20 euro – Cat’s Eye Nebula

Not just impressive, the discovery of the Cat’s Eye Nebula by the German-British astronomer Wilhelm Herschel (1738–1822) on 15 February 1786 helped turn what had been merely an assumption in physics into an immutable law. Indeed, despite appearing mysteriously misty, veiled and softly focused on this extraordinarily shaped and coloured coin, the Cat’s Eye Nebula, also known as NGC 6543, has provided modern science with crystal-clear insights. 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. NGC 6543 was the first planetary nebula to be studied in detail using spectroscopy. Making it possible for scientists to deduce its composition from the light emitted by the celestial body, this contributed to the insight that all observable celestial bodies consist of the same chemical elements as the Earth. This, in turn, led to an enormous gain in knowledge as it supported the scientific assumption that the laws of physics are the same throughout the universe. To date, no discovery has been made that casts the slightest doubt on this assumption. Before the (cosmic) law, we are all equal.