Tribute to Pierre Binétruy

A conference and a film

On May 3rd and 4th 2018, a scientific conference was held at Paris Diderot University in tribute to Pierre Binétruy, for his numerous contributions to particle physics, supersymmetry, cosmology and gravitation but also his talent to lead the French and internationnal physics community and to outreach through his online courses.

The documentary “Intrikation” was presented to the audience at the end of those two days. You can now watch the full movie on the PCCP Youtube channel (English subtitling available):

Paris Diderot University and APC Laboratory:

Conference Pierre Binétruy: From theory to strategy of discovery


Oxford University Press: Publication Mai 2018

Gravity! The Quest for Gravitational Waves – Pierre Binétruy


Gravity changes used for early detection of earthquakes and determination of their magnitude

Researchers from IPGP, CNRS, Caltech and Paris Diderot University have observed changes in the gravitational field produced by earthquakes before the arrival of seismic waves (propagating with speeds between 3 to 10 km/s). These gravity changes (which are conceptually different from the recently detected gravitational-waves) can be used as a new potential information carrier, helping in the early detection of major earthquakes or tsunamis and in the determination of their magnitude.

This work, based on data from the 2011 Tohoku Japanese earthquake (magnitude 9.1), opens new perspectives in the seismology. Further work is required to improve the detection of this weak gravity signal, especially for smaller earthquakes. New instruments can benefit from the technology developed in the field of the detection of gravitational waves coming from distant Universe. You can learn more (below) on this joined work between seismologists and astrophysicists published in Science on December 1st.

Press release

Science article


Albert Einstein’s theory of relativity confirmed by Microscope

On December 4th, 2017 the first results analysed from the Microscope satellite confirmed the equivalence principle with a precision of 2.10-14, which is already 10 times better than the best experiments conducted so far. The goal of the mission is to reach a precision of 2.-15. Up to now, bodies still fall with the same acceleration in a vacuum and Microscope first results reconfirm Albert Einstein’s theory of general relativity, as formulated a century ago.

You will find below the press release, links to the ARXIV publications and for further explanations on the equivalence principle, you can read, or re-read, our posts:

Why test the equivalence principle
How to test the equivalence principle in space? The Microscope mission

CP190-2017 – MicroscopeV16_va

3 articles available on ARXIV :  Touboul et al  Bergé et al  Fayet

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)


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