First Detection of Gravity Waves The First Ever

First Detection of Gravity Waves The First Ever Detection of Gravity Waves R. D. Gehrz ASTRO 2001, Spring Semester 2016 1/2/2022 University of Minnesota, ASTRO 2001, Spring 2016 1 RDG

First Detection of Gravity Waves The Minnesota LIGO Group 1/2/2022 University of Minnesota, ASTRO 2001, Spring 2016 2 RDG 1

First Detection of Gravity Waves https: //www. flickr. com/photos/gsfc/4538255799 Note that a spherically symmetric spinning object produces no gravity waves. 1/2/2022 University of Minnesota, ASTRO 2001, Spring 2016 3 RDG 1

First Detection of Gravity Waves Predictions of General Relativity 1/2/2022 University of Minnesota, ASTRO 2001, Spring 2016 4 RDG 1

First Detection of Gravity Waves Gravitational Waves • Gravitational waves are ripples in the curvature of spacetime that propagate as waves, travelling outward from the source. • Predicted in 1916 by Albert Einstein on the basis of his theory of general relativity • gravitational waves transport energy as gravitational radiation • https: //en. wikipedia. org/wiki/Gravitational_wave • https: //www. theguardian. com/science/2016/feb/09/gravitational-waves-everything-you-need-to-know 1/2/2022 University of Minnesota, ASTRO 2001, Spring 2016 5 RDG 1

First Detection of Gravity Waves Gravity Wave Theory • is the flat space metric • g is the metric tensor that describes the curvature of space • h is the radiation field 1/2/2022 University of Minnesota, ASTRO 2001, Spring 2016 6 RDG 1

First Detection of Gravity Waves Indirect Evidence for the Existence of Gravity Waves • Joseph Taylor and Russell Hulse in 1974: The Decay rate of pulses from pulsars in binary pulsars is consistent with loss of orbital energy by gravitational radiation • 1993 Nobel Prize in Physics 1/2/2022 University of Minnesota, ASTRO 2001, Spring 2016 7 RDG 1

First Detection of Gravity Waves What are Prospects for the Direct Detection of Gravity Waves? 1/2/2022 University of Minnesota, ASTRO 2001, Spring 2016 8 RDG 1

First Detection of Gravity Waves Have a Very Small Amplitude 1/2/2022 University of Minnesota, ASTRO 2001, Spring 2016 9 RDG 1

First Detection of Gravity Waves What Happens When a Gravitational Wave Passes by Earth? https: //www. youtube. com/watch? v=Wg. E 6 lb_i 78 A 1/2/2022 University of Minnesota, ASTRO 2001, Spring 2016 10 RDG 1

First Detection of Gravity Waves Early Experiments • 1/2/2022 Joseph Weber: 1960’s Experiments with large metal bars covered with strain gauges • Results were claimed but never confirmed • Sensitivity was way too low to detect predicted signals University of Minnesota, ASTRO 2001, Spring 2016 11 RDG 1

First Detection of Gravity Waves LIGO • Laser Interferometer Gravitational-Wave Observatory (LIGO) • Two widely separated installations • Hanford Washington • Livingston, Louisiana • Operated in unison as a single observatory • See more at: http: //www. ligo. org/about. php#sthash. Ki. Cf. Ugy. E. dpuf 1/2/2022 University of Minnesota, ASTRO 2001, Spring 2016 12 RDG 1

First Detection of Gravity Waves The LIGO Interferometers Livingston, LA Hanford, WA • 4 Km legs • 2000 miles apart (light travel time = 11 ms) • N/S Separation is 1100 miles (light travel time = 6 ms) 1/2/2022 University of Minnesota, ASTRO 2001, Spring 2016 13 RDG 1

First Detection of Gravity Waves About LIGO’s Interferometer • https: //www. ligo. caltech. edu/page/what-is-interferometer • https: //www. ligo. caltech. edu/page/ligos-ifo • Fringes: https: //www. youtube. com/watch? v=7 a. R 8 Hm. Wj. Hs 4 1/2/2022 University of Minnesota, ASTRO 2001, Spring 2016 14 RDG 1

First Detection of Gravity Waves What Happens When a Gravitational Wave Passes a LIGO Interferometer? http: //www. airspacemag. com/videos/how-ligo-works/? no-ist 1/2/2022 University of Minnesota, ASTRO 2001, Spring 2016 15 RDG 1

First Detection of Gravity Waves The Size of a Proton 1/2/2022 University of Minnesota, ASTRO 2001, Spring 2016 16 RDG 1

First Detection of Gravity Waves The Data 1/2/2022 University of Minnesota, ASTRO 2001, Spring 2016 17 RDG 1

First Detection of Gravity Waves The Chirp Signal https: //www. youtube. com/watch? v=VFk. J 4 Qf 8 y. Hw 1/2/2022 University of Minnesota, ASTRO 2001, Spring 2016 18 RDG 1

First Detection of Gravity Waves What We Think Produced the Signal https: //www. flickr. com/photos/gsfc/4538255799 1/2/2022 University of Minnesota, ASTRO 2001, Spring 2016 19 RDG 1

First Detection of Gravity Waves What We Conclude from Models of the Chirp • The wave form of the chirp is consistent with the in-spiral and merger of two massive black holes in a binary system • The black hole masses are 36 M⊙ and 29 M⊙ • The final black hole mass is 62 M⊙ • 3. 0 M⊙c 2 was radiated in gravitational waves • The event happened 1. 3 Gyr ago • The event happened in the southern hemisphere (7 ms delay, signal first detected in Louisiana) 1/2/2022 University of Minnesota, ASTRO 2001, Spring 2016 20 RDG 1

First Detection of Gravity Waves The Astrophysical Implications of this Detection We now have a new window on the Universe. Astrophysicists now have “ears” as well as eyes! 1/2/2022 University of Minnesota, ASTRO 2001, Spring 2016 21 RDG 1