1. The LIGO Project ( Laser Interferometer Gravitational-Wave Observatory) Rick Savage - LIGO Hanford Observatory

2. 2 LIGO Project Collaboration between California Institute of Technology (Caltech) and the Massachusetts Institute of Technology (MIT) Goal: Direct detection of gravitational waves. Open a new observational window to the universe. Funded by the National Science Foundation »~ $365,000,000 - largest project ever funded by NSF S5 Science Run scheduled to begin in October, 2005 »Goal: One year of data at design sensitivity

3. 3 LIGO Observatories

4. 4 Gravitational Waves Predicted by A. Einstein in 1915 – General relativity “Ripples in the curvature of spacetime.”

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

6. 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 for Newtonian gravity! (discovered in 1859) Mercury Sun perihelion Image from Jose Wudka Urbain Le Verrier, discoverer of Mercury’s perihelion shift anomaly Image from St. Andrew’s College

7. 7 Einstein’s Answer: General Relativity  Space and time (spacetime) are curved.  Matter causes this curvature – “matter tells space how to curve”  “Space tells matter how to move”  This looks to us like gravity  General relativity predicts 43 arc sec. of perihelion shift for Mercury due to the curvature of spacetime near the sun. Photo from Northwestern U.

8. 8 Bending of light trajectory by massive objects 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

9. 9 Do they exist? Yes. Observation of energy loss caused by gravitational gadiation 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.

10. 10 Supernova: Death of a Massive Star Spacequake should precede 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 Computer simulations are not quite able to fully model SN implosions. Credit: Dana Berry, NASA

11. 11 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

12. 12 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

13. 13 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

14. 14 How to Catch Them Laser Interferometer GW: oscillating quadrupolar strain in space

15. 15 The Challenge for LIGO Even the most energetic sources will generate length changes in LIGO of about ~10 -18 meters i.e. 0.000000000000000001 meters

16. 16 Distance scale over 34 orders of magnitude

17. 17 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

18. 18 Can we build interferometers that sensitive? 1e-19 m

19. 19 Relative phase measurement via interference Constructive and destructive interference of water waves Light exhibits both particle (photon) and wave (electromagnetic) properties Lasers provide coherent light waves Michelson interferometer splits the wave into two perpendicular paths to interrogate the relative lengths of the arms.

20. 20 Hanford Observatory 4 km 2 km

21. 21 Livingston Observatory 4 km

22. 22 Initial LIGO Interferometers Laser end test mass 4 km (2 km) Fabry-Perot arm cavity recycling mirror input test mass beam splitter Power Recycled Michelson Interferometer with Fabry-Perot Arm Cavities Power Recycled Michelson Interferometer with Fabry-Perot Arm Cavities signal

23. 23 Vacuum chambers: quiet environment for mirrors View inside Corner Station Standing at vertex beam splitter

24. 24 Vibration Isolation Systems »Reduce in-band seismic motion by 4 - 6 orders of magnitude »Compensate for microseism at 0.15 Hz by a factor of ten »Compensate (partially) for Earth tides

25. 25 Seismic Isolation – Springs and Masses damped spring cross section

26. 26 Core Optics Suspension and Control

27. 27 Core Optics Installation and Alignment

28. 28 Remote-controlled Interferometer

29. 29 Initial LIGO Sensitivity Goal Strain sensitivity < 3x10 -23 1/Hz 1/2 at 200 Hz Displacement Noise »Seismic motion »Thermal Noise »Radiation Pressure Sensing Noise »Photon Shot Noise »Residual Gas

30. 30 Real Hanford 4 km noise budget

31. 31 Modeling and data analysis efforts well underway Several LSC analysis groups already setting upper limits on the strength and rate of GW sources »Bursts – e.g. supernovae »Binary inspirals – NS-NS, NS-BH, BH-BH »Periodic sources – e.g. pulsars »Stochastic sources – GW analog of the big bang "Colliding Black Holes" Credit: National Center for Supercomputing Applications (NCSA) Detection of simulated waveforms G. Mendell and M. Landry, LHO

32. 32 http://einstein.phys.uwm.edu/ Like SETI@home, but for LIGO/GEO data 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 many times more computing power at low cost Einstein@home

33. 33 Einstein@home

34. 34 http://einstein.phys.uwm.edu/

35. 35 Advanced LIGO Now being designed by the LIGO Scientific Collaboration Goal: »Quantum-noise-limited interferometer »Factor of ten increase in sensitivity »Factor of 1000 in event rate. One day > entire initial LIGO data run