By Gemini!

Orion the hunter and his court of brilliant stars dominate the winter sky. Over his left shoulder (marked by the red supergiant Betelgeuse) is a pair of bright stars. These are the Gemini twins. The brighter, easterly one is Pollux, his brother is Castor.

These stars were especially important for mariners in the ancient world. When they rose at the same time as the sun (called the "heliacal" rising), they signaled that the days of calm seas were at hand. For luck, the mariners would swear, "By Gemini;" this became in time "by jimini," and thus the famous cricket guiding Pinocchio.

Castor blazes blue-white, Pollux orange. People have known that since ancient times, but now we know how to read the stars. The orange color of Pollux tells us that it is midway in temperature between our yellow Sun and red Betelgeuse: about a thousand degrees cooler than the Sun. The blue-white of Castor says that it is a very hot star.

Though hot stars are more massive than cool ones, they exhaust their fuel much more quickly. Castor will last only several hundred million years. A tremendous time, true, but only a fraction of the Sunšs lifetime of ten billion years or Pollux' estimated thirty billion year life.

A pair of starlike objects is now rising in the east. The brighter, orange one is the planet Saturn; the dimmer is the star Regulus. Halfway between Regulus and Pollux is the spectacular Beehive star cluster. It looks like a fuzzy spot to the naked eye, and the ancient name, Praesepe, means manger. Appropriate for this season, don't you think?

(12/27/06)