An international team of astronomers has discovered one of the greatest features ever seen in the center of the Milky Way – a pair of massive radio bubbles that rise hundreds of light years above and below the central region of our galaxy.
This hourglass-like feature, dwarfing all other radio structures in the Galactic Center, is likely the result of a phenomenally energetic outburst that erupted near the supermassive Black Hole of the Milky Way several million years ago.
"The center of our galaxy is relatively quiet compared to other galaxies with very active central black holes," said Ian Heywood of Oxford University and lead author of an article in the journal Nature. "Nonetheless, the Milky Way's central black hole may occasionally become unusually active, devouring massive dust and gobs of lime on a regular basis, and it is possible that such cravings caused severe outbursts that ignited this previously unseen feature." , "
Heywood and his colleagues used the MeerKAT telescope from the South African Radio Astronomical Observatory (SARAO) to map large regions in the center of the galaxy and observe at wavelengths close to 23 centimeters. Such radio emission is generated in a process called synchrotron radiation in which electrons that move near the speed of light interact with strong magnetic fields. This generates a characteristic radio signal that can be used to track energetic regions in space. This light light penetrates easily into the dense clouds of dust that block visible light from the center of the galaxy.
By examining the nearly identical size and shape of the twin bubbles, the researchers have found convincing evidence that these features were caused by a violent eruption that has run in opposite directions through the interstellar medium for a short period of time.
"The shape and symmetry of what we've observed strongly suggests that a staggering event occurred a few million years ago near the central black hole of our galaxy," said William Cotton, an astronomer at the National Radio Astronomy Observatory in Charlottesville, Virginia, and co-author on the paper. "This eruption may have been triggered by huge amounts of interstellar gas falling on the black hole, or a massive burst of star formation hurling shockwaves through the galactic center, and these bubbles actually bubbled in the hot, ionized gas near galactic center, energize, and create radio waves that we might discover here on Earth at some point. "
The area surrounding the black hole in the center of our galaxy is very different from the Milky Way area and is a region of many secrets. Among them are very long and narrow filaments that can not be found anywhere else and whose origin since its discovery 35 years ago is an unsolved mystery. The filaments appear as ten light-years long and about a light year wide radio structures.
"The radio bubbles discovered by MeerKAT provide information on the origin of the filaments," said Farhad Yusef-Zadeh of Northwestern University in Evanston, Illinois, and a co-author of the newspaper. "Almost all of the more than a hundred filaments are trapped by the radio bubbles."
The authors suggest that the close association of the filaments with the bubbles implies that the energetic event that creates the radio bubbles is also responsible for the acceleration of the electrons required to generate the radio emission from the magnetized filaments.
"These huge bubbles have so far been obscured by the extremely bright radio radiation from the center of the galaxy," said Fernando Camilo of SARAO in Cape Town and co-author of the newspaper. "Removing the bubbles from the background noise was a technical tour de force made possible only by MeerKAT's unique features and ideal location," says Camilo. "With this unexpected discovery, the Milky Way is experiencing a novel manifestation of galaxy-matter outflows of matter and energy ultimately driven by the central black hole."
According to the researchers, the discovery of these bubbles near the center of our home galaxy brings us one step closer to understanding spectacular activities taking place in more distant Milky Way relatives throughout the universe.
The National Radio Astronomy Observatory is a National Science Foundation facility operated in partnership with Associated Universities, Inc.
Reference: "Inflation of 430 Parsec Bipolar Radio Bubbles in the Galactic Center by an Energetic Event", I. Heywood et al., Nature.
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