Castor and Pollux sink to the horizon in spring
You can find Pollux and Castor, the twin stars of Gemini, in the west-northwest sinking lower each night from mid-May through mid-June. You might even be able to catch them for a few nights after that. This is the same Pollux and Castor that rose in the east-northeast in the early evenings around New Year’s Day. At that time of year, they pointed straight up from the horizon. It’s also the same two stars that shone nearly overhead in the cold nights of February and March.
Now, in the much warmer evenings of late spring, Gemini stands on the west-northwestern horizon, with Pollux and Castor forming a horizontal line in the twilight. The twin stars twinkle atop the constellation, while the sun, still in eastern Taurus, approaches the foot of Gemini and lies below the horizon.
Castor and Pollux photo gallery
Bottom line: Castor and Pollux, the brightest stars in Gemini the Twins, sink toward the horizon on spring evenings, disappearing from summer’s night sky.