LIGO and Virgo make first detection of gravitational waves produced by colliding neutron stars

17 August 2017 – 12:41:04 UTC: For the first time, scientists have directly detected gravitational waves in addition to light from the spectacular collision of two neutron stars.

This marks the first time that a cosmic event has been viewed in both gravitational waves and light. The discovery was made using the U.S.-based Laser Interferometer Gravitational-Wave Observatory (LIGO); the Europe-based Virgo detector; and some 70 ground- and spacebased observatories.

Neutron stars are the smallest, densest stars known to exist and are formed when massive stars explode in supernovas. As these neutron stars spiraled together, they emitted gravitational waves that were detectable for about 100 seconds; when they collided, a flash of light in the form of gamma rays was emitted and seen on Earth about two seconds after the gravitational waves. In the days and weeks following the smashup, other forms of light, or electromagnetic radiation — including X-ray, ultraviolet, optical, infrared, and radio waves — were detected.

The image shows the localization of the gravitational-wave (from the LIGO-Virgo 3-detector global network), gamma-ray (by the Fermi and INTEGRAL satellites) and optical (the Swope discovery image) signals from the transient event detected on the 17th of August, 2017. The colored areas show the sky localization regions estimated by the gamma-ray observatories (in blue) and by the gravitational-wave detectors (in green). The insert shows the location of the apparent known galaxy NGC4993: on the top image, recorded almost 11 hours after the gravitational-wave and gamma-ray signals had been detected, a new source (marked by a reticle) is visible: it was not there on the bottom picture, taken about three weeks before the event.


The observations have given astronomers an unprecedented opportunity to probe a collision of two neutron stars. For example, observations made by the U.S. Gemini Observatory, the European Very Large Telescope, and the Hubble Space Telescope reveal signatures of recently synthesized material, including gold and platinum, solving a decadeslong mystery of where about half of all elements heavier than iron are produced.

Theorists have predicted that when neutron stars collide, they should give off gravitational waves and gamma rays, along with powerful jets that emit light across the electromagnetic spectrum. The gamma-ray burst detected by Fermi, and soon thereafter confirmed by the European Space Agency’s gamma-ray observatory INTEGRAL, is what’s called a short gamma-ray burst; the new observations confirm that at least some short gamma-ray bursts are generated by the merging of neutron stars — something that was only theorized before. “For decades we’ve suspected short gamma-ray bursts were powered by neutron star mergers,” says Fermi Project Scientist Julie McEnery of NASA’s Goddard Space Flight Center.

“Now, with the incredible data from LIGO and Virgo for this event, we have the answer. The gravitational waves tell us that the merging objects had masses consistent with neutron stars, and the flash of gamma rays tells us that the objects are unlikely to be black holes, since a collision of black holes is not expected to give off light.”

At the moment of collision, the bulk of the two neutron stars merged into one ultradense object, emitting a “fireball” of gamma rays. The initial gamma-ray measurements, combined with the gravitational-wave detection, also provide confirmation for Einstein’s general theory of relativity, which predicts that gravitational waves should travel at the speed of light.

You can read this full paper written by Jennifer Chu, MIT News Office below:

LIGO and Virgo make first detection of gravitational waves produced by colliding neutron stars

Watch this short video on the

Detecting a Kilonova Explosion

And to know more, here are some recent publications:

Gravitational Waves and Gamma-Rays from a Binary Neutron Star Merger: GW170817 and GRB 170817A

GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral

Straight to the source: the LIGO-Virgo global network of interferometers opens a new era for gravitational wave science

The Virgo collaboration and the LIGO Scientific Collaboration report the three-detector observation of gravitational waves. This result highlights the scientific potential of a global network of gravitational wave detectors, by delivering a better localization of the source and access to polarizations of gravitational waves.
The two Laser Interferometer Gravitational-Wave Observatory (LIGO) detectors, located in Livingston, Louisiana, and Hanford, Washington, USA and the Virgo detector, located at the European Gravitational Observatory (EGO) in Cascina, near Pisa, Italy, detected a transient gravitational-wave signal produced by the coalescence of two stellar mass black holes.


Localisation of the Gravitational Wave source.

In yellow : localisation from the 2 LIGO detectors.

In green : localisation using datas from 3 detectors (LIGO et Virgo).

In purple : more precise localisation after detailed data analysis.

© Collaboration LIGO-Virgo



The press release is here.


The full publication:

GW170814: A Three-Detector Observation of Gravitational Waves
from a Binary Black Hole Coalescence
B. P. Abbott etal.
(LIGO Scientific Collaboration and Virgo Collaboration)


VIRGO joins LIGO for a data-taking period

On August 1st 2017, the VIRGO detector based in Europe has officially joined the American-based twin LIGO detectors for a simultaneous data-taking period. The improved sensitivity of the VIRGO detector now allows confirming a detection and locating sources of gravitational waves with greater accuracy.

After the completion of this observational period, the VIRGO operation will proceed to further improve the sensitivity of the detector and to gain more knowledge about the main sources of noise that are currently limiting mesurements.

“Today, for the first time, we have a network of three second generation detectors capable of localizing the source of a gravitational-wave signal. This is a major achievement and the best is yet to come: the sensitivity of the involved detectors will progressively improve and more detectors are expected to join in the next years, opening exciting perspectives for the multi-messenger investigation of our universe”, concludes Giovanni Losurdo from INFN Pisa former leader of the “Advanced VIRGO” project.

The full LSC VIRGO announcement here.

Image: Virgo aerial view – ©EGO-VIRGO

LISA Pathfinder to successfully achieve its mission

We have exceeded not only the requirements set for LISA Pathfinder, but also the accuracy required for LISA at all frequencies: we are definitely ready to take the next step.” Karsten Danzmann*

We started our LISA Pathfinder Saga on June 18th 2015, and followed with you and the researchers involved, this exciting mission for exactly two years. The goal of LISA Pathfinder was to validate the technology that will be used for the future LISA mission. That is, having two test masses placed in each of the three spacecraft of the LISA constellation, which is designed to detect gravitational waves in space.

Nonetheless the LISA Pathfinder mission exceeded its objectives, and the LISA mission has just been selected as the third large-class mission in ESA’s Science Programme. Along with a third detection of gravitational waves emitted from the coalescence of two black holes, announced last month by the Advanced LIGO collaboration, we are definitively starting the era of Gravitational Astronomy.

The LISA Pathfinder mission performed its final tests and will receive its last command on July 18th 2017.


You can read everything about the achievements of the LISA Pathfinder mission on the ESA website:


This has been a splendid journey that we enjoyed following with you. And we can certainly expect more like this in the coming years.


*Director at the Max Planck Institute for Gravitational Physics, director of the Institute for Gravitational Physics of Leibniz Universität Hannover, Germany, Co-Principal Investigator of the LISA Technology Package, and lead proposer of LISA.

Image: LISA Pathfinder in space. Credit: ESA/C. Carreau

Gravitational wave mission LISA selected by ESA Science Program Committee

ESA (the European Space Agency) has chosen the Laser Interferometer Space Antenna (LISA) for its third large-class mission (L3) in the agency’s Cosmic Vision science program. The LISA trio of satellites is meant to study gravitational waves in space.

This is a major milestone in the development of LISA. The next big step will be the adoption, expected around 2021/2022.

In France, the APC Laboratory has a central role in LISA, since today the laboratory is coordinating, with the support of CNES and other partner laboratories, the two main French contributions considered for LISA: setting up of the Scientific Data Treatment Centre, and the Performance Management, Integration & Payload Tests.

For more information:

ESA web

NASA web

Photo Lisa concept
AEI/Milde Marketing/Exozet

Grant Pierre Binétruy

As many of you have expressed the wish to contribute somehow to the continuation of Pierre Binétruy’s work, we have conceived the project to create a research grant bearing his name.

If thus you wish to make a gift on behalf of Pierre, we suggest you participate in the creation of this research grant bearing his name. All donations received since April 1st 2017 will fund this grant.

Donations to the Grant Pierre Binétruy can be made to the Endowment Fund Physique de l’Univers which he directed: Your donations to the grant Pierre Binétruy

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