Compound of five tetrahedra

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Compound of five tetrahedra
Type
Regular compound
Coxeter symbol {5,3}[5{3,3}] {3,5}[1]
Index UC5, W24
Elements
(As a compound)
5 tetrahedra:
F = 20, E = 30, V = 20
Dual compound Self-dual
Symmetry group chiral icosahedral (I)
Subgroup restricting to one constituent chiral tetrahedral (T)
3D model of a compound of five tetrahedra

The

compound polyhedron is also a stellation of the regular icosahedron. It was first described by Edmund Hess
in 1876.

It can be seen as a faceting of a regular dodecahedron.

As a compound

It can be constructed by arranging five

rotational icosahedral symmetry (I), as colored in the upper right model. It is one of five regular compounds which can be constructed from identical Platonic solids
.

It shares the same vertex arrangement as a regular dodecahedron.

There are two enantiomorphous forms (the same figure but having opposite chirality) of this compound polyhedron. Both forms together create the reflection symmetric compound of ten tetrahedra.

It has a

density
of higher than 1.

spherical tiling

Transparent Models
(Animation)

Five interlocked tetrahedra

As a stellation

It can also be obtained by stellating the icosahedron, and is given as Wenninger model index 24.

Stellation diagram Stellation core Convex hull
Icosahedron

Dodecahedron

As a faceting

Five tetrahedra in a dodecahedron.

It is a faceting of a dodecahedron, as shown at left.

Group theory

The compound of five tetrahedra is a geometric illustration of the notion of

orbits and stabilizers
, as follows.

The symmetry group of the compound is the (rotational)

tetrahedral group
T of order 12, and the orbit space I/T (of order 60/12 = 5) is naturally identified with the 5 tetrahedra – the coset gT corresponds to which tetrahedron g sends the chosen tetrahedron to.

An unusual dual property

Compound of five tetrahedra

This compound is unusual, in that the

enantiomorph of the original. If the faces are twisted to the right, then the vertices are twisted to the left. When we dualise
, the faces dualise to right-twisted vertices and the vertices dualise to left-twisted faces, giving the chiral twin. Figures with this property are extremely rare.

See also

References

  1. ^ Regular polytopes, p.98
  • .
  • , 3.6 The five regular compounds, pp.47-50, 6.2 Stellating the Platonic solids, pp.96-104
  • . (1st Edn University of Toronto (1938))

External links

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
The stellation process on the icosahedron creates a number of related
compounds with icosahedral symmetry
.