Picture of the month
![](http://upload.wikimedia.org/wikipedia/commons/thumb/e/e2/Ortho_solid_011-uniform_polychoron_53p-t0.png/360px-Ortho_solid_011-uniform_polychoron_53p-t0.png)
Credit: Tom Ruen
Orthographic projection of the Great grand 120-cell a star polychoron with Schläfli symbol {5,5/2,3}. It is one of 10 regular Schläfli-Hess polychora.
The Schläfli-Hess polychora are the complete set of 10 regular self-intersecting star polychora (four-dimensional polytopes). They are named in honor of their discoverers: Ludwig Schläfli and Edmund Hess. Each is represented by a Schläfli symbol {p,q,r} in which one of the numbers is 5/2. They are thus analogous to the regular nonconvex Kepler-Poinsot polyhedra.
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