A black hole surrounded by huge rings--V404 Cygni

Published on 7 August 2021 at 23:02

The image shows a spectacular set of rings surrounding a black hole, as captured by NASA's Chandra X-ray Observatory and the Neil Gehrels Swift Observatory. These X-ray images of the giant rings reveal information about dust within our galaxy like the X-rays taken at airports and doctor's offices.


A black hole exists within the binary system V404 Cygni, which is located approximately 7,800 light-years from Earth. The black hole is actively pulling material away from its companion star—an object with half the mass of the Sun—into a disk around the invisible object. Astronomers refer to these systems as "X-ray binaries" because they glow in X-rays.

 

Swift detected a burst of X-rays from V404 Cygni on June 5, 2015. High-energy rings were formed from light echoes, a phenomenon caused by the burst. Instead of sound waves bouncing off canyon walls, the light echoes were produced when a burst of X-rays from the black hole system bounced off of dust clouds between V404 Cygni and Earth. Unlike household dust, cosmic dust consists of tiny, solid particles.

In this composite image, X-rays from Chandra (light blue) were combined with optical data from the Pan-STARRS telescope in Hawaii that show the stars in the field of view. There are eight concentric rings in the image. Each ring is created by X-rays from V404 Cygni flares observed in 2015 reflecting off different dust clouds. (This is an artist's illustration showing how the rings seen by Chandra and Swift were made. It shows only four rings, rather than eight).

The rings tell astronomers about the black hole's behavior and the landscape between V404 Cygni and Earth.

 

The researchers also used the rings to probe the properties of the dust clouds themselves. They compared the X-ray spectra—that is, the brightness of X-rays over a range of wavelengths—to computer models of dust with different compositions. Different dust compositions will result in different amounts of X-rays being absorbed and prevented from being detected by Chandra. It is similar to how different parts of our bodies or luggage absorb different amounts of X-rays, giving information about their structure and composition.

 

It was determined that the dust contains a mixture of graphite and silicate grains. They also found that the densities of the dust clouds are not uniform in all directions when analyzing the inner rings with Chandra.

 

Several studies have been published about the 2015 V404 Cygni outburst which caused these rings. It might still take astronomers many years to continuously analyze the outburst of 2015, as it did with previous outbursts in 1938, 1956, and 1989.


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