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This session at the APS Joint Spring Meeting explores gravitational waves, their origins, and the importance of detecting them. The presentation highlights the current status and future prospects of gravitational wave detectors worldwide.
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Looking towards gravitational wave detection Lisa Barsotti – LIGO/MIT for the Ligo Scientific Collaboration Session APS1: Einstein's Waves and Cosmology 2009 Joint Spring Meeting of the New England of APS and AAPT LIGO-G0900432 Friday–Saturday, May 8–9, 2009; Boston, Massachusetts
Outline • What are Gravitational Waves? Where do they come from? Why do we care? How can we detect them? • Gravitational wave detectors in the world: current status and prospective
2 polarizations propagating at the speed of light Image Credit: K. Thorne (Caltech) , T. Carnahan (NASA GSFC) What Are Gravitational Waves? Ripples in space-time Generated by astrophysical objects with changing mass distribution (supernovae, pulsars, coalescing binary systems BH-BH, NS-NS ) Predicted by General Relativity, indirectly observed, never measured
Why do we care? • New way of exploring the Universe: gravitational wave astrophysics strong field General Relativity (black holes) cosmology: probing the early Universe • Test of General Relativity’s predictions: existence and behavior of GW, quantum gravity (the graviton) Whispers from the early universe Mustafa Amin
How can we detect them? With a set of freely-falling test masses…
h How can we detect them? Michelson Interferometer LASER Photo-detector
VIRGO cluster h Binary NS coalescence Some numbers for ground-based detectors h r ~ 18 Mpc M 1.4M☼ R 20 km forb 400 Hz h ~10-22
h Radius of PROTON How can we detect them? Michelson Interferometer ~ 4km LASER Photo-detector
SUSPENDED MIRRORS LASER Fabry-Perot Cavity Photo-detector A Typical GW Detector
H1 & H2 L1 LIGO Facilities 4km beam tubes
Detector Sensitivity to GW Audio-frequency region: tens of Hz – 10 kHz • Limited by: • Seismic Noise • Thermal Noise • Shot Noise
Coalescence of 2 neutron stars, each of 1 ½ solar masses Prof. SCOTT A. HUGHES (MIT) Unfortunately, real life is MUCH harder than that… Few events expected (~1 every 10 years) • Different sources which require different method of analysis • External disturbances mimic GW signal Detector Sensitivity to GW Livingston control room THERE IT IS…EASY!!!!
GW Sources and Analysis Methods Short Continuous TEMPLATE BINARY INSPIRALS PULSARS UNMODELED BURSTS Stochastic Background See LINDY BLACKBURN’s talk
GEO VIRGO LIGO H1&H2 TAMA LIGO L1 Ground-Based GW Network (2007, Science Run S5-VSR1) Credit: C. Mayhew & R. Simmon (NASA/GSFC), NOAA/ NGDC, DMSP Digital Archive
S2: Feb.- Apr. 2003 59 days BNS reach ~ 1Mpc S3: Oct. ‘03 - Jan. ‘04 70 days BNS reach ~ 3Mpc Science Requirement. document (1995) S1: Aug. - Sep. 2002 17 days BNS reach ~100kpc S4: Feb. - Mar. 2005 30 days BNS reach ~ 15Mpc S5: Nov 2005 – Oct 2007 First Generation Detectors: LIGO
First Generation Detectors: GEO 600 Shorter than LIGO and VIRGO Advanced optical configuration
2006 2007 91% duty cycle 81% 75% single detector, 53% triple coincident The S5/VSR1 Science Run
Initial LIGO 2007 Initial LIGO Enhanced LIGO Advanced LIGO 100 million light years Enhanced LIGO 2009 Credit: R.Powell, B.Berger Advanced LIGO ~2014 Path to Advanced Detectors Detection rate X 1000 ~ A few events per months Courtesy of S. Waldman
From Initial LIGO to Advanced LIGO • Higher input power • Improved readout scheme Enhanced LIGO: NOW!! S6 starting in 2 months • Improved seismic isolation • Advanced optical configuration, bigger mirrors, better coatings to reduce thermal noise, fused silica suspensions…. Installation of Advanced Suspensions (under test at the LASTI facility @ MIT)
From VIRGO to Advanced VIRGO • Similar improvement as for Advanced LIGO • Comparable target sensitivity • Advanced suspensions already installed Virgo +: NOW!! S6/VSR2 starting in 2 months From GEO to GEO HF • Test of Advanced technologies (squeezing) • Tuned for high frequencies Both running with Advanced LIGO in 2013
GEO advVIRGO advLIGO H1&H2 advLIGO L1 ? ? Ground-Based GW Network (~2014) Credit: C. Mayhew & R. Simmon (NASA/GSFC), NOAA/ NGDC, DMSP Digital Archive
Beyond 2015: Space Detectors LISA pathfinder to test LISA technology: 2011 LISA mission: 2019-2020 ? Laser Interferometer Space Antenna Complementary to ground-based detectors
Summary • First generation detectors worked at their design sensitivity • Network of ground-based detectors: common plans, coordinated data analysis effort (S5 data analysis in progress) • Intermediate upgrade under commissioning, new set of data in 2009-2010 (S6) • Second generation detectors on the way • Gravitational wave astronomy is coming!