Aerial view of the EGO site, location of the Virgo interferometer
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May 2018 News

Upgrading and commissioning the Virgo detector

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May 2018 news May 2018 news

As planned, the Virgo and LIGO detectors stopped taking data for the ‘Observation Run 2’ - O2 - on the 25th of August, 2017. For both collaborations, this marked the beginning of a new and busy period, which is scheduled to last at least one year (see timelines on the left). During this time, the sensitivity of all three instruments (that is, their ability to detect signals even fainter than those observed in 2015 and 2017 or coming from similar sources, but located further away in the universe) should be improved significantly. Then, in early 2019, the data-taking period – O3 – will start and last for about one calendar year.

For more information, please click here.

On the Virgo side, three phases were foreseen.

First, commissioning activities were undertaken until mid-autumn, in order to improve our knowledge of the detector configuration that was used to take data, and to fix issues identified during the August 2017 run. Indeed, for all large facilities such as Virgo, the golden rule is to disturb the instrument as little as possible while it is running. Only issues preventing the taking of data are promptly fixed and only straightforward improvements are allowed. Therefore, it was only after the end of the O2 run that people working in the Virgo control room were able to carry out many different tests and modify the hardware and software configurations of the detector.

Instrument upgrades were implemented from the end of November 2017 until the middle of March 2018. Several pieces of hardware were replaced or modified. Notable upgrades included:

  • The installation of a more powerful, ultra-stable input laser: the larger the power circulating in the detector, the more sensitive it is, in particular in the high-frequency range: above a few hundred hertz. With the new laser, the O3 input power is expected to increase by up to a factor of three in comparison with the O2 data-taking period.
  • The replacement of the steel wires suspending the mirrors forming the 3-km long Fabry-Perot cavities - four mirrors in total - with fused silica - ‘glass’ - wires. This lower-dissipation material helps in reducing friction at the anchor levels, hence the suspension thermal noise, which represents the dominant fundamental noise impacting upon the Virgo sensitivity in the medium-frequency region, where it is at its best. These fibers have high breaking strengths, but they are fragile, which makes the whole process - from the production of the fibers in a dedicated lab at EGO, to the suspension of the mirror from its superattenuator structure - challenging. In parallel, the vacuum quality has been improved. About a year and half ago, particle contamination of the vacuum caused some fused-silica fibers to break inside the detector. At that time, the mirrors were again suspended from steel wires and the upgrade to fused-silica fibers was postponed to the O2-O3 long shutdown.
  • The addition of a squeezed vacuum source - a ’squeezer’ - provided by the Albert Einstein Institute in Hannover, Germany. This instrument, installed at the output port of the interferometer - where the power exists that results from the interference between the laser beams circulating in the 3-km long arms - helps to ’beat’ the quantum noise limit, i.e. to reduce the laser shot-noise, which is dominant at high frequency, below its normal level. This counter-intuitive effect is due to the quantum nature of light: any electromagnetic wave, such as the Virgo laser beam, is defined by two quantities, an amplitude and a phase, both of which are fluctuating. The fluctuations of the phase – also known as ’phase noise’ – matter more than the amplitude fluctuations for Virgo. With a squeezer, one can move part of the phase noise to the amplitude noise – the Heisenberg principle states that one cannot decrease both fluctuations: if one goes down, the other should increase – and hence improve the instrument sensitivity. This technique has been successfully implemented in GEO 600 and LIGO: this is the first time it will be tried in Virgo.

Following the completion of all of these upgrades, Virgo is now back in commissioning mode. The first aim is to learn how to control the detector, which has been significantly modified, and then to improve the sensitivity – by at least a factor of two by the end of the year. This will be challenging but the first results are promising: the best O2 sensitivity – the all-time record sensitivity for Virgo – was surpassed in early June.

Posted: 17/07/2018
GW170817

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

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GW170817 GW170817

Discovery marks first cosmic event observed in both gravitational waves and light.

For the first time, scientists have directly detected gravitational waves — ripples in space and time — 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 space-based observatories.

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.

Science Papers and supplementary materials

Posted: 16/10/2017
GW170814

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

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GW170814 GW170814

A fourth gravitational-wave signal coming from the merger of two stellar mass black holes located about 1.8 billion light-years away was detected on the 14th of August 2017, at 10:30:43 UTC. GW170814 is the first event observed by the global 3-detector network, including not only the two twin Advanced LIGO detectors but the Advanced Virgo detector as well.

Following a multi-year upgrade programme and several months of commissioning, the Advanced Virgo detector joined the LIGO "Observation Run 2" data-taking period on the 1st of August. The three instruments worked together until the 25th of August.

GW170814 demonstrates the potential of a 3-detector network, both in terms of localization of a source in the sky and in terms of the testing of Einstein's theory of general relativity. The best GW170814 skymaps, computed by an analysis that uses all of the available information from the three instruments, cover just 60 square degrees (to be compared with several hundreds of square degrees for the LIGO-only network) and GW170814 data have allowed the LIGO-Virgo collaboration to probe, for the first time, the polarization of gravitational waves.

Therefore, GW170814 holds great promise for the future of multimessenger astronomy. Additional results, based on data from the three-detector network, will be announced in the near future by the LIGO-Virgo Collaboration; the analysis of the data is currently being finalized.

Posted: 27/09/2017
DQ_META_ITF_Mode O2 stripchart

A very exciting LIGO-Virgo Observing run draws to a close on the 25th of August

DQ_META_ITF_Mode O2 stripchart DQ_META_ITF_Mode O2 stripchart

The Virgo and LIGO Scientific Collaborations have been observing since November 30, 2016 in the second Advanced Detector Observing Run ‘O2’, searching for gravitational-wave signals, first with the two LIGO detectors, then with both LIGO and Virgo instruments operating together since August 1, 2017. Some promising gravitational-wave candidates have been identified in data from both LIGO and Virgo during our preliminary analysis, and we have shared what we currently know with astronomical observing partners. We are working hard to assure that the candidates are valid gravitational-wave events, and it will require time to establish the level of confidence needed to bring any results to the scientific community and the greater public. We will let you know as soon we have information ready to share.

The picture shows the Virgo duty cycle during the whole data taking period: we have been taking science data more than 80% of the time over four weeks!

Posted: 25/08/2017
First detection

First detection of gravitational waves

First detection First detection

On the 14th of September 2015, a gravitational wave was detected for the first ever time. This first detection was announced to the world on the 11th of February 2016:

Posted: 11/02/2016

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 role is currently being advertised within the Virgo Collaboration:

Roles at 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

Jo van den Brand, Spokesman of Virgo

Phone: +31 620 539 484

Email: jo@nikhef.nl

Web: https://www.nikhef.nl/~jo

Addresses: Nikhef, National Institute for Subatomic Physics, Amsterdam, The Netherlands.
VU University Amsterdam, Faculty of Sciences, Department of Physics and Astronomy.
European Gravitational Observatory - EGO, Cascina (PI), 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.