Andromeda galaxy

The MESSEIR 31 galaxy - the Andromeda galaxy - is one of the closest galaxies to us, at less than 3 million light-years. It is recognisable to the naked eye in the country sky as a small, elongated milky spot in the constellation of Andromeda. It was mentioned for the first time in 964 by the Persian astronomer Al-Sufi.

It was in this galaxy that the astronomer Hubble discovered a peculiar variable star in 1923 that allowed him to know the real distance of the object: it was then understood that this was not a nebula within our galaxy but another much more distant galaxy, and an idea of the immensity of our universe began to be understood.