Small triambic icosahedron

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Small triambic icosahedron
DU30 small triambic icosahedron.png
Type Dual uniform polyhedron
Index DU30, 2/59, W26
(As a star polyhedron)
F = 20, E = 60
V = 32 (χ = −8)
Symmetry group icosahedral (Ih)
Dual polyhedron small ditrigonal icosidodecahedron
Stellation diagram Stellation core Convex hull
First stellation of icosahedron facets.png Icosahedron.png
Pentakis dodecahedron.png
Pentakis dodecahedron

In geometry, the small triambic icosahedron is the dual to the uniform small ditrigonal icosidodecahedron. It is composed of 20 intersecting isogonal hexagon faces. It has 60 edges and 32 vertices, and Euler characteristic of −8. Its external surface also represents the B stellation of the icosahedron.

If the intersected hexagonal faces are divided and new edges created, this figure becomes the triakis icosahedron. The descriptive name triakis icosahedron represents a topological construction starting with an icosahedron and attaching tetrahedra to each face (not necessarily regular tetrahedra). With the proper height of each such tetrahedron above the triangular base, this figure becomes a Catalan solid by the same name and the dual of the truncated dodecahedron.

The nonconvex uniform polyhedra great stellated dodecahedron and great dodecahedron, as viewed as surface topologies, can also be constructed as icosahedron with pyramids, the first with much taller pyramids, and the second with inverted ones.

It is also a uniform dual, and is the dual of the small ditrigonal icosidodecahedron. Other uniform duals which are also stellations of the icosahedron are the medial triambic icosahedron and the great triambic icosahedron.

As a stellation[edit]

First stellation of icosahedron.pngStellation icosahedron B.png

This figure is also the first stellation of the icosahedron, and given as Wenninger model index 26.

This stellation is a popular subject for construction in modular origami, often made of thirty Sonobe units.


External links[edit]

Notable stellations of the icosahedron
Regular Uniform duals Regular compounds Regular star Others
(Convex) icosahedron Small triambic icosahedron Medial triambic icosahedron Great triambic icosahedron Compound of five octahedra Compound of five tetrahedra Compound of ten tetrahedra Great icosahedron Excavated dodecahedron Final stellation
Zeroth stellation of icosahedron.png First stellation of icosahedron.png Ninth stellation of icosahedron.png First compound stellation of icosahedron.png Second compound stellation of icosahedron.png Third compound stellation of icosahedron.png Sixteenth stellation of icosahedron.png Third stellation of icosahedron.png Seventeenth stellation of icosahedron.png
Zeroth stellation of icosahedron facets.png First stellation of icosahedron facets.png Ninth stellation of icosahedron facets.png First compound stellation of icosahedron facets.png Second compound stellation of icosahedron facets.png Third compound stellation of icosahedron facets.png Sixteenth stellation of icosahedron facets.png Third stellation of icosahedron facets.png Seventeenth stellation of icosahedron facets.png
The stellation process on the icosahedron creates a number of related polyhedra and compounds with icosahedral symmetry.