Aries — 2nd Decan (10°–20°)
The second decan of Aries covers 10° to 20° of the sign. Under both major decan-rulership systems, this one is ruled by the Sun — another coincidence between Triplicity and the Chaldean system, which diverge again at the next decan.
Last reviewed: 2026-07-20
Historical fact
Like every decan, this 10° segment originates in the ancient Egyptian decan system — minor constellations marking the passage of nighttime hours, documented from around 2100 BCE, long before their merger with the 12-sign zodiac in the Hellenistic period. In this specific decan, the two rulership systems coincide again: both Triplicity and the continuous Chaldean cycle point to the Sun as ruler — a coincidence that doesn't repeat at Aries' third and final decan.
Interpretation — Triplicity System (Modern Astrology)
In the Triplicity system, the second decan of any Fire sign is ruled by the next same-element sign's ruler in zodiacal order — for Aries, that's the Sun, ruler of Leo. The result is Aries energy with a layer of expressiveness and desire for recognition typical of Leo, added to the sign's initial drive.
Interpretation — Chaldean System (Hellenistic Tradition)
In the Chaldean system's continuous cycle, the sequence of the 7 classical planets (Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon) places the Sun as the second ruler after Mars — coinciding, in this specific case, with the Triplicity result. Starting from the next decan, though, the two systems part ways.
This section presents one tradition's interpretation, not a verifiable fact.
Frequently asked questions
- Does Aries' 2nd decan have the same ruler in both systems?
- Yes, in this specific case: under both Triplicity and the Chaldean system, the Sun rules this decan. It's a coincidence that occurs across Aries' first two decans, but doesn't repeat at the third.
- What changes between Aries' 1st and 2nd decan?
- The 1st decan is ruled by Mars, Aries' own ruler, read as the sign's purest expression. The 2nd, ruled by the Sun, is read as a layer of expressiveness and desire for recognition added to Aries' initial drive.
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).