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There is a ring of cool gas wrapped around the supermassive Black Hole of the Milky Way



There is a lot going on in the center of our galaxy. There is a supermassive black hole called Sagittarius A-Star, which attracts material with its irresistible appeal. In this amazing neighborhood, where the laws of physics are unbelievable, astronomers have discovered a ring of cold gas.

Sagittarius A-Star or Sag. A * is 26,000 light-years from Earth and about 4 million times as massive as our Sun. All this mass means an overwhelming gravitational energy pulling material towards A *. However, before sucking material over the bleed horizon, it is in a rotating accretion disk.

Astronomers have known this for some time. Sagging. A * is a bright X-ray source because the material in the disk is compressed and heated, releasing X-rays. It is not just heated. it is overheated to 1

0 million degrees Celsius (18 million degrees Fahrenheit). X-ray observatories in space could observe all of this up to a tenth of the light year from the hole itself.

A view of Sgr A * and the supermassive black hole 26,000 light-years from Earth in the center of the Milky Way. Credit: Chandra Telescope, NASA.

But there is also a large amount of "cold" hydrogen gas within a few light years from the hole. This gas is only cold compared to the other gas. It's about 10,000 degrees Celsius. The contribution of this cooler gas to the black hole environment was unknown. At least until now.

"We hope these new ALMA observations will help the Black Hole reveal some of its secrets."

Elena Murchikova, lead author of the work, astrophysicist at the Institute for Advanced Study at Princeton, New Jersey.

A new study with the Atacama Large Millimeter / Sub-Millimeter Array (ALMA) has now given us our first picture of this cold gas body. Her article about this work appears in the Nature issue of June 6th. That's how they did it.

There is enough radiation near the center of the galaxy for hydrogen atoms to lose their electrons. Then they win them back in a continuous cycle. The recombination releases energy in a certain millimeter-wavelength signal. This signal can be transmitted to the ground with very little signal loss.

  Three of the dishes that make up the Atacama Large Millimeter / Submillimed Array (ALMA). Photo credits: H. Calderón - ALMA (ESO / NRAO / NAOJ)
Three of the courts that make up the Atacama Large Millimeter / Submillimed Array (ALMA). Source: H. Calderón – ALMA (ESO / NRAO / NAOJ)

ALMA is a very fine device, powerful and sensitive, and it can be tuned to this special signal. With this power and sensitivity, astronomers have created the first image of the disk of cold gas at a distance of only a hundredth of a light-year from Sag. ON*. Through their observations, astronomers can map the location of this cloud and track its movement. They also measured the size of the hydrogen cloud and it contains about one-tenth of the mass of Jupiter or one ten-thousandth of the mass of the sun.

"We were the first to depict this elusive disc and examine its rotation.

Elena Murchikova, lead author of the thesis, astrophysicist at the Institute for Advanced Study at Princeton, New Jersey.

The Doppler effect also comes into play. As the hydrogen recombination signal moves toward Earth, its frequency shifts to the bluer part of the spectrum. By mapping these shifts, astronomers were able to determine that the gas ring revolved around the black hole.

  The ALMA image of the disk of cool hydrogen gas flowing around the supermassive black hole in the center of our galaxy. The colors represent the movement of the gas relative to the earth: the red part moves away, so that the radio waves detected by ALMA are slightly stretched or shifted to obtain the
ALMA image of the disc with the surrounding cool hydrogen gas the supermassive black Hole in the center of our galaxy. The colors represent the movement of the gas relative to the earth: the red part moves away so that the radio waves captured by ALMA are easily stretched or shifted into the "redder" part of the spectrum. The blue color stands for gas that moves towards the earth. The radio waves are therefore easily shifted to the "bluer" part of the spectrum. The crosshair indicates the position of the black hole. Photo credits: ALMA (ESO / NAOJ / NRAO), E.M. Murchikova; NRAO / AUI / NSF, S. Dagnello

Since the environment of a black hole is so chaotic, a lot of work is needed to understand everything that is going on there. This information will help scientists to understand this environment and how a black hole consumes matter.

"We were the first to depict this elusive slice and study its rotation," said Elena Murchikova, a member of the Astrophysics Unit at the Institute for Advanced Study at Princeton, New Jersey, and lead author of the paper. "We also investigate the accretion of the black hole. This is important as this is our closest supermassive black hole. Nevertheless, we still do not have a good understanding of how the accretion works. We hope that these new ALMA observations will help the Black Hole reveal some of its secrets.

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