1. Birth of Stars and Planets 15 March 2016

2. Stars Self-luminous balls of gas Produce energy through nuclear fusion: like a controlled H-bomb Some of this reaches Earth and provides the energy for life

3. © 2014 Pearson Education, Inc. Figure 8.2 Star Forming Region: Stellar Nursery

4. Stellar Nurseries Stars are born in large interstellar clouds of gas: Giant Molecular Clouds Make-up: ¾ Hydrogen, ¼ Helium, 1-2% heavier elements, called ‘metals’ Life is made from the metals! Each cloud can make thousands of stars Stars form in the center of broad spinning disks

5. © 2014 Pearson Education, Inc. Figure 8.1 Stars Life Cycle

6. Eagle Nebula Star-forming Region

7. © 2014 Pearson Education, Inc. Table 8.1 Contents of the Solar Nebula

8. © 2014 Pearson Education, Inc. Figure 8.4 Disks around other stars

9. © 2014 Pearson Education, Inc. Figure 8.4a

10. © 2014 Pearson Education, Inc. Figure 8.4b

11. © 2014 Pearson Education, Inc. Figure 8.3 Stages of Planet Formation

12. Lives of Stars Metals are crucial to life, they are made in stars When a star dies, it returns these to the spaces between stars, the ‘interstellar medium’ New stars incorporate the metals, also into their surrounding disks, where planets form Thus, life depends on the life cycle of stars! ‘We are stardust’ (Joni Mitchell)

15. Stellar nursery in Orion

16. Orion Nebula

17. Protostars in Aquila

18. Protostars erupt

19. Stars form in spiral arms

20. Summary: Birth of Stars Originally only gas and dust, no stars First stars form from Giant Molecular Clouds Later stars include metals essential to life from earlier stars: solid planets possible Stars form in the spiral arms Star forms from disk, then planets too

21. Origin of the Solar System It’s a fundamental problem in astronomy We must explain the characteristics of our own system, and of planets around other stars Elements were made inside stars Stars formed from giant molecular clouds Planets form in a disk around the protostar Giant planets form from accretion onto cores Terrestrial planets are only the cores

22. © 2014 Pearson Education, Inc. Chapter Opener Protoplanetary Disk

23. © 2014 Pearson Education, Inc. Unnumbered Figure 2 Page 229

24. Characteristics of our Solar System Regular planet orbits Planets are closely spaced Terrestrial and Jovian planets Asteroids and comets leftover Satellites and rings imitate a miniature Solar System

25. © 2014 Pearson Education, Inc. Figure 8.5 The Frost Line

26. © 2014 Pearson Education, Inc. Figure 8.6 Planet Formation from Planetesimals

27. © 2014 Pearson Education, Inc. Figure 8.7 METEORITEMETEORITE

28. © 2014 Pearson Education, Inc. Figure 8.8

29. © 2014 Pearson Education, Inc. Figure 8.9 Clean up!

30. © 2014 Pearson Education, Inc. Figure 8.10 Impacts Continue!

31. © 2014 Pearson Education, Inc. Figure 8.11

32. © 2014 Pearson Education, Inc. Figure 8.11a

33. © 2014 Pearson Education, Inc. Figure 8.11b

34. © 2014 Pearson Education, Inc. Figure 8.12 Moon Formation

35. © 2014 Pearson Education, Inc. Unnumbered Figure 4 Page 229

36. © 2014 Pearson Education, Inc. Figure 8.13 Summary

37. © 2014 Pearson Education, Inc. Figure 8.14

38. © 2014 Pearson Education, Inc. Unnumbered Figure 3 Page 229

41. Stages in planet formation Dust collects in the mid-plane of the protoplanetary disk Grows by mutual collisions: ‘accretion’ Planetesimals (about 1km across) grow and collide Giant collisions are the final stage Giant planet cores are bigger outside the frost-line: they attract gas to become gas giants like Jupiter Star ignites: the gas and dust blown away

43. Leftovers Near the Sun (inside frost-line, also known as snow line or ice line) rocky objects become asteroids Far from the Sun (outside frost-line) icy objects form the comets and Kuiper Belt Objects

44. Density waves and propellers in a forming disk

46. Final Cleanup!