Sky survey image of Cygnus
Copyright: ESA and Digitized Sky Survey. Image processing by ESA/ECF
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The Cygnus region of the night sky is a familiar feature to sky-watchers in Europe. The stars representing this mythical swan soar overhead during the summer months, every year. The Integral science team chose that region to test the new satellite because it contains one of the most famous, and therefore well-studied, high-energy sources in the night sky: Cygnus X-1. Observing this black hole has allowed scientists to fine-tune the working of Integral, ready for the time when the world's astronomers will be invited to use this world-leading space observatory.
Cygnus X-1 is about 10 000 light years from Earth and one of the brightest high-energy emitters in the sky. It was discovered in the 1960s and is thought to be a black hole, ripping its companion star to pieces. The companion star, HDE 226868, is a blue supergiant with a surface temperature of around 31 000K. It orbits the black hole once every 5.6 days.
Last Update: 1 September 2019
