The most extensive black-hole merger ever observed appeared to yield a black hole with a mass of 150 times that of the Sun, challenging certain established theories. Now, researchers claim to have identified, for the first time, evidence of the long-sought vibrations generated by the resultant black hole as it settled into a spherical form.
These findings introduce a novel and rigorous assessment for Albert Einstein’s general relativity—the gravitational theory providing intricate predictions about both black holes and gravitational waves, according to Steven Giddings, a theoretical physicist at the University of California, Santa Barbara. He remarks that the current exploration represents an entrance into uncharted territory in the realm of physics.
Badri Krishnan, a physicist and one of the study’s authors, reveals that he had engaged in this form of analysis as a theoretical concept in the early stages of his career. Reflecting on those earlier endeavors, he expresses surprise at witnessing such a measurement during his lifetime. Krishnan, currently affiliated with Radboud University in the Netherlands, highlights the unexpected nature of the achievement. The study‘s results were recently published in Physical Review Letters.
Following the advent of gravitational-wave astronomy in 2015, the identification of merging black holes has transitioned into a regular event. The paired detectors of the Laser Interferometer Gravitational-Wave Observatory (LIGO), situated in Washington State and Louisiana, are currently detecting these mergers at an average rate of more than once a week.
Data obtained from the Laser Interferometer Gravitational-Wave Observatory (LIGO) and the Virgo observatory in Italy, typically exhibit gravitational wave signatures from the spiral and merging process of two massive objects. This information, derived from the frequency of their orbits leading up to the merger, unveils the masses of the individual objects and the resultant single black hole. Generally, more massive objects have longer merging orbits, resulting in lower-frequency gravitational waves.
Among the numerous events recorded, GW190521, identified by its discovery date of May 21, 2019, stood out due to its exceptionally low merging frequency. It entered the sensitivity range of LIGO and Virgo only during its final two orbits.
Researchers, independent of the LIGO-Virgo collaboration, sought to investigate whether the gravitational waves from this event carried not just pre-merger information but also details from the immediate post-merger moments. When two black holes merge, the resulting black hole assumes an asymmetrical shape. However, black holes attain stability only when adopting a spherical (or spheroidal in the case of rapid spinning) form. Within milliseconds, they transition into the lowest-energy, symmetrical shape.
Similar to how a bell emits specific frequencies based on its shape, the stabilized black hole undergoes a ‘ringdown’ process, emitting gravitational waves with frequencies determined by its mass and spin, explains Krishnan. The measurement of ringdown frequencies offers an alternative approach to estimating the black hole’s properties compared to the analysis of spiraling frequencies.
Krishnan and his colleagues reexamined data from the GW190521 event to search for indications of the ringdown phenomenon. In their findings, they identified two distinct ringdown frequencies, collectively indicating that the resulting black hole weighs approximately 250 times the mass of the Sun—a significantly heavier mass range than the original analysis conducted by the LIGO-Virgo team.
Resources
- JOURNAL Castelvecchi, D. (2023). Gravitational waves from mega black-hole collision reveal long-sought ‘ringing.’ Nature. [Nature]
- JOURNAL Capano, C. D., Cabero, M., Westerweck, J., Abedi, J., Kastha, S., Nitz, A., Wang, Y., Nielsen, A. B., & Krishnan, B. (2023). Multimode Quasinormal Spectrum from a Perturbed Black Hole. Physical Review Letters, 131(22). [Physical Review Letters]
- JOURNAL Abbott, R., Abbott, T. D., Abraham, S., Acernese, F., Ackley, K., Adams, C., Adhikari, R. X., Adya, V. B., Affeldt, C., Agathos, M., Agatsuma, K., Aggarwal, N., Aguiar, O. D., Aich, A., Aiello, L., Ain, A., Ajith, P., Akçay, S., Allen, G., . . . Zweizig, J. (2020). GW190521: A Binary Black Hole Merger with a Total Mass of 150 M⊙. Physical Review Letters, 125(10). [Physical Review Letters]
- JOURNAL Abbott, R., Abbott, T. D., Abraham, S., Acernese, F., Ackley, K., Adams, C., Adhikari, R. X., Adya, V. B., Affeldt, C., Agathos, M., Agatsuma, K., Aggarwal, N., Aguiar, O. D., Aich, A., Aiello, L., Ain, A., Ajith, P., Akçay, S., Allen, G., . . . Zweizig, J. (2020b). Properties and astrophysical implications of the 150 M ⊙ Binary Black Hole Merger GW190521. The Astrophysical Journal, 900(1), L13. [The Astrophysical Journal]
Cite this page:
APA 7: TWs Editor. (2023, December 2). A Mega Black-Hole Collision and Its Aftermath: Gravitational Waves and the Long-Sought ‘Ringing.’ PerEXP Teamworks. [News Link]
