Image caption: Infographic on the binary black hole merger that produced the GW231123 signal. Credit: LIGO
Scientists have detected the most massive black hole collision ever observed, creating one more than 240 times heavier than our Sun. The discovery was made using ultra-sensitive equipment that can detect ripples in space itself.
The discovery was made by the LIGO-Virgo-KAGRA (LVK) collaboration involving over 1,600 scientists from around the world, using the US National Science Foundation funded LIGO Hanford and Livingston Observatories.
Two enormous black holes, weighing about 100 and 140 times more than our Sun, crashed into each other in a cosmic collision that happened billions of years ago. The gravitational wave signal produced from this cosmic crash - named GW231123 - only reached Earth in November 2023, where they were picked up by the LIGO detectors in the United States.The combination of data from the two observatories were essential in the detection.
The gravitational waves from these massive black holes challenge current astrophysical models. Until now, the biggest black hole merger LVK collaboration had detected was only 140 times the mass of the Sun (GW190521). This new collision is almost twice as massive.
The finding of GW231123 was presented at the Institute of Physics 24th International Conference on General Relativity and Gravitation (GR24) and the 16th Edoardo Amaldi Conference on Gravitational Waves , held jointly as the GR-Amaldi meeting in Glasgow this week.
Aerial view of the Laser Interferometer Gravitational Wave Observatory (LIGO detector in Hanford, Washington. Credit: LIGO
Dr Charlie Hoy , a Research Fellow at the University of Portsmouth's Institute of Cosmology and Gravitation and a member of LIGO (Laser Interferometer Gravitational Wave Observatory) Scientific Collaboration, is a leading member of the team who deciphered the data and a co-author of the paper presented at the conference.
Dr Hoy said: "These black holes were spinning incredibly fast - almost at the maximum speed Einstein's theory of relativity allows. This makes them extremely difficult to study and challenges everything scientists thought they knew about how black holes form.
"This makes the signal difficult to model and interpret. It's an excellent case study for pushing forward the development of our theoretical tools."
"This is the most massive black hole binary we've observed through gravitational waves, and it presents a real challenge to our understanding of black hole formation," added Professor Mark Hannam , from Cardiff University and also a member of the LIGO Scientific Collaboration. "Black holes this massive are forbidden through standard stellar evolution models. One possibility is that the two black holes in this binary formed through earlier mergers of smaller black holes."
Black holes are invisible, but when they collide, they create ripples in space-time called gravitational waves. These waves travel across the universe at the speed of light, and by the time they reach Earth, they're incredibly tiny - smaller than 1/10,000th the width of a proton.
Gravitational-wave detectors such as LIGO in the United States, Virgo in Italy, and KAGRA in Japan are designed to measure minute distortions in spacetime caused by violent cosmic events like black hole mergers. The fourth observing run began in May 2023 and further observations from the first half of the run (up to January 2024) will be published later in the summer.
As a recognised international centre of research excellence, the University of Portsmouth's Institute of Cosmology and Gravitation (ICG) brings together more than 70 researchers - faculty, postdoctoral fellows and PhD students - tackling some of the Universe's most profound mysteries, from the earliest moments after the Big Bang to the large-scale structure of galaxies, dark energy and gravitational waves.
Its world-class impact was confirmed in REF 2021, where 100 per cent of ICG research was rated world-leading or internationally excellent.
The institute's contributions include roles in major international projects such as Euclid , LISA (Laser Interferometer Space Antenna) , the LIGO gravitational wave detectors , and the Dark Energy Spectroscopic Instrument (DESI) .
