Observing the "shake" of merging black holes will help scientists figure out if there are axions, ultra-light particles of dark matter, or other candidates for the role of "nature's sixth force." This is the conclusion reached by astronomers who published an article in the journal Physical Review D.
For a long time, scientists believed that the universe consists of the matter that we see, and which forms the basis of all stars, black holes, nebulae, dust clusters and planets. But the first observations of the speed of movement of stars in nearby galaxies showed that the stars on their outskirts move in them at an impossibly high speed, which was about 10 times higher than calculations based on the masses of all the stars in them showed.
The reason for this, according to scientists today, was the so-called dark matter - a mysterious substance, which accounts for about 75% of the mass of matter in the Universe. Typically, each galaxy has about 8-10 times more dark matter than its visible cousin, and this dark matter holds the stars in place and prevents them from scattering.
Today, almost all scientists are convinced of the existence of dark matter, but its properties, in addition to its obvious gravitational influence on galaxies and galaxy clusters, remain a mystery and a subject of controversy among astrophysicists and cosmologists. For a long time, scientists have assumed that it is composed of superheavy and "cold" particles - "wimps" that do not manifest themselves in any way, except by attracting visible clusters of matter.
The unsuccessful search for "WIMPs" in the past two decades has led many theorists to believe that dark matter can actually be "light and fluffy" and consist of so-called axions - ultra-light particles similar in mass and properties to neutrinos. Their first search also ended in vain, which makes this invisible substance even more mysterious.
Baumann and his colleagues have formulated a highly unorthodox way to find these particles by studying what is happening in the vicinity of a pair of rotating black holes preparing to merge with each other.
As the scientists noted, their movement will in a special way affect the structure of the surrounding space-time, contributing to the appearance of axions and other ultralight particles, and preventing their mutual annihilation and self-destruction.
As a result, the black holes will be surrounded by a kind of "atmosphere" or "cloud" of axions, as scientists call this structure. It will behave like an artificial atom, slowing down their movement, emitting gravitational waves and in a special way influencing the process of their merging.
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This influence, in turn, will be especially pronounced during the so-called "jittery" - a special phase in the life of a newborn black hole, when it dumps excess rotational energy in the form of gravitational waves. At this time, it does not look like a perfect ball, but like an elongated or stretched ellipse, gradually acquiring a "normal" shape.
As the calculations of Baumann and his colleagues show, if axions or other light particles exist, then their cloud will abruptly disappear after the merger and during the beginning of "jitter", will weaken the gravitational waves generated by this process and introduce unique distortions in them.
Can such fluctuations be found? Ground-based gravitational telescopes such as LIGO and ViRGO, according to astrophysicists, are unlikely to be able to solve this problem, since it would require finding a pair of black holes in the Milky Way, very close to merging. This is highly unlikely.
On the other hand, the orbital observatory LISA, capable of tracking supermassive black holes in other galaxies, should be able to cope with this task, and find traces of all possible light particles.
If this idea justifies itself, then such pairs of black holes, as scientists believe, will become for us a kind of "gravitational colliders", capable of really looking for "new physics" beyond the Standard Model.