Hot gas bubble observed around Sagittarius A*

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A hot gas bubble observed around Sagittarius A*

The Milky Way and the location of its central black hole as seen from ALMA.

A hot spot associated with a gas bubble has been observed orbiting Sagittarius A *, the black hole at the center of the Milky Way, using the European Southern Observatory's ALMA antenna array associated with the EHT (Event Horizon Telescope) initiative.

Image of the Sagittarius A* black hole along with an artist's impression showing where the hot spot and its orbit around the black hole.

We think we're watching a bubble of incandescent gas gliding around Sagittarius A* in an orbit similar in size to that of the planet Mercury, but completing a full rotation in just about 70 minutes. This requires a mind-blowing velocity of about 30% of the speed of light! explains in a press release the astrophysicist Maciek Wielgus, of the Max Planck Institute for Radio Astronomy in Germany.

This detection will allow astrophysicists to better understand the dynamic environment of the black hole , whose first image was unveiled last May.

  • Primordial black holes are very small. They would have formed during the big bang in the extremely dense regions of the primordial Universe.
  • Intermediate black holes oscillate between 100 and 10,000 solar masses.
  • Stellar black holes have a mass 10 to 20 times that of the Sun.
  • Supermassive black holes are found at the center of most galaxies and their mass is millions or even billions of times that of the Sun.

It was during the calibration of the data collected by the eight radio telescopes associated with the EHT that Mr. Wielgus and his colleagues detected indications of an eruption hidden in the ALMA measurements.

These types of flares, previously observed by X-ray and infrared telescopes, are thought to be associated with what are known as “hot spots, bubbles of hot gas that orbit very rapidly and proximity to the black hole,” the scientists note in the statement.

“What is really new and interesting is; is that such flares have so far only been clearly present in X-ray and infrared observations of Sagittarius A*. For the first time, we see a very strong indication that orbiting hotspots are also present in radio observations.

—Maciek Wielgus

Perhaps these hot spots detected under infrared waves are a manifestation of the same physical phenomenon: as soon as the hot spots emitting in the infrared cool, they become visible in the longer wavelengths , such as those observed by ALMA and EHT, added his colleague Jesse Vos, from Radboud University in the Netherlands.

The idea that the flares came from magnetic interactions in very hot gases orbiting very close to Sagittarius A* was accepted by a majority of astrophysicists, but these recent observations confirm it.

Researchers now want to track hotspots across frequencies using coordinated observations in different wavelengths.

The success of such an effort would be a real milestone for our understanding physics of flares in the galactic center, estimates Ivan Marti-Vidal of the University of Valencia in Spain.

In addition, scientists hope to be able to directly observe the gas clusters around from the black hole to learn more about this energy monster.

“Hopefully, we may one day be able to claim that we know what happens in Sagittarius A*. »

— Maciek Wielgus

Details of this work are published in the journal Astronomy & Astrophysics (in English).

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