Black Holes, Einstein, LIGO, and the Nobel Prize

Rick Savage LIGO Hanford Observatory

Anacortes Public Library Sept. 27, 2018 LIGOLIGO--G1801911G1801911-v1-v1 Overview What I hope you will take away with you.

● LIGO: new kind of astronomical observatory » Sensing gravitational waves, not light waves

● Sensing gravitational waves is difficult » LIGO instruments measure VERY small length variations

● First direct observation of GWs (100 years after GR) » merger on Sept 14, 2015

● LIGO is helping to solve mysteries of Astrophysics » on Aug 17, 2017

● The ERA of gravitational-wave Astronomy has begun » Right here in Washington.

LIGO-G1801911-v1 Anacortes Public Library Sept. 27, 2018 2 400 Years of Optical Astronomy

Credit: Wellcome Library, London. Wellcome Images LIGO-G1801911-v1 Anacortes Public Library Sept. 27, 2018 3 Electromagnetic Wave Observatories Keck Observatory Mauna Kea Hawaii

Credit: R. Peterson, W.M. Keck Observatory

LIGO-G1801911-v1 Anacortes Public Library Sept. 27, 2018 4 Electromagnetic Wave Observatory ALMA Observatory Atacama Desert Chile

Credit: Carlos Padilla – AUI/NRAO

LIGO-G1801911-v1 Anacortes Public Library Sept. 27, 2018 5 Hubble Space Telescope

Credit: European Space Agency

LIGO-G1801911-v1 Anacortes Public Library Sept. 27, 2018 6 Hubble eXtreme Deep Field Image

Credit: NASA, ESA, G. Illingworth, D. Magee, and P. Oesch (University of California, Santa Cruz), R. Bouwens (Leiden University), and the HUDF09 Team

LIGO-G1801911-v1 Anacortes Public Library Sept. 27, 2018 7 What about objects or events that don’t emit light?

Credit: LIGO/Caltech/MIT/Sonoma State (Aurore Simonnet)

LIGO-G1801911-v1 Anacortes Public Library Sept. 27, 2018 8 Birth and Death of Stars

● Stars begin as huge clouds of hydrogen and helium that formed during the Big Bang 13.8 billion years ago ● Gravity causes this “cosmic dust” to form into stars ● Fusion reactions counteract compressive forces of gravity and cause stars to “shine” ● Elements, up to Iron synthesized in fusion reactions ● Gravitational collapse and Supernova explosion when fuel exhausted ● If progenitor massive enough, formation of Neutron Star or

Black Hole Credit: European Southern Observatory (ESO)

LIGO-G1801911-v1 Anacortes Public Library Sept. 27, 2018 9 Albert Einstein 1915 General Relativity

● Space and time interconnected – spacetime

● Massive objects curve spacetime

● Gravity is curvature in spacetime

LIGO-G1801911-v1 Anacortes Public Library Sept. 27, 2018 10 Albert Einstein 1916 Gravitational Waves

● Ripples in the curvature of spacetime that propagate at the speed of light

Binary black hole system Waveform contains details of the black holes and the merger

Credit: Kip Thorne ● Allow us to observe events that we can’t “see” with light.

LIGO-G1801911-v1 Anacortes Public Library Sept. 27, 2018 11 Manifestation of a passing

● Spacetime alternately stretched and compressed in perpendicular directions

● Laser interferometer is an ideal instrument for measuring length variations along perpendicular paths » Pioneering study - R. Weiss, MIT 1972

LIGO-G1801911-v1 Anacortes Public Library Sept. 27, 2018 12 Measuring differential length changes with interferometry

Mirror differential motion mirr or mirroMirror r Beamsplitter

Interference Photo Detector Laser Source

GW signal

● Laser interferometer ● Length change proportional to » “Ideal” instrument for detecting GWs length of the arms » Longer arms better

LIGO-G1801911-v1 Anacortes Public Library Sept. 27, 2018 13 4 km-long laser interferometers

LIGO Livingston Observatory near Baton Rouge, Louisiana

LIGO Hanford Observatory

LIGO-G1801911-v1 Anacortes Public Library Sept. 27, 2018 14 Laser “interfere – ometer” for ultra- precise length difference measurements

Credit: LIGO/T. Pyle

LIGO-G1801911-v1 Anacortes Public Library Sept. 27, 2018 15 The challenge: 10-18 meters

● Gravitational waves cause VERY small length variations ● For LIGO, length changes about one 1/1000 diameter of a proton

● Einstein doubted that they would ever be detected by humans.

● It took us 100 years to do it!

LIGO-G1801911-v1 Anacortes Public Library Sept. 27, 2018 16 Ultra-sensitive instruments in ultra-high vacuum envelopes

LIGO-G1801911-v1 Anacortes Public Library Sept. 27, 2018 17 Test mass suspensions - isolating the mirrors from ground motion

Reaction Monolithic (welded), Quadruple pendulum mass Test mass all-glass final stage with reaction mass chain

LIGO-G1801911-v1 Anacortes Public Library Sept. 27, 2018 18 A long time ago in a galaxy far, far away …

» 1.3 billion years ago, 1.3 billion light years from earth ...

» Gravitational waves reached Earth on Sept. 14, 2015

LIGO-G1801911-v1 Anacortes Public Library Sept. 27, 2018 19 Sept. 14, 2015 Hanford and Livingston observatories

LIGO-G1801911-v1 Anacortes Public Library Sept. 27, 2018 20 Simulation of spacetime warpage caused by black holes merging

Credit: The Simulating eXtreme Spacetimes (SXS) project. LIGO-G1801911-v1 Anacortes Public Library Sept. 27, 2018 21 GW150914 event

● Two Black Holes » 36 times the mass of our Sun » 29 times the mass of our Sun ● Collided to form a 62 solar mass Black Hole ● Three solar masses of matter converted into energy in GWs in 0.2 sec. ● Most luminous event ever observed » 50 times a bright as all the stars in the Universe combined

● About 100 billion galaxies in the Universe ● About 100 billion stars in each galaxy » About ten thousand stars for every grain of sand on the Earth ● If every star had a planet like Earth orbiting it » And if every one of these Earths consumed as much energy as Earth ● GW150914 could fuel all these Earths for ten thousand years

LIGO-G1801911-v1 Anacortes Public Library Sept. 27, 2018 22 Instrumentalists and Astronomers

LIGO-G1801911-v1 Anacortes Public Library Sept. 27, 2018 23 New Astrophysics Heaviest intermediate-mass BHs

Credit: LIGO/Caltech/MIT/Sonoma State (Aurore Simonnet)

LIGO-G1801911-v1 Anacortes Public Library Sept. 27, 2018 24 First direct detection of GWs

● Confirm the existence of GWs

● Consistent with GR

● Existence of binary black hole systems

● Coalescence within the age of the Universe

● Population estimates

LIGO-G1801911-v1 Anacortes Public Library Sept. 27, 2018 25 Stockholm celebration December 2017

LIGO-G1801911-v1 Anacortes Public Library Sept. 27, 2018 26 VIRGO detector joins LIGO observing run Aug. 2017

Credit: The Virgo collaboration/CCO 1.0

LIGO-G1801911-v1 Anacortes Public Library Sept. 27, 2018 27 LIGO-VIRGO detection Aug. 14, 2017

Credit: LIGO/Caltech/MIT/LSC

LIGO-G1801911-v1 Anacortes Public Library Sept. 27, 2018 28 Binary Black Hole Mergers Detected with Gravitational Waves

Credit: LIGO/Caltech/MIT/Sonoma State (Aurore Simonnet)

LIGO-G1801911-v1 Anacortes Public Library Sept. 27, 2018 29 Merger GRB start 2500 Lightcurve from Fermi/GBM (10 50 keV) 2250 2000 1750 1500

Event rate (counts/s) 1250 Merger GRB start 2500 Lightcurve from Fermi/GBM (10 50 keV) Lightcurve from Fermi/GBM (50 300 keV) 22501750 20001500 17501250 Aug. 17, 2017: simultaneous gamma 15001000 ray and gravitational wave detection

Event rate (counts/s) 1250750 Event rate (counts/s) Lightcurve from Fermi/GBM (50 300 keV) 1750 Lightcurve from INTEGRAL/SPI-ACS 1200001500 (> 100 keV)

1175001250

1150001000

112500750 Event rate (counts/s) Event rate (counts/s) Lightcurve from INTEGRAL/SPI-ACS Gravitational-wave time-frequency map 120000400 (> 100 keV) 300 117500 200 115000

112500100 Frequency (Hz) Event rate (counts/s)

50 400 10Gravitational-wave8 time-frequency6 4 map 2 0 2 4 6 300 Time from merger (s) 200

LIGO-G1801911100 -v1 Anacortes Public Library Sept. 27, 2018 30 Frequency (Hz)

50 10 8 6 4 2 0 2 4 6 Time from merger (s) GW170817: Binary neutron star merger

LIGO-G1801911-v1 Anacortes Public Library Sept. 27, 2018 31 Observed by more than 70 electromagnetic observatories

LIGO-G1801911-v1 Anacortes Public Library Sept. 27, 2018 32 GW160817 Birth of multi-messenger astronomy

● Confirmation of kilonova scenario – synthesis of heavy elements ● Confirmation of NS mergers as cause for short GRBs ● Propagation speed of GWs compared with light ● Independent measure of Hubble’s constant ● Testing laws of physics (GR) in the extreme gravity regime ● Hints at EOS for neutron stars NSF/LIGO/Sonoma State University/A. Simonnet

LIGO-G1801911-v1 Anacortes Public Library Sept. 27, 2018 33 Synthesis of heavy elements like Gold, Platinum, Uranium, etc.

Credit: Jennifer Johnson

LIGO-G1801911-v1 Anacortes Public Library Sept. 27, 2018 34 Objects observed via gravitational waves.

LIGO-Virgo/Frank Elavsky/Northwestern University

LIGO-G1801911-v1 Anacortes Public Library Sept. 27, 2018 35 Busy past couple of years ….

● Physics World 2016 LIGO’s gravitational-wave discovery » “… goes to the LIGO Scientific Collaboration for its revolutionary, first-ever direct observations of gravitational waves."

Credit: Physics World Feb. 11, 2016 ● Physics World 2017 Breakthrough of the Year First multimessenger observation of a neutron-star merger » “… we believe that the multimessenger observation of GW 170817 epitomizes the collaborative nature of and is a shining example of how our knowledge of the universe can move forwards when people from all over the world join together with a common scientific cause.” (Credit: NASA / AEI / ZIB / M Koppitz and L Rezzolla) LIGO-G1801911-v1 Anacortes Public Library Sept. 27, 2018 36 What are we doing now? Upgrading the detectors - improving sensitivity

● LIGO’s third observing run scheduled to begin February 2019

LIGO-G1801911-v1 Anacortes Public Library Sept. 27, 2018 37 What’s next … Peering through the new window of GW Astronomy

Credit: Hubble Space Telescope

LIGO-G1801911-v1 Anacortes Public Library Sept. 27, 2018 38 Please come visit!

● In person: LIGO Hanford Observatory, Richland, WA Public tours second Saturday of every month » LIGO Livingston Observatory, Livingston, LA

● On the web: ligo.caltech.edu

LIGO-G1801911-v1 Anacortes Public Library Sept. 27, 2018 39