Faculty of Science E-newsletter

Recently, the Laser Interferometer Gravitational-wave Observatory (LIGO) Scientific Collaboration and the Virgo Collaboration (Virgo) reported the discovery of GW190521, the first ever detected intermediate-mass black hole which reaches a mass larger than was thought possible. Professor Tjonnie Li and Professor Juan Calderon Bustillo of Department of Physics lead the only group in Hong Kong involved with the work of LIGO, and have been deeply involved in the analysis of the signal.

To date, we have known about two different populations of black holes. Stellar black holes with masses less than about 100 times that of the Sun and supermassive black holes with up to billions of times the mass of the Sun. GW190521 was detected on 21 May, 2019 by three interferometers and the detailed analysis of the signal indicates that the creature with 142 solar masses was produced by the fusion of two black holes of approximately 85 and 66 times the mass of the Sun, which is the first evidence of a black hole in this mass range. The ground-breaking discovery helps scientists to understand how stars live and die and suggests them to revisit the current models of black hole formation.

Further reading:

Abbott, R., Abbott, T. D., Abraham, S., Acernese, F., Ackley, K., Adams, C., ... & Agatsuma, K. (2020). GW190521: A Binary Black Hole Merger with a Total Mass of 150 M⊙. Physical Review Letters, 125(10), 101102. DOI: https://doi.org/10.1103/PhysRevLett.125.101102

Abbott, R., Abbott, T. D., Abraham, S., Acernese, F., Ackley, K., Adams, C., ... & Agatsuma, K. (2020). Properties and astrophysical implications of the 150 M⊙ binary black hole merger GW190521. The Astrophysical Journal Letters, 900(1), L13. DOI: https://doi.org/10.3847/2041-8213/aba493

University Press Release