ALMA image of the disk of cool hydrogen gas flowing around Sagittarius A*. The colours represent the motion of the gas relative to Earth: the red portion is moving away and the blue colour represents gas moving toward Earth.
Credit: ALMA (ESO/NAOJ/NRAO), E.M. Murchikova; NRAO/AUI/NSF, S. Dagnello
In the galactic centre (SagittariusA* ) is located a supermassive black hole – SMBH (4 × 106 solar masses). This SMBH is surrounded by a huge reservoir of hot (107 kelvin) and cooler (102 to 104 kelvin) gas within a few parsecs.
X-ray observations have provided constraints on the amount of hot gas in the accretion zone of the black hole, however the mass in cooler gas has been unconstrained so far. Recently, Atacama Large Millimeter/submillimeter Array (ALMA) observations reveal this nebulous disk of cool, interstellar gas wrapped around Sagittarius A*. Thanks to its sensitivity it detected this faint radio signal source and produced the first-ever image of this “cool” gas disk.
This radiating “ring” gives new insights into the accretion process and reveals the funneling of material onto the surface of a black hole. Based on these observations the astronomers mapped the location and traced the motion of this gas. The estimation of the mass of this “cool” structure is approximately 10−4 solar masses.
Publication: Elena M. Murchikova, E. Sterl Phinney, Anna Pancoast, Roger D. Blandford. A cool accretion disk around the Galactic Centre black hole. Nature, 2019; 570: 83%u201386 DOI: 10.1038/s41586-019-1242-z