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

2. Looking for Gravitational waves, not Electromagnetic waves 2 New kind of astronomical observatory

3. General relativity – gravitational waves Laser Interferometer GW: oscillating quadrupolar strain in spacetime “Matter tells spacetime how to curve. Spacetime tells matter how to move.” J. A Wheeler Albert Einstein 1916 3

4. LIGO: Laser Interferometer Gravitational- wave Observatory 3002 km (L/c = 10 ms) Caltech MIT Managed and operated by Caltech & MIT with funding from NSF Goal: Direct observation of gravitational waves Open a new observational window on the Universe Livingston, LA Hanford, WA 4

5. 5 Movie http://www.einsteinsmessengers.org/

6. Detection of gravitational waves Michelson interferometer - differential length change sensor 6

7. LIGO detectors Laser 4 km-long Fabry-Perot arm cavity recycling mirror test masses beam splitter Power recycled Michelson interferometer with Fabry-Perot arm cavities Power recycled Michelson interferometer with Fabry-Perot arm cavities signal 7

8. Even the most energetic sources will generate oscillating length changes in LIGO of about ~10 -18 meters i.e. 0.000000000000000001 meters 8 The Challenge for LIGO

9. 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 9

10. H1 detector sensitivity – July 10, 2010 10 10 -19 meters S6 science run – July 2009 to October 2010

11. H1 detector range – July 10, 2010 11 Sketch: Kip Thorne 1 Mpc = 1 million parsecs 1 parsec ~ 3 light years

12. How Far is 20 MegaParsecs? Speed of light is 300,000,000 meters/second One parsec = 3.26256 light years One year = 365 x 24 x 60 x 60 = 31,536,000 seconds LIGO trying to sense motions of 0.0000000000000000001 meters caused by cosmic events 600,000,000,000,000,000 meters away (36 orders of magnitude in distance) 20 parsec x 3.26256 LY/parsec x 31,536,000 seconds/ LY x 300,000,000 meters/ sec = 617,328,552,960,000,000 meters 12

13. No detections - data still being analyzed Astrophysical results – upper limits »“If LIGO didn’t see it, then it can’t be bigger than …” »CRAB pulsar – “no more than 4 percent of the energy loss of the pulsar is caused by the emission of gravitational waves.” (Caltech press release) »Gamma ray burst GRB070201 – LIGO “results give an independent way to reject hypothesis of a compact binary progenitor in M31” (Isabel Leonor for the LIGO Scientific Collaboration) 13 What have we learned so far?

14. What’s next? Advanced LIGO Quantum noise limited interferometer Factor of 10 increase in sensitivity Factor of 1000 increase in event rate 14

15. 15 Laser source: 10 W to 200 W Diode-pumped YAG lasers

16. Vibration isolation: passive to active 16 Geophones and accelerometers on payload Active feedback control – 6 deg. of freedom Masses and damped springs

17. Test mass suspensions 17 Quadruple pendulum with reaction masses 40 kg test masses Single pendulum

18. 18 Advanced LIGO ~2014 Hubble telescope WFPC2 image (NASA - JPL) Searching (listening) for gravitational waves from cosmic events located 10 times farther away (~500 million light years)