Sagittarius A*, the supermassive black hole at the center of the Milky Way, has experienced a significant increase in activity in the recent past after absorbing space objects in its vicinity, AFP and Agerpres reported.

The “banquet” took place 200 years ago, and NASA’s Imaging X-ray Polarimetry Explorer (IXPE) satellite recently captured echoes of the event, according to a study published Wednesday in the journal Nature.

Sagittarius A* (Sgr A*), so named after its discovery in the constellation Sagittarius, is located 27,000 light-years from Earth, in the center of our galaxy. It was observed in the 1990s by astrophysicists, and its presence was proven in images a year ago.

With a mass of about four million suns and an age of 13 billion years, it “has always been considered a dormant black hole,” Frédéric Marin of the Strasbourg Astronomical Observatory told AFP.

Sgr A* is quiescent, like most supermassive black holes at the centers of galaxies, which have absorbed all the matter within the radius of their gravitational field.

“We can imagine a bear going into hibernation after devouring everything around it,” added the researcher from the National Center for Scientific Research (CNRS) in France.

The black hole “woke up” only 200 years ago

But his team discovered that in the late 19th century (a period established by estimating the distance) the “monster” came out of a state of torpor and swallowed gases and dust that passed too close to it for several months or even a year before falling back into “hibernation “.

During this period, Sgr A* was “at least a million times brighter than today,” explained Frédéric Maren, meaning a power equivalent to that of extremely active supermassive black holes in the source of quasars, such as its relative M87* in the Messier 87 galaxy located at distance of 55 million light years from us.

Sgr A*’s growing appetite was revealed by unusual emission from its neighboring molecular clouds — giants of frozen gas and dust that are “cold by definition” and that “shouldn’t emit as much X-ray light (invisible to the human eye, na),” according to the researcher.

“The intensity of X-rays between sleep and wakefulness can be compared to a firefly hidden in a forest that suddenly becomes as bright as the Sun,” the CNRS added in a statement.

Researchers don’t know what caused Sagittarius A* to come out of hibernation

After a million seconds of observations, the IXPE satellite was able to detect the polarization of this X-ray light, namely its electric field and magnetic field oscillating in a specific direction.

Like a “star compass,” the polarization pointed in the direction of Sgr A*, suggesting that it was the source of the radiation reflected by the molecular clouds. Thus, the black hole “released an echo of its past activity, which we were able to observe for the first time,” said the scientist, the French representative of the international consortium of the IXPE mission.

The density of a black hole makes it so that nothing can escape it, not even light. But before the matter crosses the final boundary (called the event horizon) to be absorbed forever, it rotates, heats up, and emits light.

“It’s like a swan song” indirectly transmitted by the molecular clouds around Sgr A*. What exactly caused this “awakening” remains to be determined. A drifting cloud before falling into a black hole? A star who dared to approach her?

Additional observations by IXPE, planned for September, should contribute to a better understanding of the activity cycle of Sgr A* and will likely lift a corner of the veil that envelops the origin of supermassive black holes, a mystery of astronomy.

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