Known as the “father of the black hole” for coining this term, American theoretical physicist John Wheeler is also the author of a curious idea called “baldness theory”, which proposes that “black holes have no hair”.
As funny as it may seem (after all, Wheeler had no hair either), the thesis reflects one of the most striking properties of black holes: its simplicity, that does not allow to identify its training mechanism or its time of origin.
Now, this simplicity, one of the few cases in physics where complexity decreases instead of increasing, is helping a team led by researchers at the University of Cardiff in the UK to determine how and where they formed them.
Published, the study tests the hypothesis that the population of the observed black holes currently is widely composed of objects formed in dense environments, where mergers occurred repeatedly, which can alter our understanding of these objects.
These cosmic genetic memory tests use so-called gravitational waves, dynamic disturbances in the spacetime tissue, which propagate as a result of interactions between matter and gravity in its most extreme form.
Analyzing the spin patterns of black holes
To test their hypotheses, the team examined a public catalog with 69 gravitational wave events involving binary black holes detected by the Ligo and Virgo observatories, located respectively in the US and Italy.
They found that the spin, a black hole “movement signature” (which tells us how fast and in which direction it is spinning), changes when it reaches a particular mass. This suggests that This spin may be the result of a long series of previous mergers.
When they claim that the spin changes with the mass, the authors talk about changes in this “working pattern” that would not be expected if the black hole “fed” only matter, gradually. The changes suggest that.
According to the main author of the study, Fabio Antonini of the University of Cardiff, “as we observe more black hole mergers with gravitational wave detectors such as Ligo and Virgo, it is increasingly clear that black holes display diverse masses and spins.”
For the theoretical astrophysicist, this is a strong indication that they may have formed in different ways. However, identifying “which of these training scenarios is the most common has been challenging,” he concludes.
Analyzing gravitational wave data, ripples in the spacetime that allow us to “hear” black holes collisions, The team was able to identify a “turn point” in the mass of black holes where its spin pattern changes consistently.
It was as if they had discovered a spins -based dividing line: on one side, black holes below a certain mass with a type of rotation, and, above this mass, black holes formed by successive collisions within stars.
Creating a paradigm to identify black holes
The result of this study is a reliable way to identify how some black holes have formed, without depending on specific theories or complex mathematical models.
If so far it was very difficult to know for sure the origin of black holes, the new method emerges as a kind of unique fingerprint. He reveals the story of the black hole clearly and independently of the theory or model chosen to study it.
For co-author Isabel Romero-Shaw, a researcher at Cambridge University, the study shows that the “way he [buraco negro] Gira is a strong indicator that belongs to a group of high mass black holes. ”
These objects form. In this scenario, explains the postdoctoral student in a release, “small black holes collide and repeatedly merge with each other.”
In addition to providing new data to refine computational models that simulate black holes formation, this study will guide how to detections of gravitational wave will be done in the future.
Thus, when Ligo and other more advanced detectors (such as the future einstein telescope) capture unpublished signs of black hole mergers, scientists will be prepared to compare these signs with the predictions of updated models, in a continuous cycle of improvement.
