The paradox of Milky Way galaxy's supermassive black hole Sagittarius A* (Sgr A*) getting a feed of faintly glowing accretion disk of collapsing stars has been answered by a new simulation model.

Observations and images captured by many Telescopes including NASA's Chandra had reaffirmed this anomaly. According to images taken from NASA's Chandra X-ray Observatory, the material around Sgr A* looks faint and diffused.

Extensive Observations

Extensive observing campaigns by Chandra telescope had captured unprecedented X-ray images and energy signatures of multi-million-degree gas swirling around Sgr A*.

The black hole pulls in gas from the winds of a disk-shaped distribution entity of massive stars albeit with a weaker glow.

Scientists at Princeton University and the U.S. Department of Energy's (DOE) Princeton Plasma Physics Laboratory (PPPL) have addressed the dichotomy of faint glow from the accretion disk's feed to the massive black hole at Milky Way.

The paper has been published online in Physical Review Letters providing the basis for the simulation of the extraordinary processes.

The inference is that less than one percent of the material from the disc reaches the event horizon from the black hole's gravitational domain. As a result, X-ray emission near the black hole looks faint. One reason is the captured material losing heat and angular momentum before falling into the black hole after ejecting matter.

The black hole Sgr A* is some 26,000 light years from Earth and is a rare black hole in the universe where the flow of matter nearby can be witnessed.

Accretion disks are essentially plasma clouds orbiting black holes with the latter exerting intense gravitational field produced by stars that shrink into a fraction of their original size.

As the graveyard of collapsed stars, the "event horizon" will not let even the light escape. Conceptually, accretion disks falling into event horizons must be the brightest sources of electromagnetic radiation in the universe; however, the paradox still persists.

New Modeling

In the new modeling, accretion disc swirling down into supermassive Sagitarius*A with a subdued glow has been interpreted with a different dynamics.

Despite Milky Way black hole enjoying gravitational mass that is four million times greater than the sun, the accretion disk plasma is "radiatively weak" as borne by the meager radiation emitted.

"So the question is, why is this disk so quiescent?" asks lead author Matthew Kunz, who is an assistant professor of astrophysical sciences at Princeton University.

Researchers highlight the Sagittarius A* accretion disk's plasma as hot, dilute yet "collisionless", implying trajectories of protons and electrons inside the plasma seldom intersect.

This non-collisionality makes Sagittarius A* accretion disk different from other radioactive disks in other black holes.

To address the case of collisionless particles, the paper treats such plasmas not as a macroscopic fluid but "kinetic" ones to trace their paths.

The kinetic approach helps to understand why accretion disk region around the Sagittarius A* hole has limited light.

Changing Binaries

Technically, black hole X-ray binary systems operate with one black hole pulling in material from nearby companion stars to stay bright and emit X-rays.

Black hole X-ray binaries in Milky Way are plenty but they emit relatively little X-rays. There are 80 systems in Milky Way as black hole X-ray binaries which are changing dramatically between faint emission (quiescent state) and bright emission (outburst state) stages.

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