James-Webb observes Milky Way black hole activity like never before

The monster lurking at the heart of the Milky Way, which “weighs” the trifle of 4 million of our sun, is known for its tranquility. It is not the most active black hole in the observable Universe, that is to say it does not devour a huge amount of matter, at least not enough to see its crown and its accretion disk emit large amounts of radiation. However, the matter that revolves around it remains turbulent, magnetically active, and periodically produces what astrophysicists call flares (bursts or eruptions in the language of Etienne Klein…).

An eruption in the mid-infrared for the first time

Since the 1990s, using telescopes scanning space at different wavelengths (mainly X-rays and far infrared), astronomers have studied these flares around the supermassive black hole in the Milky Way, called Sagittarius A* ( or more simply Sgr A*), but none had been observed in mid-infrared. This is why many astronomers were impatiently awaiting the availability of NASA's space telescope, the James Webb Space Telescope (JWST)whose infrared sensors are the most powerful to date. A observation campaign was therefore carried out and a flare was observed.

We can describe this event as a large flash of light, mobile, because it is driven by the dynamics of the rotating accretion disk, most often forming along magnetic lines caused by the turbulence of matter. This resembles the flares that can be observed in the Sun's corona. They can be produced by a star that is torn apart by the gravity of the black holeor by a cloud of gas recklessly entering this dangerous zone.

Here is a flare in the solar corona:

This flare observed for the first time in mid-infrared was not powerful enough to release an X flashastronomers know this because the Chandra space telescope did not detect anything over the same period. It is not yet possible to determine its precise cause, but the event will undoubtedly allow us to know more about this black hole in particular and astrophysics in general. Let us remember, however, that Sgr A* being located 28,000 light years from us, this event occurred 28,000 years ago while the Earth was shivering in the middle of its so-called late glacial period…