Surprise discovery: First glimpse of cold gas disc around black hole in our galaxy's core

The findings help explain why the first photo of a black hole captures the far away M87 & not Sag A* in our galaxy core.

The Atacama Large Millimeter Array (ALMA) telescope in Chile has observed an interstellar gas wrapped around the black hole that is at the core of our galaxy. This disk of cold gases has never been seen before and the scientists at National Radio Astronomy Observatory (NRAO) believes it is the black hole siphoning material into itself. The results of these observations have been published in the peer-review journal Nature.

Elena Murchikova, a member in astrophysics at the Institute for Advanced Study in Princeton, New Jersey, USA said, “We were the first to image this elusive disk and study its rotation. We are also probing accretion onto the black hole. This is important because this is our closest supermassive black hole. Even so, we still have no good understanding of how its accretion works. We hope these new ALMA observations will help the black hole give up some of its secrets.”

Surprise discovery: First glimpse of cold gas disc around black hole in our galaxys core

Artist impression of a ring of cool, interstellar gas surrounding the supermassive black hole at the center of the Milky Way. New ALMA observations reveal this structure for the first time. Image credit: NRAO/AUI/NSF; S. Dagnello

The "cold" gas ring is made up of hydrogen in what is a new discovery for scientists about black holes. Until now, scientists have only managed to capture the hot region of the gas around the accretion disc. The hot gas is estimated at 10 million degrees Celsius – hot enough to be seen with an X-ray telescope. Interestingly, the amount of cold hydrogen gas seen in the image is roughly one-tenth of Jupiter's mass – one ten-thousandth the mass of the Sun – according to the ALMA scientists.

ALMA image of the disk of cool hydrogen gas flowing around the supermassive black hole at the center of our galaxy. The colors represent the motion of the gas relative to Earth: the red portion is moving away, so the radio waves detected by ALMA are slightly stretched, or shifted, to the “redder” portion of the spectrum; the blue color represents gas moving toward Earth, so the radio waves are slightly scrunched, or shifted, to the “bluer” portion of the spectrum. Credit: ALMA (ESO/NAOJ/NRAO), E.M. Murchikova; NRAO/AUI/NSF, S. Dagnello

ALMA image of the disk of cool hydrogen gas flowing around the supermassive black hole at the center of our galaxy. The colors represent the motion of the gas relative to Earth: the red portion is moving away, so the radio waves detected by ALMA are slightly stretched, or shifted, to the “redder” portion of the spectrum; the blue color represents gas moving toward Earth, so the radio waves are slightly scrunched, or shifted, to the “bluer” portion of the spectrum. Image credit: ALMA (ESO/NAOJ/NRAO), E.M. Murchikova; NRAO/AUI/NSF, S. Dagnello

Researches mapped the wavelength of the radio light comings off the black hole disc with the help of a physics phenomenon called the "Doppler effect", where the change in wavelength of light (waves) is measured relative to the movement of our own planet in the solar system. The new information gathered from these observations can help scientists figure out how black holes consume matter, as well as how they interact with their neighborhood.

Black holes are considered a central part of every galaxy in the universe. At the heart of the Milky Way galaxy is the Sagittarius A* or Sag A*, a supermassive black hole, which has a mass of about 4 million times that of the Sun.

The Earth is 26,000 light years away from the black hole. In the regions around a black hole are stars, dust clouds, and hot and cold gases.

In April 2019, the Event Horizon Telescope released the first-ever direct photograph from the edge of a black hole.

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