Bubble of hot gas discovered spinning around Milky Way black hole

Astronomers say they have detected signs of a gas bubble circling the black hole at the centre of our galaxy at what they called a "mind-blowing" pace – around 30 percent of the speed of light.

Astronomers have spotted signs of a 'hot spot' orbiting Sagittarius A*, the black hole at the centre of our galaxy. This illustration indicates its estimated orbit. © AFP PHOTO / EHT COLLABORATION / ESO / M. KORNMESSER

The detection of the bubble, which only survived for a few hours, is hoped to provide insight into how black holes work.

The supermassive black hole Sagittarius A* sits in the middle of the Milky Way, some 27,000 light years from Earth, and contains the mass of more than 4 million Suns. Its immense gravitational pull gives our galaxy its characteristic swirl.

The first ever image of Sagittarius A* was revealed in May by the Event Horizon Telescope Collaboration, which links radio dishes around the world aiming to detect light as it disappears into black holes.

• Snapping Sagittarius A*: How scientists captured the first image of our galaxy’s black hole

Scientists involved in the Event Horizon project speak to the US House Committee on Science, Space and Technology in May 2019. AFP - ANDREW CABALLERO-REYNOLDS

One of those dishes, the ALMA radio telescope in Chile's Andes mountain range, picked up something "really puzzling" in the Sagittarius A* data, said Maciek Wielgus, an astrophysicist at Germany's Max Planck Institute for Radio Astronomy.

Just minutes before ALMA's radio data collection began, the Chandra Space Telescope observed a "huge spike" in X-rays, Wielgus told AFP.

This burst of energy, thought to be similar to solar flares on the Sun, sent a hot bubble of gas swirling around the black hole, according to a new study published by Wielgus and colleagues in the journal Astronomy and Astrophysics.

• Mapping our galaxy’s black hole

This infographic details the locations of the participating telescopes of the Event Horizon Telescope and the Global mm-VLBI Array. © ESO/O. Furtak

While scientists did not directly observe the bubble, they were able to follow its orbit by tracking how the brightness and angle of light from Sagittarius A* changed.

The gas bubble, also known as a hot spot, had an orbit similar to Mercury's trip around the Sun, Wielgus said.

But while it takes Mercury 88 days to make that trip, the bubble did it in just 70 minutes. That means it travelled at around 30 percent of the speed of light.

"So it's an absolutely, ridiculously fast-spinning bubble," Wielgus said, calling it "mind-blowing".

The hot spot is believed to be the product of superheated gas around Sagittarius A* interacting with the black hole's magnetic field.

(with AFP)