On Sept. 16, NASA's Swift satellite detected a rising tide of high-energy X-rays from a source toward the center of our Milky Way galaxy. The outburst, produced by a rare X-ray nova, announced the presence of a previously unknown stellar-mass black hole.
An X-ray nova is a short-lived X-ray source that appears suddenly, reaches its emission peak in a few days and then fades out over a period of months. The outburst arises when a torrent of stored gas suddenly rushes toward one of the most compact objects known, either a neutron star or a black hole.
Named Swift J1745-26 after the coordinates of its sky position, the nova is located a few degrees from the center of our galaxy toward the constellation Sagittarius. While astronomers do not know its precise distance, they think the object resides about 20,000 to 30,000 light-years away in the galaxy's inner region. The pattern of X-rays from the nova signals that the central object is a black hole.
Ground-based observatories detected infrared and radio emissions, but thick clouds of obscuring dust have prevented astronomers from catching Swift J1745-26 in visible light.
The black hole must be a member of a low-mass X-ray binary (LMXB) system, which includes a normal, sun-like star. A stream of gas flows from the normal star and enters into a storage disk around the black hole. In most LMXBs, the gas in the disk spirals inward, heats up as it heads toward the black hole, and produces a steady stream of X-rays.
But under certain conditions, stable flow within the disk depends on the rate of matter flowing into it from the companion star. At certain rates, the disk fails to maintain a steady internal flow and instead flips between two dramatically different conditions -- a cooler, less ionized state where gas simply collects in the outer portion of the disk like water behind a dam, and a hotter, more ionized state that sends a tidal wave of gas surging toward the center.
This phenomenon, called the thermal-viscous limit cycle, helps astronomers explain transient outbursts across a wide range of systems, from protoplanetary disks around young stars, to dwarf novae - where the central object is a white dwarf star - and even bright emission from supermassive black holes in the hearts of distant galaxies.
An X-ray nova is a short-lived X-ray source that appears suddenly, reaches its emission peak in a few days and then fades out over a period of months. The outburst arises when a torrent of stored gas suddenly rushes toward one of the most compact objects known, either a neutron star or a black hole.
Named Swift J1745-26 after the coordinates of its sky position, the nova is located a few degrees from the center of our galaxy toward the constellation Sagittarius. While astronomers do not know its precise distance, they think the object resides about 20,000 to 30,000 light-years away in the galaxy's inner region. The pattern of X-rays from the nova signals that the central object is a black hole.
Ground-based observatories detected infrared and radio emissions, but thick clouds of obscuring dust have prevented astronomers from catching Swift J1745-26 in visible light.
The black hole must be a member of a low-mass X-ray binary (LMXB) system, which includes a normal, sun-like star. A stream of gas flows from the normal star and enters into a storage disk around the black hole. In most LMXBs, the gas in the disk spirals inward, heats up as it heads toward the black hole, and produces a steady stream of X-rays.
But under certain conditions, stable flow within the disk depends on the rate of matter flowing into it from the companion star. At certain rates, the disk fails to maintain a steady internal flow and instead flips between two dramatically different conditions -- a cooler, less ionized state where gas simply collects in the outer portion of the disk like water behind a dam, and a hotter, more ionized state that sends a tidal wave of gas surging toward the center.
This phenomenon, called the thermal-viscous limit cycle, helps astronomers explain transient outbursts across a wide range of systems, from protoplanetary disks around young stars, to dwarf novae - where the central object is a white dwarf star - and even bright emission from supermassive black holes in the hearts of distant galaxies.
Contacts and sources:
NASA
From internet sources this model is a stabilized ratio between the weight of the galactic nucleus (black hole) and the weight of the galaxy it centers on. As it ages, it loses gas pressure, permitting horizontal jetting sending mass/matter to the galactic rim as new blue planets. Gas emissions accompany this emission and the conversion of mass to matter. This enormous volume of gas fills up the spiral galaxy which appears as an elliptical. The gas spreads, cools, and a starless dark forms. The cold gas shell holds the dismembered stars/planets as gas. At the thinnest, coldest (zero K) this phase changes to hot/dense as demonstrated by science. See thin and cold equals hot and dense search.
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