Astronomy Picture of the Day

Explanation: This dramatic image of an interacting pair of galaxies was made using the 1.5 metre telescope at the Cerro Tololo Inter-American Observatory near La Serena, Chile. NGC 1531 is the background galaxy with a bright core just above centre and NGC 1532 is the foreground spiral galaxy laced with dust lanes. The pair is about 70 million light-years away in the southern constellation Eridanus. These galaxies lie close enough together so that each feels the influence of the other's gravity. The gravitational tug-of-war has triggered star formation in the foreground spiral as evidenced by the young, bright blue star clusters along the edge of the front spiral arm. Though the spiral galaxy in this pair is viewed nearly edge-on, astronomers believe the system is similar to the face-on spiral and companion known as M51, the Whirlpool Galaxy.