Nobel Lecture: LIGO and gravitational waves II^*

Figure 1

Figure 1 is the gravitational wave discovery figure that was observed by members of the LIGO Scientific Collaboration within minutes after the event was recorded in Advanced LIGO. Each of the three figures shows the detected “strain” signals in units of ${10}^{-21}$ vs time. The top trace is the observed waveform detected in the Hanford, Washington interferometer, and the middle trace is the observed waveform in Livingston, Louisiana. The two signals are almost identical, but are shifted by 6.9 msec and are superposed in the bottom trace. From the Caltech/MIT/LIGO Lab.

Figure 2

The LIGO Interferometers in Hanford, Washington and Livingston, Louisiana. From the Caltech/MIT/LIGO Lab.

Figure 3

The evolving improved sensitivity of Initial LIGO.

Figure 4

Advanced LIGO sensitivity goal.

Figure 5

Advanced LIGO multistage suspension system for the test masses with active-passive seismic isolation.

Figure 6

The physics interpretation of the observed event as a binary black hole merger.

Figure 7

The statistical significance of the event as a generic transient event on the left, and directly searching for events from a merger on the right.

Figure 8

Event characteristics of reported black hole mergers in LIGO.

Figure 9

Masses of observed black hole mergers in LIGO.

Figure 10

Tests of the inclusion of a dispersion term in general relativity. Upper limits are shown on the presence of a dispersion term.

Figure 11

The Virgo Suspended Mass Interferometer in Cascina, Italy.

Figure 12

Black hole merger GW170814 showing LIGO-Hanford, LIGO-Livingston and Virgo signals on the left, and the reconstructed direction of the gravitational wave on the right.

Figure 13

The first observation of binary neutron star merger. Time-frequency representations of gravitational wave event GW170817, observed by the LIGO-Hanford (top), LIGO-Livingston (middle), and Virgo (bottom) detectors.

Figure 14

The main parameters of GW170817.

Figure 15

Fermi short gamma ray burst signal observed 1.7 s after the gravitational wave signal in the same region of the sky.

Figure 16

Determination of the Hubble constant from gravitational wave data. The blue curve shows the relative probability of different values of $H_0$ with the peak at $70\mathrm{km}{\mathrm{s}}^{-1}{\mathrm{Mpc}}^{-1}$. The dashed and dotted blue vertical lines are the limits of 68.3% and 95.4% credible intervals for $H_0$. Our gravitational wave results are in agreement with both Planck and SHoES. Note that we cannot distinguish from just one event between these two, which disagree with each other at the 95.4% probability level.

Figure 17

The electromagnetic campaign for counterparts to GW170817.

Figure 18

Typical LIGO sensitivity during the O1 data run, the Advanced LIGO design sensitivity, and the estimated sensitivity achievable with the $\mathrm{A}+$ upgrades. $\mathrm{A}+$ will involve a variety of improvements over the present LIGO, including implementing squeezed light, improved optical coatings and test masses, and possibly cryogenic cooling.

Figure 19

Fully exploiting the LIGO sites. Employing improved technologies, a factor of x10 improvement over O1 sensitivities appears possible.

Figure 20

LIGO Laboratory Directorate members including Barry Barish, Jay Marx, Dave Reitze, and Albert Lazzarini.

Figure 21

LIGO Scientific Collaboration Spokespersons including Rai Weiss, Peter Saulson, Dave Reitze, Gabriela Gonzalez, and David Shoemaker.

Figure 22

LIGO Site Heads including Fred Raab, Mike Landry, Mark Coles, Mike Zucker, and Joe Giaime.

Figure 23

Advanced LIGO members including Dennis Coyne, Peter Fritschel, Daniel Sigg, and Valery Frolav.

Figure 24

LIGO Lab, Senior Scientists, including Stan Whitcomb, Rana Adakari, Matt Evans, and Alan Weinstein.