Cygnus X-1

Completed 2018-12-21. Available releases:

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Cygnus X-1 (named for being the first-noticed X-ray source in the constellation Cygnus) is a black hole of 13–23 solar masses in a binary pair with a blue supergiant star, HDE 226868, of 25–35 solar masses. The star and hole orbit each other at approximately 0.2 AU and the system is about 6070 light years from Earth. Cygnus X-1 was not the first black hole discovered, but it was the first to be widely accepted as such. It is one of the brightest X-ray sources in the sky.

Contrary to other artistic depictions, Cygnus X-1 does not actually rip material off of the star's surface (it is instead fed by the star's stellar wind). The stellar wind is collected and falls into an accretion disk. Orbital potential energy is slowly transferred to the material, causing it to heat up along a blackbody radiation spectrum, eventually to the point of emitting X-rays. The disk is shown slightly blue-shifted on the left and slightly red-shifted on the right owing to the hole's rotation (although this may be difficult to pick out in the scan). As the material reaches close to the black hole, it is gradually redshifted to infinity, explaining the darker area near the center. The upper edge of the disk is also gravitationally lensed into a bulge. Some material also spews out axially (there are multiple mechanisms by which this happens, and they're all rather physically complicated). In the case of Cygnus X-1, the jets emit only weakly in the optical regime.

Artistically, this is acrylic paint on a canvas panel. The corona was done with very thin paints; the accretion disk was done with very thick paints in many layers, and the star has lots of both. I had a hard time reproducing the colors in the scan; I had to do a lot of postprocessing to get it to look more-faithful, and I'm still not happy with it. The painting itself looks good though.

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