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

LIGO-G W LIGO: Portal to Spacetime2 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 & 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 LIGO: Portal to Spacetime3

LIGO-G W LIGO: Portal to Spacetime4

LIGO-G W LIGO: Portal to Spacetime5 LIGO (Washington)LIGO (Louisiana) The Laser Interferometer Gravitational-Wave Observatory Brought to you by the National Science Foundation; operated by Caltech and MIT; the research focus for more than 500 LIGO Scientific Collaboration members worldwide.

LIGO-G W LIGO: Portal to Spacetime6 LIGO Laboratories Are Unique National Facilities  Observatories at Hanford, WA (LHO) & Livingston, LA (LLO)  Support Caltech & MIT campuses LHO LLO

LIGO-G W LIGO: Portal to Spacetime7 Part of Future 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 LIGO: Portal to Spacetime8 LIGO Laboratory & Science Collaboration LIGO Laboratory (Caltech/MIT) runs observatories and research/support facilities at Caltech/MIT LIGO Scientific Collaboration is the body that defines and pursues LIGO science goals »>400 members at 44 institutions worldwide (including LIGO Lab) »Includes GEO600 members & data sharing »Working groups in detector technology advancement, detector characterization and astrophysical analyses »Memoranda of understanding define duties and access to LIGO data

LIGO-G W LIGO: Portal to Spacetime9 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; Zwicky finds shortage of luminous matter in galaxy clusters »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 »1970’s  Vera Rubin documents “missing mass”, a.k.a. “dark matter” in individual galaxies »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 this and other mysteries

LIGO-G W LIGO: Portal to Spacetime10 Big Questions for 21 st Century Science Images of light from Big Bang imply 95% of the universe is composed of dark matter and dark energy. What is this stuff? The expansion of the universe is speeding up. Is it blowing apart? There are immense black holes at the centers of galaxies. How did they form? What was it like at the birth of space and time? WMAP Image of Relic Light from Big Bang Hubble Ultra-Deep Field

LIGO-G W LIGO: Portal to Spacetime11 A Slight Problem Regardless of what you see on Star Trek, the vacuum of interstellar space does not transmit conventional sound waves effectively. Don’t worry, we’ll work around that!

LIGO-G W LIGO: Portal to Spacetime12 John Wheeler’s Picture of General Relativity Theory

LIGO-G W LIGO: Portal to Spacetime13 General Relativity: A Picture Worth a Thousand Words

LIGO-G W LIGO: Portal to Spacetime14 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 LIGO: Portal to Spacetime15 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 LIGO: Portal to Spacetime17 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 LIGO: Portal to Spacetime18 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 LIGO: Portal to Spacetime19 Supernovae time evolution The Brilliant Deaths of Stars Images from NASA High Energy Astrophysics Research Archive

LIGO-G W LIGO: Portal to Spacetime20 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

LIGO-G W LIGO: Portal to Spacetime21 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

LIGO-G W LIGO: Portal to Spacetime22 Catching Waves From Black Holes Sketches courtesy of Kip Thorne

LIGO-G W LIGO: Portal to Spacetime23 Sounds of Compact Star Inspirals Neutron-star binary inspiral: Black-hole binary inspiral:

LIGO-G W LIGO: Portal to Spacetime24 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 LIGO: Portal to Spacetime25 Searching for Echoes from Very Early Universe Sketch courtesy of Kip Thorne

LIGO-G W How does LIGO detect spacetime vibrations?

LIGO-G W LIGO: Portal to Spacetime27 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 LIGO: Portal to Spacetime28 Laser Beam Splitter End Mirror Screen Viewing Sketch of a Michelson Interferometer

LIGO-G W LIGO: Portal to Spacetime29 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

LIGO-G W LIGO: Portal to Spacetime30 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 LIGO: Portal to Spacetime31 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 LIGO: Portal to Spacetime32 Suspended Mirror Approximates a Free Mass Above Resonance

LIGO-G W LIGO: Portal to Spacetime33 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 LIGO: Portal to Spacetime34 Thermal Noise Observed in 1 st Violins on H2, L1 During S1 Almost good enough for tracking calibration.

LIGO-G W LIGO: Portal to Spacetime35 Vacuum Chambers Provide Quiet Homes for Mirrors View inside Corner Station Standing at vertex beam splitter

LIGO-G W LIGO: Portal to Spacetime36 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 LIGO: Portal to Spacetime37 Seismic Isolation – Springs and Masses damped spring cross section

LIGO-G W LIGO: Portal to Spacetime38 Seismic System Performance Horizontal Vertical HAM stack in air BSC stack in vacuum

LIGO-G W LIGO: Portal to Spacetime39 Evacuated Beam Tubes Provide Clear Path for Light

LIGO-G W LIGO: Portal to Spacetime40 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 LIGO: Portal to Spacetime41 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 LIGO: Portal to Spacetime42 Steps to Locking an Interferometer signal Laser X Arm Y Arm Composite Video

LIGO-G W LIGO: Portal to Spacetime43 Watching the Interferometer Lock for the First Time in October 2000 signal X Arm Y Arm Laser

LIGO-G W LIGO: Portal to Spacetime44 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 LIGO: Portal to Spacetime45 We Have Continued to Progress…

LIGO-G W LIGO: Portal to Spacetime46 And despite a few difficulties, science runs started in 2002…

LIGO-G W LIGO: Portal to Spacetime47 Binary Neutron Stars: S1 Range Image: R. Powell

LIGO-G W LIGO: Portal to Spacetime48 Binary Neutron Stars: S2 Range Image: R. Powell S1 Range

LIGO-G W LIGO: Portal to Spacetime49 Binary Neutron Stars: Initial LIGO Target Range Image: R. Powell S2 Range

LIGO-G W LIGO: Portal to Spacetime50 What’s next? Advanced LIGO… Major technological differences between LIGO and Advanced LIGO Initial Interferometers Advanced Interferometers Open up wider band Reshape Noise Quadruple pendulum Sapphire optics Silica suspension fibers Advanced interferometry Signal recycling Active vibration isolation systems High power laser (180W) 40kg

LIGO-G W LIGO: Portal to Spacetime51 Binary Neutron Stars: AdLIGO Range Image: R. Powell LIGO Range

LIGO-G W LIGO: Portal to Spacetime52 Stops on walking tour: »Show camera images on screen 2 in auditorium »Weber Bar »Beam Tube enclosure & tube segment »Overpass »Control Room

LIGO-G W LIGO: Portal to Spacetime53 Camera shots These are images that come off of the optics inside the vacuum chambers We use a fat beam to minimize dispersion as the beam travels The graininess that you see is due to slight imperfections in the mirrors When we lose lock, the reflections disappear as the light ceases to resonate in the arms

LIGO-G W LIGO: Portal to Spacetime54 Weber Bar One of four bars that Joseph Weber ran simultaneously in 1969 and afterwards to detect grav waves Weber pioneered the field at the University of Maryland Bar is a gift to LIGO from UM 5-ft length, 3-ft diameter, 6500 pounds of Al alloy A grav wave would stretch the atoms out of their positions. They would then recoil from the elastic inter-atomic forces. This effect, taken over all the atoms in the bar, would produce a ringing in the bar like what occurs in a tuning fork. These vibrations would be transmitted to the piezo crystals that are glued to the top of the bar and amplified up to a measurable voltage Bars are narrow-band detectors. Weber searched for GW waves at 1660 Hz in his 1969 paper Using a different bar in 1966, Weber showed that he could measure a stretch in the bar that was the width of an atom (strain of 10^16) and subsequent reports of successful detections were not corraborated LIGO is a broad-band microphone, sensitive to a range of frequencies. Separate mirrors yield a longer baseline and greater sensitivity. Interferometry is a more sensitive technology

LIGO-G W LIGO: Portal to Spacetime55 Beam Tube Segment Tube construction was undertaken by CBI 1-foot width 3/8” low-hydrogen steel was robotically spiral-welded at the Pasco facility into 60-foot sections Sections were trucked to the site and welded together in a portable clean room that moved down the arms Each section was leak-checked, as were the completed tubes Each tube was baked out through electrical heating (~200 C) for ~one month Tubes are insulated and covered by several hundred concrete beam tube enclosures Arms are held at about a trillionth of an atmosphere of vacuum Beams from two interferometers run side-by-side in the tube Tube diameter can accommodate additional beams Bellows are inserted periodically on the arms to allow for expansion/contraction. Horizontal supports hold the tube up

LIGO-G W LIGO: Portal to Spacetime56 Overpass Light stays in the arms for roughly a millisecond during lock ~100 round trips of the light in the arms shrinks and sharpens the dark fringe, increasing our sensitivity Largest-amplitude ground motion is the earth tides, which stretch the arms by ~1/3 mm each tidal cycle. We control the laser wavelength and use fine actuators at the end stations to make sure that the light sees a consistent arm length The microseism is smaller than the tides, somewhat less than a micron, but is much faster (~micron per second). Microseisms are produced by the energy of ocean waves which couples into the sea floor and moves out across land masses We use the voice coil actuators to hold off the microseism. We are implementing a feed- forward strategy to use the tidal actuators to offset the microseism as well We have seismometers in each building and we monitor a host of other environmental effects

LIGO-G W LIGO: Portal to Spacetime57 Control Room Separate control stations for each interferometer All interferometer control is delivered from here via computers ~12,000 data channels send data to the control room. A small subset of these are data from the interferometer itself Additional computers are dedicated to the vacuum system, the electronic log and data monitoring The room next door collects and stores data as it comes in. The Linux cluster in the auditorium building can hold terabytes of data and can be accessed by collaborators for analysis of fresh data. Data is written to tape and archived at Caltech