Castor (Alpha Geminorum) -- Six Star System in Gemini
Castor the Mortal Twin
Castor and Pollux are the brightest stars in the constellation Gemini. In mythology
they were twins at birth, but Castor was conceived by a mortal and Pollux by a god
(both on the same night). The twins were close, but immortals do not die, and the
time came when Castor left Pollux alone in the world of the living. Pollux spent his
time with the gods in Elysium and in the Netherworld (Hades) with his beloved brother.
In the stars, it is symbolic that the bright twins of Gemini, Castor and Pollux, disappear
at the same time, together, when setting on the western horizon.
Castor is one of the finest double stars in small telescopes. In reality, Castor is a
multiple star system containing six suns. Each of the three components A, B and C
shown in the drawing each have a red-dwarf companion which is below the ability of
my telescope to detect. The C-component is also a red-dwarf and appears orange
through the telescope. Also, of interest is that the C-component is an eclipsing binary
(one of the stars passes in front of the other as seen from Earth), and thus changes in
brightness. The bright components of Caster (A & B) orbit around each other every
4 hundred years, while the orbit of the twin red-dwarfs (component C) around A and B
takes thousands of years.