Direct observa1on of gravita1onal waves from the merger and inspiral of two black holes Bruce Allen Max Planck Ins1tute for Gravita1onal Physics (Albert Einstein Ins1tute, AEI) February 12, 2016 Gravita1onal waves: the discovery which shows that Einstein was right Avignon 24.4.2017 2 Outline • Brief introduc7on to gravita7onal waves • On 14 September 2015, 4 days before star7ng its first observa7onal run O1, Advanced LIGO recorded a strong gravita7onal wave burst • Source unambiguous. In source frame: merger of a 29 and 36 solar mass BH • What did we see? How do we know it is two black holes? How can we be sure it is real? What was going on “behind the scenes”? What do we learn? Other discoveries from O1 • Status of O2, prospects for the future References: PRL 116, 061102 (2016); PRX 6, 041015 (2016); Annalen der Physik, 529, 1600209 (2017). Avignon 24.4.2017 3 Discovery Paper Selected for a Viewpoint in Physics week ending PRL 116, 061102 (2016) PHYSICAL REVIEW LETTERS 12 FEBRUARY 2016 “In the first 24 hours, not Observation of Gravitational Waves from a Binary Black Hole Merger B. P. Abbott et al.* (LIGO Scientific Collaboration and Virgo Collaboration) only was the page for (Received 21 January 2016; published 11 February 2016) On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in frequency from 35 to 250 Hz with a peak gravitational-wave strain of 1.0 × 10−21. It matches the waveform your PRL abstract hit predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203 000 years, equivalent to a significance greater 160 0.03 380,000 @mes, but the than 5.1σ. The source lies at a luminosity distance of 410þ Mpc corresponding to a redshift z 0.09þ . −180 −0.04 5 4 ¼ In the source frame, the initial black hole masses are 36−þ4 M and 29−þ4 M , and the final black hole mass is 4 0.5 2 ⊙ ⊙ 62−þ4 M , with 3.0−þ0.5 M c radiated in gravitational waves. All uncertainties define 90% credible intervals. PDF of the paper was These observations⊙ demonstrate⊙ the existence of binary stellar-mass black hole systems. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger. downloaded 230,000 DOI: 10.1103/PhysRevLett.116.061102 I. INTRODUCTION The discovery of the binary pulsar system PSR B1913 16 þ @mes. This is far more hits In 1916, the year after the final formulation of the field by Hulse and Taylor [20] and subsequent observations of equations of general relativity, Albert Einstein predicted its energy loss by Taylor and Weisberg [21] demonstrated the existence of gravitational waves. He found that the existence of gravitational waves. This discovery, than any PRL ever, anD the linearized weak-field equations had wave solutions: along with emerging astrophysical understanding [22], transverse waves of spatial strain that travel at the speed of led to the recognition that direct observations of the light, generated by time variations of the mass quadrupole amplitude and phase of gravitational waves would enable the frac@on of @mes that moment of the source [1,2].Einsteinunderstoodthat studies of additional relativistic systems and provide new gravitational-wave amplitudes would be remarkably tests of general relativity, especially in the dynamic small; moreover, until the Chapel Hill conference in strong-field regime. 1957 there was significant debate about the physical Experiments to detect gravitational waves began with it resulteD in a DownloaD reality of gravitational waves [3]. Weber and his resonant mass detectors in the 1960s [23], Also in 1916, Schwarzschild published a solution for the followed by an international network of cryogenic reso- field equations [4] that was later understood to describe a nant detectors [24]. Interferometric detectors were first was unusually high. black hole [5,6], and in 1963 Kerr generalized the solution suggested in the early 1960s [25] and the 1970s [26].A to rotating black holes [7]. Starting in the 1970s theoretical study of the noise and performance of such detectors [27], work led to the understanding of black hole quasinormal and further concepts to improve them [28],ledto proposals for long-baseline broadband laser interferome- HunDreDs of thousanDs of modes [8–10], and in the 1990s higher-order post- Newtonian calculations [11] preceded extensive analytical ters with the potential for significantly increased sensi- studies of relativistic two-body dynamics [12,13]. These tivity [29–32]. By the early 2000s, a set of initial detectors advances, together with numerical relativity breakthroughs was completed, including TAMA 300 in Japan, GEO 600 in Germany, the Laser Interferometer Gravitational-Wave people actually wanteD to in the past decade [14–16], have enabled modeling of binary black hole mergers and accurate predictions of Observatory (LIGO) in the United States, and Virgo in their gravitational waveforms. While numerous black hole Italy. Combinations of these detectors made joint obser- candidates have now been identified through electromag- vations from 2002 through 2011, setting upper limits on a reaD the whole paper!” variety of gravitational-wave sources while evolving into netic observations [17–19], black hole mergers have not previously been observed. a global network. In 2015, Advanced LIGO became the first of a significantly more sensitive network of advanced detectors to begin observations [33–36]. *Full author list given at the end of the article. A century after the fundamental predictions of Einstein and Schwarzschild, we report the first direct detection of Published by the American Physical Society under the terms of Robert Garistro the Creative Commons Attribution 3.0 License. Further distri- gravitational waves and the first direct observation of a bution of this work must maintain attribution to the author(s) and binary black hole system merging to form a single black PRL editor the published article’s title, journal citation, and DOI. hole. Our observations provide unique access to the 0031-9007=16=116(6)=061102(16) 061102-1 Published by the American Physical Society Avignon 24.4.2017 4 Gravita1onal Waves ⇤˙ /June 1916 ⇤ << ⇤ It follows that the gravita@onal fielD propagates at the speeD out light. We will inves@gate these gravita@onal wave solu@ons anD the sources that give rise ⇤˙ /⇤ >> ⇤ to them. H2H2 df d⇥ =¯h 0 inflation • Spin 2 massless, propagate at c gw 4π2c3 f • For v<<c, dominant radia7on f d⇥gw 16 ⇥inflation 1 14 quadrupolar = (1 + Z )− 10− ⇥ df 9 ⇥ eq ≈ 0 • Quadrupole luminosityplanck G d3 d3 L = Q Q Kopie für Lizenzkunden der TIB Hannover, geliefert und ausgedruckt für Max-Planck-Institut fuer Gravitationsphysik Bibliothek Bibliothek, 04.04.13 5c5 dt3 ab dt3 ab ⇥ ⇥ Avignon 24.4.2017 5 0-1 b) Test Mass Advanced LIGO Detectors H1 Livingston & 10 ms light travel time Hanford = 4 km y L 3000 km aparta) L1 ΔL/L b) Test Mass Test Mass Sensi7ve from 30 to 2000 Hz Power• Beam Recycling Lx = 4 km H1 • Strain h=SplitterΔL/L 10 ms light travel time • In 100 Hz band at = 4 km -22 y Laser 20 W 100 kW Circulating Power L minimum, r.m.s. noise h~10 a) L1 Source Test Test O1 noise a factor ~3 above Mass Mass Signal• Recyclingdesign sensi7vity Test Photodetector Mass Avignon 24.4.2017 6 Power Beam L = 4 km Recycling Splitter x Laser 20 W 100 kW Circulating Power Source Test Test Mass Mass Signal Recycling Photodetector copyright: caltech/MIT LIGO Lab, 2016 Avignon 24.4.2017 7 GW150914 • Engineering run had begun 17 August 2015, for tuning, calibra7on, injec7on tests, and noise characterisa7on studies. • First observing run O1 (“science opera7ons mode”) scheduled to start on 18 September 2015 • VIRGO not opera7ng (under construc7on) GEO-600 lost lock 10 minutes before (AND not sufficiently sensi7ve at low frequencies) • Event at 09:50 UTC on 14 September 2015, four days before planned O1 start 02:50 at LIGO Hanford, WA 04:50 at LIGO Livingston, LA 11:50 in Germany Avignon 24.4.2017 8 AEI Hannover, September 14, 2015 Marco Drago Andrew Lundgren • Monday morning 11:50 • At 12:54, Marco sent an email to the • coherent waveburst pipeline running collabora7on, asking for confirma7on at caltech, event database had ~1000 that it’s not a hidden test signal entries (hardware injec7on) • Marco and Andy checked injec7on • Next hours: flurry of emails, decision flags and logbooks, data quality, made to lock down sites, freeze instrument Qscans of LHO/LLO data. state • called LIGO operators: “everyone’s gone home” Avignon 24.4.2017 9 Black hole separation (R ) 4 3 2 1 0.5 S Inspiral Merger Ringdown 0 2 residuals -0.5 The Chirp 1 ) 1 -21 ) -21 0 ΔL/L 0 Strain (10 Strain (10 -1 H1 measured strain, bandpassed -1 H1 estimated strain incident L1 measured strain, bandpassed H1 estimated strain, bandpassed 0.2 0.25 0.3 0.35 0.4 0.45 0.2 0.25 0.3 0.35 0.4 0.45 Time (seconds) Time (seconds) • Bandpass filtered 35-350 Hz, • Signal visible to the naked eye: some instrumental and ~200 ms calibra7on lines removed • “Instantaneous” SNR ~5, • Hanford inverted, shioed 7.1 op7mal filter SNR ~ 24 ms earlier Avignon 24.4.2017 10 What could it be? copyright: Salford University Avignon 24.4.2017 11 Gravita1onal waves from orbi1ng masses 1m Equations orbital angular Gm2 r 2Gm Newton : frequency