The Life Cycle of Stars: From Nebula to Black Hole

1. Life Cycle of Stars Stage 1: Nebula – Latin for “cloud” • Nebula – cloud of Hydrogen gas and dust in space, the birthplace of stars • Gas and dust begin to collide, then contract and heat up due to gravity

2. Orion Constellation

3. Orion Nebula

4. Horsehead Nebula in Orion

5. Pleiades Cluster

6. Pleiades Nebula

8. Pleiades Nebula

10. Life Cycle of Stars Stage 2: Protostar • Protostar – As a nebula contracts, a small star is formed • Hydrogen particles fuse together to make Helium (nuclear fusion), a star’s “fuel.”

11. Drawing of a Protostar

12. Hubble image of a Protostar

13. Hubble image of a Protostar

14. Life Cycle of Stars Stage 3: Main Sequence Star • When the force pushing outward (fusion) and the force pulling inward (gravity) are equal, the star joins the main sequence. • Where 90% of stars spend their lives

19. Colors • What makes stars different colors? • Their temperature • Which color is the hottest? • Blue • White • Yellow • Orange • Red • Which color is our sun?

20. Life Cycle of Stars What happens next depends on the star’s mass (size). • Low and Medium mass stars: Stage 4 – Red Giant (Beginning of the end) • A star begins to die when it runs out of Hydrogen in the core. • When the H is depleted, the He starts to fuse, and becomes Carbon and Oxygen. The core contracts, and the outer layers expand. • Red Giant– the star gets bigger and cools down

24. Life Cycle of Stars Stage 5 – Death of Star: • Once a Red Giant gets too massive, it collapses under its own gravity, and the core gets denser and hotter. • Planetary nebula – the outer layers get farther from the core, making the force of gravity weaker. Then they drift off into space.

25. Hourglass Planetary Nebulaaround a dying star

26. Dying Star – “The eye of God”

27. Life Cycle of Stars Stage 5 – Death of Star (cont.) • White dwarf – Once the outer layers have drifted away, all that is left is the dead core (no fusion). • It is small and very dense (1/2 the mass of the sun, but only the size of the Earth).

28. White dwarf compared to the Earth

29. Hubble image of a white dwarf

30. Nebula Protostar Death of Stars: Low and Medium Mass Main Sequence Star Red Giant Planetary Nebula White Dwarf

31. Life Cycle of the Sun • Our sun is a medium sized, main sequence star. • It is a middle-aged star that is yellow in color. • It will eventually become a red giant, planetary nebula, and a white dwarf.

32. Life Cycle of Stars • High Mass Stars: Stage 4 – Supergiant (Beginning of the end) • Supergiant – greater than 10 x’s size of the sun; the core contracts, and the outer layers expand.

33. Supergiant compared to the sun

34. Life Cycle of Stars • Stage 5 – Death of Star: • A supergiant fuses heavier elements (C, O, Mg, N) and gets bigger until it gets to Fe (no more fusion). • Supernova – The core collapses, then the rest of the star collapses, sending a shockwave that creates an explosion.

37. Supernova - Crab Nebula

38. Life Cycle of Stars • Neutron Star – the super dense dead core of a supergiant • It is small and super dense (mass greater than the sun, but the size of a large city).

39. Neutron Star

41. Life Cycle of Stars • Black Hole – When the extremely dense core of a supergiant collapses, the gravity is so strong that not even light can escape.

42. Drawing of a Black Hole

43. Nebula Protostar Death of Stars: High Mass Stars Main Sequence Star Red Super Giant Supernova Neutron Star Black Hole

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