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Disc structure characteristic of the simulation of a misaligned disc around a rotating black hole. Credit: K. Pounds et al. / University of Leicester
A team of British astronomers reports the first detection of matter falling into a black hole at 30% of the speed of light, located at the center of the distant galaxy PG211 + 143. The team, led by Professor Ken Pounds from the University of Leicester, used data from the European Space Agency's observatory XMM-Newton to observe the black hole. Their results appear in a new paper in Monthly Notices from the Royal Astronomical Society.
Black holes are objects with gravitational fields so powerful that even the light does not move fast enough to escape their grip, hence the description "black". They are extremely important in astronomy because they provide the most efficient way to extract the energy of the materials. As a direct consequence, the accumulation of gases in the black holes must lead to the most energetic phenomena of the Universe.
The center of almost all galaxies – like our own Milky Way – contains a so-called supermassive black hole, with masses of millions to billions of times the mass of our Sun. With enough material falling into the hole, they can become extremely bright and are considered a quasar or active galactic core (AGN).
However, the black holes are so compact that the gas almost always turns too much to fall directly. Instead, it revolves around the hole, gradually approaching an accretion disk – a sequence of circular orbits of decreasing size. As the gas spirals, it moves faster and faster and becomes hot and bright, turning the gravitational energy into radiation that astronomers observe.
The orbit of the gas around the black hole is often assumed to be aligned with the rotation of the black hole, but there is no compelling reason for this to be the case. In fact, summer and winter are the reason why the daily rotation of the Earth does not match its annual orbit around the Sun.
Until now, it was unclear how a misaligned rotation could affect the gas drop. This is particularly relevant for supermassive black hole feeding, as matter (interstellar gas clouds or even isolated stars) can fall in any direction.
The XMM-Newton spacecraft. Credit: ESA
Using the XMM-Newton data, Professor Pounds and his collaborators examined X-ray spectra (where X-rays are scattered by wavelength) of galaxy PG211 + 143. This object is found at more A billion light-years away in the direction of the constellation Berenices and is a Seyfert galaxy, characterized by a very bright AGN resulting from the presence of the massive black hole at its core.
The researchers found that the spectra were strongly shifted in red, showing that the observed material was falling into the black hole at the enormous speed of 30% of the speed of light, about 100,000 kilometers per second. The gas has almost no rotation around the hole and is detected extremely close to it in astronomical terms, at a distance of only 20 times the size of the hole (its event horizon, the boundary of the region where escape is no longer possible).
The observation is in close agreement with recent theoretical work, also in Leicester and using the British supercomputer Dirac simulating the "tearing" of misaligned accretion disks. This work showed that the rings of gas can break and collide with each other, canceling their rotation and letting the gases fall directly to the black hole.
Professor Pounds, of the Department of Physics and Astronomy at the University of Leicester, said: "The galaxy we observed with XMM-Newton has a black hole of 40 million solar masses, very bright and obviously well fed. A strong wind was detected, indicating that the hole was overfed. Although such winds are now present in many active galaxies, the PG1211 + 143 provided another, the detection of the material dipping directly into the hole itself.
He continues: "We were able to track a group of matter the size of the Earth for about a day because it was fired toward the black hole, accelerating up to one-third the speed of light before it went off. to be engulfed by the hole. "
Another implication of the new research is that the chaotic accretion of misaligned disks may be common for supermassive black holes. Such black holes then rotated quite slowly, being able to accept much more gas and grow their masses faster than was generally believed, explaining why the black holes that formed at the beginning of the Universe quickly gained very large masses.
Explore more:
Image: Black hole premium captured in the center of the Milky Way
More information:
K A Pounds et al. An ultra fast stream in the PG1211 + 143 bright Seyfert Monthly Notices from the Royal Astronomical Society (2018). DOI: 10.1093 / mnras / sty2359
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