The center of Via Lctea is a lively place to say the least. A lot happens around Sagittarius A * (Sgr A *), the black hole with a mass four million times that of the Sun. The region’s nuclear wind, for example, sculpted two twin spheres of dust, gases and cosmic rays. that emerge from the black hole, above and below the galactic plane, extending for a total of 50 thousand light years: the Fermi bubbles.
But an international team of researchers has discovered something new inside these bubbles, a cold, dense gas that is launched from the center of the Milky Way “like a bullet”. Exactly how the ejected gas still remains a mystery, but scientists believe that this loss may have important implications for the future of our galaxy.
“When you expel a lot of mass, you are losing some of the material that could be used to form stars, and if you lose enough, the galaxy will not be able to form stars anymore,” says astrophysicist Naomi McClure-Griffiths of the Australian National University (ANU) , one of the authors of the study published in Nature.
To find the dense and cold molecular gas clouds, the researchers studied clouds of atomic hydrogen previously identified in Fermi bubbles, using the Atacama Pathfinder Experiment radio telescope to look for their spectral signature. Thus, two clouds were found containing at least 380 and 375 solar masses of molecular gases and moving at 240 kilometers per second and 300 kilometers per second, respectively.
The research team analyzed the two clouds, now known as MW-C1 and MW-C2, and found that they were much colder than the gases previously described in the Via Lctea wind. “In terms of temperature, the difference between hot gas and cold gas is around 1,000,” says McClure-Griffiths.
Cold gas measures around -212C and is “very dense”, which makes it much more difficult to move compared to diffuse hot gas. “One way of thinking about it is that you can blow the smoke away from your face, but you can’t blow a stone,” explains the astrophysicist.
The study also raises new questions about what is happening in our galactic center now. “The wind in the center of Via Lctea has been the subject of much debate since the discovery, a decade ago, of Fermi bubbles,” recalls McClure-Griffiths. “We observed that not only are hot gas coming from the center of our galaxy, but also cold and very dense gas, which, being heavier, moves less easily.”
It is also unclear whether this gas is expelled by Sgr A * or if it is blown by thousands of massive stars in the center of the galaxy. “We don’t know how the black hole or the formation of stars can produce this phenomenon, and it gets more complicated as we learn more about it,” says Enrico Di Teodoro, of Johns Hopkins University, the article’s lead author.
“This is the first time that something like this has been observed in our galaxy. We see this type of process happening in other galaxies. But with external galaxies, you get much more massive black holes, the activity of star formation is bigger, which makes it more It is easy for the galaxy to expel material. And these other galaxies are obviously very far away, we cannot see them in many details “, he adds.
Via: Science Alert / CNet