1. The Life Cycle
of Stars
(Text Ref. Page )

2. Learning goals We are learning how stars are created or born.
We are learning to identify the stages of a stars lifecycle.

3. The Life Cycle of a Star
the life cycle of a star is determined by its mass

4. Birth & Early Life
all stars begin from a nebula which is a massive cloud of interstellar gas and dust

5. Birth and early life
parts of the nebula collapse on themselves creating a stronger gravitational force
as gravity increases more gas and dust is pulled in eventually forming a protostar

6. Birth and early life
a protostar is a massive concentration of gas and dust

7. Birth and early life
as the mass and gravity increases, it becomes a tightly packed sphere of matter
atoms in core become so tightly packed the pressure rises and nuclear fusion begins (H atoms fuse to form He atoms)

8. Birth & Early Life
outward pressure from the core and the gravity pulling toward the centre of the star counteract
star stabilizes at a particular size

9. Hertzsprung-Russell Diagram
Hertzsprung-Russell Diagram plots absolute magnitude against star surface temperature

10. Main Sequence Phase
90% of stars fit in the main sequence on the Hertzsprung-Russell Diagram
a star spends the majority of its life as a main sequence star undergoing nuclear fusion until its hydrogen is used up

11. Main Sequence Phase
a star then becomes a red giant or a red super giant depending on its mass

12. Old Age
a star with a mass equal to or less than the Sun becomes a Red Giant
red giant: a large, red star at/or near the end of its life cycle

13. Old Age
a star with a mass greater than the Sun becomes a red Supergiant

14. The Death of a Star
A star that has the same or lesser mass than the sun becomes a white dwarf

15. Stars like the Sun white dwarf: a small, hot, dim star
the white dwarf becomes dimmer and dimmer until the light goes out

16. The Death of a Star
A star that has a bigger mass than the Sun becomes a supernova then either a neutron star or a black hole

17. Stars Bigger than the Sun
supernova: a stellar explosion that occurs at the end of a massive star’s life

18. Stars Bigger than the Sun
neutron stars: an extremely dense star made up of tightly packed neutrons results when a massive star collapses

19. Stars Bigger than the Sun
black hole: an extremely dense quantity of matter in space from which no light or matter can escape

20. Learning goals We are learning how stars are created or born.
We are learning to identify the stages of a stars lifecycle.

21. Homework
Page 382 questions 3, 4, 8 , 10