← Encyclopedia of Astrology · lesson 180/235
Castor
Castor marks the head of the leading twin in the constellation Gemini, beside its brighter brother Pollux. It looks like a single white star of the second magnitude, but a telescope shows it is a family of six suns bound together. In myth Castor was the horseman of the Dioscuri, the twin brothers sailors prayed to. In astrology it is read as a star of the mind: writing, learning, quick wit and versatility, with a reputation for sudden turns of fortune.
In the zodiac
Castor now stands at about 20° Cancer, even though the constellation it belongs to is Gemini — the stars and the signs drifted apart long ago. Through precession it moves forward about one degree every 72 years, so a chart from 1950 places it about a degree earlier, near 19° Cancer.
Its nature
Ptolemy gave the star in the head of the leading twin the nature of Mercury, and noted that it was also called the star of Apollo. The tradition linked it with keen intelligence, eloquence and success through the mind, and later writers added sudden honours that could be followed by sudden losses. Modern astrologers usually read that as changeability: a bright, restless intellect that does best when it has somewhere steady to land.
In a chart
Only a close conjunction is usually counted, within about a degree or a degree and a half. With Mercury or the Moon, Castor tends to sharpen curiosity and a gift for language; on the Sun or the Midheaven, it may point to work with ideas, teaching or writing. On the Ascendant it is often read as a lively, quick-witted manner. It colours the point it touches rather than acting on its own.