Follow the leader

Image: ESA/Hubble/NASA/J. Dalcanton/Dark Energy Survey/DOE/FNAL/NOIRLab/NSF/AURA.

This line of galaxies is a cosmic coincidence behind the interacting system Arp-Madore 2105-332, which is a pair of galaxies 200 million light years away in the suitably small constellation of Microscopium. Gravitational tendrils from each galaxy reach out to one another, pulling stars and galaxies out and unravelling both galaxies. It’s all fairly standard as far as interacting galaxies go, but what is remarkable is that line of numerous galaxies in the background. These galaxies are completely unrelated to Arp-Madore 2105-332 – it’s just a chance alignment, but it makes for a remarkable vista. Some of the distant galaxies in the line appear red, drained of star-forming gas and with only older stars left. One is a classic blue spiral perhaps like our own galaxy. Looking around the image, the objects with diffraction spikes are stars in our Milky Way. Everything else in this image is a galaxy, mostly too faint or too far away to be resolved as anything but a smudge of light.