Astrology & myths · Hellenistic astrology · Ptolemy, Tetrabiblos I.17 (domicile)
Why Leo is the Sun's sign
Each planet in classical astrology has a “house”, a sign it rules. The Sun has only one: Leo.
The reasoning
Ptolemy explains that Cancer and Leo are the most northern signs, closest to the zenith for his readers and so most productive of heat and of warmth. He gives them to the two greatest heavenly bodies, the "luminaries": Leo to the Sun, Cancer to the Moon.
A northern point of view
That reasoning was made for the Northern Hemisphere, where the Sun stands highest in the months of Cancer and Leo. In the Southern Hemisphere those are winter months; the scheme kept its assignments anyway, which is one reason to treat it as a symbolic system with a history rather than as a description of the sky (NASA on the seasons).
Astrology and myth are presented here as symbolic and historical traditions, not as predictions. The sky's positions and times on this site are calculated the same way in every lens.
Sources
- LacusCurtius (Bill Thayer) Ptolemy, Tetrabiblos, Book I, ch. 4–24 (trans. F. E. Robbins, Loeb 1940) (opens in a new tab) for the Sun heats and somewhat dries (I.4); diurnal (I.7); house Leo (I.17); exalted in Aries, depressed in Libra (I.19) · checked 2 October 2026
- NASA Space Place What Causes the Seasons? (opens in a new tab) for tilt, not distance; perihelion in January · checked 2 October 2026