Clouds of gas and dust that hide the galactic center, several light-years in size, are a kind of still that distills molecules that we never dreamed could be found in cold space. Thanks to chemical reactions that have been taking place for millions of years, we have found not only the ammonia from under the sink, the acetylene from welders or the antiseptic formaldehyde, but also enough alcohol to fill more than a thousand quadrillion bottles of whiskey, in addition to sugar. (more specifically glycolaldehyde). So up to about 150 different types of molecules. And the account continues.
Behind those clouds, hidden from our eyes, a frenetic activity is taking place: more stars are being created in it than in the galactic outskirts where we live, and the most massive stars originating from this creative explosion shed their outermost layers in the form of fearsome winds while that numerous supersonic shock waves from supernova explosions are “heard” throughout the region.
If we had an appropriate radio set, we would clearly distinguish two stations, whose music sounds like steam coming out of an old car radiator: one comes from hot, highly ionized gas by swarms of stars (themselves invisible) or by shock waves themselves. of supernovae; the other, the music of electrons moving at high speeds through the existing magnetic field that is much stronger than that of the rest of the galaxy but 500 times weaker than that of Earth.
Gamma radiation – which on our planet we create in nuclear reactors – floods space with an energy 250,000 times greater than that of visible light , a radiation that comes from the annihilation of an electron with its antimatter twin, the positron, at an inconceivable rhythm; ten billion tons of antimatter are consumed every second : it is the Great Annihilator , whose catalog name is rather less poetic: 1E 1740.7-2942. It is probably a stellar black hole, although totally different from what we could find anywhere else in our galaxy. It is hidden behind an enormous cloud of gas, a graveyard of positrons created in that antimatter factory that is the black hole and whose position is indicated by two jets of matter 5 light-years long. But this one is not in the center, but very close, only 350 light-years from the nucleus.
The entire central area is called Sagittarius A. Nearly a thousand X-ray sources have been detected there , most of them such fantastical objects as white dwarfs, neutron stars, black holes, and extremely hot gas clouds. Around us we can also distinguish, like champagne bubbles, the remnants of supernovae that exploded long ago, and two star-forming zones, Sagittarius B1 and B2. As it can be seen Sagittarius A is a complex radio source in which we have been able to identify its three main components: Sagittarius A East, the rest of a supernova 25 light-years wide and whose explosion had to be 30 to 100 times more powerful than a typical supernova; Sagittarius A West, which looks like a three-armed spiral but is actually a collection of clouds of gas and dust orbiting and falling on the third component, and finally Sagittarius A* (Sgr A*), a very bright radio source and compact. Well, behind that nondescript name hides a super black hole of 3 million solar masses and about 15 million kilometers in diameter, less than a quarter of the diameter of Mercury’s orbit. If the X marks the place where the treasure is buried, the super black holes indicate where the center of the galaxies is located.
But the surprises do not end here. In 2015 astronomers found a powerful X-ray emission just 10 light-years from the center and so far they have not been able to discover who is responsible. There is talk that it may be thousands of stellar corpses packed together , such as white dwarfs, neutron stars… But no one is sure. That same year, 44 protoplanetary disks of low-mass stars were also discovered within 2 light-years of the galactic heart. This is important because it is the first time that the formation of low-mass stars in the center has been observed. These disks are found in two clusters located 2 and 2.6 light-years from Sgr A*, and could eventually form planets. Of course, this whole set is adorned with around 3,000 stars that orbit Sgr A* in less than a human lifetime.
In 2001 our galactic center grew 45 times brighter for 3 hours . The energy released corresponds to what would be expected if a piece of matter with the mass of a comet had fallen into the black hole. Obviously this has not been the biggest of the outbursts. Yes, it was the one two million years ago, when it released a tremendous amount of high-energy radiation into space, 100 million times more powerful than its current emission: what is called a Seyfert explosion was produced. Perhaps our ancestors, back in the African savannah, saw the flash…
The most interesting thing is that the record of that explosion is preserved in a faint glow that is observed in the Magellanic stream, a long ribbon of gas composed mainly of hydrogen that extends around the Milky Way and located halfway between our galaxies. satellite the Magellanic Clouds. Observations from the Hubble Space Telescope suggest that this intergalactic stream emerged from the Small Cloud about two billion years ago. Well, that subtle glow in the current is the consequence of that high-energy jet that came out of the heart of our galaxy two million years ago and hit the Magellanic Stream, making it shine in the same way that the solar wind causes the polar lights in the earth. A shine that still lasts.
