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GEMINI
The Twins
Gemini - Alexander Jamieson - 1822
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Following the mighty Orion across our wintry night sky is the constellation of Gemini, the twins. According to Greek myth the twins were actually quadruplets, born of Leda, wife of Tyndareus. One night the ever lustful Zeus (Jupiter), king of the gods, came to Leda in the form of a swan, and seduced her. Her husband also came to her that night, and nine months later Leda gave birth first to an egg, the result of her union with Zeus, from which emerged Pollux (the pugilist, or boxer), and a sister, who was to become Helen of Troy, both immortal offspring of Zeus. Then Leda gave birth to her husband's mortal progeny: Castor (the horseman), and Clytaemnestra, who became the wife of King Agamemnon, the king who went to war with Troy.
As twin brothers, Castor and Pollux were inseparable. They shared many adventures, including sailing with Jason and the Argonauts in search of the Golden Fleece. When Castor was killed in a fight, Pollux was so filled with loss that he begged his father, Zeus, to take away his immortality, so that he might die, and be with his brother. Zeus was so moved by this display of love and loyalty he not only granted the wish of Pollux, he placed their forms in the heavens, as a testament to the strength of brotherly love. It is also written that Zeus's brother, Poseidon (Neptune), was so moved he granted the twins power over the winds and the waves, so that sailors for centuries have worshiped the twins, and invoked their mercy on the high seas.
St. Elmo's Fire (an electrical glow that sometimes occurs in the rigging of ships during storms), was known as Ledaean Lights, after the twins' mother, Leda, and the phrase, by jimminy, actually comes from the ancient sea faring vow, by Gemini ! The twins even appear in the Bible. In Acts 28:11 Paul the apostle writes, "And after three months we departed in a ship of Alexandria, which had wintered in the isle, whose sign was Castor and Pollux."
Although Castor, "The Horseman", is designated as the alpha star in the constellation, it is actually the dimmer of the twins, with a magnitude of 1.59, leading to speculation that the star was brighter in ancient times. Although Castor appears as a single, bright white star to the naked eye, it is actually one of the most complex multiple star systems in the sky, consisting of no less than six separate stars, organized into three binary systems, gravitationally bound to each other. The Castor system is 45 light years from Earth.
Pollux, from the Greek for "Pugilist" or "Boxer" is the brighter of the two twins, with a magnitude of 1.16, making it the 17th brightest star in the sky. Pollux is a K0 yellow giant, shining with a bright golden hue. It is the 17th brightest star in the sky, 11 times larger than the Sun, with a surface temperature of 4500 °C,.
The most exciting thing about Pollux is that in 2006 a planet was found in orbit around it. It's a large planet, over twice the size of our Jupiter, which is why we were able to detect it. Small, rocky planets like Earth, are a lot harder to find. But where there's one planet orbiting a star, there's usually more. And out of the almost 500 stars known to support planetary systems, Pollux is not only the brightest of them all, it is also the fourth closest, only 33.6 light years from Earth.
In addition to the brilliant Pollux, there are five other stars in Gemini that are known to support planetary systems, and one of these, Tau Geminorium, with a magnitude of 4.4, is also big and bright and easy to see with the naked eye. It sits right in the middle of Castor's chest, and hosts one of the largest planets ever found, over 11 times larger than Jupiter. It is very much farther away than Pollux however, at a distance of 300 light years. Most stars that we've discovered so far with planets are beyond naked eye visibility, so Gemini is quite exceptional in having not one, but two very bright stars with known solar systems. This constellation is an exciting, in-your-face visual confirmation for all to see that there are other planets out there. And as we all know, where there are planets, there might be life. Perhaps our first contact with extraterrestrial life will be from a planet orbiting a star in the constellation Gemini.
These two star clusters are located within the same field of view, and are a fine sight in binoculars, or a backyard telescope. The larger, sparser cluster, M35, is 2,000 light years away, and the smaller, denser cluster, NGC 2158, is 16,000 light years away.
NGC 2392 is known as the Eskimo Nebula, or the Clown's Head Nebula, because that's what it looks like through a small telescope. Through the eyes of the Hubble Space Telescope, as seen below, its true nature as an expanding cloud of gas left over from the explosion of a giant star (remnant of a supernova) becomes apparent.
Gemini contains another supernova remnant, IC 443, discernible only in large telescopes. The insert shows what is left of the core of the original star, transformed by the supernova explosion into a super dense neutron star (named J0617), and leaving a comet-like tail behind it as it moves through the super-heated gas of the nebula.
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