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Astronomers discover Ring around the supermassive black hole of the Milky Way


  Cool accretion disk around the galactic center Black Hole

Artistic representation of a ring of cool interstellar gas surrounding the supermassive Black hole in the middle of the Milky Way. New ALMA observations reveal this structure for the first time. Credit: NRAO / AUI / NSF; S. Dagnello

Through decades of study, astronomers have developed a clearer picture of the chaotic and crowded neighborhood around the supermassive Black Hole in the center of the Milky Way. Our galactic center is about 26,000 light-years from Earth, and its supermassive black hole, known as Sagittarius A * (a "star"), is 4 million times the mass of our Sun.

We now know that this region is full of wandering stars, interstellar dust clouds, and a large reservoir of both phenomenally hot and comparatively colder gases. These gases are expected to orbit the black hole in a giant accretion disk located a few tenths of a light-years from the event horizon of the black hole.

So far, astronomers, however, could only make the delicate, hot image part of this flow of enriching gas, which forms an approximately spherical flow and showed no apparent rotation. It is estimated that its temperature is 10 million degrees Celsius (18 million degrees Fahrenheit) or about two thirds of the temperature at the core of our Sun. At this temperature, the gas glows strongly in the X-ray light, so that it can be examined with space-based X-ray telescopes to the order of about one-tenth light-year from the black hole.

Also, previous observations with millimeter-wavelength telescopes have shown that this hot, glowing gas contains a huge supply of comparatively cooler hydrogen gas (about 10,000 degrees Celsius or 18,000 degrees Fahrenheit) within a few light years of the black hole. The contribution of this cooler gas to the accretion stream on the black hole was previously unknown.

  Accretion disk around the galactic center Black Hole

ALMA image of the disk of cool hydrogen gas flowing around the supermassive black hole in the middle 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. Credit: ALMA (ESO / NAOJ / NRAO), E.M. Murchikova; NRAO / AUI / NSF, S. Dagnello

Although our black hole in the galactic center is relatively quiet, the radiation around it is strong enough to cause hydrogen atoms to constantly lose and reconnect with their electrons. This recombination produces a characteristic millimeter-wavelength signal that reaches the earth with very little loss.

The Atacama Large Millimeter / Submillimeter Array ( ALMA ) was able to detect this faint radio signal and the first image of the cooler gas disk at about a hundredth of a light-year distance (or about 1000 times Distance from the earth to the sun). from the supermassive black hole. These observations enabled astronomers to both determine the location and track the movement of that gas. The researchers estimate that the amount of hydrogen in this cool disk is about one-tenth of the Jupiter mass or one ten-thousandth of the solar mass.

By mapping the wavelength shifts of this radiolight due to the Doppler (light from objects moving toward Earth is slightly shifted to the "bluer" portion of the spectrum, while light from objects moving away slightly displaces into the "reder" portion "Part will be postponed.) The astronomers could clearly see that the gas revolves around the black hole. This information provides new insights into the way black holes devour matter, and the complex interaction between a black hole and its galactic neighborhood.

Member of Astrophysics at the Institute for Advanced Study at Princeton, New Jersey, and lead author of the thesis. "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 contribute to the black hole revealing some of its secrets.

Publication: EM Murchikova et al. 19659017] (function (d, s, id) {
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