Cat's Eye Cluster

The Cat's Eye Cluster is a Class IX Milky Way globular cluster, also known as M4 and NGC 6121. It is one of the oldest compact formations in the universe. In addition to 100,000 tightly packed stars, white dwarfs among them, the cluster also hosts several planets, including the famous M4 Planet, as well as a millisecond pulsar.

The structure of M4 is one of the most loose, or open, of the globular clusters, and has a central "bar" of stellar concentration across its core region.