In three-dimensional space, a stellation extends facets of a polyhedron to form a new figure. Usually, this is achieved by extending faces or edges and planes of a polyhedron, until they generate new vertices that bound a newly formed figure.
This article mainly lists various stellations belonging to uniform polyhedra, such as those of the regular Platonic solids and the semiregular Archimidean solids. It also lists stellations featuring unbounded vertices.
Experimentation with star polygons and star polyhedra since the fourteenth century AD led the way to formal theories for stellating polyhedra:
It was in 1619 that the first mathematical description of a stellation was given, by Johannes Kepler in his landmark book, Harmonices Mundi : the process of extending the edges (or faces) of a figure until new vertices are generated, which collectively form a new figure. [11] [12] [b] Using this method, Kepler was able to discover the small stellated dodecahedron and the great stellated dodecahedron [13] [14] [15] (the latter, a solid Jamnitzer previously studied). [8] In 1809, Louis Poinsot rediscovered Kepler's star figures and discovered a further two, the great icosahedron and great dodecahedron; [16] he achieved this by experimenting assembling regular star polygons and convex regular polygons (i.e. pentagons, pentagrams and equilateral triangles) on vertices of the regular icosahedron and dodecahedron. [17] Three years later, Augustin-Louis Cauchy proved, using concepts of symmetry, that these four stellations are the only regular star-polyhedra, [18] [19] eventually termed the Kepler–Poinsot polyhedra.
Coxeter et al. (1938) details, for the first time, all stellations of the regular icosahedron with specific rules proposed by J. C. P. Miller. [20] Generalizing these (Miller's rules) for stellating any uniform polyhedron yields the following: [21]
These rules are ideal for stellating smaller uniform solids, such as the regular polyhedra; however, when assessing stellations of other larger uniform polyhedra, this method can quickly become overwhelming. (For example, there are a total of 358,833,072 stellations to the rhombic triacontahedron using this set of rules.) [22] To address this, Pawley (1973) proposed a set of rules that restrict the number of stellations to a more manageable set of fully supported stellations that are radially convex, [23] [24] such that an outward ray from the center of the original polyhedro (in any direction) crosses the stellation surface only once [25] (that is to say, all visible parts of a face are seen from the same side). [c]
In the 1948 first edition of Regular Polytopes , H. S. M. Coxeter describes the stellation process as the reciprocal action to faceting , [28] identifying the four Kepler-Poinsot polyhedra as stellations and facetings of the regular dodecahedron and icosahedron. [29] [30] He specifies the construction of a star polyhedron as a stellation of its core (with congruent face-planes), or by faceting its case — the former requires the addition of solid pieces that generate new vertices, while the latter involves the removal of solid pieces, without forming any new vertices. [31] [d]
Lists for polyhedral stellations contain non-convex polyhedra; some of the most notable examples include: [e]
Examples of stellations that topologically do not fit into standard definitions of uniform polyhedra are listed further down (i.e. stellations of hemipolyhedra). [33]
Image | Name | Stellation core | Face diagram | Refs. | Notes |
---|---|---|---|---|---|
![]() | Great dodecahedron | Regular dodecahedron | W21 | *, ¶ | |
![]() | Great stellated dodecahedron | W22 | |||
![]() | Small stellated dodecahedron | W20 | * | ||
![]() | Great icosahedron | Regular icosahedron | W41,C7 | ||
![]() | Compound of two tetrahedra | Regular octahedron | W19 | † (‡), ¶ | |
![]() | Compound of five tetrahedra | Regular icosahedron | W24,C47 | † | |
![]() | Compound of ten tetrahedra | W25,C22 | |||
![]() | Compound of five octahedra | W2,C3 | |||
![]() | Compound of five cubes | Rhombic triacontahedron | |||
![]() | Compound of cube and octahedron | Cuboctahedron | W43 | ‡, ¶ | |
![]() | Compound of dodecahedron and icosahedron | Icosidodecahedron | W47 | ||
![]() | Compound of great icosahedron and great stellated dodecahedron | W61 | ‡ | ||
![]() | Compound of great dodecahedron and small stellated dodecahedron | Rhombic triacontahedron | |||
![]() | Small triambic icosahedron | Regular icosahedron | W1,C2 | ¶ | |
![]() | Final stellation of the icosahedron | W13,C8 | |||
![]() | First stellation of the rhombic dodecahedron | Rhombic dodecahedron |
* Kepler-Poinsot polyhedron (star polyhedron with regular facets)
† Regular compound polyhedron (vertex, edge, and face-transitive compound)
‡ Compound of dual regular polyhedra (Platonic or Kepler-Poinsot duals)
¶ First/outermost stellation of stellation core
"Stellation core" describes a stellated regular (Platonic), semi-regular (Archimedean), or dual to a semi-regular (Catalan) figure.
" Face diagram " represents the lines of intersection from extended polyhedral edges that are used in the stellation process.
"Refs." (references) such as indexes found in Coxeter et al. (1999) using the Crennells' illustration notation (C), and Wenninger (1989) (W).
The table below is adapted from research by Robert Webb, using his program Stella. [38] It enumerates fully supported stellations and stellations per Miller's process, of the regular Platonic solids as well as the semi-regular Archimedean solids and their Catalan duals. In this list, the elongated square gyrobicupola and its dual polyhedron are not included (these are sometimes considered a fourteenth Archimedean and Catalan solid, respectively). The base polyhedron stellation core is included as a zeroth convex stellation (following the Crennells' indexing), with stellation totals the sum of chiral and reflexible stellations. [f]
"Cell types" are sets of symmetrically equivalent stellation cells, where "stellation cells" are the minimal 3D spaces enclosed on all sides by the original polyhedron's extended facial planes.
"?" denotes an unknown total number of stellations; however, the number of reflexible stellations are sometimes known for these (where chiral stellations are excluded).
The regular tetrahedron and cube do not generate stellations when extending their faces, since their vertices only form one possible convex hull. [39]
The stella octangula (or stellated octahedron) is the only stellation of the regular octahedron. [39] This stellation is made of self-dual tetrahedra, as the simplest regular polyhedral compound: [47]
Figure | Stellation |
---|---|
Stellated octahedron stella octangula | |
All stellations of the regular dodecahedron are Kepler-Poinsot polyhedra:
Regular dodecahedron | Small stellated dodecahedron | Great dodecahedron | Great stellated dodecahedron |
---|---|---|---|
![]() | ![]() | ![]() | ![]() |
![]() | ![]() | ![]() | ![]() |
Platonic solid | Kepler–Poinsot solids | ||
Coxeter et al. (1938) detailed the stellations of the regular icosahedron with rules proposed by J. C. P. Miller. As found in Coxeter et al. (1999), the following table lists all stellations of the icosahedron per the Crennells' indexing (in it, the regular icosahedron (or snub octahedron) stellation core is indexed as "1'):
Stellations of the regular icosahedron [48] | ||||||
---|---|---|---|---|---|---|
Crennell | Cells | Faces | Figure | Face diagram | ||
A | 0 | ![]() | ||||
B | 1 | ![]() | ||||
C | 2 | ![]() | ||||
4 | D | 3 4 | ![]() | |||
5 | E | 5 6 7 | ![]() | |||
F | 8 9 10 | ![]() | ||||
G | 11 12 | ![]() | ||||
H | 13 | ![]() | ||||
9 | e1 | 3' 5 | ![]() | |||
10 | f1 | 5' 6' 9 10 | ![]() | |||
11 | g1 | 10' 12 | ![]() | |||
12 | e1f1 | 3' 6' 9 10 | ![]() | |||
13 | e1f1g1 | 3' 6' 9 12 | ![]() | |||
14 | f1g1 | 5' 6' 9 12 | ![]() | |||
15 | e2 | 4' 6 7 | ![]() | |||
16 | f2 | 7' 8 | ![]() | |||
17 | g2 | 8' 9'11 | ![]() | |||
18 | e2f2 | 4' 6 8 | ![]() | |||
19 | e2f2g2 | 4' 6 9' 11 | ![]() | |||
20 | f2g2 | 7' 9' 11 | ![]() | |||
21 | De1 | 4 5 | ![]() | |||
Ef1 | 7 9 10 | ![]() | ||||
23 | Fg1 | 8 9 12 | ![]() | |||
24 | De1f1 | 4 6' 9 10 | ![]() | |||
25 | De1f1g1 | 4 6' 9 12 | ![]() | |||
Ef1g1 | 7 9 12 | ![]() | ||||
27 | De2 | 3 6 7 | ![]() | |||
28 | Ef2 | 5 6 8 | ![]() | |||
29 | Fg2 | 10 11 | ![]() | |||
De2f2 | 3 6 8 | ![]() | ||||
31 | De2f2g2 | 3 6 9' 11 | ![]() | |||
32 | Ef2g2 | 5 6 9' 11 | ![]() | |||
f1 | 5' 6' 9 10 | ![]() | ||||
34 | e1f1 | 3' 5 6' 9 10 | ![]() | |||
35 | De1f1 | 4 5 6' 9 10 | ![]() | |||
36 | f1g1 | 5' 6' 9 10'12 | ![]() | |||
37 | e1f1g1 | 3' 5 6' 9 10'12 | ![]() | |||
38 | De1f1g1 | 4 5 6' 9 10'12 | ![]() | |||
39 | f1g2 | 5' 6'8'9' 10 11 | ![]() | |||
40 | e1f1g2 | 3' 5 6'8'9' 10 11 | ![]() | |||
41 | De1f1g2 | 4 5 6'8'9' 10 11 | ![]() | |||
42 | f1f2g2 | 5' 6'7'9' 10 11 | ![]() | |||
43 | e1f1f2g2 | 3' 5 6'7'9' 10 11 | ![]() | |||
44 | De1f1f2g2 | 4 5 6'7'9' 10 11 | ![]() | |||
45 | e2f1 | 4'5' 6 7 9 10 | ![]() | |||
46 | De2f1 | 35' 6 7 9 10 | ![]() | |||
Ef1 | 5 6 7 9 10 | ![]() | ||||
48 | e2f1g1 | 4'5' 6 7 9 10'12 | ![]() | |||
49 | De2f1g1 | 35' 6 7 9 10'12 | ![]() | |||
50 | Ef1g1 | 5 6 7 9 10'12 | ![]() | |||
51 | e2f1f2 | 4'5' 6 8 9 10 | ![]() | |||
52 | De2f1f2 | 35' 6 8 9 10 | ![]() | |||
53 | Ef1f2 | 5 6 8 9 10 | ![]() | |||
54 | e2f1f2g1 | 4'5' 6 8 9 10'12 | ![]() | |||
55 | De2f1f2g1 | 35' 6 8 9 10'12 | ![]() | |||
56 | Ef1f2g1 | 5 6 8 9 10'12 | ![]() | |||
57 | e2f1f2g2 | 4'5' 6 9' 10 11 | ![]() | |||
58 | De2f1f2g2 | 35' 6 9' 10 11 | ![]() | |||
59 | Ef1f2g2 | 5 6 9' 10 11 | ![]() |
" Cells " (du Val notation) correspond to the internal congruent spaces formed by extending face-planes of the regular icosahedron.
A subset of these are illustrated in Wenninger (1989), alongside constructions for physical models (W19–W66). [49]
The rhombic dodecahedron produces three fully supported stellations; these were described in Luke (1957): [51] [52]
Stellation | Figure | Face diagram |
---|---|---|
![]() | ![]() | |
![]() | ![]() | |
3 | ![]() | ![]() |
4 | ![]() | ![]() |
An additional fourth stellation is possible under Miller's rules. [53] The first stellation of the rhombic dodecahedron is notable for being able to form a honeycomb in three-dimensional space, using copies of itself. [50]
In Wenninger (1983), a unique family of stellations with unbounded vertices are identified. [33] These originate from orthogonal edges of faces that pass through centers of their corresponding dual hemipolyhedra. The following is a list of these stellations; specifically, of non-convex, uniform hemipolyhedra (with coincidental figures in parentheses).
Image | Name | Stellation core |
---|---|---|
![]() | Tetrahemihexacron | Tetrahemihexahedron |
![]() | Hexahemioctacron (octahemioctacron) | Octahemioctahedron |
![]() | Small dodecahemidodecacron (small icosihemidodecacron) | Small icosihemidodecahedron |
![]() | Great icosihemidodecacron (great dodecahemidodecacron) | Great dodecahemidodecahedron |
![]() | Small dodecahemicosacron (great dodecahemicosacron) | Great dodecahemicosahedron |
This family of stellations does not strictly fulfill the definition of a polyhedron that is bound by vertices, and Wenninger notes that at the limit their facets can be interpreted as forming unbounded elongated pyramids, or equivalently, prisms (indistinguishably). [54] Of these, only the tetrahemihexahedron would produce a stellation without another coincidental figure, the tetrahemihexacron.
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