Leo — 2nd Decan (10°–20°)
The second decan of Leo covers 10° to 20° of the sign. Here the two major decan-rulership systems coincide: under both Triplicity and the Chaldean system, this decan is ruled by Jupiter.
Last reviewed: 2026-07-20
Historical fact
The origin of decans is tied to a practical need in Ancient Egypt: tracking time during the night. To do this, 36 small constellations — the decans — were identified, each rising on the horizon at roughly ten-day intervals, with records appearing on coffin lids and astronomical tables from around 2100 BCE. This Egyptian system only merged with the Babylonian-Greek 12-sign zodiac in the Hellenistic period, when each sign came to be divided into 3 decans of 10° with their own planetary rulership. In this second decan of Leo, the two assignment systems coincide: both Triplicity and the continuous Chaldean cycle point to Jupiter as ruler.
Interpretation — Triplicity System (Modern Astrology)
In Triplicity, a Fire sign's second decan is ruled by the next same-element sign's ruler — for Leo, that's Jupiter, ruler of Sagittarius. The result is Leo's shine and confidence gaining a layer of expansion, generosity, and optimism: the search for recognition broadens into a search for greater meaning, and Leo's self-expression takes on a more philosophical, enthusiastic reach.
Interpretation — Chaldean System (Hellenistic Tradition)
In the Chaldean system's continuous cycle, after Saturn in the previous decan, the next ruler in the 7-planet sequence is Jupiter — coinciding, in this specific case, with the Triplicity result. The convergence reinforces the reading: this decan combines Leo's expressive vitality with Jupiter's characteristic generosity, optimism, and broad vision, with no contradiction between the two systems.
This section presents one tradition's interpretation, not a verifiable fact.
Frequently asked questions
- Does Leo's 2nd decan have the same ruler in both systems?
- Yes, in this specific case: under both Triplicity and the Chaldean system, Jupiter rules this decan. It's a coincidence that doesn't occur in the previous decan, ruled by the Sun (Triplicity) and Saturn (Chaldean).
- What changes between Leo's 1st and 2nd decan?
- The 1st decan has opposite rulers in each system — the Sun under Triplicity, Saturn under Chaldean — contrasting free expression with discipline. The 2nd, ruled by Jupiter in both systems, reads more unified: expansion, generosity, and optimism added to Leo's shine.
Sources
- Nicholas Campion. A History of Western Astrology (2009).
- Claudius Ptolemy. Tetrabiblos (c. 150).
- Vettius Valens. Anthology (Hellenistic astrology) (c. 175).
- Otto Neugebauer, Richard A. Parker. Egyptian Astronomical Texts (1960).