Hubble's Variable Nebula is unusual due to its varying appearance. It can change in brightness and apparent structure in a matter of weeks. The nebula was named for Edwin Hubble who extensively studied it over an extended period of time. Its variability is attributed to dense clouds of dust that pass close by the nebula and its illuminating star. The clouds of dust cast shadows on the nebula as they move by. The nebula lies approximately 2,500 light years from our location in the direction of the constellation of Monoceros.