A Galactic Hybrid, UGC 12591

This image showcases the remarkable galaxy UGC 12591. Classified as an S0/Sa galaxy, UGC 12591 fits somewhere between a lenticular and a spiral in the morphological classifications of galaxies. The galaxy and its halo together contain several hundred billion times the mass of the Sun, which is four times the mass of the Milky Way — a very massive object. Clocked at speeds of up to 1.1 million miles per hour, it also rotates extremely quickly. Observations with Hubble are helping astronomers to understand the mass of UGC 1259, and to determine whether the galaxy grew slowly by itself over time, or whether it might have grown unusually massive by colliding and merging with another large galaxy at some point in its past.