The treat, rejected by the black hole, becomes a gold mine for science

The treat, rejected by the black hole, becomes a gold mine for science

This illustration shows the infrared image in a false color of the area around the core of the Milky Way, with the super-massive black hole Sag A *. The marker shows the location of a black hole that glows faintly due to the accretion of matter; other objects are stars or dense clouds orbiting around a black hole or in its vicinity. The image scale is about one light year.

Remember, the mysterious cloud of gas that moves on a head-on course with a supermassive black hole in the center of our galaxy? Well, astronomers are still trying to figure out why it was not absorbed by the black hole, and why it didn’t trigger cosmic fireworks.

But at the same time, the researchers revealed some interesting new things about the monster of singularity, hiding at a distance of more than 25,000 light years from Earth.

In 2011, astronomers noticed a cloud of gas rushing through the innermost corners of the Galactic bulge. Ahead of the course of an object known (not romantically) like "G2" was the supermassive black hole Sagittarius A * (or just Sgr A *). After some calculations, it became clear that this cloud would pass within 250 distances between the Sun and the Earth from the black hole, which is close enough to be tightened by the powerful gravity of the black hole. It was really exciting: for the first time in the history of mankind, we will be able to study the material before it fell into a black hole as we approach the dazzling finale.

At that time, it was believed that G2 consists of a collection of nebulae from stellar gases. It was also assumed that due to the extremely powerful tidal deformation, the cloud would be elongated, like noodles, with tendrils retracting into the accretion disk of a black hole. It was hoped that somewhere along the way, the emissions from the beams of this gas, interacting with the extreme spatio-temporal environment of the horizon Sgr A * of events, would be detected as X-ray flashes — perhaps the largest eruptions we’ve ever seen come from Sgr A *. We would witness our black hole in action; from the discovery of the fall of an object to the ultimate destruction of this object, when matter is transformed into energy and a black hole creates a cosmic celebration.

But ... nothing happened.

Something happened, but the destruction of G2 did not become something out of the ordinary and astrophysicists tried to understand what happened ... or, more precisely, why it did not happen.

The current hypothesis is that G2 is not a collection of lost gases, as it was believed, it can be a star enveloped in a cloud of gravitationally bound gas. When meeting directly with Sgr A *, the cloud retains its integrity, and very little gas was detached from the masked star. If there is no falling substance, then there is no cosmic firework - astronomers are disappointed. In a new study published in the Monthly Notices of the Royal Astronomical Society (MNRAS), astronomers Michael McCourt and Anne-Marie MADIGAN of the Harvard-Smithsonian Center for Astronomy (CFA) described their study of G2, showing that although little material was torn off, the event helped explore the extreme environment around Sgr A *. Of particular interest: they may have guessed where the black hole would find another feast.

McCourt and Madigan tracked G2, as well as another gas cloud called “G1”, passing near Sgr A *. It just so happened that the clouds went so close that they went through the “accretion flow” of a black hole. In other words, these clouds can be used as indicators to see the structure of matter that regularly falls into a black hole.

Since both clouds follow a similar trajectory around a black hole, small changes in gaseous objects can be measured. And the evolution of these clouds revealed the characteristics of the interstellar matter surrounding Sgr A *.

"Despite the fact that it is not yet clear whether these objects contain built-in stars, their expanded gaseous envelopes evolve independently of each other, like gas clouds," they write. "We believe that evolution is in accordance with the concept of G-clouds (G1 and G2), rotating clockwise in the disk. Our analysis allows us for the first time to uniquely identify the axis of rotation of the accretion flow: we localized the axis of rotation within 20 degrees, finding an orientation in according to the size of the jet detected in X-ray observations, and also according to the nuclear disk, the massive torus of molecular gas (approximately) 1,5 parsecs (5 light-years) from Sgr A *. In general, the observations of G1 and G2 showed the direction in which the material moves when it falls into a black hole, thereby leading to the rotation of the black hole's accretion disk. In addition, they found that the black hole does not feed on the stellar winds of nearby stars, but rather material from a massive ring of material, with a radius of about 5 light-years around it.

So G2 did not cause exciting flares and X-ray emissions, which astronomers predicted in 2011, but it turns out that G2 (and also G1) were much more useful not to feed the black hole; instead, they revolve around the center of the galaxy, providing tantalizing clues as to the nature of the gravitational monster living in the center of the Milky Way.

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