LIGO and Virgo make first detection of gravitational waves produced by neutron star collision - School of Science, the University of Tokyo
Oct 18, 2017

LIGO and Virgo make first detection of gravitational waves produced by neutron star collision


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

An international team of scientists including researchers at the University of Tokyo have detected both gravitational waves and light from a spectacular neutron star collision.

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 including the Subaru (Hawaii), MOA-II (New Zealand), Mt. John B&C (New Zealand), and IRSF (South Africa) telescopes.

LIGO Hanford Observatory. Photo by C. Gray.


LIGO Livingston Observatory. Photo courtesy of LIGO Laboratory.


Virgo Detector. Photo courtesy of European Gravitational Observatory.


Computer simulation of gravitational waves from GW170817. T. Dietrich, et al., LIGO-G1702003.


Computer simulation of gravitational waves from GW170817. T. Dietrich, et al., LIGO-G1702003.


Neutron stars are the smallest, densest stars known to exist and are formed when massive stars explode in supernovae. As these neutron stars spiraled together, they emitted gravitational waves that were detectable on Earth for over 6 minutes. When they collided, a flash of gamma rays was emitted and detected by Earth-orbiting satellites about 2 s after the gravitational waves passed through the Earth. In the hours, days, and weeks following the collision, other forms of light, or electromagnetic radiation were detected, including X-ray, ultraviolet, optical, infrared, and radio waves — a true multi-messenger discovery.

The initial gravitational-wave detection was made by the GstLAL signal detection system developed by Kipp Cannon (U-Tokyo) together with colleagues at other universities around the world. The discovery has given astronomers an unprecedented opportunity to probe a collision of two neutron stars. For example, the Japanese collaboration of Gravitational-Wave Electromagnetic Follow-up Observations (J-GEM) conducted intensive follow-up observations in optical and near-infrared wavelengths using the Subaru, MOA-II, B&C, and IRSF telescopes (Publication 2). They confirmed that the time evolution of the luminosity and spectral energy distribution of the neutron star merger are well explained by a so-called kilonova explosion, which originates from collision of two neutron stars (Publication 3).

From B. P. Abbott, et al., “GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral” Phys. Rev. Lett., 119:161101 (2017).


“This discovery changes our expectations for Japan's KAGRA detector” says Cannon. “People had feared that gravitational-wave detectors might only be useful in a network if they all had similar sensitivities, but GW170817's electromagnetic counterpart was only discovered because of the information provided by Advanced Virgo, which was still new and not operating as sensitively as the LIGO detectors, just like KAGRA will be. We're now very excited waiting to see what discoveries will be made with the first data from KAGRA.”

“It is tremendously exciting to experience a rare event that transforms our understanding of the workings of the universe,” says France A. Córdova, director of the National Science Foundation (NSF), which funds LIGO. “This discovery realizes a long-standing goal many of us have had, that is, to simultaneously observe rare cosmic events using both traditional as well as gravitational-wave observatories. Only through NSF's four-decade investment in gravitational-wave observatories, coupled with telescopes that observe from radio to gamma-ray wavelengths, are we able to expand our opportunities to detect new cosmic phenomena and piece together a fresh narrative of the physics of stars in their death throes.”

LIGO is funded by the NSF, and operated by Caltech and MIT, which conceived of LIGO and led the Initial and Advanced LIGO projects. Financial support for the Advanced LIGO project was led by the NSF with Germany (Max Planck Society), the U.K. (Science and Technology Facilities Council) and Australia (Australian Research Council) making significant commitments and contributions to the project.

More than 1,200 scientists and some 100 institutions from around the world participate in the effort through the LIGO Scientific Collaboration, which includes the GEO Collaboration and the Australian collaboration OzGrav. Additional partners are listed at

The Virgo collaboration consists of more than 280 physicists and engineers belonging to 20 different European research groups: six from Centre National de la Recherche Scientifique (CNRS) in France; eight from the Istituto Nazionale di Fisica Nucleare (INFN) in Italy; two in the Netherlands with Nikhef; the MTA Wigner RCP in Hungary; the POLGRAW group in Poland; Spain with the University of Valencia;  and the European Gravitational Observatory, EGO, the laboratory hosting the Virgo detector near Pisa in Italy, funded by CNRS, INFN, and Nikhef.


Publication details


1. Physical Review Letters

2. and 3. Publications of the Astronomical Society of Japan

4. Detection Papers (LIGO Caltech)


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

2. "J-GEM observations of an electromagnetic counterpart to the neutron star merger GW170817"

3. "Kilonova from post-merger ejecta as an optical and near-infrared counterpart of GW170817"


1. B. P. Abbott et al. (LIGO Scientific Collaboration and Virgo Collaboration)

2. Yousuke Utsumi*, Masaomi Tanaka, Nozomu Tominaga, Michitoshi Yoshida, Sudhanshu Barway, Takahiro Nagayama, Tetsuya Zenko, T., Kentaro Aoki, Takuya Fujiyoshi, Hisanori Furusawa, Koji S. Kawabata, Shintaro Koshida, Chien-Hsiu Lee, Tomoki Morokuma, et al.

3. Masaomi Tanaka*, Yousuke Utsumi, Paollo A. Mazzali, Nozomu Tominaga, Michitoshi Yoshida, Yuichiro Sekiguchi, Tomoki Morokuma, et al.


1. 10.1103/PhysRevLett.119.161101

2. 10.1093/pasj/psx118

3. 10.1093/pasj/psx121

Paper links






National Astronomical Observatory of Japan

Subaru Telescope, National Astronomical Observatory of Japan

Center for Computational Astrophysics, National Astronomical Observatory of Japan

Gravitational Wave Project Office, National Astronomical Observatory of Japan


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