We’ve been staring, cosmically speaking, at these all along – without really “seeing” them.
But now, an international team of astronomers has identified a pair of bubbles, hundreds of light-years tall and dwarfing all other structures in that part of the Milky Way, that may have emanated from a long-ago eruption of the black hole at the heart of our galaxy.
It’s an enormous, hourglass-shaped structure that the researchers think “likely is the result of a phenomenally energetic burst that erupted near the Milky Way’s supermassive black hole several million years ago,” they said in a statement.
In layman’s terms: Something exploded – most likely, Sagittarius A*, the black hole at the center of the Milky Way – and these are the remnants.
Emitting radio waves, they stretch 700 light-years on either side of the galactic plane, according to Science Alert.
These bubbles are different than the huge gamma-ray bubbles discovered by the Fermi Gamma-ray Space Telescope in 2010, Science Alert noted. Those span 50,000 light-years, spanning above and below the galactic plane.
“These latest bubbles are something new, and astronomers haven't seen them before,” Science Alert clarified. “But they are amongst the biggest structures at the center of our galaxy, and they reveal new information about the dynamics of our galactic nucleus.”
The new discovery was made possible by the South African Radio Astronomy Observatory’s MeerKAT telescope, which consists of 64 interconnected radio antennae that offer unprecedented sensitivity in radio wavelengths and is in a key spot in the Southern Hemisphere for taking detailed images of the galactic center, said Science Alert.
Northwestern University physicist Farhad Yusef-Zadeh, a professor of physics and astronomy at the Weinberg College of Arts and Sciences, first caught a whiff of these structures in the 1980s, the school said in a statement. That’s when he found large-scale, highly organized magnetic filaments in the center of the Milky Way, 25,000 light-years from Earth.”
Their origin was one of the many unsolved mysteries of that part of the galaxy, but were at the very least measured and identified as radio structures tens of light-years long and one light-year wide, the researchers said.
“The radio bubbles discovered with MeerKAT now shed light on the origin of the filaments,” Yusef-Zadeh said in the researchers’ statement. “Almost all of the more than 100 filaments are confined by the radio bubbles.”
“The center of our galaxy is relatively calm when compared to other galaxies with very active central black holes,” said Ian Heywood of the University of Oxford, lead author of the study, in a statement. “Even so, the Milky Way’s central black hole can — from time to time — become uncharacteristically active, flaring up as it periodically devours massive clumps of dust and gas. It’s possible that one such feeding frenzy triggered powerful outbursts that inflated this previously unseen feature.”
Fifteen institutions, including Northwestern University, contributed to the research. So did Oxford University, the South African Radio Astronomy Observatory in Cape Town and the National Radio Astronomy Observatory in Charlottesville, Virginia.
“These enormous bubbles have until now been hidden by the glare of extremely bright radio emission from the center of the galaxy,” said Fernando Camilo of SARAO in Cape Town and co-author on the paper, in the researchers’ statement. “Teasing out the bubbles from the background noise was a technical tour de force, only made possible by MeerKAT’s unique characteristics and ideal location. With this unexpected discovery we’re witnessing in the Milky Way a novel manifestation of galaxy-scale outflows of matter and energy, ultimately governed by the central black hole.”
The findings, published in the Sept. 11 issue of the journal Nature, point to the fact that the solar system lies in a relatively placid area of the galaxy compared to the bustling hub.
“It’s good that we don’t live at the nucleus of our galaxy,” Yusef-Zadeh told NBC News. “It’s an exciting place to study, but it’s a hostile place.”