Extending hundreds of light years above and below the galactic plane, the bubbles were likely created by an eruption at the galactic core within the past few million years, according to a paper published on Wednesday in Nature. The burst must have been roughly equal to 100 star explosions in order to produce such large structures.
"These enormous bubbles have until now been hidden by the glare of extremely bright radio emission from the center of the galaxy," said study co-author Fernando Camilo, chief scientist at the South African Radio Astronomy Observatory, in a statement.
Camilo is part of an international team led by Ian Heywood, an astrophysicist at the University of Oxford, which detected the bubbles. The discovery was made with the MeerKAT radio telescope, a facility with 64 radio antennae, located north of the town of Carnarvon, South Africa.
MeerKAT became operational in 2018, and the new study is based off some of its very first observations. "Teasing out the bubbles from the background noise was a technical tour de force, only made possible by MeerKATs unique characteristics and ideal location,” Camilo said.
The center of the Milky Way is profoundly influenced by Sagittarius A*, a supermassive black hole with a mass equivalent to four million Suns. Though this black hole is relatively tranquil compared to ones observed in other galactic cores, it still occasionally binges on gas, dust, and even stars. Scientists think they may have observed one of these episodes earlier this year, for instance.
The radio bubbles detected by Heywood’s team were most likely belched out by Sagittarius A* after an unusually big gulp of material. The blowout sent jets of charged particles rocketing away from the galactic core, which were sculpted into the modern bubbly shape in part by the intense magnetic field lines surrounding the black hole.
“With this unexpected discovery were witnessing in the Milky Way a novel manifestation of galaxy-scale outflows of matter and energy, ultimately governed by the central black hole," Camilo said.