1. The Dark Side of the Universe Lecture 26

2. Homework • Read Ch. 24: Life in the Universe • HW: MasteringAstronomy Chapter 24

3. Final Exam Time: Thursday, Dec 13 at 11:30am in VLSB2050. Topics: - 25% material covered before midterm 1. - 25% material covered between midterms 1 and 2. - 50% material covered after midterm 2. Review Session:  Tuesday, Dec 4 at 5pm in VLSB2050 (same room)

4. Discussion Sectionsand Office Hours

5. Student Evaluations • Thank you for evaluating the course and me (Prof. Geoff Marcy)! Instructor: Geoff Marcy Course: C12 Semester: Fall 2012

6. The Dark Side of the Universe Lecture 26

7. You, me, stars, grey matter, white matter, antimatter… Most of the Universe is Dark

8. How do we know the Universe is Dark? Example 1: Stars would be moving too fast if there were only luminous matter Mercury Earth Jupiter Solar System: “Keplerian orbits”

9. How do we know the Universe is Dark? Example 1: Stars would be moving too fast if there were only luminous matter Galaxies: “Flat rotation curve”

10. How do we know the Universe is Dark? Example 2: Bending of light - gravitational lensing

11. How do we know the Universe is Dark?

12. How do we know the Universe is Dark? Four images of the same galaxy

13. How do we know the Universe is Dark?

14. How do we know the Universe is Dark?

15. How do we know the Universe is Dark? Example 3: Cosmic Microwave Background CMB:very cold (-270.275 C, -454.495 F) and nearly uniform relic radiation left over from the hot big bang

16. How do we know the Universe is Dark? Example 3: Cosmic Microwave Background If you had microwave eyes: (1965)

17. (1992) 17 (2010)

18. How do we know the Universe is Dark? White points: WMAP (2010) 7-year data Red curve: Theoretical prediction for a universe made of 73% dark energy, 23% dark matter, 4% atoms

19. How do we know the Universe is Dark? Example 4: Distant supernovae After Before 19

20. How do we know the Universe is Dark? Example 4: Distant supernovae are standard candles

21. How do we know the Universe is Dark? Example 4: Distant supernovae are standard candles

22. How do we know the Universe is Dark? Kowalski et al (2008) Supernovae probe Dark Energy CMB probes Concordance region: 73% dark energy 23% dark matter 4% atoms Dark Matter

23. Planets? What can dark matter be? Not enough mass: even Jupiter weighs only 0.1% of the Sun Rocks, gas, oceans are all made of quarks. The “normal” stuff cannot be > 4%.

24. Black Holes? What can dark matter be? Graveyards of massive stars, but massive stars are rare and made of normal atoms. Once formed, black holes suck in normal matter. So you can’t hide much dark matter in it.

25. Anti-matter? What can dark matter be? Antimatter and matter have identical mass but opposite quantum numbers (electric charge, spin…) Antimatter and matter annihilate each other into flashes of easily detectable gamma rays Recall PET = Positron Emission Tomography Hardly “dark” !

26. WIMPs What can dark matter be? Top candidate: But it takes more than wimps to find WIMPs! Direct Detection: CDMS-II, Edelweiss etc Accelerator: Large Hadron Collider

27. Cryogenic Dark Matter Search

29. Supernova ExplosionsasStandard Candles Type Ia supernovae, which give off a standard amount of light. The distance to the galaxy that contains the supernova: Compare how bright they know the explosion should be with how bright the explosion appears. Using the inverse square law of light, they can compute the distance to the supernova and thus to the supernova's home galaxy.

31. Accelerating Expansion of the Universe:Dark Energy

32. Large Hadron Collider (17 mile tunnel)

33. You, me, stars, grey matter, white matter, antimatter… Most of the Universe is Dark ??? WIMPS ?