Small black holes are surrounded by hot and flat disks of matter

(ORDO NEWS) — Observations of the near-Earth black hole X-1 in the constellation Cygnus using the orbiting X-ray observatory IXPE have helped astronomers figure out that the glowing disks of matter surrounding small black holes are flat structures with unusual properties.

Professor of the University of Turku (Finland) Yuri Poutanen announced this.

“Our measurements of the polarization of radiation from the X-1 black hole in the constellation Cygnus indicate that this object is surrounded by a flat hot disk of matter, which produces unusually highly polarized radiation.

His discovery was a big surprise, since the existence of this radiation is difficult to explain taking into account other properties of this object,” Poutanen said at the High Energy Astrophysics Today and Tomorrow (HEA-2022) conference, held this week at the IKI RAS.

Stellar-mass black holes, resulting from the gravitational collapse of large stars, are extremely difficult to detect even at a small distance from the Earth.

Astronomers usually learn about their existence only if there is a luminary next to them, whose matter black holes are constantly dragging onto themselves. As a rule, such star systems are extremely rare in galaxies, which complicates the search for stellar-mass black holes.

One of the closest yet brightest objects of its kind, Cygnus X-1, is located in the constellation Cygnus at a distance of 6,000 light-years from Earth. It is a pair of a large star, whose mass is about 40 times that of the sun, and a black hole X-1, which is about half as large as the star in this parameter.

Source of black hole glow

As Poutanen noted, this object became one of the first targets for observations using the IXPE X-ray observatory.

It was jointly launched in 2021 by NASA and the Italian Space Agency to study cosmic sources of X-rays. It is a telescope, which is equipped with a set of three gas detectors capable of determining the direction of the “twisting” of X-rays incident on the mirrors of the observation device.

Scientists have taken advantage of this feature of IXPE and the short distance to the X-1 black hole to make the first-ever observations of how the accretion disk, the luminous cloud of matter that surrounds this object, and other stellar-mass black holes adjacent to large stars, works.

It is an accumulation of plasma, which the attraction of a black hole is constantly pulling from the outer shells of a neighboring star.

Until now, scientists did not know how this disk of matter is arranged and how it produces X-ray glow.

This discovery, as noted by a professor at the University of Turku, made Cygnus X-1 an even more interesting object for study, since scientists cannot yet explain such a high level of polarization of the X-ray produced by it, taking into account other properties of the accretion disk, including its inclination angle.

This indicates the presence of unique and yet unexplored processes that generate X-rays, the astrophysicist summed up.

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