IRAS 13224âÂÂ3809 is a highly active and fluctuating Seyfert 1 galaxy in the constellation Centaurus about 1 billion light-years from Earth. The galaxy is notable due to its centrally located supermassive black hole that is closely studied by astronomers using x-ray astronomy, particularly X-ray reverberation echo mapping techniques, in an effort to better understand the inner workings, including mass and spin, of black holes.