The LIGO Scientific Collaboration and the Virgo Collaboration report the first joint detection of gravitational waves, ripples in the fabric of space and time, first predicted by Albert Einstein more than a century ago. This is the fourth announced detection of a signal from two black holes in their final orbits and then their coalescence into a single black hole. A paper about the event, GW170814, will be published in the journal Physical Review Letters.
Coalescence of two orbiting black holes. Image credit: S. Ossokine & A. Buonanno, Max Planck Institute for Gravitational Physics / Simulating eXtreme Spacetimes Project / T. Dietrich, Max Planck Institute for Gravitational Physics / R. Haas, NCSA.
The GW170814 signal was detected on August 14, 2017, at 10:30:43 a.m. UTC using the two Laser Interferometer Gravitational-Wave Observatory (LIGO) detectors located in Livingston, Louisiana, and Hanford, Washington, and the Virgo detector, located near Pisa, Italy.
It is the fourth announced detection of a binary black-hole system (previously confirmed detections – GW150914, GW151226, and GW170104) and the first significant gravitational-wave signal recorded by the Virgo detector.
GW170814 factsheet. Image credit: LIGO Scientific Collaboration / Anuradha Gupta / Zoheyr Doctor.
New population of binary black holes. The three previously confirmed detections by LIGO, plus one lower-confidence detection (LVT151012), are shown along with the fourth confirmed detection (GW170814). Image credit: LIGO / Caltech / Sonoma State / Aurore Simonnet.
Comparison of gravitational-wave signal templates from recent LIGO/Virgo observations. This figure shows reconstructions of the four confident and one candidate (LVT151012) gravitational wave signals detected by LIGO and Virgo to date, including the most recent detection GW170814 (which was observed in all three detectors). Each row shows the signal arriving at the Hanford detector as a function of time. The thickness of the curves indicates the 90% confidence interval on the model parameters. Only the portion of each signal that LIGO was sensitive to is shown here (the final seconds leading up to the black hole merger). Image credit: LIGO / Virgo / B. Farr, University of Oregon.
The detection is especially important because it highlights the scientific potential of a three-detector network of gravitational-wave detectors.
“This is just the beginning of observations with the network enabled by Virgo and LIGO working together,” said MIT senior research scientist Dr. David Shoemaker, spokesperson of the LIGO Scientific Collaboration.
“With the next observing run planned for Fall 2018 we can expect such detections weekly or even more often.”
“It is wonderful to see a first gravitational-wave signal in our brand new Advanced Virgo detector only two weeks after it officially started taking data,” added Dr. Jo van den Brand of Nikhef and VU University Amsterdam, spokesperson of the Virgo Collaboration.
“That’s a great reward after all the work done in the Advanced Virgo project to upgrade the instrument over the past six years.”
GW170814 infographic. Image credit: Virgo Collaboration.
The GW170814 signal was emitted during the final moments of the merger of two black holes with masses about 31 and 25 times the mass of the Sun and located approximately 1.8 billion light-years away.
The newly produced spinning black hole has about 53 solar masses, which means that about 3 solar masses were converted into gravitational-wave energy during the coalescence.
Skymap of the LIGO/Virgo black hole mergers. This 3D projection of the Milky Way Galaxy onto a transparent globe shows the probable locations of the three confirmed black-hole merger events observed by the two LIGO detectors – GW150914 (dark green), GW151226 (blue), GW170104 (magenta) – and a fourth confirmed detection (GW170814, light green, lower-left) that was observed by Virgo and the LIGO detectors. Also shown (in orange) is the lower significance event, LVT151012. The outer contour for each represents the 90% confidence region; the innermost contour signifies the 10% confidence region. The addition of Virgo shows a dramatic increase in the sky localization. Image credit: LIGO / Virgo / Caltech / MIT / Leo Singer / Axel Mellinger.
Probable location of GW170814. Image credit: Virgo Collaboration.
The volume of Universe that is likely to contain the source of the GW170814 signal shrinks by more than a factor of 20 when moving from a two-detector network to a three-detector network.
The sky region for GW170814 has a size of only 60 square degrees, more than 10 times smaller than with data from the two LIGO interferometers alone; in addition, the accuracy with which the source distance is measured benefits from the addition of Virgo.
“This increased precision will allow the entire astrophysical community to eventually make even more exciting discoveries, including multi-messenger observations,” says Georgia Tech Professor Laura Cadonati, the deputy spokesperson of the LIGO Scientific Collaboration.
“A smaller search area enables follow-up observations with telescopes and satellites for cosmic events that produce gravitational waves and emissions of light, such as the collision of neutron stars.”
“The addition of the third observatory has widened the window on the Universe,” added Professor Carlos Lousto, from the Rochester Institute of Technology.
“We now can pinpoint where those black holes collided in the Universe with 10 times higher precision than we had with only two detectors.”
_____
B.P. Abbott et al (LIGO Scientific Collaboration & Virgo Collaboration). 2017. GW170814: A three-detector observation of gravitational waves from a binary black hole coalescence. Physical Review Letters, in press;
