)

Answer 6

• Star becomes large and luminous
• Ejects large amounts of mass
• No fusion
• Left with C/O core and thin shells of H/He