Science & Technology

A new type of cataclysm event in space

The artist’s view of black holes and neutron star mergers.Credits: © Carl Knox, OzGrav – Swinburne University

  • Gravitational wave detectors have observed a new type of cataclysmic event in space: the fusion of neutron stars and black holes.
  • This phenomenon was detected twice in January 2020.
  • Some hypotheses can explain the existence of such mixed pairs. Further observation will be needed to resolve the issue.

Another missing part has just been added to the knowledge of cosmic phenomena. The first detection of gravitational waves announced in collaboration with LIGO, Virgo and KAGRA[1] It is the result of a “mixed” merger between a black hole and a neutron star.[2] Discovery published on June 29, 2021 Astrophysical Journal LetterIncludes CNRS researchers working in Virgo’s scientific collaboration.

Only a few years after the first observations of gravitational waves, this technology has created an extensive repertoire of phenomena, including giant space objects. LIGO and Virgo detectors have already observed black hole pairs (or binaries) and, less often, neutron star mergers. However, the gravitational waves detected in January 2020 provide evidence of the existence of a new type of system. From the date of detection, the signals named GW200105 and GW200115 were generated by a process that was predicted but never observed. It is a combination of “mixed pairs” called NSBH pairs, each composed of a neutron star and a black hole. ..[3]

Gravitational waves contain valuable information about the source, such as the masses of the components that make up the binary. Signal analysis shows that the GW200105 resulted from the merger of black holes and neutron stars with masses 8.9 and 1.9 times the mass of the Sun, respectively, about 900 million years ago, while the GW200115 was an NSBH pair united at about 1. It became clear that it arose from. Billions of years ago, the mass was 5.7 and 1.5 times that of the Sun. The difference in mass between the components of the system indicates that they are actually mixed binaries. The mass of a heavy object corresponds to the mass of a black hole, and the mass of a light object corresponds to the mass of a neutron star. The difference between the two masses can also explain why the telescope did not detect an optical signal. When a neutron star approaches a black hole, it can theoretically be torn by tidal forces, causing flare of electromagnetic radiation. However, in the two cases observed, the black hole was much larger and may have devoured the neutron star with a bite, leaving no trace.

Mass in Stella Cemetery

The masses of neutron stars and black holes measured through gravitational waves (blue and orange) and electromagnetic observations (yellow and purple). GW200105 and GW200115 are emphasized as a fusion of neutron stars and black holes. Credits: © LIGO-Virgo / Frank Elavsky, Aaron Geller / Northwestern

Several hypotheses have been proposed to explain the formation of mixed NSBH binaries. The first is the evolution of a pair of stars that orbit each other. Towards the end of their lives, one of the stars will become a black hole and the other will become a neutron star, but they will still rotate around each other. Another hypothesis, the dynamic interaction hypothesis, is that the two components of a pair are formed independently in a very dense stellar medium and then come together. These results pave the way for the detection of other mixed binaries and the observation and understanding of extreme phenomena of similar nature.

Black hole neutron star infographic


  1. Gravitational waves are small ripples in space-time, first observed in 2015, a century after Albert Einstein predicted their existence in his general theory of relativity.
  2. A neutron star is the wreckage of a giant star that collapsed at the end of its life.
  3. The confidence levels of the two signals are different. The statistical significance of GW200105 is not very high, but the shape of the signal and the parameters inferred from it indicate the origin of astrophysics.

For more information on this study A new type of cataclysm event in space: astrophysicists detect first black hole and neutron star merger..

Reference: R. Abbott, TD Abbott, S. Abraham, F. Asernese, K. Acre, A. Adams, C.”Observation of Gravitational Waves from Two Neutron Stars-Black Hole Coalescence” by Adams, RX Adikali, VB Adia C. Afeld […] AB Zimmerman, Y. Zlochower, ME Zucker, J. Zweizig, and LIGO Scientific Collaboration, Virgo Collaboration, and KAGRA Collaboration, June 29, 2021 Astrophysical Journal Letter..
DOI: 10.3847 / 2041-8213 / ac082e

About Virgo, LIGO and KAGRA

Virgo Collaboration currently consists of approximately 690 members from 15 countries. The European Gravitational Observatory (EGO) hosts Virgo detectors near Pisa, Italy, funded by the Center National de la Recherche Scientifique (CNRS) in France, Istituto Nazionale di Fisica Nucleare (INFN) in Italy, and Nikhef in the Netherlands. Is being offered. ..

LIGO is funded by the National Science Foundation Network (NSF) and is run by the California Institute of Technology and MIT, who devised and led the project. Financial support for the Advanced LIGO project was led by the NSF, with Germany (Max Planck Society), the United Kingdom (Science and Technology Facilities Council) and Australia (Australian Research Council-OzGrav) making significant contributions and contributions to the project. .. Approximately 1,300 scientists from around the world are participating in this effort through LIGO Scientific Collaboration, including GEO Collaboration.

The KAGRA laser interferometer is located in Kamioka, Japan. The host organization is the Institute for Cosmic Ray Research (ICRR), University of Tokyo, co-sponsored by the National Astronomical Observatory of Japan (NAOJ) and the High Energy Accelerator Research Organization (KEK). Construction of KAGRA was completed in 2019, and data acquisition began in February 2020 at the final stage of execution called “O3b”. The KAGRA Scientific Congress is made up of more than 470 members from 14 countries / regions.

The scientific treatise announcing this discovery is co-signed by 102 French scientists and works with eight teams at CNRS and related universities that are part of the Virgo Collaboration.

  • ‘Astroparticule et cosmologie’ Lab (CNRS / Université de Paris);
  • Artemis Institute (CNRS / Cote d’Azur Observatory / University of Cote d’Azur);
  • g-MAG team, “Institutlumi è rematière” (CNRS / Université Claude Bernard Lyon 1), “Institut des nanotechnologies de Lyon” (CNRS / Ecole Centrale de Lyon / INSA Lyon / Université Claude Bernard Lyon 1 / CPE) Scientist Lyon), “Center National de la Recherche Scientifique” (CNRS / Sorbonne University) and Navier Institute (CNRS / Ecole De Pomparitech / Gustave Eiffel University);
  • ‘Institut de physique des 2 infinis de Lyon’ (CNRS / Université Claude Bernard Lyon 1);
  • ‘Institut pluridisciplinaire Hubert Curien’ (CNRS / Université de Strasbourg);
  • ‘Laboratoire d’Annecy de physique des particules’ (CNRS / Université Savoie Mont Blanc);
  • ‘Laboratoire Kastler Brossel’ (CNRS / University of Sorbonne / ENS-PSL / Collège de France);
  • “Laboratoire de physique des 2 infinis – Irène Joliot-Curie” (CNRS / Université Paris-Saclay).

Some authors have been associated with the above teams while working at other laboratories:’Institut Foton’ (CNRS / Université Rennes 1 / Insa Rennes), Lagrangelaboratory (CNRS / Université Côte d’Azur / Observatoire Côte d’Azur) , “Laboratoire de physique et d’étude des matériaux” (CNRS / Sorbonne University / ESPCI Paris).

A new type of cataclysm event in space A new type of cataclysm event in space

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