0.00 $
 0 item(s)

Stellated octahedron (or compound of two tetrahedra)

Stellated octahedron

--- . ---

Red pyramid pass through white, or vice versa. Or maybe it is a complex of pyramids directed in different directions of the world. These figures are always a mystery.

--- . ---

The presented image of this polyhedron illustrates exactly its second name - the compound of two tetrahedra. So you can imagine a red tetrahedron pointing up through which a beige tetrahedron goes down.

However, mathematicians prefer to call the polyhedron as stellated octahedron.

The stellated octahedron could be defined as a regular polyhedron, since all its faces are regular triangles of the same size and all angles between them are equal. But in fact, this geometric solid is not the sixth regular polyhedron on par with the five known Platonic solids. The reason is that the word convex is present in the definition of a regular polyhedron, that is, all faces must lie on one side of the plane passing through any of them.

Discovery history

stella octangula
The star octahedron was first depicted in 1509 in a book De divina proportione written by the mathematician, Luca Pacioli (1445-1514) with illustrations from Leonardo da Vinci.
The stellated octahedron was made in the form of an eight frame tetrahedra interconnected.
 
Then, almost 100 years later, the polyhedron was rediscovered by Johann Kepler; the Stella octangula, the octagonal star, was named after him.
 
It is this illustration of a stellate octahedron that is controversial about how this polyhedron was discovered.
 
Stellated octahedron piecemeal

The first possible variant is to attach 8 tetrahedra to the sides of the octahedron
 
Or continue the planes parallel to the sides of the octahedron, getting the same 8 tetrahedra at the intersection of the planes. In other words, create a star-shaped octahedron.

Stellated octahedron piecemeal

Second way: Combine two tetrahedrons.
Which clearly illustrates the color of the faces in two colors - red and beige.

 

compound of two tetrahedra
 

Video. Rotation of a polyhedron

Video. Polyhedron transform

Video from our partners - the ART KOSEKOMA team, clearly demonstrates how you can transform an octahedron into a star form and get two tetrahedrons.

First, the faces of the octahedron, drawing out, make a star form. Then the video clip shows how a stellated octahedron can be decomposed into two tetrahedrons.

Polyhedron properties

stellated octahedron inscribed in a cube

2. An interesting feature of the polyhedron. If all the pointed tops are interconnected, the intersection lines correspond exactly to the edges of the cube.
Thus, the stellated octahedron can be inscribed in a cube.

 

shadow stellated octahedron
stellated octahedron and the star of david

3. If you look at the polyhedron from above, or at the shadow cast, the outlines of the pattern will create a regular hexagonal star.
The hexagonal star in the form of two intersecting triangles is the oldest symbol, which is referred to as the Star of David (another name is the Seal of King Solomon).

Net 1

net Stellated octahedron
The first of the proposed assembly options is to glue a stellated octahedron from a single net. This option is most often found in educational literature. However, the limitation is the size of the sheet. In the event that this is an A4 sheet, then the dimensions of the finished polyhedron are very modest.
 

Net 2

The second option, separately collected octahedron and 8 blanks in the form of pyramids. Then, all blanks are alternately glued to the sides of the octahedron. This option is preferable for beginner modellers.

Net 3

net Stellated octahedron
On the the Internet, we met a very unusual version of the assembly, also in the form of a single net.
 

Stellated octahedron from the set "Magic Edges"

To assemble a polyhedron, we can offer you ready-made nets - cut and folded.
To do this, you need to use the details of the kit Magic Edges 15.
In addition, in the release itself you will find information about the structure of the polyhedron.

 
magic edges 15 stellated octahedron
 
Rotation of the finished polyhedron. The polyhedron is assembled from the kit - "Magic edges 15".
 

 

Popular

Production. Issue Magic Edges №27

We open the veil of the secrets - how our products are made. And let's do it on the example of...

Challenging task about a polyhedron

(challenging task called “the star”) It consists of 6 symmetrical small bars of complex shapes...

School project

In the second half of the 19th century, a new way of teaching was born in the US schools - the...

Truncated great dodecahedron from metal

The monument to the “Truncated large dodecahedron” polyhedron was discovered in Obninsk (Russia)...

Outer sphere of polyhedra

The perfection of the spherical shape has long attracted the attention of thinkers and scientists...

Polyhedra in architecture. Part 2

The “business card” of the Republic of Belarus is a new building of the National Library in Minsk. The...