UGC 12591

UGC 12591 is a spiral galaxy in the constellation Pegasus. It is located approximately 400 million light-years from Earth. It is the spiral galaxy with the highest known rotational speed of about 500 km/s, almost twice that of the Milky Way galaxy. The high rotational speed means the galaxy must be very massive at the center; the galaxy has a mass estimated at 4 times that of the Milky Way.
UGC 12591 is relatively isolated; the nearest galaxy to it is 3.55 million light-years away. However, its morphology suggests a merger or accretion event in its past: it is somewhat lenticular-like, with a central bulge and dust lanes reminiscent of the Sombrero Galaxy.