Picture of the month

The night sky holds many stunning views, and this is certainly one of them. This pair of galaxies called Arp 142 is better known as the Porpoise Galaxy, although it rather looks like a penguin guarding its egg. Reprocessed recently, this image by the Hubble Space Telescope reveals in magnificent detail the strange shape of a former normal spiral galaxy (NGC 2936, on top) now stretched and twisted by the gravitational force of its elliptical companion (NGC 2937, below). The blue skin of the “penguin” comes from massive, young and hot stars recently formed by gas compression due to the gravitation interaction. On the contrary, the white colour of the “egg” means that there is currently very little gas and star-forming activity in this galaxy, which is mainly composed of old stars. The brownish dust lines artistically cross near the penguin’s eye, which is the core of the spiral galaxy and likely the last part to be disrupted in the merging process foreseen in about a billion years from now, far away in the Hydra constellation.

About the author

Compiled by Marc Türler, ISDC and Observatory of the University of Geneva, and CHIPP, University of Zurich.