Last year, scientists announced that they had finally observed gravitational waves, the elusive and long sought-after ripples in the fabric of spacetime that were first posited by Albert Einstein. The waves came from a catastrophic event — the collision of two black holes located about 1.3 billion light years away from Earth — and the released energy undulated across the universe, much like ripples in a pond.
The detection by the upgraded Laser Interferometer Gravitational-Wave Observatory (Advanced LIGO), along with two subsequent gravitational wave discoveries, confirmed a major prediction of Einstein’s 1915 general theory of relativity and heralded a new era in physics, allowing scientists to study the universe in a new way by using gravity instead of light.
But a fundamental question remains unanswered: How and why do black holes collide and merge?
In order for the black holes to merge, they must start out very close together by astronomical standards, no more than about a fifth of the distance between the Earth and the Sun. But only stars with very large masses can become black holes, and during the course of their lives, these stars expand to become even larger.
A new study published in Nature Communications uses a model called COMPAS (Compact Object Mergers: Population Astrophysics and Statistics) in an attempt to answer how large binary stars that would eventually become black holes fit within a very small orbit. COMPAS allows the researchers to pursue a kind of “paleontology” for gravitational waves.
“A paleontologist, who has never seen a living dinosaur, can figure out how the dinosaur looked and lived from its skeletal remains,” said Ilya Mandel from the University of Birmingham in the UK, the paper's senior author, in a statement. “In a similar way, we can analyze the mergers of black holes, and use these observations to figure out how those stars interacted during their brief but intense lives."