First there was an amateur astronomer: Giuseppe Donatiello found an interesting "spot" in the Dark Energy Camera data on the 4-meter Víctor M. Blanco telescope. Then, using the larger 8.1-meter Gemini North telescope, the professionals took a closer look and confirmed that the object, then named Pegasus V, was an ultra-faint dwarf galaxy on the edge of the Andromeda Galaxy. The observations revealed that the galaxy appears to be extremely poor in heavier elements compared to similar dwarf galaxies, which means that it is very old and probably represents a fossil of the first galaxies in the universe. In…