1. LIGO-G020518-02-W What If We Could Listen to the Stars? Fred Raab LIGO Hanford Observatory

2. LIGO-G020518-02-W What If We Could Listen to Stars?2 LIGO’s Mission is to Open a New Portal on the Universe In 1609 Galileo viewed the sky through a 20X telescope and gave birth to modern astronomy »The boost from “naked-eye” astronomy revolutionized humanity’s view of the cosmos & astronomers have “looked” into space to uncover the natural history of our universe LIGO’s quest is to create a radically new way to perceive the universe, by directly listening to the vibrations of space itself LIGO consists of large, earth-based, detectors that will act like huge microphones, listening for the most violent events in the universe

3. LIGO-G020518-02-W What If We Could Listen to Stars?3 LIGO (Washington)LIGO (Louisiana) The Laser Interferometer Gravitational-Wave Observatory Brought to you by the National Science Foundation; operated by Caltech and MIT; the research focus for more than 500 LIGO Scientific Collaboration members worldwide.

4. LIGO-G020518-02-W What If We Could Listen to Stars?4 LIGO Laboratories Are Unique National Facilities  Observatories at Hanford, WA (LHO) & Livingston, LA (LLO)  Support Facilities @ Caltech & MIT campuses LHO LLO

5. LIGO-G020518-02-W What If We Could Listen to Stars?5 Part of Future International Detector Network LIGO Simultaneously detect signal (within msec) detection confidence locate the sources decompose the polarization of gravitational waves GEO Virgo TAMA AIGO

6. LIGO-G020518-02-W What If We Could Listen to Stars?6 Big Question: What is the universe like now and what is its future? New and profound questions exist after nearly 400 years of optical astronomy »1920’s  Milky Way discovered to be just another galaxy »1930’s  Hubble discovers expansion of the universe; Zwicky finds shortage of luminous matter in galaxy clusters »mid 20 th century  “Big Bang” hypothesis becomes a theory, predicting origin of the elements by nucleosynthesis and existence of relic light (cosmic microwave background) from era of atom formation »1960’s  First detection of relic light from early universe »1970’s  Vera Rubin documents “missing mass”, a.k.a. “dark matter” in individual galaxies »1990’s  First images of early universe made with relic light »2003  High-resolution images imply universe is 13.7 billion years old and composed of 4% normal matter, 24% dark matter and 72% dark energy; 1 st stars formed 200 million years after big bang. We hope to open a new channel to help study this and other mysteries

7. LIGO-G020518-02-W What If We Could Listen to Stars?7 Big Questions for 21 st Century Science Images of light from Big Bang imply 95% of the universe is composed of dark matter and dark energy. What is this stuff? The expansion of the universe is speeding up. Is it blowing apart? There are immense black holes at the centers of galaxies. How did they form? What was it like at the birth of space and time? WMAP Image of Relic Light from Big Bang Hubble Ultra-Deep Field

8. LIGO-G020518-02-W What If We Could Listen to Stars?8 A Slight Problem Regardless of what you see on Star Trek, the vacuum of interstellar space does not transmit conventional sound waves effectively. Don’t worry, we’ll work around that!

9. LIGO-G020518-02-W What If We Could Listen to Stars?9 John Wheeler’s Picture of General Relativity Theory

10. LIGO-G020518-02-W What If We Could Listen to Stars?10 General Relativity: A Picture Worth a Thousand Words

11. LIGO-G020518-02-W What If We Could Listen to Stars?11 The New Wrinkle on Equivalence Not only the path of matter, but even the path of light is affected by gravity from massive objects Einstein Cross Photo credit: NASA and ESA A massive object shifts apparent position of a star

12. LIGO-G020518-02-W What If We Could Listen to Stars?12 Gravitational Waves Gravitational waves are ripples in space when it is stirred up by rapid motions of large concentrations of matter or energy Rendering of space stirred by two orbiting black holes:

13. LIGO-G020518-02-W What Phenomena Do We Expect to Study With LIGO?

14. LIGO-G020518-02-W What If We Could Listen to Stars?14 Gravitational Collapse and Its Outcomes Present LIGO Opportunities f GW > few Hz accessible from earth f GW < several kHz interesting for compact objects

15. LIGO-G020518-02-W What If We Could Listen to Stars?15 Supernova: Death of a Massive Star Spacequake should preceed optical display by ½ day Leaves behind compact stellar core, e.g., neutron star, black hole Strength of waves depends on asymmetry in collapse Observed neutron star motions indicate some asymmetry present Simulations do not succeed from initiation to explosions Credit: Dana Berry, NASA

16. LIGO-G020518-02-W What If We Could Listen to Stars?16 The “Undead” Corpses of Stars: Neutron Stars and Black Holes Neutron stars have a mass equivalent to 1.4 suns packed into a ball 10 miles in diameter, enormous magnetic fields and high spin rates Black holes are the extreme edges of the space-time fabric Artist: Walt Feimer, Space Telescope Science Institute

17. LIGO-G020518-02-W What If We Could Listen to Stars?17 Gravitational-Wave Emission May be the “Regulator” for Accreting Neutron Stars Neutron stars spin up when they accrete matter from a companion Observed neutron star spins “max out” at ~700 Hz Gravitational waves are suspected to balance angular momentum from accreting matter Credit: Dana Berry, NASA

18. LIGO-G020518-02-W What If We Could Listen to Stars?18 Catching Waves From Black Holes Sketches courtesy of Kip Thorne

19. LIGO-G020518-02-W What If We Could Listen to Stars?19 Detection of Energy Loss Caused By Gravitational Radiation In 1974, J. Taylor and R. Hulse discovered a pulsar orbiting a companion neutron star. This “binary pulsar” provides some of the best tests of General Relativity. Theory predicts the orbital period of 8 hours should change as energy is carried away by gravitational waves. Taylor and Hulse were awarded the 1993 Nobel Prize for Physics for this work.

20. LIGO-G020518-02-W What If We Could Listen to Stars?20 Sounds of Compact Star Inspirals Neutron-star binary inspiral: Black-hole binary inspiral:

21. LIGO-G020518-02-W What If We Could Listen to Stars?21 Searching for Echoes from Very Early Universe Sketch courtesy of Kip Thorne

22. LIGO-G020518-02-W How does LIGO detect spacetime vibrations?

23. LIGO-G020518-02-W What If We Could Listen to Stars?23 Important Signature of Gravitational Waves Gravitational waves shrink space along one axis perpendicular to the wave direction as they stretch space along another axis perpendicular both to the shrink axis and to the wave direction.

24. LIGO-G020518-02-W What If We Could Listen to Stars?24 Laser Beam Splitter End Mirror Screen Viewing Sketch of a Michelson Interferometer

25. LIGO-G020518-02-W What If We Could Listen to Stars?25 Core Optics Suspension and Control Local sensors/actuators provide damping and control forces Mirror is balanced on 1/100 th inch diameter wire to 1/100 th degree of arc Optics suspended as simple pendulums

26. LIGO-G020518-02-W What If We Could Listen to Stars?26 Suspended Mirror Approximates a Free Mass Above Resonance

27. LIGO-G020518-02-W What If We Could Listen to Stars?27 How Small is 10 -18 Meter? Wavelength of light, about 1 micron One meter, about 40 inches Human hair, about 100 microns LIGO sensitivity, 10 -18 meter Nuclear diameter, 10 -15 meter Atomic diameter, 10 -10 meter

28. LIGO-G020518-02-W What If We Could Listen to Stars?28 Vacuum Chambers Provide Quiet Homes for Mirrors View inside Corner Station Standing at vertex beam splitter

29. LIGO-G020518-02-W What If We Could Listen to Stars?29 Vibration Isolation Systems »Reduce in-band seismic motion by 4 - 6 orders of magnitude »Little or no attenuation below 10Hz »Large range actuation for initial alignment and drift compensation »Quiet actuation to correct for Earth tides and microseism at 0.15 Hz during observation HAM Chamber BSC Chamber

30. LIGO-G020518-02-W What If We Could Listen to Stars?30 Seismic Isolation – Springs and Masses damped spring cross section

31. LIGO-G020518-02-W What If We Could Listen to Stars?31 Seismic System Performance 10 2 10 0 10 - 2 10 - 4 10 - 6 10 - 8 10 -10 Horizontal Vertical 10 -6 HAM stack in air BSC stack in vacuum

32. LIGO-G020518-02-W What If We Could Listen to Stars?32 Evacuated Beam Tubes Provide Clear Path for Light

33. LIGO-G020518-02-W What If We Could Listen to Stars?33 All-Solid-State Nd:YAG Laser Custom-built 10 W Nd:YAG Laser, joint development with Lightwave Electronics (now commercial product) Frequency reference cavity (inside oven) Cavity for defining beam geometry, joint development with Stanford

34. LIGO-G020518-02-W What If We Could Listen to Stars?34 Core Optics Substrates: SiO 2 »25 cm Diameter, 10 cm thick »Homogeneity < 5 x 10 -7 »Internal mode Q’s > 2 x 10 6 Polishing »Surface uniformity < 1 nm rms »Radii of curvature matched < 3% Coating »Scatter < 50 ppm »Absorption < 2 ppm »Uniformity <10 -3 Production involved 6 companies, NIST, and LIGO

35. LIGO-G020518-02-W What If We Could Listen to Stars?35 Sensing the Effect of a Gravitational Wave Laser signal Gravitational wave changes arm lengths and amount of light in signal Change in arm length is 10 -18 meters, or about 2/10,000,000,000,000,000 inches

36. LIGO-G020518-02-W What If We Could Listen to Stars?36 Steps to Locking an Interferometer signal Laser X Arm Y Arm Composite Video

37. LIGO-G020518-02-W What If We Could Listen to Stars?37 Watching the Interferometer Lock for the First Time in October 2000 signal X Arm Y Arm Laser

38. LIGO-G020518-02-W What If We Could Listen to Stars?38 Why is Locking Difficult? One meter, about 40 inches Human hair, about 100 microns Wavelength of light, about 1 micron LIGO sensitivity, 10 -18 meter Nuclear diameter, 10 -15 meter Atomic diameter, 10 -10 meter Earthtides, about 100 microns Microseismic motion, about 1 micron Precision required to lock, about 10 -10 meter

39. LIGO-G020518-02-W What If We Could Listen to Stars?39 Background Forces in GW Band = Thermal Noise ~ k B T/mode Strategy: Compress energy into narrow resonance outside band of interest  require high mechanical Q, low friction x rms  10 -11 m f < 1 Hz x rms  2  10 -17 m f ~ 350 Hz x rms  5  10 -16 m f  10 kHz

40. LIGO-G020518-02-W What If We Could Listen to Stars?40 Thermal Noise Observed in 1 st Violins on H2, L1 During S1 Almost good enough for tracking calibration.

41. LIGO-G020518-02-W What If We Could Listen to Stars?41 We Have Continued to Progress…

42. LIGO-G020518-02-W What If We Could Listen to Stars?42 And despite a few difficulties, science runs started in 2002…

43. LIGO-G020518-02-W What If We Could Listen to Stars?43 Binary Neutron Stars: S1 Range Image: R. Powell

44. LIGO-G020518-02-W What If We Could Listen to Stars?44 Binary Neutron Stars: S2 Range Image: R. Powell S1 Range

45. LIGO-G020518-02-W What If We Could Listen to Stars?45 Binary Neutron Stars: Initial LIGO Target Range Image: R. Powell S2 Range

46. LIGO-G020518-02-W What If We Could Listen to Stars?46 What’s next? Advanced LIGO… Major technological differences between LIGO and Advanced LIGO Initial Interferometers Advanced Interferometers Open up wider band Reshape Noise Quadruple pendulum Sapphire optics Silica suspension fibers Advanced interferometry Signal recycling Active vibration isolation systems High power laser (180W) 40kg

47. LIGO-G020518-02-W What If We Could Listen to Stars?47 Binary Neutron Stars: AdLIGO Range Image: R. Powell LIGO Range