LIGO-G W What If We Could Listen to the Stars? Fred Raab LIGO Hanford Observatory

LIGO-G W Listen to the Stars2 LIGO’s Mission is to Open a New Portal on the Universe In 1609 Galileo viewed the sky through a 20X telescope and gave birth to modern astronomy »The boost from “naked-eye” astronomy revolutionized humanity’s view of the cosmos »Ever since, astronomers have “looked” into space to uncover the natural history of our universe LIGO’s quest is to create a radically new way to perceive the universe, by directly listening to the vibrations of space itself LIGO consists of large, earth-based, detectors that will act like huge microphones, listening for the most violent events in the universe

LIGO-G W Listen to the Stars3 LIGO (Washington)LIGO (Louisiana) The Laser Interferometer Gravitational-Wave Observatory Brought to you by the U.S. National Science Foundation; operated by Caltech & MIT; research focus for more than 400 LIGO Scientific Collaboration members worldwide.

LIGO-G W Listen to the Stars4 LIGO Laboratories Are Operated as National Facilities in the US…

LIGO-G W Listen to the Stars5 …And as Part of an International Detector Network LIGO Simultaneously detect signal (within msec) detection confidence locate the sources decompose the polarization of gravitational waves GEO Virgo TAMA AIGO

LIGO-G W Listen to the Stars6 Big Question: What is the universe like now and what is its future? New and profound questions exist after nearly 400 years of optical astronomy »1850’s  Olber’s Paradox: “Why is the night sky dark?” »1920’s  Milky Way discovered to be just another galaxy »1930’s  Hubble discovers expansion of the universe »mid 20 th century  “Big Bang” hypothesis becomes a theory, predicting origin of the elements by nucleosynthesis and existence of relic light (cosmic microwave background) from era of atom formation »1960’s  First detection of relic light from early universe »1990’s  First images of early universe made with relic light »2003  High-resolution images imply universe is 13.7 billion years old and composed of 4% normal matter, 24% dark matter and 72% dark energy; 1 st stars formed 200 million years after big bang. We hope to open a new channel to help study these and other mysteries

LIGO-G W Listen to the Stars7 A Slight Problem Regardless of what you have seen on Star Trek, the vacuum of interstellar space does not transmit conventional sound waves effectively. Don’t worry, General Relativity will allow us to work around that!

LIGO-G W Listen to the Stars8 John Wheeler’s Picture of General Relativity Theory

LIGO-G W Listen to the Stars9 General Relativity: A Picture Worth a Thousand Words

LIGO-G W Listen to the Stars10 The New Wrinkle on Equivalence 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

LIGO-G W Listen to the Stars11 Gravitational Waves Gravitational waves are ripples in space when it is stirred up by rapid motions of large concentrations of matter or energy Rendering of space stirred by two orbiting black holes:

LIGO-G W What Phenomena Do We Expect to Study With LIGO?

LIGO-G W Listen to the Stars13 Gravitational Collapse and Its Outcomes Present LIGO Opportunities f GW > few Hz accessible from earth f GW < several kHz interesting for compact objects

LIGO-G W Listen to the Stars14 Supernovae time evolution The Brilliant Deaths of Stars Images from NASA High Energy Astrophysics Research Archive

LIGO-G W Listen to the Stars15 The “Undead” Corpses of Stars: Neutron Stars and Black Holes Neutron stars have a mass equivalent to 1.4 suns packed into a ball 10 miles in diameter, enormous magnetic fields and high spin rates Black holes are the extreme edges of the space-time fabric Artist: Walt Feimer, Space Telescope Science Institute

LIGO-G W Listen to the Stars16 Catching Waves From Black Holes Sketches courtesy of Kip Thorne

LIGO-G W Listen to the Stars17 Detection of Energy Loss Caused By Gravitational Radiation 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.

LIGO-G W Listen to the Stars18 Sounds of Compact Star Inspirals Neutron-star binary inspiral: Black-hole binary inspiral:

LIGO-G W Listen to the Stars19 Searching for Echoes from Very Early Universe Sketch courtesy of Kip Thorne

LIGO-G W How does LIGO detect spacetime vibrations?

LIGO-G W Listen to the Stars21 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.

LIGO-G W Listen to the Stars22 Laser Beam Splitter End Mirror Screen Viewing Sketch of a Michelson Interferometer

LIGO-G W Listen to the Stars23 Core Optics Suspension and Control Local sensors/actuators provide damping and control forces Mirror is balanced on 1/100 th inch diameter wire to 1/100 th degree of arc Optics suspended as simple pendulums

LIGO-G W Listen to the Stars24 Suspended Mirror Approximates a Free Mass Above Resonance

LIGO-G W Listen to the Stars25 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

LIGO-G W Listen to the Stars26 Vacuum Chambers Provide Quiet Homes for Mirrors View inside Corner Station Standing at vertex beam splitter

LIGO-G W Listen to the Stars27 Vibration Isolation Systems »Reduce in-band seismic motion by orders of magnitude »Little or no attenuation below 10Hz »Large range actuation for initial alignment and drift compensation »Quiet actuation to correct for Earth tides and microseism at 0.15 Hz during observation HAM Chamber BSC Chamber

LIGO-G W Listen to the Stars28 Seismic Isolation – Springs and Masses damped spring cross section

LIGO-G W Listen to the Stars29 Seismic System Performance Horizontal Vertical HAM stack in air BSC stack in vacuum

LIGO-G W Listen to the Stars30 Evacuated Beam Tubes Provide Clear Path for Light

LIGO-G W Listen to the Stars31 All-Solid-State Nd:YAG Laser Custom-built 10 W Nd:YAG Laser, joint development with Lightwave Electronics (now commercial product) Frequency reference cavity (inside oven) Cavity for defining beam geometry, joint development with Stanford

LIGO-G W Listen to the Stars32 Core Optics Substrates: SiO 2 »25 cm Diameter, 10 cm thick »Homogeneity < 5 x »Internal mode Q’s > 2 x 10 6 Polishing »Surface uniformity < 1 nm rms »Radii of curvature matched < 3% Coating »Scatter < 50 ppm »Absorption < 2 ppm »Uniformity <10 -3 Production involved 6 companies, NIST, and LIGO

LIGO-G W Listen to the Stars33 Steps to Locking an Interferometer signal Laser X Arm Y Arm Composite Video

LIGO-G W Listen to the Stars34 Watching the Interferometer Lock for the First Time in October 2000 signal X Arm Y Arm Laser

LIGO-G W Listen to the Stars35 Why is Locking Difficult? One meter, about 40 inches Human hair, about 100 microns Wavelength of light, about 1 micron LIGO sensitivity, meter Nuclear diameter, meter Atomic diameter, meter Earthtides, about 100 microns Microseismic motion, about 1 micron Precision required to lock, about meter

LIGO-G W Listen to the Stars36 LIGO Sensitivity Livingston 4km Interferometer May 01 Jan 03

LIGO-G W Listen to the Stars37 S1 Analysis Working Groups Data from S1 is being analyzed by LSC working groups for: »Detector Characterization – monitors of data quality, instrument diagnostics, tuning displays »Binary Inspirals – modeled chirps from BH’s, NS’s, MACHO’s »Bursts – unmodeled deviations from stationarity; independent searches; searches triggered on GRB’s, SN’s »Periodic Sources – known pulsar search; work toward all-sky search for unknown pulsars »Stochastic Background – early universe

LIGO-G W Listen to the Stars38 Status as of March 2003  First triple coincidence run (S1) completed (17 days with ~23% triple coincidence duty factor)  On-line data analysis systems (Beowulf parallel supercomputer) functional at LHO and LLO  S1 coincidence analyses with GEO & TAMA are first science analyses with international laser-GW network  First science data analysis ongoing  Interferometer control system still being commissioned and tuned, so expect better performance  Working to increase immunity to high seismic noise periods (especially important at LLO)  S2 running 14Feb03 – 14Apr03

LIGO-G W Listen to the Stars39 Future Plans Improve reach of initial LIGO to run 1 yr at design sensitivity Advanced LIGO technology under development with intent to install by 2008 Planning underway for space-based detector, LISA, to open up a lower frequency band ~ 2015

LIGO-G W Listen to the Stars40 And despite a few difficulties, science runs started in 2002…

LIGO-G W Listen to the Stars41 Background Forces in GW Band = Thermal Noise ~ k B T/mode Strategy: Compress energy into narrow resonance outside band of interest  require high mechanical Q, low friction x rms  m f < 1 Hz x rms  2  m f ~ 350 Hz x rms  5  m f  10 kHz

LIGO-G W Listen to the Stars42 Thermal Noise Observed in 1 st Violins on H2, L1 During S1 Almost good enough for tracking calibration.

LIGO-G W Listen to the Stars43 Sensing the Effect of a Gravitational Wave Laser signal Gravitational wave changes arm lengths and amount of light in signal Change in arm length is meters, or about 2/10,000,000,000,000,000 inches