Gravitational-Wave Astronomy LARGE SCIENTIFIC PROJECT the International Gravitational-Wave Network. Virgo joined the the data taking in 2024 and the Japanese detector KAGRA, located underground and designed to operate at cryogenic temperatures, joined the run despite a sensitivity still insufficient for full scientific contribution. However, it continues to make steady progress, and will become the first cryogenic interferometer once fully operational. A fifth detector, LIGO-India, is currently under construction as a collaboration between the United States( providing instrumentation) and India( providing infrastructure such as the vacuum tubes and site). Once completed, it will significantly improve the localization accuracy of the network. Since the beginning of O4, more than 200 candidate events have been identified( by rapid search algorithms), mainly binary black hole mergers, with a detection rate of approximately 2 – 3 per week. The full analyses are forthcoming, but some“ exceptional” systems have already been identified, including a merger that produced a final black hole of about 200 solar masses, in the intermediate-mass black hole region. These events are of great interest, not only because they expand the taxonomy of astrophysical objects, but also because they challenge formation theories. In particular, at least one of the black holes observed in the GW231113 event( 23 November 2023) appears to lie within the“ mass gap” between 60 and 130 solar masses, where no black hole remnants are expected due to pair-instability supernova.
Ten Years of Gravitational-Wave Astronomy
Ten years after the first detection( GW150914), the global detector network has observed nearly 300 candidates gravitational-wave sources, including about 200 published events at the time of writing( September 2025, see [ 19 ]). This corresponds to mainly black holes mergers, while two confirmed neutron star mergers and a few mixed events( black hole + neutron star) have been identified. Thanks to the LIGO – Virgo – KAGRA collaboration, new astrophysical windows have been opened. Gravitational-waves allow us to:
• Perform tests of general relativity
• Address key cosmological questions such as the value of the Hubble constant
• Explore the mass distribution and formation pathways of black holes
• Probe the interior structure of neutron stars
• Localize transient for rapid electromagnetic follow-up
While advanced data analysis techniques, play a crucial role in improving detection efficiency, the future of gravitational-wave science
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[ 10 ] B. P. Abbott et al.( LIGO Scientific Collaboration and Virgo Collaboration), Phys. Rev. Lett. 116, 061102( 2016)
[ 11 ] J. Aasi et al., Class. Quantum Grav. 32, 074001( 2015) [ 12 ] F. Acernese et al., Class. Quantum Grav. 32, 024001( 2015)
[ 13 ] B. P. Abbott et al.( LIGO Scientific Collaboration and Virgo Collaboration), Phys. Rev. Lett. 119, 141101( 2017)
[ 14 ] B. P. Abbott et al.( LIGO Scientific Collaboration and Virgo Collaboration), Phys. Rev. Lett. 119, 161101( 2017)
[ 15 ] E. Pian et al., Nature 551, 67( 2017) [ 16 ] B. P. Abbott et al., Nature 551, 85( 2017) [ 17 ] M. Tse et al., Phys. Rev. Lett. 123, 231107( 2019)
[ 18 ] LIGO Scientific Collaboration, Virgo Collaboration, KAGRA Collaboration, " GWTC-3: Compact Binary Coalescences Observed by LIGO and Virgo During the Second Part of the Third Observing Run," arXiv: 2111.03606( 2021)
[ 19 ] https:// ligo. org / detections / o4a-catalog / fundamentally depends mainly on instrumental progress: better mirrors, more powerful lasers, improved isolation systems, more sophisticated squeezing schemes— and crucially, sensitivity at lower frequencies( down to 10 Hz or even below), where technical and environmental noise sources are most challenging. Many R & D efforts around the world are now focused on preparing upgrades to LIGO and Virgo in the 2030s, and on the next-generation observatories: the Einstein Telescope( ET) in Europe and Cosmic Explorer( CE) in the United States. These facilities, currently under study, are designed to have much longer arms and are therefore far more sensitive. So, happy 10 th birthday GW150914, and happy birthday to LIGO, Virgo, and KAGRA. Looking forward to new surprises and to a new sky made by spacetime vibrations.
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