Decan One · 0°–10°
Jupiter ♊
May 21 – May 31
Expanded by Jupiter — the Gemini who chases big ideas and far countries, curiosity with philosophy in it.
Gemini, the Twins.
May 21 – Jun 20 · Mutable Air · Ruled by Mercury
Gemini is the zodiac's quicksilver — the mutable air sign that thinks out loud and lives at the speed of curiosity. Ruled by Mercury, the messenger, it is wired for language, connection, and the restless joy of finding out. Its symbol is a pair of twins, because a Gemini rarely holds just one idea at a time.
Plate · The Reading
The sign, at a glance.
Element
Air 気
Modality
Mutable
Ruling Planet
Mercury ☿
Symbol
The Twins ♊
Polarity
Expressive
House
Third the 3rd
Brightest Stars
Pollux β Gem
Season
Late Spring
Plate · The Myth
Two brothers who refused to be parted.
Gemini's stars are Castor and Pollux, the Dioscuri — twin brothers born to the same mother but different fathers, so that one, Pollux, was immortal, and the other, Castor, was not. They were inseparable in life: horsemen, adventurers, protectors of sailors. When Castor was killed in a quarrel, Pollux was inconsolable, and rather than live forever without his brother, he begged Zeus to let him share his own immortality. Zeus honoured the request in a way only a god would — the twins now alternate, one day among the gods on Olympus, the next in the underworld, always together, never quite in the same place. He set them in the sky as a single constellation.
That myth is the whole temperament of the sign. Gemini is mutable air — the most changeable of an already restless element. Mutable signs adapt; air thinks and communicates. Together they make a mind that moves fast, holds two sides of everything at once, and is never bored because there is always another idea, another person, another question to chase.
"A Gemini is not two-faced. It is genuinely interested in both faces."
Mercury, the ruler, is the planet of language, logic, and quick exchange — the messenger who moves between worlds, exactly like the twins. This is why Gemini governs the astrological third house: the house of communication, siblings, short journeys, and everyday learning, the near and constant traffic of the mind.
Read well, a Gemini placement in your chart is not flightiness — it is a map of where you stay curious. It marks the corner of life where you refuse to stop asking, learning, and talking your way toward understanding.
Plate · The Temperament
Two minds, one restless sky.
Every strength a sign is proud of casts a shadow it would rather not discuss. Gemini's quickness is both its gift and its trap, depending on whether it lands or keeps moving.
At its best
CuriousQuick-wittedAdaptableCommunicativeVersatilePlayfulPerceptive
At its shadow
RestlessScatteredIndecisiveInconsistentEasily boredSuperficial
Plate · The Constellation
Castor and Pollux — the twin stars.
Find the two bright stars sitting side by side, and you have found the heads of the twins. Pollux, the brighter of the pair, is a calm orange giant with a planet of its own circling it; Castor, just beside it, looks like a single star but is really a remarkable system of six stars bound together — a fitting secret for the sign of doubles and hidden second selves. Together they crown the constellation, two lights that the eye always reads as a pair.
Plate · The Three Decans
Not one Gemini, but three.
Each sign divides into three ten-degree decans, and tradition gives each its own sub-ruler. It is the oldest answer to why two people of the same sign can feel nothing alike — a Gemini born in the first ten days is not the same Gemini as one born in the last.
Decan Two · 10°–20°
Mars ♊
Jun 1 – Jun 10
Sharpened by Mars — the debater's Gemini: quick, competitive, a mind used as a blade.
Decan Three · 20°–30°
Sun ♊
Jun 11 – Jun 20
Lit by the Sun — the performer's Gemini, wit turned outward, most comfortable with an audience.
Plate · The Sky Right Now
Where Gemini is tonight.
Live from real astronomy
Reading the sky…
Working out where the constellation sits from your point of view.
Assuming mid-northern latitudes
Light that left before you did
Pollux lies roughly 34 light-years away — a calm orange giant with a planet of its own in orbit. The light reaching your eye tonight left that star around 1992, and has been travelling ever since. You are not looking at Pollux. You are looking at its past.
The same stars, other eyes
What others saw here
The Babylonians knew these two as the Great Twins, Meshlamtaea and Lugalirra — divine gatekeepers rather than mortal brothers. The pairing is older than the Greek story laid over it.
Plate · The Mirror
Is this actually you?
Rate how well each statement fits. Answer honestly — the result is more interesting that way.
Plate · Questions, Not Answers
What Gemini is good at asking.
Astrarium does not predict. But a tradition four thousand years old is very practised at asking the right question — and these are the ones this sign keeps returning to.
Which of your two minds have you been listening to lately?
What conversation have you been avoiding by staying interesting instead of honest?
What would you learn if you were not worried about being bored?
The traits, rulerships and decans on this page are the Western astrological tradition as codified in Ptolemy's Tetrabiblos (2nd century CE) and refined through medieval Arabic and Renaissance sources. They describe what the tradition holds about the sign — not verified claims about people born under it. The astronomy is separate and real: see our editorial standards.
Plate · The Company It Keeps
Who keeps up with Gemini.
Astrological compatibility is a starting question, not an answer — a real chart holds far more than sun signs. Traditionally, Gemini moves most easily with the other air signs and the fire signs its ideas can set alight.
Plate · Go Deeper
Where does your mind really run?
Your sun sign is one line of the story. Cast your full birth chart to see where Mercury, the third house, and your Gemini placements actually fall.