The Antennae Galaxies in Collision From the NASA Astronomy Picture of the Day web site M57: Rings Around the Ring Nebula Ou4: A Giant Squid Nebula The Hercules Cluster of Galaxies Arp 81: 100 Million Years Later Stephan's Quintet Plus One The Antennae Galaxies in Collision Spiral Galaxies in Collision Seyfert's Sextet Mercury in Accentuated Color Colors of Mercury A Double Ringed Basin on Mercury Unusual Hollows Discovered on Planet Mercury