Ernst Hartwig discovered the first supernova outside the Milky Way in the Andromeda nebula.

In 1885 Hartwig was the first to observe the new bright star in the Andromeda nebula which was later considered the first historically registered supernova outside of the Milky Way (indication S and SN la, maximum brightness about 6 magnitudes). Some other astronomers also noticed the supernova but Hartwig understood what he had seen and very quickly made it known by telegraph. It is very hard to overestimate the importance of supernovas in contemporary astronomy: the observation of supernovas is the basis for the theory of the evolution of stars and cosmology, also for several branches of physics.

The Andromeda constellation