They observe, for the first time, a star 'spaghetted' by a black hole

By 27/04/2021 Portal

For decades, astronomers have been detecting bursts of electromagnetic radiation from black holes. And they have always been clear that these energy emissions are the result of the destruction of stars, devoured by the black hole, but they had never had the opportunity to observe the real aspect of that process.

Now, a team of astronomers led by Giacomo Cannizzaro and Peter Jonker, both from the SRON Space Research Institute in the Netherlands, has managed, for the first time, to observe the absorption lines caused by the strands of a 'spaghettified' star. The work has just been published in 'Monthly Notices of the Royal Astronomical Society'.

Most stars in the Universe die due to natural causes, either by violently breaking free of their outer layers or by simply cooling little by little once their fuel has been exhausted. Some, as is the case of the largest and most massive, explode in the form of a supernova after a rapid gravitational collapse, unable to support their own mass.

But stars that live in the innermost parts of their galaxies may not be so lucky. In fact, at the heart of most galaxies lurk enormous supermassive black holes, so large that they can exceed several billion times the mass of the Sun. And the stars that come within their reach are in serious danger of falling apart. be trapped and destroyed by those black holes, which before devouring them destroy them, breaking them into fine filaments.

What is spaghettization
If any of us were unfortunate enough to be caught in a black hole and fell straight into it, we would see our body stretch out until it looked like a long, thin piece of spaghetti. This is because the gravity of the black hole is so extreme that our feet, a little closer to the hole, would feel it more strongly than our head, just a little further away. The result is that our body would stretch, in a process that astronomers colloquially call 'spaghettization', although scientific publications usually use the official term 'Tidal Disruption Event'.

Something similar happens with stars. The extreme gravity of black holes pulls much harder on one side of trapped stars than the other, stretching them like rubber.

After a star has been transformed into a thin strand reminiscent of spaghetti, it hurtles toward the black hole, emitting a brief burst of radiation. Astronomers have been recording these explosions for decades and assuming they were due to tidal disruption events. But they had never seen the real filaments.

And that is precisely what the authors of this study have achieved, who have observed for the first time the spectral absorption lines of one of these star filaments while looking at one of the poles of a supermassive black hole. It was already known that many black holes of this class have around their equator a bright disk of material captured by their enormous gravity, but the absorption lines on the pole of a black hole suggest the existence of a long strand that twists many times around it. Something like a skein of tangled thread: the actual filaments of a freshly torn star.

The researchers knew that they were looking at the pole of a black hole because they captured . «In addition – assures Cannizzaro – the absorption lines are narrow. "They are not Doppler-widened, as you would expect when looking at a rotating disk."