The Southern Summer

Abstract

This intriguing pair of interacting galaxies lies about 55 million light-years away in the direction of the constellation of Eridanus (The River). The larger galaxy is NGC 1532, and it is a dusty spiral system rather like the Milky Way, seen almost edge-on. It appears to be interacting with a smaller companion, NGC 1531. This latter is a largely gasless spiral. The interaction is mostly indicated by the anomalous burst of star formation in the nearest spiral arm in NGC 1532 and some curiously displaced emission nebulae that appear to be close to NGC 1531, which seems to be in the background. Less obvious here are large plumes and recently formed clusters of blue stars in the outer arms of NGC 1532. All these features are signatures of the immense tidal forces stirred up as galaxies collide.