Discoveries keep bubbling in the middle of the Milky Way.
From this point, colossal bubbles spew out, spewing out radio waves discovered using a new telescope. The structures are a sign of an activity boost from the region around the now sleepy, supermassive black hole in the center of the galaxy, researchers report on 12 September on Nature .
A picture of The Ethereal Bubbles demonstrates the capabilities of the MeerKAT radio telescope of the South African Radio Astronomical Observatory, a series of 64 dishes spanning an eight-kilometer area near Carnarvon. The finished telescope began in spring 2018 with the data acquisition.
These radio-wave-emitting bubbles extend hundreds of light years above and below the Milky Way. And they point to "something out of the ordinary that happened in the galactic center," says astrophysicist Ian Heywood of Oxford University.
Heywood and colleagues estimate that in an event with enormous amounts of energy – which corresponds to the explosion of about 100 stars – matter was spewed out of the region around the black hole a few million years ago. Fast, electrically charged particles, which in this case are accelerated by magnetic fields, generate the radio waves of the bubbles, according to the team.
A passing black hole that fed madness a long time ago could have spawned bubbles as the behemoth swallowed matter and spewed the surplus out. Or the bubbles can be the result of a lot of stars forming around the black hole. These stars could eventually explode in supernovae and eject their innards.
The bubbles are lighter at their edges, suggesting that A shock wave from the material plows outward, the researchers found. That is, whatever the bubbles produced was not a continuous process, but one that turned on after a period of rest.
These radio bubbles are "a piece of the mosaic" in the center of the galaxy, says astrophysicist Jun-Hui Zhao of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, who was not involved in the discovery. In March, astronomers reported X-ray chimneys bubbling from the heart of the galaxy ( SN: 3/20/19 ). These chimneys overlap with the newly discovered radio structures, suggesting a common origin. And earlier observations revealed huge gamma-ray bubbles that are much larger than the X-ray and radio structures on either side of the galaxy ( SN: 11/9/10 ).
Recognition of new mosaic pieces such as the radio bubble could help scientists determine the origin of some of the previously discovered oddities. For example, the bubbles encase a series of mysterious structures known as radiofilaments, tall, thin stripes discovered in the 1980s. Although it is still unclear how the filaments form, it combines the new result with the radio bubbles.
"This is truly the first time you have seen the clear relationship between effluents and the illumination of these filaments," says astronomer Daniel Wang of the University of Massachusetts, Amherst, who was not involved in the research. "That's a fantastic picture."