1. Gravitational Lensing: How to See the Dark J. E. Bjorkman University of Toledo Department of Physics & Astronomy

2. The Dark Between the Light

3. Dark Matter How do we know its there? Answer: It affects the motion of everything we can see. – Cluster Simulation Cluster Simulation – Rotation Velocities Rotation Velocities

4. Galactic Rotation Curves

5. Missing Mass in our Galaxy

6. What is the Dark? MACHOs (Massive Compact Halo Objects) – low mass stars - "brown dwarves" – "almost" stars (planets, e.g. Jupiters) – black holes of less than solar mass – The VW graveyard WIMPs (Weakly Interacting Massive Particles) – heavy neutrinos (10 to 1000 GeV) – new particles predicted by Supersymmetry - 'neutralinos' – exotic particles – e.g. axions (particles with mass < 0.1 eV) Modified Gravity - on galactic scales.

7. Where is the Dark?

8. Gravity Bends Light (Einstien)

9. Gravitational Lenses

10. Einstein tells Eddington gravity bends starlight.

11. Eclipse Astrometry How do we know the stars moved?

12. Relativity Verified

13. Discovery of a Gravitational Lens

14. Galaxies as Lenses

15. A Lensing Simulation

16. A Lens Gallery

17. Galaxy Clusters as Lenses

18. Measuring the Dark 0.5% of Universe is luminous 99.5% of Universe is dark matter

19. “Stellar Lenses” Orion behind a Black Hole

20. Gravitational Microlenses What are microlenses? – Stellar mass (or smaller) lenses – Images are unresovled (milliarcsecond separation) – Lens focuses light – Object appears brighter (several magnitudes!) That’s absurd! – You’ll never see one in a million years! Answer – just look at million stars every night!

21. Microlensing Searches Toward the Magellanic Clouds – MACHO (MAssive CompactHalo Objects collaboration) – EROS (Experience pour la Recherche d'Objets sombres) – DUO (Disk Unseen Objects) Toward the Galactic Bulge – OGLE (Optical Gravitational Lensing Experiment) Toward M31: – AGAPE (Andromeda Galaxy Amplified Pixel Experiment) – MEGA

22. Ogling the Stars

23. AGAPE at M31

24. Looking Through a Lens

25. A Lens in Motion

26. What You Really See

27. Looking for Lenses in Haystacks

28. Frequency of Events

29. How Big is the Lens? How Close did it get?

30. What are They?

31. Follow-Up Monitoring PLANET (Probing Lensing Anomalies NETwork) Garching Spectroscopic Monitoring Group GMAN (Global Microlensing Alert Network) MPS (Microlensing Planet Search Project) MOA (Microlensing Observations in Astrophysics)

32. Looking Through Bifocals Binary Stars as Lenses

33. Binary Stars as Lenses

34. Looking for Planets

35. The Planet Search

36. Micolensing Results They Exist! Future surveys will detect 1/day Fewer than expected toward LMC/SMC – 50% of halo may be Machos (M = 0.5Msun) More than expected toward Galactic center – Masses are few 0.1 Msun – May indicate presence of bar (i.e., Milky Way is a barred spiral) About 10% are binary events Planets – No definite detections, yet – Fewer that 1/3 of lenses have Jupiter-mass planets at 1-4 AU