US, WASHINGTON (ORDO NEWS) — As in all other large galaxies, a supermassive black hole exists in the center of the Milky Way. Compared to similar objects in other galaxies, this hole is a sleeping giant: only occasionally does the desire to absorb stars, gas clouds and asteroids wake up in it, so that astronomers only register insignificant radiation in its environment.
But for a couple of years now, the situation has begun to change, albeit slightly, according to Emmanuelle Mossoux from the University of Liège and her colleagues from Belgium and France in a report published in the scientific journal Astronomy and Astrophysics. In the X-ray wavelength range, the activity of a black hole, whose mass is four million solar masses, has definitely increased.
Moss and her group used active data obtained by three X-ray telescopes placed in space, namely, the instruments of the American satellites Chandra and Swift, as well as the European XMM Newton.
Using these data, they observed changes in the X-ray activity of a source called Sagittarius A * in the constellation Sagittarius. It is in this source, 26 thousand light-years distant from the Earth, that the central black hole of the Milky Way is located. Although it does not emit light, astronomers observe how it, with its gravitational force, causes stars and hydrogen clouds to move along narrower trajectories. If some celestial body is too close, it is caught by extreme tidal forces and disappears forever in the gravitational funnel of a black hole, not even having time to make a dying scream in the form of a beam of electromagnetic radiation.
So scientists interpret the constant bursts of x-ray radiation from Sagittarius A *. From 1999 to 2018, a total of 121 such outbreaks were recorded. However, not all flashes are recorded, because telescopes are not constantly directed at Sagittarius A *. In fact, one can proceed on average from one X-ray outbreak per day, and this was the case until at least 2014. After that, as the results of the study show, their number tripled.
This is confirmed by the results of the work of the same authors in 2017. Their new report is complemented by data analysis for the period from 2016 to 2018. As Moss explained, the increased activity of the hole is just one of the possible interpretations of these results. X-ray flashes could also be caused by a sudden change in the configuration of the magnetic field of the hole: “Only on the basis of the data obtained by us cannot determine what physical process underlies this phenomenon. For this, research is needed in other wavelength ranges, for example, in the near infrared or in the radio range.”
Streams of matter close the hole view
Observations made with the VLT (Very Large Telescope) telescope in Chile and the Keck 10-meter telescope in Hawaii in April and May 2019 really established increased activity of Sagittarius A * in the near infrared range. Data from earlier observations in this wavelength range have not yet been analyzed. The latest data from the 2019 Swift satellite in any case confirms that the radiation from the black hole is still intense. But it is still premature to do a detailed analysis of the 2019 data, because scientists do not yet have corresponding data from the Chandra and XMM Newton satellites.
The result is interesting, but its significance is not yet clear – this is the opinion of Heino Falcke from the University of Nijmegen in the Netherlands, who himself did not participate in the study. Like Moss, he believes that it is too early to draw far-reaching conclusions: “X-ray radiation is extremely sensitive to the slightest changes in plasma flows around a black hole.
After all, in the sea for a short time a couple of high waves arise, and then the calm phase reappears. The picture becomes more interesting when the sea level rises, that is, when more material gets into the black hole. But there are no signs of this.”
Falke is one of the leading scientists participating in the Event Horizon Telescope project, which in April 2019 published a photo of the black hole of the M 87 galaxy. Increased accretion, that is, the entry of new matter into the hole, may complicate the implementation of their plan to obtain image of a black hole in the Milky Way: “If the volume of accretion increases greatly, the plasma may become opaque and close our view of the black hole. But for now, fortunately, we are far from that.”
However, in any case, humanity will have to wait longer for a photograph of another black hole than planned: “The Covid-19 pandemic was a blow for us,” says Falke. – Reluctantly, we had to abandon the 2020 campaign, and an increasing number of telescopes are limiting their work. At this time, there are more important tasks than looking at the sky. It will not go anywhere next year.”
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