Osterreich - 20 euro, Cat’s Eye Nebula, 2026

The Cat's Eye Nebula is a planetary nebula in the northern constellation of Draco, discovered by William Herschel on February 15, 1786. It was the first planetary nebula whose spectrum was investigated by the English amateur astronomer William Huggins, demonstrating that planetary nebulae were gaseous and not stellar in nature. Such a planetary nebula is formed when a star similar to our Sun, with no more than a few solar masses, reaches the end of its activity and becomes a red giant. The core contracts, the star’s envelope swells and pulsates, and with each pulse parts of the star’s atmosphere and outer layers are blown into space. The ejected matter is gaseous, has a temperature of about 10,000 kelvin and moves away from the star in all directions at several dozen kilometres per second.