Black holes, some of the most captivating entities in the cosmos, possess an immense gravitational pull so strong that not even light can escape. The groundbreaking detection of gravitational waves in 2015, caused by the coalescence of two black holes, opened a new window into the universe. Since then, dozens of such observations have sparked the quest among astrophysicists to understand their astrophysical origins. Thanks to the POSYDON code’s recent major advancements in simulating binary-star populations, a team of scientists, including some from the University of Geneva (UNIGE), Northwestern University and the University of Florida (UF) predicted the existence of merging massive, 30 solar mass black hole binaries in Milky Way-like galaxies, challenging previous theories. These results are published in Nature Astronomy.
Stellar-mass black holes are celestial objects born from the collapse of stars with masses of a few to low hundreds of times that of our sun. Their gravitational field is so intense that neither matter nor radiation can evade them, making their detection exceedingly difficult. Therefore, when the tiny ripples in spacetime produced by the merger of two black holes were detected in 2015, by the Laser Interferometer Gravitational-wave Observatory (LIGO), it was hailed as a watershed moment. According to astrophysicists, the two merging black holes at the origin of the signal were about 30 times the mass of the sun and located 1.5 billion light-years away.
Bridging Theory and Observation
What mechanisms produce these black holes? Are they the product of the evolution of two stars, similar to our sun but significantly more massive, evolving within a binary system? Or do they result from black holes in densely populated star clusters running into each other by chance? Or might a more exotic mechanism be involved? All of these questions are still hotly debated today.
The POSYDON collaboration, a team of scientists from institutions including the…