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Starwatch: Celestial twins ride on Orion’s shoulders

April 6, 2019 GMT

All winter long the great constellation Orion the Hunter has roamed our skies, with its bright belt of three stars in nearly a perfect row.

Orion isn’t alone, either. He’s surrounded by a tight group of bright constellations that are home to some of the brightest stars we see any time of the year. I lovingly refer to them as “Orion and his gang.” As darkness sets much later now, Orion’s gang dominates most of the western half of the Rochester heavens, with Orion himself standing a little ways above the southwestern point of the horizon.

As spring progresses, Orion and his gang start out the evening lower and lower in the west, and by around mid-June they’re completely gone from the evening sky. We won’t see them again until next autumn as the Earth, in its orbit around the sun, turns us away from that direction of space. As much as I love summer and warmer evenings, it’s tough seeing some of my best celestial buddies go away on summer vacation.

Speaking of buddies, one of the brightest members of Orion’s gang is the constellation Gemini the Twins, that appears to be standing just above and a little to the left of Orion’s shoulders.

Gemini lives up to its name in a couple of ways. First of all, its brightest stars, Castor and Pollux, are easily seen with the naked eye, side-by-side and nearly equal in brightness. Nowhere else in the sky will you find two identical stars as close to each other as they are.

Secondly, the stars Castor and Pollux mark the heads of the Greek mythological twins. Even in light polluted skies, unless you’re really in the middle of a big city, you’ll see crooked lines of stars below both Castor and Pollux that outline the bodies of the twin brothers. They look like celestial stickmen appearing to be joined shoulder to shoulder.

This weekend, look for a very thin waxing crescent moon to the far lower right of Gemini, just above the western horizon. As the week goes on, the crescent will grow fatter as it moves eastward from night to night toward Gemini. On Thursday night the nearly first quarter (half) moon shines brightly between the legs of the Twins.

Six-star system

Astronomically the star Castor, at 50 light-years away, is one of the most interesting stars on the celestial stage. Castor looks like one star to the naked eye, but with modern telescopes astronomers have resolved that Castor is actually a collection of six stars all dancing around each other in a complex orbital pattern. If you lived on a planet in that system, you would have six sunrises and six sunsets every day. Pollux is a single giant star, more than 10 times the diameter of our sun, and shining a little more than 34 light-years away. Just one light year equals almost 6 trillion miles!

Back in 2006 astronomers concluded that Pollux has at least one large planet orbiting it. There could easily be other smaller ones as well.

The best small to moderate telescope target in Gemini the Twins is Messier object 35, or M35 for short. It’s also called the shoe buckle cluster since it appears to be on the foot of twin Castor. It’s a beautiful open cluster of young stars that occupies the area of the full moon in our sky. It’s easy to find, right next to Castor’s foot. The cluster lies over 2,700 light-years away, and its age of 100 million years makes the stars in the cluster stellar toddlers, believe it or not. M35 is a must-see with your scope.

Mythological tale

According to Greek mythology, Castor and Pollux were the maternal twin sons of Leda, the mortal queen of Sparta. The twins had two different fathers. How can that be if they’re twins? Castor’s father was Leda’s husband King Tyndarus, while Pollux was the child of Leda and Zeus, the king of the Greek Gods. This certainly wasn’t the fault of Leda though. She was tricked by the very devilish Zeus, who broke his way into many marriages. Zeus seduced Leda by magically transforming himself into the likeness of King Tyndarus. Because of that treachery Castor was a pure mortal, but Pollux was a half god.

That didn’t matter to Castor and Pollux. They were inseparable and the best of friends. As they grew into young men together, Castor became an expert horseman and Pollux a championship boxer. But even though they had separate vocations they remained very close.

One of their claims to fame was they were on the ship of the Argonauts in the famed voyage of Jason and the Argonauts, who set sail in pursuit of the fabled Golden Fleece. During the voyage the mighty ship was tossed in a violent and massive nocturnal thunderstorm and was in danger of slipping under the raging sea. Allegedly Castor and Pollux calmed the seas, and the Twins have been the patron saints of sailors ever since.

Years later tragedy struck. A family feud broke out between Castor and Pollux and their cousins about ownership of a large herd of cattle. Angry words turned into flying fists, and in the rumble Castor was violently struck by a large rock, instantly killing him. Pollux was grief stricken and begged his real father, Zeus, to allow him to die too, so he could join his brother in the netherworld. That wasn’t possible because Pollux was immortal, but despite his devilish nature Zeus had a soft spot in his heart for his son. He magically raised Castor out of the netherworld, transformed his body into stars, and placed him into the heavens. Zeus then performed the same magic on Pollux, and placed him right next to his brother so they could be together for all time in the constellation we call Gemini.

Celestial Hugging this Week: On Monday and Tuesday the waxing crescent moon will pass by the planet Mars and the constellation Taurus the Bull in the evening western sky.