Searching for Gravitational Waves with LIGO

1. Searching for gravitational waves with LIGOAn introduction to LIGO anda few things gravity waveMichael LandryLIGO Hanford ObservatoryCalifornia Institute of TechnologySpokane Astronomical SocietyNov 2, 2007

2. LIGO in 30 seconds 1. Gravitational Waves: Not EM waves, not particles 2. Gravitational Waves: Never before directly detected

3. Gravitational wave astronomy in 30 seconds

4. Talk overview • Sources • What are gravitational waves? • Why look for them? • Sources: what makes them? • Observatories • LIGO. Networks. • Interferometers • Overview of a Michelson interferometer • Some LIGO installations • Strain curves and Science mode running • Briefly! Einstein@home: a search for continuous gravitational waves

5. Gravity: the Old School Sir Isaac Newton, who invented the theory of gravity and all the math needed to understand it

6. Newton’s theory: good, but not perfect! • Mercury’s orbit precesses around the sun-each year the perihelion shifts 560 arcseconds per century • But this is 43 arcseconds per century too much! (discovered 1859) • This is how fast the second hand on a clock would move if one day lasted 4.3 billion years! Mercury Urbain Le Verrier, discoverer of Mercury’s perihelion shift anomaly Sun Image from St. Andrew’s College perihelion Image from Jose Wudka

7. Einstein’s Answer: General Relativity • Space and time (spacetime) are curved. • Matter causes this curvature • Space tells matter how to move • This looks to us like gravity Picture from Northwestern U.

8. 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 Space is curved. Really. A massive object shifts apparent position of a star

9. 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.

10. Why look for Gravitational Radiation? • Because it’s there! (presumably) • Test General Relativity: • Quadrupolar radiation? Travels at speed of light? • Unique probe of strong-field gravity • Gain different view of Universe: • Sources cannot be obscured by dust / stellar envelopes • Detectable sources some of the most interesting, least understood in the Universe • Opens up entirely new non-electromagnetic spectrum

11. What’s left behind when a star dies? Stars live… Stars die… Ordinary star Supernova And sometimes they leave behind exotic corpses… Black holes (credit : NASA/CXC/A. Hobart) Neutron stars, pulsars (credit : W. Feimer/STSI)

12. What might make Gravitational Waves? • Compact binary inspiral: “chirps” • NS-NS waveforms are well described • BH-BH need better waveforms • Supernovae / GRBs: “bursts” • burst signals in coincidence with signals in electromagnetic radiation / neutrinos • all-sky untriggered searches too • Cosmological Signal: “stochastic background” • Pulsars in our galaxy:“periodic” • search for observed neutron stars • all-sky search (computing challenge)

13. Compact binary inspirals Sources I Neutron-star binary inspiral: Black-hole binary inspiral:

14. Orbital decay:strong indirect evidence Emission of gravitational waves Neutron Binary System – Hulse & Taylor PSR 1913 + 16 -- Timing of pulsars 17 / sec · · ~ 8 hr • Neutron Binary System • separated by ~2x106 km • m1 = 1.44m; m2 = 1.39m; e = 0.617 • Prediction from general relativity • spiral in by 3 mm/orbit • rate of change orbital period

15. Orbital decay:strong indirect evidence Emission of gravitational waves Neutron Binary System – Hulse & Taylor PSR 1913 + 16 -- Timing of pulsars 17 / sec See “Tests of General Relativity from Timing the Double Pulsar” Science Express, Sep 14 2006 The only double-pulsar system know, PSR J0737-3039A/B provides an update to this result. Orbital parameters of the double-pulsar system agree with those predicted by GR to 0.05% · · ~ 8 hr • Neutron Binary System • separated by ~2x106 km • m1 = 1.44m; m2 = 1.39m; e = 0.617 • Prediction from general relativity • spiral in by 3 mm/orbit • rate of change orbital period

16. Burst sources: supernovae Sources II • 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

17. 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

18. “Stochastic” background Sources III A stochastic GW background may be: i) an analog of the CMB (discovered by Penzias and Wilson, measured by COBE and WMAP) ii) a summation of sources from a more recent (astrophysical) epoch Credit: Bell Telephone Laboratories Credit: WMAP science team, NASA

19. Neutron and quark stars Sources IV Continuous GW may be due to: i) neutron stars ii) quark stars with some form of asymmetry

20. 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

21. 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

22. End Mirror End Mirror Beam Splitter Laser Screen Sketch of a Michelson Interferometer Viewing

23. Gravitational Wave Detection • Suspended Interferometers • Suspended mirrors in “free-fall” • Michelson IFO is “natural” GW detector • Broad-band response (~50 Hz to few kHz) • Waveform information (e.g., chirp reconstruction) Fabry-Perot cavity 4km g.w. output port power recycling mirror • LIGO design length sensitivity: 10-18m

24. Gravitational wave changes arm lengths and amount of light in signal Sensing the Effect of a Gravitational Wave Change in arm length is 10-18 meters, or about 2/10,000,000,000,000,000 inches Laser signal

25. LIGO sites LIGO (Washington) (4km and 2km) LIGO (Louisiana) (4km) Funded by the National Science Foundation; operated by Caltech and MIT; the research focus for more than 500 LIGO Scientific Collaboration members worldwide.

26. The LIGO Observatories • Adapted from “The Blue Marble: Land Surface, Ocean Color and Sea Ice” at visibleearth.nasa.gov • NASA Goddard Space Flight Center Image by Reto Stöckli (land surface, shallow water, clouds). Enhancements by Robert Simmon (ocean color, compositing, 3D globes, animation). Data and technical support: MODIS Land Group; MODIS Science Data Support Team; MODIS Atmosphere Group; MODIS Ocean Group Additional data: USGS EROS Data Center (topography); USGS Terrestrial Remote Sensing Flagstaff Field Center (Antarctica); Defense Meteorological Satellite Program (city lights). LIGO Hanford Observatory (LHO) H1 : 4 km arms H2 : 2 km arms 10 ms LIGO Livingston Observatory (LLO) L1 : 4 km arms

27. An International Network of Interferometers Simultaneously detect signal (within msec) Virgo GEO LIGO TAMA detection confidence locate the sources decompose the polarization of gravitational waves AIGO (proposed)

28. Vacuum Chambers Provide Quiet Homes for Mirrors View inside Corner Station Standing at vertex beam splitter

29. All-Solid-State Nd:YAG Laser Custom-built 10 W Nd:YAG Laser, joint development with Lightwave Electronics (now commercial product) Cavity for defining beam geometry, joint development with Stanford Frequency reference cavity (inside oven)

30. Core Optics Suspension and Control Optics suspended as simple pendulums Shadow sensors & voice-coil actuators provide damping and control forces Mirror is balanced on 30 micron diameter wire to 1/100th degree of arc

31. Evacuated Beam Tubes Provide Clear Path for Light Vacuum required: <10-9 Torr

32. Evacuated Beam Tubes Provide Clear Path for Light • Bakeout facts: • 4 loops to return current, 1” gauge • 1700 amps to reach temperature • bake temp 140 degrees C for 30 days • 400 thermocouples to ensure even heating • each site has 4.8km of weld seams • full vent of vacuum: ~ 1GJ of energy Vacuum required: <10-9 Torr

33. damped springcross section Seismic Isolation – Springs and Masses

34. 102 100 10-2 10-6 Horizontal 10-4 10-6 10-8 Vertical 10-10 LIGO detector facilities Seismic Isolation • Multi-stage (mass & springs) optical table support gives 106 suppression • Pendulum suspension gives additional 1 / f 2 suppression above ~1 Hz Transfer function Frequency (Hz)

35. Interferometer Length Control System • Multiple Input / Multiple Output • Three tightly coupled cavities • Employs adaptive control system that evaluates plant evolution and reconfigures feedback paths and gains during lock acquisition 4km (photodiode)

36. S1 S2 S3 S4 S5 - current 15Mpc Calibrated output: LIGO noise history 80kpc 1Mpc S1 S2 Curves are calibrated interferometer output: spectral content of the gravity-wave channel

37. The road to design sensitivity…

38. 2 2 2 2 4 4 4 4 1 1 1 1 3 3 3 3 10-21 10-22 E3 E7 E5 E9 E10 E8 Runs S1 S2 S3 S4 S5 Science First Science Data Time line 2007 1999 2000 2001 2002 2003 2004 2005 2006 2 4 2 4 4 1 3 1 3 2 4 3 1 3 Inauguration First Lock Full Lock all IFO Now 4K strain noise at 150 Hz [Hz-1/2] 10-17 10-18 10-20 E2 E11 Engineering Coincident science runs with GEO and TAMA

39. LIGO Hanford control room

40. Einstein@home • Like SETI@home, but for LIGO/GEO data • American Physical Society (APS) publicized as part of World Year of Physics (WYP) 2005 activities • Use infrastructure/help from SETI@home developers for the distributed computing parts (BOINC) • Goal: pulsar searches using ~1 million clients. Support for Windows, Mac OSX, Linux clients • From our own clusters we can get ~ thousands of CPUs. From Einstein@home hope to get order(s) of magnitude more at low cost • Great outreach and science education tool • Currently : ~160,000 active users corresponding to about 85Tflops, about 200 new users/day http://einstein.phys.uwm.edu/

41. What would a pulsar look like? • Post-processing step: find points on the sky and in frequency that exceeded threshold in many of the sixty ten-hour segments • Software-injected fake pulsar signal is recovered below Simulated (software) pulsar signal in S3 data

42. Final S3 analysis results • Data: 60 10-hour stretches of the best H1 data • Post-processing step on centralized server: find points in sky and frequency that exceed threshold in many of the sixty ten-hour segments analyzed • 50-1500 Hz band shows no evidence of strong pulsar signals in sensitive part of the sky, apart from the hardware and software injections. There is nothing “in our backyard”. • Outliers are consistent with instrumental lines. All significant artifacts away from r.n=0 are ruled out by follow-up studies. WITH INJECTIONS WITHOUT INJECTIONS

43. Summary remarks • LIGO achieved design sensitivity in Nov 05, a major milestone • LIGO/GEO then launched the coincident S5 science run, which is to ran until Sep 30, 2007 • Host of searches underway: analyses ongoing of S3, S4, and S5 data – no detections yet! • Future: • Enhanced LIGO upgrade slated for fall 2007-spring 2009, factor of 2-3 in sensitivity improvement • Advanced LIGO upgrade slated for ~2011 to dramatically improve sensitivity We should be detecting gravitational waves regularly within the next 10 years!

44. A hope for the near future: The Beginning of a New Astronomy… LIGO - Virgo LIGO+ Virgo+ AdvLIGO AdvVirgo