1. Adaptive Optics for Astronomy Kathy Cooksey

2. AO Basics Photons –Travel in straight lines Wavefront –Line perpendicular to all photons’ paths Atmospheric turbulence –Due to temperature differences –Acts like many lenses –Distorts wavefront AO System –Corrects wavefront –Makes it linear

3. Photons Travel in Straight Lines

4. Wavefronts

5. Atmospheric Turbulence

6. Lick Observatory, 1 m telescope Long exposure image Short exposure image “Perfect” image: diffraction limit of telescope Distant stars should resemble “points” if it were not for turbulence in Earth’s atmosphere

7. Speckle Images Turbulence changes rapidly with time Sequence of short snapshots of star Much slower than real time Applied Optics Group (Imperial College), Herschel 4.2-m Telescope

8. AO Straighten Wavefront BEFORE AFTER Incoming, distorted wavefront (“aberrated”) DEFORMABLE MIRROR Corrected wavefront

9. AO in Action Lick Observatory adaptive optics system Star without adaptive optics Star with adaptive optics

10. AO Specifics: Correcting for Atmosphere and Improving Images Even the largest ground-based astronomical telescopes have no better resolution than an 8” backyard telescope!

11. Basic AO Process (a) Measure details of blurring from “guide star” near object you want to observe (b) Calculate shape to apply to deformable mirror to correct blurring (c) Light from both guide star and astronomical object is reflected from deformable mirror

12. Schematic of AO System

13. Gemini: AO in “Action”

14. How to Measure Distortion Shack-Hartmann Wavefront Sensor …you will see this again

15. Ground-based AO Complements Space Telescopes Advantages of AO on 8-10 m ground-based telescopes Four times better spatial resolution in infrared Better faint-object sensitivity at wavelengths > 2 microns Outstanding infrared spectroscopy –Higher spectral & spatial resolution Advantages of 2.4 m Hubble Space Telescope Full wavelength coverage, from UV to visible to near- infrared light Can “see” virtually whole sky More precise brightness measurements Very sensitive spectroscopy for faint objects in infrared –Lower spectral & spatial resolution

16. Beautiful AO Images

17. Satellites for the Small Adaptive Optics has opened up study of smaller bodies of solar system Double Asteroid 90 AntiopeEugenia and its moon Merine et al. CFHTMerine et al. Keck

18. Neptune at 1.65 microns Without adaptive optics With Keck adaptive optics June 27, 1999 2.3 arc sec May 24, 1999

19. Neptune Movie AO allows us to monitor weather on outer planets Institute for Astronomy (University of Hawaii) CFHT

20. Titan Occults Two Stars Occultation is when planet or moon passes in front of star Original Titan “subtracted”

21. Sharmer et al. Swedish Solar Vacuum Telescope Lightbridges on Sun Lightbridges discovered with AO Those shown are ~5000 km in length –Golden Gate ~2 km Believed to be “normal” solar granulation that penetrates strongly magnetic sunspot umbras

22. AO Reveals Faint Companions to Bright Stars Mike Brown (CalTech)

23. Galactic Center UCLA Galactic Center Group

24. Evidence for Black Hole at Center of Milky Way Black hole is revealed by presence of fast moving stars at small radii Stellar orbits in central parsec, 1995-2006

25. NGC 6934 from Gemini North Adaptive Optics allows us to discern separate stars in crowded cores of globular clusters Gemini Obs., NSF, & U. Hawaii IfA

26. Summary of Astronomical AO Remove effect of atmospheric turbulence –“Twinkle” of stars Must “sense” blurring of star –Either real or laser “star” Computers calculate how to correct light –Send this signal to deformable mirror Resulting performance can equal or exceed Hubble Space Telescope in some areas Astronomers use AO to study asteroids, moons, planets, stars, and galaxies

27. More AO Tidbits

28. Titan’s Surface at Keck Without AO Typical at 1.65 μm With AO At 1.581 μm (surface window)

29. Surface Reflectivity Model inputs: Haze optical depth Optical properties of haze particles (varies with depth) Model outputs: Image of atmosphere Atmospheric properties: Haze optical depth, variation with altitude AO image Surface albedo map Model image of atmosphere

30. AO Image Sequence of 216 Kleopatra Movie of the asteroid Kleopatra, observed during seven-hour period with CFHT AO System Merine et al. CFHT

31. Extra-Solar Planetary System Science with AO Dust disks as signatures of planetary systems Close-up views of forming planetary systems Detection and characterization of planets

32. eXtreme Adaptive Optics Planet Imager XAOPI project (in progress) System at Keck observatory First images of extra- solar planets