Moon and Gemini stars at dawn August 5 and 6

Star chart: Crescent moon and Gemini stars with constellations Orion and Gemini marked.
On August 5 and 6, 2021, the waning crescent moon is sweeping past Castor and Pollux, the Gemini “twins.” Look to the right of them along the horizon, and you’ll see mighty Orion the Hunter – ghost of the shimmering summer dawn – returning to the morning sky.

Moon and Gemini stars

On the mornings of August 5 and 6, 2021, you’ll find the waning crescent moon in front of the constellation Gemini the Twins. Gemini’s two brightest stars, Castor and Pollux, represent twin brothers in Greek mythology. These two stars don’t look alike. Pollux is slightly brighter than Castor and more golden in color. But no two bright stars in our sky lie so near one another. Their brightness and proximity have made Castor and Pollux a symbol of brotherly love for centuries.

Ancient tale of the Twins

There are multiple versions of the ancient tale of the Twins. In Greek mythology, both Castor and Pollux were born from the same mortal mother, Leda, with different fathers. Castor, the mortal brother, was sired by Tyndareus, a mortal king of Sparta. Pollux, the immortal brother, was the son of Zeus, the king of the gods, who seduced Leda in the form of a swan.

It’s said that – when the mortal brother Castor was slain in battle – his immortal brother Pollux was inconsolable. He begged his father Zeus to relieve him of the bonds of immortality. Zeus granted his request, and so Pollux joined his brother in death, choosing togetherness with his brother over eternal life. According to the legend, Zeus allowed the brothers to live together in the heavens as the constellation Gemini the Twins.

But, it’s said, the heavenly twins must spend a portion of the year in Hades, the underworld and land of the dead in Greek mythology. And so, in our sky, these two stars – Castor and Pollux – disappear from the sky for a while each year. They go behind the sun, as seen from our earthly vantage point.

Star chart, stars in black on white, of constellation Gemini near Orion and Taurus.
Constellation chart of Gemini via International Astronomical Union.

Sun in Gemini from June 21 to July 21

From the vantage point of Earth, the sun annually passes in front of the constellation Gemini from about June 21 to July 21 each year. Gemini is lost in the sun’s glare for that month at least, and is not visible in our nighttime sky. Thus it could be said that the heavenly twins dwell in the underworld during that time of year.

Of course, it’s really Earth that’s doing the moving. The Earth’s yearly orbit around the sun causes the sun in our sky to travel full circle in front of the constellations of the zodiac every year. At this time of year, as Earth moves around the sun and the seasons inevitably shift, Castor and Pollux return to the sky before dawn.

As we look east before sunrise for Gemini’s return, it’s easy to imagine the fond brothers returning from the underworld, a tribute to the redemptive power of brotherly love.

Marble statue of two unclothed, curly-haired, similar-looking Greek youths standing next to each other.
Castor and Pollux, the Twins of ancient Greek mythology.

Bottom line: The moon has now waned to a slim crescent phase. It’s near the stars Castor and Pollux – the legendary Gemini “twins” – on August 5 and 6, 2021.

August 4, 2021

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Bruce McClure

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