The stella octangula (eight-pointed star), also known as the stellated octahedron, is the polyhedral compound of two tetrahedra. It was given its name by Johannes Kepler in 1609, though it was known to earlier geometers. It is both the simplest regular polyhedral compound and the simplest non-convex uniform polyhedron.

The vertices of the two tetrahedra define a cube and the intersection of the two an octahedron, which shares the same face-planes as the compound. Thus it is the first (and only) stellation of the octahedron. (See Wenninger model W₁₉)

If the stellated octahedron is considered as a singular concave polyhedron as the surface of the union of the two tetrahedron, rather than as a compound, it shares the same topology as the convex triakis octahedron, both with 24 triangle faces. The triakis octahedron has shorter isosceles triangle faces, while the stellated octahedron has equilateral triangles.

See also

• Polyhedron
• Merkaba
• Polyhedron models

Prismatoid polyhedra | Polyhedral stellation | Polyhedral compounds

Sterntetraeder | 星型八面体 | Stella octangula | Stella octangula