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♊ Gemini, 21 May – 20 June. The third sign, mutable air, ruled by Mercury. The glyph is the Roman numeral two with serifs, and the constellation earns it: two nearly parallel columns of stars ending in the bright pair Castor and Pollux, the closest thing in the sky to an obvious picture. The sign runs out at the June solstice, handing the year over at its longest day.
Religion and myth
The Babylonian name is MUL.MAŠ.TAB.BA.GAL.GAL, "the Great Twins", and the twins are gods with real cult: Lugal-irra and Meslamta-ea, a paired underworld deity associated with Nergal, worshipped as gatekeepers who stand either side of the door to the land of the dead. Their twinned statues were set at thresholds. MUL.APIN also records a "Lesser Twins" pair nearby. This is one of the cases where the Mesopotamian layer is unambiguously religion rather than star-naming.
The Greek twins are the Dioscuri, Castor and Polydeuces — Latin Pollux — sons of Leda. Polydeuces was fathered by Zeus and immortal; Castor was fathered by Tyndareus and was not. When Castor was killed in a cattle raid Polydeuces refused immortality alone, and Zeus let the brothers alternate, one day in Hades and one on Olympus. The sky pair keeps that arrangement: as one rises the other is going down.
This attachment is unusual in the zodiac because it is not only literary. The Dioscuri had substantial cult. They were Sparta's own gods, represented by the dokana, two upright beams joined by crossbars. Rome dedicated a Temple of Castor and Pollux in the Forum in 484 BCE after they were said to have appeared at the battle of Lake Regillus, and sailors across the Mediterranean prayed to them — the twin electrical glow now called St Elmo's fire was read as the brothers arriving to save a ship. Where Aries and Libra carry stories, Gemini carries a religion people actually practised.
Key dates
| Date | Event |
|---|---|
| c. 1000 BCE (contested) | MUL.APIN lists the Great Twins, Lugal-irra and Meslamta-ea, among the stars in the path of the Moon. |
| 484 BCE | The Temple of Castor and Pollux is dedicated in the Roman Forum — evidence that the twins were cult, not just constellation. |
| 5th century BCE (contested) | Gemini becomes the third of twelve equal 30° signs in Babylonian astronomy. |
| c. 275 BCE | Aratus's Phaenomena names the pair in the standard Greek scheme. |
| c. 150 CE | Ptolemy catalogues Gemini in the Almagest; the Tetrabiblos gives Mercury the rulership. |
| present | With about 24 degrees of precessional drift since the frames coincided in the third century CE, the Sun spends nearly all of tropical Gemini against the stars of Taurus, crossing into the constellation Gemini only around 21 June. |
In the year
Gemini is the last stretch of spring, the mutable sign that empties into the solstice. In the Mediterranean agricultural year it covers the run-up to the grain harvest, and in the sailing year it sits in the safest open-sea season. The Roman festival of Vestalia (7–15 June) and the solstice itself fall at its far edge. Mercury as ruler fits the transitional character the modality already describes: this is the part of the year that is on its way somewhere.
Related
- Gemini — the constellation itself: the real stars, not the calendar slice.
- Western Zodiac
- World Zodiacs
- Mithuna — the sidereal counterpart in the Vedic zodiac.
- Calendar