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The Virgo Award 2021
ceremony: Giovanni Losurdo, Spokesperson of the Virgo Collaboration,
presenting the prize to Ilaria Nardecchia.

The Virgo Award 2021 awarded to Ilaria Nardecchia

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The Virgo Award 2021
ceremony: Giovanni Losurdo, Spokesperson of the Virgo Collaboration,
presenting the prize to Ilaria Nardecchia. The Virgo Award 2021
ceremony: Giovanni Losurdo, Spokesperson of the Virgo Collaboration,
presenting the prize to Ilaria Nardecchia.

Today, the Virgo Collaboration assigned the first ever Virgo Award, a prize that will be given annually to one Early Career Virgo Member who has made a significant and sustained contribution to the experiment. This year's winner of the award is Ilaria Nardecchia, member of the Virgo Group and the INFN group of the University of Roma Tor Vergata.

The prize was awarded to Dr. Nardecchia "in recognition of her many relevant and continued contributions to the Virgo experiment, in particular of her deep involvement in the modeling and experimental activities which led to a successful implementation of the Virgo Thermal Compensation System."

The jury that selected the winner was composed of leading scientists in the field of gravitational-wave physics: Lisa Barsotti (MIT Kavli Institute - LIGO), Monica Colpi (Università di Milano Bicocca), Gabriela Gonzalez (Louisiana State University), Frank Linde (Dutch National Institute of Subatomic Physics - Nikhef), Catherine Nary Man (Centre national de la recherche scientifique - CNRS) and Andrea Vicerè (Università di Urbino).

"The achievements of the Virgo experiment, now recognised as a pillar in contemporary physics, rely on the work of many outstanding junior scientists; not always in the spotlight", declared Giovanni Losurdo, Virgo Spokesperson. "The Virgo Award is a way to acknowledge such a crucial contribution. Congratulations to Ilaria Nardecchia, 2021 awardee, for this well deserved success!"

The award ceremony took place today at the European Gravitational Observatory, during the Virgo Week, the first in-person collaboration-wide meeting since the beginning of the pandemic.

Image: The Virgo Award 2021 ceremony: Giovanni Losurdo, Spokesperson of the Virgo Collaboration, presenting the prize to Ilaria Nardecchia.

Image credit: Virgo Collaboration/Perciballi

Posted: 18/11/2021
The Control Room of the Virgo
detector, from which the interferometer is operated.

LIGO, VIRGO AND KAGRA OBSERVING RUN PLANS

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The Control Room of the Virgo
detector, from which the interferometer is operated. The Control Room of the Virgo
detector, from which the interferometer is operated.

15 November 2021 update; next update by 15 March 2022

The LIGO, Virgo, and KAGRA scientific collaborations are closely coordinating in order to begin the fourth observation period (O4) together and have today announced that, despite local and global adversities, they plan to start the run in mid-December, 2022.

LIGO has a sensitivity goal of 160-190 Mpc for binary neutron stars. Virgo aims for a target sensitivity of 80-115 Mpc. KAGRA should be running with greater than 1 Mpc sensitivity by the beginning of O4 and will work to improve the sensitivity toward the end of the run.

"Even if the pandemic is having different impacts on the detector sites", said Alessio Rocchi, LIGO-Virgo-KAGRA Joint Run Planning Committee co-chair, "the LIGO, Virgo, and KAGRA collaborations have been working together to start the O4 Observing run at the same time. We believe this is the best strategy to maximise the science outcome of the run and the chances for multimessenger observations."

"Despite the difficulties due to the pandemic, last spring we were able to complete the installation for O4; the Advanced Virgo+ Phase I", stated Raffaele Flaminio, Advanced Virgo+ project leader. "Among several upgrades, Phase I involved the installation of a more powerful laser, the reconfiguration of the interferometer to enhance its bandwidth and the implementation of an additional 300m-long optical cavity to reduce the effect of quantum fluctuations. Since then, we have begun the commissioning of the detector and we plan to be ready to restart data taking in one year from now."

Image: The Control Room of the Virgo detector, from which the interferometer is operated.

Image credit: Massimo D'Andrea/EGO

Posted: 15/11/2021
The image shows the 90
binary-system mergers that have been observed so far by the Advanced LIGO and
Advanced Virgo detector network. Each box represents one event, with its name
reported at the bottom of the box. The masses of the merging objects (either
black holes or neutron stars) as well as the final merged object are
indicated in solar masses. The colour of each box highlights in which of the
three observing runs the event was detected: O1, in 2015-16; O2, in 2016-17;
and O3, in 2019-20. The increase in the number of events in O3 was made
possible by the improved performance of all three of the detectors in the
network. Note that GW200105 is also shown, even though it is considered a
marginal event (meaning its astrophysical origin is uncertain), which
explains why 91 boxes are displayed.

35 new spacetime quakes detected by Virgo and LIGO

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The image shows the 90
binary-system mergers that have been observed so far by the Advanced LIGO and
Advanced Virgo detector network. Each box represents one event, with its name
reported at the bottom of the box. The masses of the merging objects (either
black holes or neutron stars) as well as the final merged object are
indicated in solar masses. The colour of each box highlights in which of the
three observing runs the event was detected: O1, in 2015-16; O2, in 2016-17;
and O3, in 2019-20. The increase in the number of events in O3 was made
possible by the improved performance of all three of the detectors in the
network. Note that GW200105 is also shown, even though it is considered a
marginal event (meaning its astrophysical origin is uncertain), which
explains why 91 boxes are displayed. The image shows the 90
binary-system mergers that have been observed so far by the Advanced LIGO and
Advanced Virgo detector network. Each box represents one event, with its name
reported at the bottom of the box. The masses of the merging objects (either
black holes or neutron stars) as well as the final merged object are
indicated in solar masses. The colour of each box highlights in which of the
three observing runs the event was detected: O1, in 2015-16; O2, in 2016-17;
and O3, in 2019-20. The increase in the number of events in O3 was made
possible by the improved performance of all three of the detectors in the
network. Note that GW200105 is also shown, even though it is considered a
marginal event (meaning its astrophysical origin is uncertain), which
explains why 91 boxes are displayed.

35 new events detected by LIGO and Virgo in their latest observation period bring to 90 the gravitational waves detected to date by the global three-interferometer network.

Most of the new signals originate from the whirling spiral of two merging black holes: cosmic quakes that shake the fabric of spacetime, generating a powerful burst of gravitational waves. Two other events, one already reported last June, were instead identified as mergers between a neutron star and a black hole, a source observed for the first time in this last LIGO-Virgo run. A further event, detected in February, 2020, could come from either a pair of black holes or from a mixed pair of a black hole with a neutron star.

The dataset, published today in the so-called third Catalog Paper, outlines the features of new populations of black holes, the masses of which, together with those of the observed neutron stars, may provide clues about how stars live and die, further broadening the horizons of gravitational astronomy.

The Catalog is accompanied by three other publications, focusing on the cosmological and astrophysical consequences of the results and on the multi-messenger search for gravitational-wave signals in coincidence with 86 very energetic bursts (Gammy Ray Bursts) detected in space by the Fermi/GBM and Swift/BAT instruments, during the second part of the third observation period. No confident GW counterparts have been observed; in parallel, no signals of a different kind (e.g. light and neutrinos) have thus far been reported by telescopes and observatories on Earth or in space following-up the GW signals, i.e. searching for signals emitted by the same source as that which emitted the gravitational waves.

At the same time, the LIGO, Virgo and KAGRA scientific collaborations have today also released the full set of calibrated data recorded by the LIGO and Virgo detectors from November, 2019, to March, 2020. This allows the whole research community to perform independent analyses and checks, maximising the wealth of scientific results.

The progress achieved in a few years by gravitational-wave scientists has been amazing, passing from the first detection to the observation of a number of events per month. This has been possible thanks to the programme of continuous technological upgrades, which have transformed the first pioneering instruments into increasingly sensitive detectors. The progress in detector sensitivity due to the technological upgrades and commissioning is evident, considering that, of the 90 gravitational-wave events published today, as many as 79 refer exclusively to the most recent observation period, which ran from April, 2019, to March, 2020.

The LIGO and Virgo observatories are currently undergoing a further upgrade and will start the upcoming fourth observing period, in the second half of 2022, with an even greater sensitivity, corresponding to a volume of the Universe almost 5 times larger than before and, therefore, a much greater probability of picking up gravitational signals.

"Among the other upgrades at Virgo, we have realised an additional optical cavity (the so-called signal-recycling cavity), which allows to improve the sensitivity band of the detector at high frequencies", said Sebastian Steinlechner, assistant professor at Maastricht University and Nikhef. "This corresponds to an increased capacity of the detector to 'listen' to the final stages of the coalescing pairs, when two black holes or stars merge into one."

The KAGRA detector in Japan is being commissioned and KAGRA plans to join the next observing period. The expansion of the network of detectors able to jointly take data will further increase the accuracy of source localisation, a key feature for future developments in multi-messenger astronomy.

Image: The image shows the 90 binary-system mergers that have been observed so far by the Advanced LIGO and Advanced Virgo detector network. Each box represents one event, with its name reported at the bottom of the box. The masses of the merging objects (either black holes or neutron stars) as well as the final merged object are indicated in solar masses. The colour of each box highlights in which of the three observing runs the event was detected: O1, in 2015-16; O2, in 2016-17; and O3, in 2019-20. The increase in the number of events in O3 was made possible by the improved performance of all three of the detectors in the network. Note that GW200105 is also shown, even though it is considered a marginal event (meaning its astrophysical origin is uncertain), which explains why 91 boxes are displayed.

Image credit: Carl Knox, OzGrav, Swinburne University of Technology

Posted: 08/11/2021

First observations of ‘mixed’ black hole and neutron star pairs

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Rainbow Swirl is an artistic
image inspired by a Black Hole Neutron Star merger event. Rainbow Swirl is an artistic
image inspired by a Black Hole Neutron Star merger event.

The Virgo, LIGO and KAGRA scientific collaborations today announced the first observation ever of binary systems consisting of a neutron star (NS) and a black hole (BH). This was made possible by the detection, in January 2020, of gravitational signals (nicknamed GW200105 and GW200115 from the dates of their detection) emitted by two systems, in which a black hole and a neutron star, rotating around each other, merged into a single compact object. The existence of these systems was predicted by astronomers several decades ago, but they had never been observed with confidence, either through electromagnetic or gravitational signals, until now. The result and its astrophysical implications have today been published in The Astrophysical Journal Letters.

"So far we have observed pairs of black holes or pairs of neutron stars through electromagnetic radiation observations or through gravitational waves. The pair of black hole and neutron star was the ‘missing binary’ astronomers were always asking about", said Astrid Lamberts, CNRS researcher of the Virgo collaboration at Artemis laboratory, Observatoire de la Côte d'Azur in Nice. "This discovery shows once again how gravitational-wave detectors are broadening our horizon, allowing us to observe what until now we literally could not see."

The gravitational signals detected in January encode valuable information about the physical features of the systems, such as the mass and distance of the two NSBH pairs, as well as about the physical mechanisms that have generated them and bring them to collapse. The signal analysis has shown that the black hole and neutron star that created GW200105 are, respectively, about 8.9 times and 1.9 times as massive as our Sun and their merger happened around 900 million years ago, hundreds of millions of years before the first dinosaurs appeared on Earth. For the GW200115 event, the Virgo, LIGO and KAGRA scientists estimate the two compact objects had masses around 5.7 (BH) and 1.5 (NS) times the Sun mass and that they merged almost 1 billion years ago.

The result announced today, alongside the dozens of detections made by Virgo and LIGO to date, allow us, for the first time, a close observation of some of the most violent and rare phenomena in the Universe and to draw an unprecedented picture of the crowded and chaotic regions that are one of the possible nursery environments of these events. Furthermore, the detailed information we have started to collect about the physics of the black hole and star mergers, gives us the chance to test the fundamental laws of physics at extreme conditions, which obviously we will never be able to reproduce on Earth. "The discovery announced today is one more gem in the treasure of the 3rd LIGO-Virgo observing run", stated Giovanni Losurdo, Virgo spokesperson and INFN researcher. "LIGO and Virgo keep unveiling catastrophic collisions, which have never been observed before, shedding light on a truly new cosmic landscape. We are now upgrading the detectors with the aim of looking much farther into the depth of the cosmos, searching for new gems, seeking a deeper understanding of the universe we live in."

To learn more, please click here.

How does a black hole and neutron star pair form and merge? (see Infographics)

How does a black hole and neutron star pair form and merge? (see Infographics)

The current astrophysical models roughly consider two main theoretical scenarios for the formation of NSBH pairs. One, called “isolated binary evolution”, starts with two stars orbiting around one another, which, at the end of their life, become, after supernova explosions, a still-bound-together black hole and neutron star. The other possibility is that the neutron star (NS) and black hole (BH) form from separate stars in unrelated supernova explosions, and only afterwards find one another. This, called “dynamical interaction”, can be triggered by different physical mechanisms in dense stellar environments, such as globular clusters, young clusters or even the accretion disks of active galactic nuclei.

Based on these different theoretical scenarios it is possible to make predictions, for example, about the orientations of the black hole and neutron star rotations with respect to the orbital motions (i.e. their so called “spins”) or, more generally, about how many NSBH pairs merge in the Universe within a given time period (a quantity called the “merger rate”).

Thanks to the detections announced today, for the first time, these predictions can be compared with the data of the two observed NSBH pairs, and we can start discriminating between the different astrophysical models.

For instance, considering that only these two NSBH events have been detected during all of the LIGO and VIRGO observing runs, it turns out that between 5 and 15 such systems merge per year within the distance of one billion light years. This rate appears to be especially consistent with both the isolated binary evolution and the dynamical interaction in young star clusters or in active galactic nuclei; however this estimated rate, as well as the measured spin values of GW200105 and GW200115, do not allow to single out just one specific formation scenario.

Image: Rainbow Swirl is an artistic image inspired by a Black Hole Neutron Star merger event.

Image credit: Carl Knox, OzGrav - Swinburne University

Posted: 29/06/2021
Researchers from IFAE
-Barcelona installing the instrumented baffle at Virgo.

Phase I of the upgrades to Advanced Virgo + completed

Researchers from IFAE
-Barcelona installing the instrumented baffle at Virgo. Researchers from IFAE
-Barcelona installing the instrumented baffle at Virgo.

Ten months after the beginning of the upgrade to Advanced Virgo+, Phase I of the installation is completed.

"Despite considerable difficulties due to the Pandemic, we are glad to announce the conclusion of the first part of the hardware upgrade to Virgo AdV+, called Phase I, in a relatively short time. -said Raffaele Flaminio, AdV+ project leader – Now an equally important and challenging phase begins, the so called commisioning phase, i.e. the fine-tuning of all the detector components after the performed upgrades, in order to reach the design sensitivity for the fourth observing run!"

The last upgrade works, that marked the end of Phase I in the past few weeks, have been the installation of the new payload for the Input Mode Cleaner and the depolyment of the sensors for fighting Newtonian noise. The new IMC payload brings in improvements on both the mechanics and surface quality of the mirror; it is also equipped with brand new baffle to absorb diffused light, instrumented to sensors that allows to monitor such diffused light, a significant source of noise for the interferometer.

Newtonian noise at Virgo is mainly due to small changes of the gravitational field around the interferometer mirrors, caused by density fluctuations of seismic origin. The newly installed sensors will allow to monitor such noise, which can later be subtracted.

Other major works in this upgrades phase concerned a more powerful laser source, the installation of a suspended Signal Recycling Mirror, that allows to increase the effect of the gravitational wave measured by the interferometer, and the upgrade of the squeezing technique, already used in the past Observing run O3.

Squeezing is a technique that uses quantum mechanics to improve the sensitivity of the detector. For the next run O4, thanks to the upgrade Virgo will be able to use a frequency-dependent squeezing so to gain in sensitivity at high frequencies (by reducing the photon counting noise) while avoid being limited at low frequencies. To make this possible a new, 300m long, ultra-low-loss optical cavity had to be installed, parallel to the 3km long North arm of Advanced Virgo, in a separated vacuum pipeline.

The goal of these and other upgrades that have been carried out is to bring Virgo, after commissioning, to a sensitivity that is about double that of the last observing period. This means that during its fourth observation run (O4) which will start next year, Advanced Virgo could be able to explore a portion of the universe about ten times bigger, with chances of detecting gravitational wave signals every day!

Image: Researchers from IFAE -Barcelona installing the instrumented baffle at Virgo.

Image credit: IFAE - Barcelona

Posted: 24/05/2021
Artist's interpretation of
				the merging of two black holes releasing gravitational waves.

Roadmap for the future of gravitational-wave research published in Nature

Artist's interpretation of
				the merging of two black holes releasing gravitational waves. Artist's interpretation of
				the merging of two black holes releasing gravitational waves.

In the latest issue of the scientific journal Nature, a roadmap dedicated to the future of gravitational wave research has been published. This is a field of research that promises to continue to challenge the most established astrophysical and cosmological scenarios in the coming years, while also providing important new observations to help in their updating.

According to the article in Nature, over the next 20 years gravitational-wave physics will be able to make a decisive contribution to the answering of some of the fundamental questions facing the entire physics community. These cover areas such as the nature of the dark matter and dark energy that pervade the cosmos, new clues as to what the 'gravitational fingerprint' of the early Universe might offer us, or the not yet fully understood physical mechanisms at play in star collapses or neutron stars. This is just to name a few of the most exciting and important challenges in physics, astrophysics and cosmology today.

In the coming years, LIGO, Virgo and KAGRA, will pass through coordinated data-taking and experimental-upgrade periods, which will help to boost their sensitivity and lead them to detect more than one gravitational event per day (during the fifth observation period, O5, after 2025). There are therefore great expectations for the new findings and results that are anticipated from the next runs.

The scientific community is convinced that it is essential to continue along this path with increasingly powerful and sensitive instruments and detectors. It is therefore important to put in place now, the roadmap that will lead in the coming years to the building and operation of new infrastructures for gravitational-wave research. The authors of this roadmap article are, in fact, all of the scientists of the Gravitational Wave International Committee (GWIC), which was set up in 1997 to facilitate international collaboration and cooperation for the construction of the main infrastructures dedicated to the detection of gravitational waves.

"The GW community has a roadmap", stated Giovanni Losurdo, Virgo spokesperson and one of the authors of the Nature paper. "An extraordinary science plan for the next two decades: a variety of existing and planned projects, which promise to continue the scientific revolution that began with the discovery of gravitational waves five years ago. Nature has published this roadmap, noting once again the increasing attention of the wider scientific community to this field. In the paper, we list a number of fundamental questions to be addressed through GW observations, which represent an extremely ambitious scientific programme, able to dramatically widen our knowledge of the cosmos."

The future generation of ground-based observatories, planned for 2030, the Einstein Telescope (in Europe) and the Cosmic Explorer (in the USA), and the LISA space mission, will be able to dramatically extend the observation window for gravitational signals and intercept not only the cosmic cataclysms produced by the fusion of black holes and neutron stars, but also the gravitational signals generated in the early phases of the life of our Universe. In addition to interferometric detectors, Pulsar Timing Array (PTA) telescopes, with their larger antenna networks, more sensitive receivers and broader bandwidth, will likely be able to follow the dynamics of the largest galaxies in the Universe. The broadest horizon of these is of course that of Multi-Messenger Astronomy, whereby gravitational observations can be crossed and complemented with those of electromagnetic telescopes and particle detectors. The observation of the merger of two neutron stars in August 2017, was the first exceptional example of this kind, with the joint observation with gravitational waves from the LIGO and Virgo interferometers and electromagnetic radiation from dozens of telescopes on the ground and in space.

Stavros Katsanevas, director of the European Gravitational Observatory, added, "The most extraordinary thing in this roadmap, is not only that the worldwide gravitational-wave community is forming a closely knit network of detectors, covering the globe, including space, and plans a coherent and well coordinated future, but that at the same time all the measures are taken so that a similarly coordinated network of observatories, detectors and satellites is currently deployed and will be deployed in the near future. This means that a multi-messenger understanding of cosmic processes, using messengers from gravitational to electromagnetic waves and cosmic rays and neutrinos, will be possible, probing events that happened millions of years ago. It will be possible to follow their evolution, second per second, from their violent beginnings and for months afterwards. This is clearly a new era of Astrophysics, the Multi-messenger era."

Image: Artist's interpretation of the merging of two black holes releasing gravitational waves.

Image credit: Science Photo Library/Alamy, Nature

Posted: 16/04/2021

Hunting for continuous emission of gravitational waves from neutron stars

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While Virgo and LIGO have been undergoing upgrades, the data from the early part of the third observing run of the detectors (from April to September, 2019), have been analysed by researchers to look for signs of continuous emission of gravitational waves from rapidly spinning neutron stars. This makes it possible to set new, clear constraints for future searches.

Theory has it that, as they rotate, neutron stars emit continuous gravitational waves, because of asymmetries in the mass distribution around the rotation axis. The asymmetries may be due, for instance, to misalignments between their symmetry and rotation axes or to imperfections, sort of ‘mountains’, in the outer crust. Through the analysis of these gravitational-wave signals, scientists can probe and study the inner structure and composition of these extremely intriguing astrophysical objects.

Researchers of the LIGO and Virgo collaborations have looked for these continuous emission signals, focusing on those emitted from neutron stars in binary systems. Due to the movement and rotation of the Earth, this wave would appear with a characteristic frequency modulation, further characterised by the binary nature of the system. After integrating the data stream over the six-month period to accumulate a large signal-to-noise ratio, no evidence of this signature modulation has been found. However, researchers have determined the maximum distance from the Earth that the search was able to probe and the maximum deformation allowed for a neutron star within this range, setting a clear constraint for future analysis. The results were released on the 25th of December on arXiv.org.

Another study, released on the same day, focuses on a particular pulsar (a rapidly rotating neutron star), known as PSR J0537-6910, located in the Large Magellanic Cloud, a “satellite” galaxy of our Milky Way. While this pulsar spins, it loses energy, as all pulsars do, but this one is special because it is both the fastest spinning young pulsar we know of and the one with the largest rate of energy loss. If all of this lost energy was light, it would be about 100,000 times the luminosity of the Sun. Actually some of the energy could be lost as gravitational waves, and, if so, how much of it?

This is what the LIGO, Virgo and KAGRA Collaborations, in conjunction with NICER (Neutron star Interior Composition Explorer, a telescope installed on the International Space Station) have set out to investigate, by looking for continuous gravitational-wave emission from PSR J0537-6910. Also in this case, no evidence of this emission was found, but once again this allows us to gain new information: less than around 14% of the star's spin-down luminosity is going into gravitational-wave production. The remaining energy has to be emitted through other mechanisms: for example X-ray and Gamma ray emissions or through the acceleration of charged particles, to create the so-called pulsar wind nebula.

Image: A pulsar (pink) can be seen at the centre of the Messier 82 galaxy in this multi-wavelength portrait. The pulsar was discovered by NASA's NuSTAR which detected the pulsar's X-ray emission.

Image credit: NASA/JPL-Caltech

Posted: 28/12/2020
Sky localisations
for the different LIGO-Virgo detections included in the O3a catalogue

Over 100 black holes detected by Virgo and LIGO in the first run of 2019

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Sky localisations
for the different LIGO-Virgo detections included in the O3a catalogue Sky localisations
for the different LIGO-Virgo detections included in the O3a catalogue

The classification and definitive analysis of the 39 events detected by Virgo and LIGO in the third observation period (which ran from April to October 2019) was published today on the ArXiv online archive. Most of these are black hole mergers, the characteristics of which, however, question some established astrophysical models and open up new scenarios. A likely merger of neutron stars and two probable 'mixed' neutron star-black hole systems were also detected in the same period.

It took a year of work and complex analysis by the researchers of the Virgo and LIGO scientific collaborations to complete the study of all of the gravitational-wave signals that were recorded by the Virgo interferometer, installed at the European Gravitational Observatory, in Italy, and the two LIGO detectors, in the US, during the data-taking period - called 'O3a' - which ran from the 1st of April to the 1st of October, 2019. Events included: 36 mergers of black holes; a likely merger of a binary system of neutron stars; and two systems that were most likely composed of a black hole and a neutron star. Among these, four “exceptional events” have, during the last year, already been published, but the catalogue released today provides, for the first time, a complete picture of the extraordinarily large number of recorded gravitational-wave signals and their sources. It represents a wealth of observations and data on the physics of black holes, barely imaginable until only a few years ago.

For more information, please click here.

"Since the end of the O2 observing run in August 2017, many efforts have been made to upgrade many of the technical components and different sectors of the detector, in order to boost the Virgo sensitivity across the whole frequency range", said Ilaria Nardecchia, researcher at the University of Roma Tor Vergata and member of the Virgo Collaboration. "We reaped the benefits of our work, because we doubled the sensitivity of the detector!"

Indeed, between September, 2017, and April, 2019, the sensitivity of the three detectors has been significantly improved. This has led, for example, to Virgo becoming capable of observing a volume of the universe almost ten times larger than in the previous observational run (O2).

"Observations with Advanced Virgo and LIGO have exceeded expectations. As well as opening a new and exciting phase in the history of human observation of the cosmos, we are seeing events that either lacked observational evidence until now, or go beyond our current understanding of stellar evolution", said Ed Porter, directeur de recherche CNRS at APC-Paris, and member of the Virgo Collaboration. "Just five years after the first detection of gravitational waves, we can say that gravitational astronomy is a concrete reality."

The detection of gravitational signals allows us, in fact, for the first time, to closely observe the dynamics of extraordinary mergers of black holes and neutron stars, which release bursts of energy equivalent to several solar masses in gravitational waves. This allows us to study, as never before, the physics of black holes, the cosmic phenomena that generate them and even the characteristics of the largest populations of black holes. Actually, the results of the present catalogue raise serious questions about the validity of some of the astrophysical scenarios and models, which until now seemed the most plausible.

In particular, the masses of black holes, presented in the O3a catalogue, question various theoretical and observational limits on the mass ranges of black hole populations. Some observations, for example, indicate the presence of compact objects (which could be either black holes or neutron stars) exactly in the gap between the mass of the heaviest neutron stars and that of the lightest black holes observed by astronomers to date. This gap could therefore narrow or even disappear. Other observed black holes have a mass with a value between 65 and 120 solar masses; a range forbidden by stellar evolution models. According to these models, the very massive stars, beyond a certain threshold, are completely disrupted by the supernova explosion, due to a process called pair instability, and leave behind only gas and cosmic dust. The existence of black holes in the range prohibited by pair instability suggests other mechanisms of black hole formation, such as the merger of smaller black holes or the collision of massive stars, but may also indicate the need to revise our description of the final stages of the lives of stars.

The publication of the O3a catalogue is the conclusion of complex work involving many phases and covering detector calibration, data characterisation and data analysis. The catalogue for each observation run is only published once researchers have the final validated dataset, thus making it possible to estimate the physical parameters (such as distance, mass and spins) of the black-hole and neutron-star mergers, as well as a confident estimate of their margins of error. Of the 39 events presented in this latest catalogue, 26 were announced immediately after detection, while 13 are reported for the first time in the paper published today. These add to the 11 gravitational-wave events reported by LIGO and Virgo for the previous runs (O1 and O2). In addition to the LIGO-Virgo events catalogue, three other articles have also been released today on the arXiv server: the global analysis of the astrophysical properties of the gravitational-waves sources; new tests of the theory of general relativity; and the search for gravitational-wave signals coincident with gamma-ray bursts."

"These papers are very important and represent a further step forward in a long and exciting journey", said Giovanni Losurdo, INFN researcher and spokesperson for the Virgo Collaboration. "We are already looking forward to the results of the second part of the third observation period (O3b). The very high number of events still to analyse and understand promises that the next catalogue will be as exciting, if not more so, than this one. Meanwhile, we are striving to implement a substantial upgrade of the Virgo detector, aiming to pursue the next run, in 2022, again with a considerably improved sensitivity."

Citizen-science projects for gravitational-wave data-analysis

Two citizen-science projects, Gravity Spy for LIGO and the European project, REINFORCE for Virgo, allow everyone to contribute to the identification of spurious signals and therefore to the discovery of new gravitational-waves signals, by collaborating directly with researchers involved in the analysis of the data of the three interferometers.

In fact, although external as well as internal noise sources are minimised, the data taken by the interferometers are still plagued by some disturbances. In some cases these are monitored by witness sensors and are then subtracted from the data in real time. Nevertheless the identification of other noises is more problematic and requires off-line dedicated analysis in order to flag them. This is the case with glitchy noises; those that are generated, for instance, by light scattered off the main laser beam and that then recombine with it. The careful studies required to claim a true gravitational-wave signal explain why the LIGO and Virgo Collaborations issue alerts of a candidate event to the scientific community soon after it has been measured. This can then either be confirmed by subsequent analysis and hence considered a true signal or not. Thanks to Gravity Spy and REINFORCE, citizen scientists can help researchers in this complex analysis work by directly accessing the data detected by the LIGO and Virgo interferometers.

Image: The image shows sky localisations for the different LIGO-Virgo detections that are included in the O3a catalogue. Each localisation - represented by shaded areas on the map - is deduced on the basis of information provided by the three detectors in the network. The day and time of arrival on Earth, a scientific name and the time it took the signal to reach the Earth from wherever in the Universe it was generated, are all recorded. The smaller the shaded area in the sky map, the better the signal has been localised. Localisation is crucial in enabling follow-up searches with different messengers, such as light or neutrinos.

Image credit: EGO/Virgo Collaboration/Greco

Posted: 28/10/2020

Quantum effects make Virgo mirrors jitter

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A quantum mechanical effect measured for the first time in the Advanced Virgo and LIGO gravitational-wave detectors.

Quantum mechanics does not only describe how the world works on its smallest scales, but also affects the motion of macroscopic objects, such as the 42 kg mirrors of the Virgo interferometer. To detect gravitational waves, Virgo and LIGO measure tiny changes in the lengths of their laser interferometer arms, changes as small as one thousandth of a proton diameter. The two detectors use laser light to measure, with the highest precision, the relative position of mirrors that are kilometres apart. For this reason, these mirrors are kept as 'still' as possible and are shielded from all possible noises of human or environmental origin. Even in the absence of any gravitational-wave signals or noise sources, these mirror position measurements would show a slight jitter. This is due to the so-called shot noise, i.e. the pattern of the randomly and irregularly arriving light particles. In both Virgo and LIGO, during the third observation period (O3), this noise was reduced by 'squeezing' the light, using a particular quantum optics technique. Unfortunately, it is not possible to do this without paying a price.

Following one of the fundamental laws of quantum mechanics - Heisenberg's uncertainty principle - a reduced shot noise results in increased radiation pressure noise: the force with which the stream of light particles pushes on the mirrors, fluctuates more strongly. As a result, the mirrors, each weighing 42 kg, move back and forth more, simply because of the effects of quantum mechanics. In fact, the shot noise affects the sensitivity of the detector at high frequencies, while the radiation-pressure noise disturbs the detection of signals with lower frequencies. Getting out of this impasse is not easy. If, on the one hand, the detectors increase sensitivity at high frequencies, and therefore to a certain type of gravitational-wave source, on the other, they become less able to identify low-frequency signals.

"Thanks to the collaboration with the Albert Einstein Institute in Hannover", explains Jean Pierre Zendri, senior researcher of the Istituto Nazionale di Fisica Nucleare (INFN) in Padova and member of the Virgo Collaboration, "we succeeded to show for the first time a clear evidence of the radiation-pressure noise on the massive detector mirrors. This was allowed by the extraordinary sensitivity of Advanced Virgo, which allows us to appreciate fluctuations of the mirror positions to less than a thousandth of a proton diameter." The results of this research have now been published in Physical Review Letters.

To further improve the detector's performance, gravitational-wave scientists are developing a new technology, called frequency-dependent squeezing, which will make it possible to reduce the quantum mechanical noise at both high and low frequencies. The implementation of this technology is actually one of the crucial steps of the upgrade of the Advanced Virgo Interferometer, which will be taking place over the coming months at the European Gravitational Observatory near Pisa in Italy.

Image: The Virgo test-mass mirror inside its actuation-cage. The mirror and actuation-cage are both suspended from a Virgo Superattenuator. A layer of protective polymer (visible in pink) still covers the mirror, preventing dust contamination during installation. On the left, two mirrors can be seen. These are part of the sensor that monitors the tiny thermal deformations of the test-mass mirror occurring during operation. Black-coated panels surround the optical elements to absorb residual stray light.

Image credit: EGO/Virgo Collaboration/Perciballi

Posted: 24/09/2020

Virgo and LIGO unveil new and unexpected black hole populations

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Virgo and LIGO have announced the detection of an extraordinarily massive merging binary system: two black holes of 66 and 85 solar masses, which generated a final black hole of 142 solar masses. Both the initial black holes, as well as the remnant, lie in a range of mass that has never before been observed, either via gravitational waves or with electromagnetic observations.

The final black hole is the most massive ever detected with gravitational waves.

The gravitational-wave event was detected by the three interferometers of the global network on the 21st of May, 2019, and is hence named GW190521. Two scientific papers reporting the discovery and its astrophysical implications have been published today (see the scientific papers here and here).

The breaking of the mass record of the Virgo and LIGO observational runs is just one of the many special features that make the detection of this exceptional merger an unprecedented discovery. A crucial aspect, which particularly drew the attention of astrophysicists, is that the remnant belongs to the class of the so-called intermediate-mass black holes (from a hundred up to a hundred thousand times the mass of the Sun).

The interest in this black-hole population is linked to one of the most fascinating and challenging puzzles for astrophysicists and cosmologists: the origin of supermassive black holes. These giant monsters, millions to billions of times heavier than the Sun and often at the centre of galaxies, may arise from the merger of 'smaller' intermediate-mass black holes. Until today, very few intermediate-mass black-hole candidates have been identified through electromagnetic observations alone and the remnant of GW190521 is the first observation of an intermediate-mass black hole via gravitational waves.

Read the full story in the EGO-Virgo press release.

Image: Artistic interpretation of the binary black hole merger responsible for GW190521. Space-time, shown as a fabric on which a view of the cosmos is printed, is distorted by the GW190521 signal. The turquoise and orange mini-grids represent the dragging effects due to the individually rotating black holes. The estimated spin axes, or self-rotations, of the black holes are indicated with the corresponding coloured arrows. The background suggests a star cluster, one of the possible environments in which GW190521 could have occurred.

Image credit: Raúl Rubio / Virgo Valencia Group / The Virgo Collaboration

Posted: 02/09/2020

GW190814 - the merger of a 23-solar-mass black-hole and an enigmatic lighter object

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Another unprecedented discovery has just been unveiled by LIGO-Virgo scientists. Data from the third observation period (O3) of the Advanced LIGO and Advanced Virgo detectors reveal that, at 21:10 (UTC) on the 14th of August, 2019, the three instruments in the network detected a gravitational-wave signal, called GW190814. The signal originated from the merger of an enigmatic couple: a binary system composed of a black hole, 23 times heavier than our sun, and a much lighter object, about 2.6 times the mass of the Sun. The merger resulted in a final black hole about 25 times the mass of the sun.

It is this lighter object that makes GW190814 so special. It may just be either the lightest black hole or the heaviest neutron star ever discovered in a binary system. Another peculiar feature of GW190814 is the mass ratio of the objects in the binary system. The factor 9 ratio is even more extreme than was the case with the first detected merger of a binary with unequal masses, GW190412.

"Once again, gravitational-wave observations are shedding light on the unknown. The lightest object in this system has a mass that has never before been observed", says Giovanni Losurdo, of Istituto Nazionale di Fisica Nucleare (Italy) and the spokesperson of the Virgo Collaboration. "A new discovery, which raises new questions. What is its nature? How did such a binary system form? Virgo, LIGO and, soon, Kagra in Japan, will continue to search for the answers and push forward the frontier of what we know about the cosmos in which we live."

The mass asymmetry causes the presence of higher multipoles in the gravitational radiation, a fact that allows stringent tests of General Relativity. Once again, all our tests confirm the prediction of Einstein’s theory. Moreover, the higher multiples allow us to disentangle the determination of the source distance from the inclination angle of the plane of the orbiting binary. We have found the source of the gravitational wave to be about 800 million light years away!

The signal was clearly detected by the three instruments, with an overall signal-to-noise ratio as high as 25. Thanks mainly to the delay between the signal arrival times at the three, well separated detectors, the network was able to localise the origin of GW190814 to within about 19deg2 in the sky. This is similar to the localisation achieved for the famous GW170817, which gave birth to multi-messenger astronomy with gravitational waves. In the case of GW190814, however, an electromagnetic counterpart has yet to be observed.

"We are very satisfied with the performance of Advanced Virgo during O3," says Maddalena Mantovani, scientist at the European Gravitational Observatory (EGO). "We reached the target sensitivity with a very good duty cycle. This is the result of the hard work of the scientists and technicians that have fine-tuned the machine to provide its best performance. Scientific discoveries such as GW190814 are the best rewards for all those days and nights spent on improving the detector."

Image: Artistic rendering of the GW190814 event, in which a smaller compact object is swallowed by a 9-times-more-massive black-hole. The matter stream between the two objects and the look of the massive black hole are an artistic invention. To the best of our knowledge, the GW190814 fusion is not thought to have emitted any light.

Image/Animation credit: Alex Andrix

Posted: 23/06/2020

GW190412: The merger of two black holes with unequal masses

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The third LIGO-Virgo observing period (O3) is offering new insights into the late inspiral and merger phase of binary black hole (BBH) systems. The first gravitational wave event GW150914, detected back in 2015, originated from a binary black hole merger, and since then this class of events has become the most prominent. This allows us to advance in the characterization of the population of astrophysical BBHs. However, the systems observed so far were formed by black holes of nearly equal masses. This balance was broken by the observation of the merger of a very special BBH on the 12th of April, 2019 at 05:30:44 UTC, just a couple of weeks after the start of O3, on the 1st of April.

The signal, named GW190412, was detected by the Advanced Virgo and the two Advanced LIGO detectors, and it was produced by a coalescing BBH system with unequal masses, one component being more than 3 times heavier than the other one. More in detail, the merged black holes had masses respectively about 30 and 8 times the mass of the Sun. The mass difference produces specific signal modulations that were predicted by theory, but have now been observed for the first time. In fact, the mass unbalance produces an unusually high intensity of gravitational radiation in the so-called "Higher Order Modes", which are detectable in GW190412 and provide yet another confirmation of the validity of Einstein’s General Relativity. GW190412 also depends on other parameters of the binary system which cause modulations that enable us to constrain the inclination of the plane of the binary with respect to the line of sight and the distance of the source; two quantities that are otherwise highly correlated.

"The Virgo and LIGO detectors are becoming more and more sensitive, the rate of detections increases and we expect new and unusual events. GW190412 is unusual and interesting, because of the large mass difference between the two coalescing black holes. We are learning that systems of this kind exist and how rare they are. This will allow us to deduce how they formed, which is something that I find exciting", says Giancarlo Cella, researcher at Istituto Nazionale di Fisica Nucleare (INFN) and the Virgo Data Analysis Coordinator.

"The unequal masses of this source caused overtones of the main signal to be visible for the very first time. This provided us with an exciting new opportunity to test an important prediction of Einstein’s theory about what happens when black holes of unequal size collide", says Anuradha Samajdar, postdoc fellow at the Dutch National Institute for Subatomic Physics (Nikhef), and member of the Virgo Collaboration.

Image: The distance inferred for the source of GW191412 versus the inclination angle of the binary’s orbit with respect to the line of sight. In general the two quantities are highly correlated but the different masses of the BH in the binary allow us to partially disentangle them. The distance is most likely about 700 Mpc, that is 2.3 billions of light years.

Image credit: LIGO Scientific Collaboration/Virgo Collaboration

Posted: 20/04/2020
A binary neutron star system just before merger: the two stars are deformed by tidal forces and are about to fuse together. The image is produced by a numerical simulation in General Relativity and shows the mass density volume rendering at nuclear densities in blue and lower density material in red. The snapshot refers to the central volume of approximately 45^3 km.

GW190425: the merger of a compact binary with total mass of about 3.4 Msun

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A binary neutron star system just before merger: the two stars are deformed by tidal forces and are about to fuse together. The image is produced by a numerical simulation in General Relativity and shows the mass density volume rendering at nuclear densities in blue and lower density material in red. The snapshot refers to the central volume of approximately 45^3 km. A binary neutron star system just before merger: the two stars are deformed by tidal forces and are about to fuse together. The image is produced by a numerical simulation in General Relativity and shows the mass density volume rendering at nuclear densities in blue and lower density material in red. The snapshot refers to the central volume of approximately 45^3 km.

On April the 25th, 2019, the network of gravitational-wave (GW) detectors formed by the European Advanced Virgo, in Italy, and the two Advanced LIGO, in the US, detected a signal, named GW190425. This is the second observation of a gravitational-wave signal consistent with the merger of a binary-neutron-star system after GW170817. GW190425 was detected at 08:18:05 UTC; about 40 minutes later the LIGO Scientific Collaboration and the Virgo Collaboration sent an alert to trigger follow-up telescope observations.

The source of GW190425 is estimated to be at a distance of 500 million light years from the Earth. It is localized in the sky within an area about 300 times broader than was the case for the BNS observed by LIGO and Virgo in 2017, the famous GW170817, which gave birth to multi-messenger astrophysics. However, unlike GW170817, no counterpart (electromagnetic signals, neutrinos or charged particles) has been found to date.

There are a few explanations for the origin of GW190425. The most likely is the merger of a BNS system. Alternatively, it might have been produced by the merger of a system with a black hole (BH) as one or both components, even if light BHs in the mass-range consistent with GW190425 have not been observed. Yet, on the basis solely of GW data, these exotic scenarios cannot be ruled out. The estimated total mass of the compact binary is 3.4 times the mass of the Sun. Under the hypothesis that GW190425 originated from the merger of a BNS system, the latter would have been considerably different to all known BNS in our galaxy, the total mass range of which is between 2.5 and 2.9 times the mass of the Sun. This indicates that the NS system that originated GW190425 may have formed differently than known galactic BNSs.

"After the surprise of the initial results", says Alessandro Nagar of the Istituto Nazionale di Fisica Nucleare (INFN) of Turin, Italy, "we have finally reached a reliable understanding of this event. Although predicted theoretically, heavy binary systems like those that might have originated GW190425 may be invisible through electromagnetic observations."

"While we did not observe the object formed by the coalescence, our computer simulations based on general relativity predict that the probability that a BH is formed promptly after the merger is high, about 96%", says Sebastiano Bernuzzi of the University of Jena, Germany.

Image: A binary neutron star system just before merger: the two stars are deformed by tidal forces and are about to fuse together. The image is produced by a numerical simulation in General Relativity (animation) and shows the mass density volume rendering at nuclear densities in blue and lower density material in red. The snapshot refers to the central volume of approximately 45 km in diameter.

Image credit: CoRe / Jena FSU

Press release - Communiqué de presse - Notas de prensa - Materiały dla prasy

Posted: 06/01/2020
O3 start

Virgo and LIGO join forces for a new year-long signal hunt

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O3 start O3 start

The Virgo and LIGO detectors are ready to start the new Observing run called O3, lasting a whole year. The hunt for gravitational waves is set to start on April 1st when the European Virgo detector, based in Italy at the European Gravitational Observatory (EGO), and the LIGO twin detectors, located in the state of Washington and Louisiana (USA), will start to take data becoming together the most sensitive gravitational wave observatory to date. During a one-year period the LIGO and Virgo Collaborations will register science data continuously, and the three detectors will operate as a global observatory.

"With respect to the second observation period O2, the Virgo sensitivity has improved by about a factor of 2, which means that the volume of the observable Universe has increased by a factor of 8", says Alessio Rocchi, researcher at INFN and Virgo’s commissioning coordinator.

"The quality of the data collected by the instruments is a determining factor to detect gravitational-wave signals buried into noise and to measure their properties", said Nicolas Arnaud, CNRS researcher currently seconded to EGO and Virgo detector characterization coordinator. "A lot of progress has been made in that direction since O2, thanks to the combined effort of the collaboration as a whole, from the instrumentalists to the data analysts".

For more information, please click here.

The scientific output of O3 is expected to be tremendous and it will potentially reveal new exciting signals coming form new sources such as the merger of mixed binaries made by a black hole and a neutron star. The O3 run will also target long lasting gravitational waves produced for instance by spinning neutron stars which are not symmetric with respect to their axis; however, the detection of such signals is still an enormous challenge and the LIGO and Virgo Collaborations are raising up to it. Furthermore, signals for the merger of binary black holes are expected to become quite common, perhaps up to one per week. Scientists also expect to observe several binary neutron star mergers.

"The new software we have built is able to send Open Public Alerts within five minutes", says Sarah Antier, postdoc at the Université Paris Diderot and responsible of the low latency program for the Virgo Collaboration. "This will allow to follow-up the gravitational wave signal with neutrino and/or electromagnetic searches, that may lead to multimessenger discoveries. Observations of many signals as we expect during O3 will give us a census of the population of stellar mass remnants and a better understanding of the violent Universe."

Since August 2017 both LIGO and Virgo have been updated and tested. In particular Virgo has fully replaced the steel wires which were used in O2 to suspend the four main mirrors of the 3 km long interferometer: the mirrors are now suspended with thin fused-silica (‘glass’) fibres, a procedure which has allowed to increase the sensitivity in the low-medium frequency region, and has a dramatic impact in the capabilities to detect mergers of compact binary systems. A second major upgrade was the installation of a more powerful laser source, which improves the sensitivity at high frequencies. Last but not least squeezed vacuum states are now injected into Advanced Virgo, thanks to a collaboration with the Albert Einstein Institute in Hannover, Germany. This technique takes advantage of the quantum nature of light and improves the sensitivity at high frequencies.

Image: The image shows the rear-side view of a suspended mirror. The coating reflects the Virgo near-infrared laser beam, but is transparent in the visible range. A scientist is finally releasing the safety stops used during installation. The 42kg-mass mirror is suspended from four thin fused-silica fibres, which are bonded to the sides of the mirror.

Image credit: EGO/Virgo Collaboration/Perciballi

Posted: 26/03/2019

About

Working in the tower

What is Virgo?

Virgo is an interferometric gravitational-wave antenna. It consists of two 3-kilometre-long arms, which house the various machinery required to form a laser interferometer.

A beam-splitter divides a laser beam into two equal components, which are subsequently sent into the two interferometer arms. In each arm, a two-mirror Fabry-Perot resonant cavity extends the optical length from 3 kilometres to approximately 100. This is because of multiple reflections that occur within each cavity and which consequently amplify the tiny distance variation caused by a gravitational wave.

The two beams of laser light that return from the two arms are recombined out of phase so that, in principle, no light reaches the so-called 'dark fringe' of the detector. Any variation caused by an alteration in the distance between the mirrors, produces a very small shift in phase between the beams and, thus, a variation of the intensity of the light, which is proportional to the wave's amplitude.

Click here for more information on the Virgo experiment and its science.

The Virgo Collaboration

Virgo is a gravitational-wave interformeter designed, built and operated by a collaboration made up of 20 laboratories in 6 countries and involves the following institutions:

CNRS INFN NIKHEF EGO WIGNER IMPAS VALENCIA

Virgo Outreach

Interesting events are always being prepared at EGO-Virgo. Please view our Outreach website for details on up and coming, as well as recent, events.

Virgo and LIGO

Virgo and the LIGO Scientific Community work together in many areas and have a specific agreement on the exchange of data. More information on the work of our LIGO colleagues is available here.

More information on the identification and follow up of electromagnetic counterparts of gravitational wave candidate events is available here.

The Virgo-EGO Scientific Forum

Virgo and EGO have also established a scientific forum - the VESF - for astrophysicists and theorists, dedicated specifically to the furthering of scientific knowledge related to Virgo. More information is available here.

A payload

ET - Einstein Telescope

The Einstein Telescope (ET) project is dedicated to the development of a critical research infrastructure for a third-generation gravitational-wave interferometer. More information about the project, which is supported by the European Commission as part of the Framework Programme 7, is available here.

Other gravitational-wave experiments

Have a look at some of the other gravitational wave experiments:

Interferometric experiments

Pulsar-timing-array experiments

Other gravitational-wave-related websites

Jobs & Fellowships

The following roles are currently being advertised within the Virgo Collaboration:

Roles at the European Gravitational Observatory (EGO) are advertised on the EGO website.

Visits

Virgo viewed from the south

Events

If you are looking for information on an up-coming or recent event, please visit our Outreach website.

Opening hours

The Reception at the EGO site is open at the following times:

  • Monday to Friday, from 08:30 to 13:00 and 14:00 to 17:30
  • Closed on Saturdays and Sundays (except when site visits are scheduled)

How to get to Virgo

Virgo is at the site of the European Gravitational Observatory (EGO), the organisation responsible for the site, and is located in:

Via Amaldi
56021 Santo Stefano a Macerata – Cascina (Pisa), Italy.

As Virgo is located in the countryside, it is not particularly easy to access without a car, as there are no public transport links directly to it.

Arriving by car

The EGO-Virgo site GPS coordinates (in DD) are:

  • Latitude: 43.6305 N
  • Longitude: 10.5021

Arriving by plane/train and taxi

The nearest airport to Virgo is Pisa Galileo Galilei International Airport.

If you are travelling by aeroplane and arrive at the Pisa Galileo Galilei International Airport, or by train and arrive at Pisa Central train station, we recommend that you call a taxi (Co.Ta.Pi Radiotaxi Pisa, +39 050 54 16 00) complete your journey to EGO-Virgo.

It takes about 20-30 minutes to reach the site coming from Pisa when coming by car. The taxi fare from Pisa to the EGO-Virgo site costs about €35-40.

What do on arrival at the EGO-Virgo site

All visitors must present themselves at the site-entrance gate, where they will be met by their EGO contact person.

Visitors' vehicles may be parked at the site, in the appropriate parking areas.

New Virgo collaborators

New Virgo collaborators must complete the association and safety procedures before starting any activity on site. To this end, they should contact the EGO Administration (Building 4, first floor, +39 050 752 522/325) and the Safety and Security Office (Building 1, +39 050 752 416/544).

Badges to access the site and an account to access the Virgo documentation will only be granted by the IT department on completion of this process.

Contact

The Virgo experiment at the European Gravitational Observatory

Address: Via Amaldi, 56021 Santo Stefano a Macerata, Cascina (Pisa), Italy.

Phone: +39 050 752 511

Fax: +39 050 752 550

Email: info@ego-gw.it

Web: http://www.virgo-gw.eu

Twitter: https://twitter.com/ego_virgo

Facebook: https://it-it.facebook.com/EGOVirgoCollaboration/

Youtube: EGO & the Virgo Collaboration - LIGO-Virgo

Instagram: LIGO-Virgo

Giovanni Losurdo, Virgo Spokesperson

Phone: +39(0) 75 2317

Email: losurdo@pi.infn.it

Web: https://www.pi.infn.it/~losurdo/

Address: INFN - Pisa Division - Largo Pontecorvo 3, Ed. C - 56127 - Pisa - Italy

The Virgo Collaboration

A full list of members of the Virgo Collaboration and their contact details is available here.

Please get in contact if you would like more information.