The Milky Way is shooting blobs of never-before-seen cold, dense gas from its center – and astronomers have no idea how or why, according to a paper published in Nature.
Hundreds of gas clouds carrying hydrogen and helium float above and below the middle of the galactic plane. Scientists led by the Australian National University (ANU) have spied another stream of gas that is cooler being ejected at a faster rate from the galaxy “like bullets.”
“When you drive out a lot of mass, you're losing some of the material that could be used to form stars, and if you lose enough of it, the galaxy can't form stars at all anymore,” said Naomi McClure-Griffiths, co-author of the paper and an astrophysics professor at the ANU.
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The team are unsure where the cold gas clouds come from, and what’s driving them out into space. Similar observations have been made in other galaxies that have active galactic nuclei – a type of supermassive black hole gobbling up neighboring matter and emitting jets of electromagnetic energy – and higher rates of star formation.
Although the Milky Way does have a supermassive black hole at its center known as Sagittarius A*, it doesn’t seem to have enough energy to shoot the cold clouds away.
“This detection of outflowing cold molecular gas in the Milky Way is a challenge for current theories of galactic winds in regular star-forming galaxies, because none of the above processes seems able to easily explain the presence of fast molecular gas in the Milky Way’s wind,” the paper reads.
The wind seems to be connected to the Fermi Bubbles, two giant structures that extend 25,000 light years above and below the Milky Way’s center. The cold gas seems to be interacting with the turbulent warmer gas at lower end of the Fermi Bubbles. Why it's moving so fast, however, remains a mystery.
Enrico Di Teodoro, co-author of the paper and a postdoctoral researcher at the John Hopkins University, said: "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.”
"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," he concluded. ®