Black holes are invisible cosmic objects with such a strong gravity that they absorb everything around, including light. To date, all black holes discovered by astronomers are either large (supermassive black holes with a mass more than one hundred thousand or even billions of times), or much smaller (black holes of stellar mass with a mass exceeding the solar one less than 100 times). Scientists have not found black holes of average mass (more precisely, until scientists were able to unambiguously detect such an object), which, however, does not mean that such black holes gravity does not exist.
Researchers from the E. Lawrence Livermore National Laboratory discovered that medium-mass black holes (if they exist) should have sufficient gravity to “return to life” white dwarfs — pro-evolved stars with a mass comparable to that of the Sun or higher, but with a much smaller radius and devoid of sources of thermonuclear energy.
To test the hypothesis, the researchers, using a supercomputer, conducted simulations of dozens of different situations that are close to the passage of a white dwarf in front of a black hole of average mass. It turned out that whenever a white dwarf was at close range from such a black hole, it “re-ignited”. The black hole gravity “launched” in the star the processes of calcium and iron formation, and the closer the star approached, the more intensively these processes proceeded. Thus, due to black holes gravity in a previously dead star, nucleosynthesis processes can be resumed, scientists suggest; at the same time, as noted, such a star will not survive for a long time and will eventually be torn apart.
In addition, as specialists have found, the “revival” of the star should create powerful electromagnetic waves, which in principle could be detected by devices in near-earth orbit; perhaps, having detected a similar process, scientists will be able to detect a black hole of average mass for the first time in the future.