Researchers from the University of Southampton, together with colleagues from the universities of Cambridge and Barcelona, have shown it’s theoretically possible for black holes to exist in perfectly balanced pairs – held in equilibrium by a cosmological force – mimicking a single black hole.
Black holes, colossal objects in the universe, possess a gravitational pull so powerful that nothing, not even light itself, can escape their grasp. They are characterized by an astonishing density, to the extent that the mass of Earth could be compressed into a space as minuscule as a pea.
In conventional models rooted in Einstein’s General Theory of Relativity, black holes are typically depicted as solitary entities, whether they remain motionless or engage in a spinning dance, seemingly isolated in the vast expanse of space.
According to these models, black holes paired together would inevitably be drawn by gravity and collide into one another.
Nevertheless, this scenario assumes a stationary Universe. But what if we consider a Universe in perpetual motion? Could it be possible for pairs of black holes to coexist harmoniously in an ever-expanding cosmos, concealing their duality within a guise of singularity?
Professor Oscar Dias from the University of Southampton introduces a novel perspective:
“The prevailing model of cosmology posits that the Universe was born from the Big Bang and, approximately 9.8 billion years ago, it fell under the influence of an enigmatic force known as ‘dark energy,’ which steadily propels the Universe forward.” Scientists have dubbed this enigmatic force the ‘cosmological constant.’
In a Universe described by Einstein’s theory, alongside this cosmological constant, black holes find themselves enveloped in a constantly accelerating cosmic backdrop. This redefines the dynamics of how black holes interact and coexist.
Through intricate numerical techniques, the research team behind this recent study demonstrates that a pair of static (non-rotating) black holes can indeed find equilibrium, with their gravitational attraction balanced by the expansion driven by the cosmological constant.
Even in the midst of a Universe continually stretching and expanding, these black holes remain fixed at a constant distance from each other. Regardless of the expansion’s relentless tugging, the gravitational pull compensates for it.
From a distant vantage point, a duo of black holes, offset in their attraction by cosmic expansion, appears as if it were a solitary black hole. Distinguishing whether it is a singular entity or a twosome of black holes could be a challenging task, as Professor Dias suggests.
Professor Jorge Santos from the University of Cambridge expands on this theory: “Our concept has been substantiated for a pair of immobile black holes, yet we believe it might be applicable to spinning ones as well. Furthermore, it appears plausible that our solution could extend to trios or even quartets of black holes, ushering in a myriad of intriguing possibilities.”
