Star Polygons · 2D
Heptagram
The seven-pointed stars {7/2} and {7/3}
Seven points on a circle can be joined in two star-shaped ways: every second point for the blunt star, every third for the sharp one. Place the seven old planets on its points and the sharp star walks the days of the week.
- Points
- 7
- Stars
- {7/2} · {7/3}
- Point angles
- 77.1° · 25.7°
Watch it drawn with compass and straightedge, hear the chord of its lines, and turn the Dimension dial to tilt it into space.
Facts
- The regular heptagon cannot be drawn with compass and straightedge (Gauss, 1796; Wantzel, 1837), so neither can these stars.
- Its points carry the planets in the Chaldean order, slowest first: Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon.
- Follow the sharp star from Saturn and you meet the Sun, the Moon, Mars, Mercury, Jupiter and Venus: Saturday, Sunday, Monday… The days are named for the planets that rule their first hours.
- Seven is the fewest points that can make two different stars in one line: five and six points make one star or none.
History and meaning
The heptagram was a seal of protection in medieval Christianity, the Elven Star of modern paganism, and a symbol of the seven days of creation. The link between planets and weekdays reaches back to Hellenistic Alexandria.
Learn it step by step
- Construct it Dürer’s HeptagonStep Dürer’s near-heptagon around the circle from P.
