Hot gas bubble discovered around supermassive black hole in the Milky Way

Astronomers have spotted a hot bubble of gas spinning at over 200 million miles per hour around the Milky Way’s supermassive black hole.

It orbits Sagittarius A* at almost a third the speed of light in an orbit similar in size to that of the planet Mercury, completing a full orbit in just 70 minutes.

Experts say the discovery could help us better understand the enigmatic and dynamic environment of the vast void at the heart of our galaxy.

The lead author Dr. Maciek Wielgus of the Max Planck Institute for Radio Astronomy in Germany said: “We think we’re looking at a hot bubble of gas orbiting Sagittarius A* in an orbit similar to that of the planet Mercury – but just about a full loop 70 minutes.’

He added, “This requires mind-blowing speeds of about 30 percent the speed of light.”

An international team discovered the “hot spot” with the ALMA (Atacama Large Millimeter/submillimeter Array) radio telescope in the Chilean Andes.

Supermassive black holes are incredibly dense regions at the centers of galaxies. They act as intense gravitational wells, sucking up dust and gas around them.

Sagittarius A* – just 26,000 light-years from Earth – is one of the few black holes in the universe where we can actually observe the flow of matter nearby.

However, because the area absorbs all ambient light, it’s incredibly difficult to see, which is why scientists have spent decades searching for evidence of black hole activity.

The observations were made by the European Southern Observatory (ESO) during a black hole imaging campaign by the Event Horizon Telescope (EHT) collaboration.

In April 2017, eight existing radio telescopes around the world were linked, resulting in the first-ever image of Sagittarius A*.

dr Wielgus and colleagues used ALMA data recorded concurrently with the EHT observations of Sagittarius A*.

There were other clues to the nature of the black hole hidden in the ALMA-only measurements.

Coincidentally, some images were taken shortly after a burst, or flare, of X-ray energy emitted from the center of the Milky Way and spotted by NASA’s Chandra Space Telescope.

This type of flare, previously observed with X-ray and infrared telescopes, is thought to be associated with “hot spots” — gas bubbles orbiting very fast and close to the black hole.

dr Wielgus said: “What’s really new and interesting is that such flares have only been clearly present in X-ray and infrared observations of Sagittarius A* so far.

“Here, for the first time, we see very strong evidence that orbital hot spots are also present in radio observations.”

Less than 1 percent of the material originally under the black hole’s gravitational influence reaches the event horizon, or point of no return, as much of it is ejected.

Consequently, X-ray emission from matter is remarkably weak, like that of most giant black holes in galaxies in the nearby Universe.

Co-author Jesse Vos, a PhD student at Radboud University in the Netherlands, said: “Perhaps these hot spots detected at infrared wavelengths are a manifestation of the same physical phenomenon.

“As infrared-emitting hot spots cool, they become visible at longer wavelengths, as observed by ALMA and the EHT.”

The flares were thought to originate from magnetic interactions in the extremely hot gas orbiting very close to the black hole. The research results support this idea.

co-author dr. Monika Moscibrodzka, also from Radboud, said: “Now we find strong evidence for a magnetic origin of these flares and our observations give us a clue to the geometry of the process.

“The new data are extremely helpful in building a theoretical interpretation of these events.”

ALMA allows astronomers to study polarized radio emission from Sagittarius A*, which can be used to reveal the black hole’s magnetic field.

An international team discovered the “hot spot” with the radio telescope ALMA (Atacama Large Millimeter/submillimeter Array) in the Chilean Andes (picture).

The data combined with theoretical models shed light on the formation of the hot spot and the environment in which it is embedded, including the magnetic field.

Stronger shape constraints than previous observations are helping to reveal the nature of our black hole and its surroundings.

Scans from ALMA and the GRAVITY instrument on ESO’s Very Large Telescope (VLT), observing in the infrared, suggest that the flare originated from a blob of gas.

It is spinning clockwise in the sky around the black hole at about 30 percent the speed of light — with the hot spot’s orbit almost head-on.

co-author dr. Ivan Marti-Vidal from the University of Valencia said: “In the future we should be able to track hot spots across frequencies using coordinated multi-wavelength observations with both GRAVITY and ALMA.

“The success of such an endeavor would be a real milestone in our understanding of the physics of flares in the galactic center.”

This widefield view in visible light shows the rich star clouds in the constellation of Sagittarius (the Sagittarius) toward the center of our Milky Way

The team also hopes to use the EHT to directly observe orbiting blobs of gas to study and learn more about the black hole.

dr Wielgus added, “Hopefully one day we can say we ‘know’ what’s going on in Sagittarius A*.”

How black holes form is still poorly understood. Astronomers believe this happens when a large cloud of gas, up to 100,000 times larger than the sun, collapses.

Many of these “seeds” then merge into much larger supermassive black holes found at the center of every known massive galaxy.

Alternatively, a supermassive black hole could originate from a giant star about 100 times the mass of the Sun that eventually forms into a black hole after running out of fuel and collapsing.

When these giant stars die, they also go into a “supernova,” a giant explosion that ejects matter from the star’s outer layers into space.

The new study was published in the journal Astronomy & Astrophysics.

WHAT IS ALMA?

Deep in the Chilean desert is the Atacama Large Millimeter Array, or ALMA for short, in one of the driest places on earth.

At an altitude of 16,400 feet, about half the cruising altitude of a jumbo jet and almost four times the height of Ben Nevis, workers had to carry oxygen tanks to complete construction.

It became operational in March 2013 and is the most powerful ground-based telescope in the world.

It’s also the tallest on the planet and one of the most expensive of its kind at nearly £1 billion (US$1.2 billion).

Deep in the Chilean desert is the Atacama Large Millimeter Array, or ALMA for short, in one of the driest places on earth. It became operational in March 2013 and is the most powerful ground-based telescope in the world