Russian physicists figure way to distinguish supercompact stellar objects from black holes

MOSCOW, June 30. /TASS/ Scientists from Moscow Institute of Physics and Technology (MIPT) together with colleagues from other Moscow institutions have devised a method of distinguishing black holes from compact massive objects, as reported by the press service of MIPT. Externally, these two types of objects are scarcely different, but can be identified by the energy spectrum of particles moving in the vicinity.

“We have shown that the black holes and supercompact objects can be distinguished by the spectra of scattered particles. If we do not observe discrete levels implying any forbidden energy values for the particles, the object belongs to black holes. If in contrast, the spectrum is discrete restricting the energy of particles to the predefined values, it is not a black hole," - said Fedor Popov, one of the coauthors of the study, a researcher at MIPT’s Laboratory of High Energy Physics.

Where the time runs down

Black holes, which have been predicted by Einstein’s theory of general relativity, have an event horizon – a boundary beyond which nothing, even light, can return to the outside world.

Black holes appear as a result of gravitational collapse of massive stellar objects when a star has “burned out” all its thermonuclear fuel and therefore collapses under the gravitation force which is no longer constrained by the gas pressure forces.

However, some astrophysicists believe that there may be compact massive objects that are formed in the same manner as black holes. These objects can be defined as stars collapsed to the size slightly exceeding the Schwarzschild radius (the Schwarzschild radius outlines the spatial region around astrophysical objects from which nothing, even the light, is able to escape because of its huge gravity - TASS). The compact massive objects from the outside should be not distinguishable from black holes and therefore now black holes and supercompact massive objects are often mixed up.

The way to figure out black holes

Russian physicists from MIPT, the Institute for Theoretical and Experimental Physics, and the National Research University Higher School of Economics have theoretically described the behavior of elementary particles in the close proximity of black holes and massive compact objects and calculated their energy spectra. It has been turned out that near the surface of an supercompact star with a radius slightly larger than the Schwarzschild radius there is a “potential hole” – an area of space where particles fall into a gravitational “trap” from which they cannot get out.

The energy spectrum of particles in the potential hole is always discrete, i.e. the particles in there have to be of rigorously defined energy values from a finite set. In the case of a black hole in the proximity of Schwarzschild sphere, it appears no potential holes and the spectrum of particles remains continuous. In this work, authors have considered only one type of particles with the zero intrinsic moment of momentum, or, in other words, with the zero spin. However, they believe that the similar effect allowing for differentiating black holes from massive compact objects should hold true for all other particles.

The article of MIPT' scientists has been published in the Physical Review D.

Worth mentioning that now there are many candidates which could be "suspected" of being black holes. Exemplarily, many astrophysicists are confident that in the center of our galaxy there is a supermassive black hole. Nevertheless, scientists have not yet been able to “see” a black hole directly, while the recent tracing of gravitational waves has acted as one of the most powerful indirect verification of their existence. According to the calculations, the signals of such character and intensity can be emitted only by merging black holes.