A bait ball, or baitball, occurs when small fish swarm in a tightly packed spherical formation about a common centre. It is a last-ditch defensive measure adopted by small schooling fish when they are threatened by predators.
The Soul Nebula (IC is a fairly large emission nebula in the constellation Cassiopeia. It is often referred to as the “Embryo Nebula” because of its characteristic shape. Its neighbour is IC 1805 (the Heart Nebula). Photo by Azin Dark Skies.