Scientists hypothesize that black holes can be born inside still-living stars and hide inside them for a long time. They look at several interesting possibilities that arise in this case.
What we don’t know about black holes
The generally accepted view of black holes is that these monsters are born in the explosions of very heavy stars and are actually their compressed cores. However, a recently published study paints a rather unexpected mechanism for their formation that may turn our understanding of them upside down.
It all started with recorded gravitational waves, which may indicate the existence of black holes with masses close to the solar mass. This is surprising, because according to modern ideas, black holes cannot form from supernovae flares if their mass is less than three solar masses. Hence, there should be another mechanism for their origin.
The researchers hypothesized that dark matter — that extremely common form of matter that no one has ever seen — could accumulate inside stars and collapse into very compact black holes. Such objects may remain undetected for long periods of time.
Strange consequences
As strange as it sounds, a black hole originating in the depths of a star like our Sun will not consume it instantly. It can grow slowly — over billions of years — and even survive the red giant stage. But when the star becomes a white dwarf, the situation changes: extremely interesting options are possible here.
According to classical theory, white dwarfs cannot turn into black holes directly. However, new calculations show that it all depends on the rotation speed of the dead star. Rotation creates a centrifugal force that can resist gravitational collapse.
If a white dwarf spins very slowly, it will completely turn into a black hole. At the same time, it will have an anomalously small mass — about one solar mass. If a little faster, an exotic object — a bare singularity — will be formed. The latter is the case when, in a certain region of space, its curvature becomes infinite, but no event horizon, that is, a surface that even light cannot leave, is formed.
Finally, if the white dwarf rotates fast enough, the accretion of its matter onto the black hole can also stop. It would exist in its depths like that, and from the outside, it would look quite normal.
Another situation occurs when a black hole originates inside a neutron star. In this case, there are no forces that can resist gravitational collapse. The star will be completely swallowed up, and the newly formed black hole will remain anomalously light.
According to phys.org
