The Sigma Orionis star cluster is a young open cluster, 1 to 5 million years old, that is part of the Orion OB Association, adjacent to the Horsehead Nebula; the star Sigma Orionis lies at its center. Within this cluster have been identified a number of free floating brown dwarf and large planet candidates.

Three of the objects (reddish, marked by triangles) in the sigma Orionis star cluster that may be free-floating planets. Credit: Zapatero Osorio, et al./Science