Just like celestial clockwork, the Earth, in its orbit around the sun, has swung in the direction of the constellation Gemini the Twins. It’s on the rise in the early evening Pottsville eastern sky just to the upper left of the great constellation Orion the Hunter.
Both Gemini and Orion adorn the heavens all night long during the holiday season. The two brightest stars of Gemini are Castor and Pollux, which mark the heads of the twins Castor and Pollux.
Seeing the rest of Gemini can be a little tricky, but it’s certainly doable. Unless you’re viewing from an area of heavy city lighting, you should be able to see two faint, crooked, but parallel lines of stars to the right of Castor and Pollux. Those are the bodies of the twins that remind me of stickmen. Castor and Pollux’s feet are not far away from Betelgeuse, the star that marks Orion’s armpit.
If you slowly and carefully scan the constellation Gemini the Twins with a small telescope or even a pair of binoculars, you’ll run into some lovely star clusters.
These are groups of young stars that were born out of the same giant hydrogen gas cloud. A charming open cluster of youthful stars is right next to the foot of Castor. It’s Messier Object 35, or M35 for short. I know you’ll want to gaze at that one again and again, and when you do, realize that this cluster of stars is nearly 3,000 light-years away. Just one light-year is almost six trillion miles. This winter, the light we see from M35 has been traveling to Earth since about 1000 BC.
Castor and Pollux are often called the twin stars not just because they’re the brightest stars in Gemini but also because they’re about the same brightness in the sky. But that’s where the similarity ends. Pollux is a giant star, more than eight million miles in diameter. That’s nine times the diameter of our sun. It’s more than thirty times more luminous than our sun and sports a surface temperatureof almost 8000 degrees F, a little cooler than our home star. In 2006 it was discovered that Pollux has a giant planet more than twice the diameter of Jupiter revolving around it. It may easily have other planets circling as well.
Gazing at the star Castor proves that heavenly looks can be really deceiving. A small to moderate telescope reveals that Castor is a beautiful double star. Still, more giant telescopes reveal that what appears to be a single star to the naked eye is actually a collection of six relatively puny stars revolving around each other in an intricate cosmic ballet. Can you imagine living on a planet like our Earthgoing around one of those stars? You’d have six sunrises and six sunsets every day. It would never get dark.
According to Greek mythology, Castor and Pollux were the twin sons of Leda, the queen of Sparta. The twins, though, had two different fathers. Castor was the son of Leda’s husband, King Tyndarus, but Pollux’s dad was Zeus, the king of the gods. If you read through the many pages of Greek mythology you quickly learn that Zeus was an outright scoundrel! The same night that Castor was conceived,
Zeus, with all his godly magic, seduced Leda by making himself look just like King Tyndarus, and Pollux was conceived. Leda had one wild night! Greek mythology stories are full of this kind of behavior.
As a result, when the twin boys were born nine months later, Castor was one hundred percent mortal, and Pollux was born a half-god. The twins grew up together in privilege, living in the castle with the finest of everything: excellent education, great fun, and lots of money! They were the best of friends as well as brothers. They hung out together all the time, even after they grew up. Castorbecame one of the finest horsemen in the land, and Pollux became a championship boxer.
The constellation Gemini is also the backdrop for the annual Gemini meteor shower that peaks the night of Dec. 13-14. Normally it’s one of the best meteor showers of the year. During the Geminids, meteors, or “shooting stars,” seem to emanate from the general direction of the constellation Gemini. This year, though, the Geminids have stiff competition, namely the full moon. All of itsbright light is going to greatly reduce the number of meteors you can spot. All is not lost though. Look for the Geminids before the peak. On Dec. 11 the moon sets by 3:30 am and around 4:30 am on the 12th . After the moon sets the sky will be a lot darker and while you won’t see as many meteors as you would during the peak but at least you won’t be totally shut out.
(Lynch is an amateur astronomer and retired broadcast meteorologist. You can contact him at mikewlynch@comcast.net.)
