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Huge "bubbles" around the black hole of the Milky Way



In its first major achievement, just over a year after its inauguration, a supersensible South African telescope has discovered two huge "radio bubbles" above and below the central region of the Milky Way. The features cover a total of 430 parsecs (1,400 light-years), which is about 5% of the distance between the solar system and the center of the galaxy.

The bubbles are gas structures that can be observed because moving electrons generate radio waves as they are accelerated by magnetic fields. This activity suggests that the bubbles are the remnants of an energetic outburst of hot gas several million years ago, according to the authors of a paper describing the features and published on September 1

1 in Nature.

One possible explanation is that the supermassive black hole in the center of the galaxy has undergone a period of intense wasting of matter that caused the eruption, the researchers say. Another event could be a "starburst event" – the near-simultaneous formation and subsequent fiery death of about 100 big stars. The shockwaves of their explosions could have punched together a hole through the thick interstellar matter of the central region of the galaxy.

Oliver Pfuhl, astronomer at the European Southern Observatory in Garching, says that both starburst and black hole activity could have been in the game and even reinforcing each other. And researchers are aware of a stellar explosion that occurred around 7 million years ago in the region. "It's fascinating to relate the radio bubble to this star-forming event," he says.

Researchers are working with the South African MeerKAT radio telescope – a forerunner of the world's largest radio telescope, the Square Kilometer Array (SKA). – They discovered the bubbles when they created a picture of the Galactic Center on the occasion of the inauguration of the observatory and tested their brand new facility from April 2018, says the observatory's chief scientist, radio station Fernando Camilo. It usually takes years for researchers to set up a new observatory to work properly and produce science. But with MeerKAT they were amazed how smooth things went. "It worked right away," says Camilo.

The bubbles could also solve an old riddle in radio astronomy. It is possible that the electrons that accelerate in them are the source of bright "filaments" of matter that extend over dozens of parsecs and overhang the galactic center that was first seen in 1984. Even larger bubbles that protrude from those seen by MeerKATs were seen in the γ part of the spectrum and could have a similar origin.

MeerKAT, with an edge of $ 4.4 billion ($ 330 million), consists of 64 radio reports, each 13.5 meters in diameter, at a remote location in the Northern Cape Province. It will form the core of the South African part of the SKA, which will be built in the 2020s. The second section of the observatory will be in Australia.

This article was reproduced with permission and first published on September 11, 2019.


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