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The star dancing around a black hole ready to eat it

There is a star that turns around a black hole from which it is slowly devoured: every 9 hours the giant rips away part of the star, producing flashes of X-rays.

When black holes swallow large quantities of matter (gas and dust) they certainly do not go unnoticed by astronomers, because on these occasions they radiate large quantities of X-rays generated by the heating of the material sucked by the black hole itself.

Their intensity is so high that it can be detected right from the Earth. But so far, nothing new. What is unusual, however, is that one of them, at some point, starts doing it on a regular basis. This is what astronomers found last year for a black hole that is located in the heart of a galaxy 250 million light years away from us: every nine hours, a very intense X-ray glow followed by the absence of emissions and so on.

THE SOLUTION! Now, after a months-long study, astronomer Andrew King of the University of Leicester in the UK thinks he has identified the cause: it would be a “dead” star, which was captured and trapped on an elliptical orbit around the black hole, near which he finds himself passing every nine hours. At each close passage, the black hole assimilates a little of the star material: “a little”, so to speak, because in reality to be literally torn away from the star is a huge amount of gas that ends up in the accretion disk located around the black hole. Every time it happens, an X-ray flash occurs.

The black hole in question is located in the core of the galaxy called GSN 069 and is relatively “light” when compared to other black holes that are located in the center of galaxies it has a mass of “just” 400,000 times the mass of the Sun. To have an idea, similar black holes generally have masses equal to tens of millions of times the mass of the Sun. But even if it is a small-sized specimen, the black hole is an active one, surrounded by a hot disc of material in growth.

AND WHAT WILL HAPPEN NEXT? According to King, the star passing by the black hole was a “red giant”, that is, a highly evolved star, similar to the conditions that will reach our Sun in 3 or 4 billion years; the periodic close passage has accelerated the final evolution towards the “white dwarf” phase, which we can imagine as the now dead core of a star that has run out of all nuclear fuel and which today has a mass equal to 0.21 times that of the Sun.

According to the scientist, the star should remain in this orbit for billions of years, continuously losing mass due to the action of the black hole, until it assumes mass like that of a planet like Earth or Venus.

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