Millions of years ago, a powerful explosion shook the center of the Milky Way, where double shock waves shoot through the air. Those waves slammed through the galaxy with bulldozers, heating all the gas and dust in their path, leaving two meaningful blobs of hot, highly energetic gamma rays in their wake.
Today those blobs are – now the Fermi Bubbles – cover half the width of our galaxy. One lobe towers 25,000 light-years above the Milky Way’s disk, and the other looms just as big. Since their discovery in 2010, the bubbles have been a monolithic mystery of our galaxy – and now we know they’re not alone.
As scientists continue to study our galaxy in every conceivable wavelength of light, strange new structures within the Fermi Bubbles – from “chimneys” of plasma slowly inflate balloons of radio energy – keep popping up. Now, a paper published December 9 in the journal Nature unveils some of the largest Fermi-known structures to date: the “eROSITA bubbles.”
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Only visible in X-ray emission, these newfound bubbles are considerably less energetic (and less hot) than the Fermi blobs, but they are nearly as gigantic, measuring about 45,000 light-years from end to end. Like the Fermi bubbles, these spheres of hot gas tower above and below the galactic plane in a distinct hourglass shape, attached to the galactic center at the point where the two blobs meet.
Given their similar shape and common center, it is likely that the Fermi and eROSITA bubbles share a physical connection and likely resulted from the same burst of galactic fireworks millions of years ago, the authors wrote in their study. What caused the bubbles to blow is still a mystery, but astronomers suspect it was a explosive eruption of energy from the central black hole of our galaxy, Sagittarius A *.
That explanation fits the newly discovered X-ray bubbles, the study authors wrote, given the amount of energy it takes to blow them up. The team calculated that it took an energy output equal to that of 100,000 supernovae (powerful stellar explosions) to create these structures – a figure comparable to the release of X-ray energy seen in other galaxies with active black holes in their centers. Even if this hypothetical explosion is millions of years old, its traces would still be visible.
“The scars left by such outbursts take a long time to heal,” study co-author Andrea Merloni, a senior scientist at the Max Planck Institute for Extraterrestrial Physics in Germany, said in a statement.
Merloni and his colleagues discovered the X-ray bubbles using the eROSITA X-ray telescope, which travels through the cosmos aboard the Russian-German Spektr-RG satellite. The telescope scans the entire sky every six months and constantly updates our view of the X-ray universe.
Originally published on Live Science.