Mysterious and inescapable black holes are among the most unusual creatures in the universe. Scientists at Germany’s HITS predicted that the “chirp” noise produced when two black holes merge occurs preferentially in two universal frequency ranges.
Detection in 2015 gravitational waves, a phenomenon hypothesized by Einstein a century ago, paved the way for the 2017 Nobel Prize in Physics and marked the beginning of the dawn of gravitational wave astronomy. The merger of two stellar-mass black holes releases gravitational waves of increasing frequency, known as chirp signals, that can be detected on Earth. By analyzing the progression of this frequency (chirp), the scientist is able to calculate the “chirp mass,” which is a mathematical expression of the combined mass of the two black holes.
So far, it has been thought that merging black holes can have arbitrary masses. But the researchers’ model suggests that some black holes arrive with standard masses, resulting in universal chirps.
Fabian Schneider, who led the HITS research, said: “The existence of a universal chirp mass not only indicates how black holes form, but also allows us to infer which stars go supernova. It can also be used.” Supernova mechanisms, uncertain core and stellar physics, and new ways for scientists to measure the accelerated cosmological expansion of the universe.
“It has a significant impact on the final fate of the star.”
A stellar-mass black hole, about 3 to 100 times the mass of the Sun, is the end point of a massive star that does not explode in a supernova but instead collapses into a black hole. The progenitors of black holes that cause mergers were originally born in binary star systems and experienced several episodes of mass exchange between their constituents. Notably, both black holes are from stars that have been stripped of their outer skins.
“The peeling of the envelope has serious consequences for the star’s final fate. For example, it makes the star more susceptible to supernova explosions, which can also lead to the explosion of the universe. Black Hole ” says Philip Podsiadrowski of the University of Oxford. He is the second author of the study and is currently Visiting Professor Klaus Chila at HITS.
“Star Graveyard” – a collection of all known populations neutron star The number of black hole remnants in massive stars is rapidly increasing, thanks to the increasing sensitivity of gravitational wave detectors and the continued search for such objects. In particular, there appears to be a gap in the distribution of chirp masses for merging binary black holes, with evidence of peaks at approximately 8 and 14 solar masses. These features correspond to the universal chirp predicted by the HITS team.
“The characteristics of the mass distribution of black holes and chirps can tell us a lot about how these objects formed,” says Eva Laplace, third author of the study.
Not in our galaxy: a black hole with a much larger mass
Since the first discovery of black hole mergers, it has become clear that black holes exist with masses much greater than those we have discovered. milky way. This is a direct result of black holes originating from stars born with a different chemical composition than the Milky Way. The HITS team was able to show that, regardless of chemical composition, stars deenveloped in close binaries form black holes with solar masses less than 9 and more than 16, but few in between. Ta.
In a black hole merger, a universal black hole mass of about 9 solar masses and 16 would logically imply a universal chirp mass, and therefore a universal sound. “While updating my lecture on gravitational wave astronomy, I realized that gravitational wave observatories were the first to discover the lack of chirp mass and hints of an excess that exactly matches the universal mass predicted by our models. ” says Fabian Schneider. “The number of black hole mergers observed is still quite small, so it is not yet clear whether this signal in the data is just a statistical coincidence.”
Whatever the outcome of future gravitational wave observations, the results will be exciting and help scientists better understand where the black holes singing in this ocean of voices come from.
References: Fabian RN Schneider, Philipp Podsiadlowski, and Eva Laplace, “Bimodal black hole mass distribution and chirp mass of binary black hole mergers,” June 15, 2023. of Astrophysics Journal Letter.
DOI: 10.3847/2041-8213/acd77a
This research was funded by the European Research Council for the second half of 2020.