The Dioscuri, Sons of Jove
Castor and Pollux, the twin stars of the constellation Gemini, while known
as the Sons of Jove, should really have been called the Sons of Leda, for Jove
was the father only of Pollux. Leda, wife of King Tyndareus of Sparta, was enticed
by Jove, who had assumed the guise of a swan. Pollux, then, was immortal while
his twin Castor, son of King Tyndareus, was mortal. The two were inseparable
and devoted to each other. Castor became an accomplished equestrian, Pollux
a champion boxer. Among other exploits, the twins were among the Argonauts in
their quest for the golden fleece. At sea, a furious storm arose, such as the
adventurers had never seen. To calm the crew, Orpheus began to play his harp
as only he could bring out the enchanting music. As he played, he called upon
the gods to save them, and miraculously the storm eased. At the same time twin
stars appeared over the heads of Castor and Pollux. Thereafter the strange lights
which sometimes appear during thunderstorms at sea, known as Saint Elmo's fire,
were called by the names of the twins, and sailors and fishermen would pray
to the twins in times of great peril. In China, the twin stars of Gemini were
known as Yin and Yang, together the essence of the contrasts of the universe.
Yin is feminine, water, darkness, winter, the Moon. Yang is male, fire, light
and heat, summer, the Sun. Their symbol is two halves making up a complete circle.
It is a symbol woven into all the religion and mythology-as well as the early
science and philosophy-of China.
Other civilizations, too, had legends of these sky twins. Early Hebrews associated
them with brothers Simeon and Levi. The Romans considered the two stars to be
Romulus and Remus, the twin founders of Rome. In the American Northwest, the
Klamath told of a boy and a girl who look down from the eastern horizon on December
evenings over Crater Lake and make it freeze. But the stars Castor and Pollux
are not identical twins. Pollux is somewhat brighter than Castor, at magnitude
1.16 compared to 1.6. Pollux is 35 light years distant from us, while Castor
lies another 8 light years beyond. Pollux is a star many times the diameter
of the Sun and 35 times as luminous. Castor is a multiple star system, consisting
of three separate close pairs.
The constellation Gemini contains other double and multiple stars. Among these are Epsilon, a third magnitude star with a ninth-magnitude companion just under two arc minutes away. Eta Geminorum is outstanding. Its third-magnitude primary is a red-giant variable with a period of 233 days and a magnitude amplitude of about one. Another interesting star is the cepheid variable Zeta, with two companions. Two other doubles are Delta and 38 Geminorum, each pair exhibiting color contrasts. Deep sky objects in Gemini include the open cluster M35, which is on the edge of naked-eye visibility. Also, the enigmatic Eskimo or Clown Face planetary nebula, NGC 2392, is worthy of observation with small telescopes.
Gemini twins, Castor and Pollux, patron saints of sailors and fishermen
Eskimo Nebula, Jim Scala photo
Points of Light
When the late-evening Bay Area skies erupted in glowing color from an aurora borealis on March 30th, who did local all-news radio station KCBS contact for expert commentary on the matter? Why, they called the EAS's own Dave Rodrigues, whose explanations of the phenomenon were played hourly on its newscasts through the following morning.
San Francisco's Lakeside Kiwanis Club heard about our region's rich variety of sundials in a talk given by Carl Trost in April.
Atlas of the Lunar Terminator, by John Westfall, is one of several recently
published guides to the Moon reviewed in the May issue of Sky and Telescope.