In 1936, in The Realm of the Nebulae, Edwin Hubble –who proved that objects previously thought of as “nebulae” were actually galaxies beyond the Milky Way–wrote that eventually, we reach the utmost limits of our telescopes where “we measure shadows and search among ghostly errors of measurement for landmarks that are scarcely more substantial.” Fast forward to today: a cold mystery gas from the center of the Milky Way, with its extreme astrophysics, has been detected “shooting like bullets” by an international team of astronomers –a phenomenon that has important implications for the future of our home galaxy.
“Galaxies can be really good at shooting themselves in the foot,” said Naomi McClure-Griffiths from The Australian National University (ANU).. “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. So, to be able to see hints of the Milky Way losing this star forming gas is kind of exciting – it makes you wonder what’s going to happen next!”
“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,” McClure-Griffiths said.”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.”
The center of the Milky Way is home to a supermassive black hole, Sagittarius A*, but it’s unclear whether this black hole has expelled the gas, or whether it was blown by the thousands of massive stars at the center of the galaxy.
The image above shows the central region of the Milky Way –a region of exotic collection of objects, including the supermassive black hole weighing about 4 million times the mass of the Sun,, clouds of gas at temperatures of millions of degrees, neutron stars and white dwarf stars tearing material from companion stars and beautiful tendrils of radio emission. The region around Sagittarius A* is shown in this new composite image with Chandra data (green and blue) combined with radio data (red) from the MeerKAT telescope in South Africa, which will eventually become part of the Square Kilometer Array. (X-Ray:NASA/CXC/UMass/D. Wang et al.; Radio:NRF/SARAO/MeerKAT
“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,” lead author Dr Enrico Di Teodoro from Johns 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. And these other galaxies are obviously a long way away, we can’t see them in a lot of detail. 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.”
The gas was observed using the Atacama Pathfinder EXperiment (APEX) operated by the European Southern Observatory (ESO) in Chile.