Statistical analysis of 740 supernova explosions found that the black holes may have no more than 40 percent of the amount of dark matter present in the Universe, which, in turn, scored another nail in the coffin of the theory of massive astrophysical compact halo objects. According to this theory, the source of dark matter can be primary black holes. The observation of two American scientists from the University of California, Berkeley, have questioned this theory.
In February 2016, the scientists laser-interferometric gravitational-wave Observatory (LIGO) announced a new era in astronomy. The researchers first discovered the predicted gravitational waves, created by a pair of colliding black holes. If you do not take into account the very surprising nature of the discovery, the detection of gravitational waves revived the old theory that dark matter is a by-product of massive astrophysical compact halo objects (MACHO), ultraplate objects that are not emitting light.
According to modern assumptions on the dark matter may account for up to 85 percent of all matter of the Universe, but physicists are still this matter is not found, so I don’t know what it is. The topic of the existence of dark matter has gathered around itself an active discussion after the American astronomer Vera Rubin in the 70-ies, studying the rotation curves of galaxies have revealed a difference between the predicted circular motion of galaxies and the observed motion (the stars at the edge of galaxies should rotate slower than those that are closer to the galactic center, but observation showed that the speed of rotation of the outer and inner stars were actually the same). This fact, known as “the problem of the rotation of the galaxy,” was one of the main evidence for the existence of dark matter. However, the question is, what is dark matter still remained and remains open.
Over the next few decades, there have been proposed many candidates for dark matter. Today, the most popular are these particles like axions or weakly interacting particles. However, the proposed several decades earlier by the theory of MACHO objects (e.g. black holes) was considered as the main source of dark matter. According to this theory, dark matter is actually made up of baryonic particles (particles of ordinary matter that can be seen), moving in interstellar space, not being bound to any planetary system, and almost (or completely) not emitting any energy. According to the theory, X may represent neutron stars, brown dwarfs, planets-orphans, and primary black holes, which appeared shortly after the Big Bang.
In the 90-ies of the theory of MACHO objects out of fashion. Scientists concentrated their search for the source of dark matter particles, however, the recent discovery LIGO again fueled interest in black holes as a possible explanation for the invisible dark matter.
As MACHO objects, according to the theory, does not radiate any energy, for the observer, these objects will be “dark”, that is invisible. Based on this, researchers expected to discover them using the effect of gravitational microlensing. The phenomenon of curvature of light waves of the observed object relative to the observer due to the very powerful gravitational field very dense and massive objects between the observed object and the observer. This effect can significantly increase the brightness of very distant stars from us and let see those objects that we cannot see it with the traditional methods of observation. The role of gravitational lenses can serve, for example, galaxies, galactic clusters, and also the same black holes.
Physics Miguel Zumalacarregui and Uros Selyakov from the University of California at Berkeley conducted a complex analysis of data 740 supernova – extremely bright explosions of stars, — to trace the contribution of primary black holes to create the effect of curvature and strengthen the light of a supernova. A supernova is often used by astronomers to measure distances in the Universe, as these objects have incredible brightness, which is very slowly reduced, allowing to conduct calculations. A study published in the journal Physical Review Letters.
Scientists assumed that the deviation in brightness for a few tenths of a percent, indicating the effect of microlensing on black holes and due to the mass of the invisible dark matter will be detected at least 8 out of 740 the observed supernovae. However, scientists have not found any deviations, indicating the microlensing black hole.
The findings of the study do not rule out black holes as sources of dark matter, but limiting their contribution to its volume within the Universe. According to estimates, even if black holes do contribute to the phenomena associated with dark matter, then is it no more than 40 percent. According to the authors, they are already and not-yet-published results of detailed analysis, which covered more than 1000 supernovae and forcing even more to reduce this figure by up to 23 percent.
“We are back to the usual discussions. What is dark matter? Looks like good options we ended. This is a task for future generations,” says Professor Ureg Selyakov.
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The new study limits the contribution of black holes to dark matter
Nikolai Khizhnyak