Black holes
For almost a century, black holes have been one of the most mysterious objects and fascinating of the universe, as they are not visible to our eyes, because I can not emit any kind of light.
They have catalyzed the attention of the most famous scientists who they clashed in heated debates. In this series of articles we will take a historical and scientific excursus of these cosmological structures, up to the latest discoveries which allowed, through the observation of black holes, to "visualize" gravitational waves.
Today they know that when a star, with a mass greater than six or seven sometimes that of our sun, at the end of its life, explodes into becoming supernova: its core contracts, its density increases and collapses under its own weight, concentrating the whole mass in a single "point" of infinite density, called singularity. This process is hypothesized by General Relativity that Einstein
he published in 1915 and foresees that singularity distorts space-time around him so deeply that not even light can come out of it: in short, this is a black hole.
In general black holes are classified according to their mass, independently from their angular momentum (spin) or from their electric charge. There are four categories of black holes: Super masses (SMBH) with mass billions of times the size of our sun; intermediate black hole with a mass of a thousand times that of the sun; stellar black hole with mass up to thirty times that of the Sun e Micro black holes with mass less than that of the Moon.
Astronomers have a lot of evidence of how small black holes and those of intermediate mass are formed when a large star reaches the end of his life. They are less certain of how black holes form and grow. One of the hypotheses most accredited by current observations, is that little black holes.
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