2022 Austria Black Hole 20 Euro Coloured Silver Proof

On the coin’s obverse, a cone rises from the flat silver surface, representing the curvature of space-time. ‘Cygnus X-1’, the name of the first black hole to be named as such, is written to the right under ‘15 M?’, the solar mass of this black hole. In German, ‘Event horizon’ marks the boundary between the observable and the unobservable in space-time, while ‘Singularity’ points to the location of maximum space-time curvature.

Reverse: The black hole vortex phenomenon is illustrated on the coin’s reverse in the shape a funnel decorated with a color-printed spiral.