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

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 began Nov. 4, »Goal: One year of data at design sensitivity

3 LIGO Observatories

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

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. 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 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 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 Do gravitational waves 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 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 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 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 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 How to Catch Them Laser Interferometer GW: oscillating quadrupolar strain in space

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

16 How Small is Meter? Wavelength of light, about 1 micron One meter, about 40 inches Human hair, about 100 microns LIGO sensitivity, meter Nuclear diameter, meter Atomic diameter, meter

17 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. Laser

18 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

19 Hanford Observatory 4 km 2 km

20 Livingston Observatory 4 km

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

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

23 Seismic Isolation – Springs and Masses damped spring cross section

24 Core Optics Suspension and Control

25 Core Optics Installation and Alignment

26 Remote-controlled Interferometers

27 What have we been doing here at LHO?

28 Hanford 4 km noise budget

29 Recent H1 performance ~ 14 Mpc

30 Daily operations – 24/7

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 Searches running on-line in control room.

33 Like 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 hope to have many times more computing power at low cost

34 Status – March 9,

35 User of the day, March 9, 2006

36 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 (S5)