40亿年后，银河系与仙女座的星系碰撞，整个宇宙将为之闪烁1

The Andromeda galaxy, a sister galaxy to the Milky Way with an estimated 400 billion stars, was discovered to be far beyond our own galaxy after Hubble"s observation of a Cepheid variable star in 1924. This event marked the first extragalactic discovery and shattered the previous belief that the Andromeda Nebula was part of the Milky Way, leading to a greater understanding of the vastness of the universe.