The center of the Milky Way is home to Sagittarius A*, a quiet supermassive black hole. This central region is full of interesting phenomena, some of which are poorly understood. And now, astronomers have found another. For the first time, they have observed clouds of molecular gas being ejected by the core of our galaxy.
Clouds of atoms have been observed being ejected from the Milky Way in the last decades. These span temperatures from millions to thousands of degrees. But researchers have discovered a cold dense gas with temperatures way below freezing being ejected from the galaxy's center "like bullets" and, as reported in Nature, they are unsure how exactly this material came to be.
“This is the first time something like this has been observed in our galaxy. We see these kind of processes happening in other galaxies. But, with external galaxies you get much more massive black holes, star formation activity is higher, it makes it easier for the galaxy to expel material,” lead author Dr Enrico Di Teodoro from Johns Hopkins University said in a statement.
The cold molecular gas was seen reaching a maximum velocity of 330 kilometers per second (about 740,000 miles) at a distance of about 8,000 light-years from the center of the Milky Way. It was also seen interacting with the warmer atomic gas around it, potentially disrupting the cold gas.
“The wind at the center of the Milky Way has been the topic of plenty of debate since the discovery a decade ago of the so-called Fermi Bubbles – two giant orbs filled with hot gas and cosmic rays,” added co-author Professor Naomi McClure-Griffiths from The Australian National University. “We’ve observed there’s not only hot gas coming from the center of our galaxy, but also cold and very dense gas. This cold gas is much heavier, so moves around less easily.”
Cold molecular gas is an important component in the nebulae (clouds of gas and dust) in which stars form. Given how sizable this outflow is, there are certainly questions regarding how this loss will impact the star-formation rate in the center of the Milky Way. Maybe it's the formation of other stars that push this gas out, or maybe Sagittarius A* in a rare moment of activity helped to push it out.
“Our own galaxy is almost like a laboratory that we can actually get into and try to understand how things work by looking at them up close,” Dr Di Teodoro said. “We don’t know how either the black hole or the star formation can produce this phenomenon. We’re still looking for the smoking gun, but it gets more complicated the more we learn about it,.”
The international collaboration observed this new phenomenon thanks to the Atacama Pathfinder EXperiment (APEX) by the European Southern Observatory.
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