Astronomers have detected a bubble of hot gas swirling around the Milky Way’s supermassive black hole at more than 200 million miles per hour.
It is orbiting Sagittarius A* at almost a third of the speed of light in an orbit similar in size to that of the planet Mercury, completing a full circle in just 70 minutes.
Experts say the discovery could help us better understand the enigmatic and dynamic environment of the huge void at the heart of our galaxy.
Lead author Dr Maciek Wielgus, from the Max Planck Institute for Radio Astronomy in Germany, said: “We think we are seeing a bubble of hot gas moving around Sagittarius A* in an orbit similar in size to that of the planet Mercury. . but doing a full loop in only about 70 minutes.’
He added: “This requires mind-boggling speed of about 30 per cent of the speed of light.”
Mysterious: Astronomers have detected a bubble of hot gas spinning around the Milky Way’s supermassive black hole at more than 200 million miles per hour. The ALMA radio telescope detected signals from a ‘hot spot’ in orbit around Sagittarius A* (pictured), the black hole at the center of our galaxy.
WHAT IS SAGITTARIUS A* AND HOW WAS IT CAUGHT ON CAMERA?
Sagittarius A, abbreviated as Sgr A, pronounced “sadge-ay-star”, owes its name to its detection in the direction of the constellation Sagittarius.
Its existence has been assumed since 1974, with the detection of an unusual radio source in the center of the galaxy.
In the 1990s, astronomers mapped the orbits of the brightest stars near the center of the Milky Way and confirmed the presence of a supermassive compact object there, work that led to the 2020 Nobel Prize in Physics.
Although the presence of a black hole was thought to be the only plausible explanation, the new image provides the first direct visual evidence.
Because it is 27,000 light-years from Earth, it appears the same size in the sky as a donut on the moon.
Capturing images of such a distant object required linking eight giant radio observatories around the planet to form a single virtual “Earth-size” telescope called the EHT.
These included the 30-meter telescope of the Institute for Millimetric Radio Astronomy (IRAM) in Spain, the most sensitive single antenna in the EHT network.
The EHT stared at Sgr A* over several nights for many hours at a time, a similar idea to long-exposure photography and the same process used to produce the first image of a black hole, published in 2019.
That black hole is called M87* because it is in the Messier 87 galaxy.
An international team detected the ‘hot spot’ using the ALMA (Atacama Large Millimeter/submillimeter Array) radio telescope in the Chilean Andes.
Supermassive black holes are incredibly dense areas at the centers of galaxies. They act as intense gravity sources that suck in dust and gas around them.
Sagittarius A*, located just 26,000 light-years from Earth, is one of the few black holes in the universe where we can witness nearby matter flow.
But because the area absorbs all of the surrounding light, it’s incredibly hard to see, which is why scientists have spent decades searching for signs of black hole activity.
The observations were made by the European Southern Observatory (ESO) during a campaign by the Event Horizon Telescope (EHT) Collaboration to image black holes.
In April 2017, eight existing radio telescopes were connected around the world, resulting in the first image of Sagittarius A*.
Dr. Wielgus and his colleagues used ALMA data recorded simultaneously with the EHT observations of Sagittarius A*.
More clues to the nature of the black hole were hidden in measurements made with ALMA alone.
By chance, some were made shortly after a burst or flash of X-ray energy was emitted from the center of the Milky Way and detected by NASA’s Chandra Space Telescope.
These types of flashes, previously observed with X-ray and infrared telescopes, are thought to be associated with “hot spots”: bubbles of gas that orbit very fast and close to the black hole.
Dr Wielgus said: “What is really new and interesting is that such flashes were only clearly present in X-ray and infrared observations of Sagittarius A* until now.”
“Here we see for the first time a very strong indication that orbiting hot spots are also present in radio observations.”
Less than one percent of the material initially within the black hole’s gravitational influence reaches the event horizon, or point of no return, because much of it is ejected.
Consequently, the X-ray emission from the material is remarkably weak, like that from most giant black holes in galaxies in the nearby universe.
Co-author Jesse Vos, a PhD student at Radboud University, the Netherlands, said: “Perhaps these hot spots detected at infrared wavelengths are a manifestation of the same physical phenomenon.”
“As infrared-emitting hotspots cool, they become visible at longer wavelengths, such as those observed by ALMA and the EHT.”
The flares were thought to originate from magnetic interactions in 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: “We now find strong evidence for a magnetic origin of these flares and our observations give us a clue about the geometry of the process.”
“The new data is extremely helpful in building a theoretical interpretation of these events.”
ALMA allows astronomers to study the polarized radio emission from Sagittarius A*, which can be used to reveal the black hole’s magnetic field.
An international team detected the ‘hot spot’ using the ALMA (Atacama Large Millimeter/submillimeter Array) radio telescope in the Chilean Andes (pictured)
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 constraints in the way than previous observations help to discover the nature of our black hole and its environment.
Scans by ALMA and the GRAVITY instrument on ESO’s Very Large Telescope (VLT), which observes in the infrared, suggest that the flare originates from an accumulation of gas.
It spins around the black hole at about 30 percent of the speed of light in a clockwise direction in the sky, with the hot spot’s orbit nearly 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 at all frequencies using coordinated multi-wavelength observations with GRAVITY and ALMA.”
“The success of such an effort would be a real milestone for our understanding of the physics of flares in the galactic center.”
This wide-field view in visible light shows the rich clouds of stars in the constellation of Sagittarius (the Archer) in the direction of the center of our Milky Way galaxy.
The team also hopes to be able to directly observe orbiting gas clumps with the EHT, to probe ever closer to the black hole and learn more about it.
Dr Wielgus added: “Hopefully, one day, we’ll feel comfortable saying we ‘know’ what’s going on in Sagittarius A*.”
How black holes form is still poorly understood. Astronomers think it happens when a large cloud of gas up to 100,000 times larger than the sun collapses.
Many of these ‘seeds’ then coalesce to form much larger supermassive black holes, which lie at the center of all known massive galaxies.
Alternatively, a supermassive black hole seed could come from a giant star, about 100 times the mass of the sun, that eventually becomes a black hole after it runs out of fuel and collapses.
When these giant stars die, they also go ‘supernova’, a huge explosion that expels matter from the star’s outer layers into deep space.
The new study has been published in the journal Astronomy and Astrophysics.