The LIGO Project

(Laser Interferometer Gravitational-Wave Observatory)

Rick Savage – Scientist

LIGO Hanford Observatory

Looking for Gravitational waves, not Electromagnetic waves

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New kind of astronomical observatory

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 Einstein1916

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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 ofgravitational waves

•Open a new observationalwindow on the Universe

Livingston, LA

Hanford, WA

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Movie

http://www.einsteinsmessengers.org/

Detection of gravitational waves

Michelson interferometer- differential length change sensor

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LIGO detectors

Laser

4 km-long Fabry-Perotarm cavity

recyclingmirror test masses

beam splitter

Power recycledMichelsoninterferometerwith Fabry-Perotarm cavities

signal

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Even the most energetic sourceswill generate oscillating length changes in LIGOof about ~10-18 meters

i.e. 0.000000000000000001 meters

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The Challenge for LIGO

How Small is 10-18 Meter?

Wavelength of light, about 1 micron100

One meter, about 40 inches

Human hair, about 100 microns000,10

LIGO sensitivity, 10-18 meter000,1

Nuclear diameter, 10-15 meter000,100

Atomic diameter, 10-10 meter000,10

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H1 detector sensitivity – July 10, 2010

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10-19 meters

S6 science run – July 2009 to October 2010

H1 detector range – July 10, 2010

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Sketch:Kip Thorne

1 Mpc = 1 million parsecs1 parsec ~ 3 light years

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

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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 wayto reject hypothesis of a compact binaryprogenitor in M31”(Isabel Leonor for the LIGO Scientific Collaboration)

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What have we learned so far?

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What’s next? Advanced LIGO

Quantum noise limited interferometer

Factor of 10 increase in sensitivity

Factor of 1000 increase in event rate

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Laser source: 10 W to 200 W

Diode-pumpedYAG lasers

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Vibration isolation: passive to active

• Geophones and accelerometers on payload• Active feedback control – 6 deg. of freedom

• Masses anddamped springs

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Test mass suspensions

• Quadruple pendulumwith reaction masses

• 40 kg test masses

• Single pendulum

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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)