Castor and Pollux in Gemini are twin stars that sink toward the horizon in the evening as summer approaches in the Northern Hemisphere. Chart via John Jardine Goss.
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.
In early to mid-June evenings, Pollux and Castor sit atop Gemini. The sun, which is below the horizon, sits near the foot of Gemini. On the solstice, June 21, the sun lies next to the lower rightmost star of Gemini. Chart via John Goss.In early June, watch the crescent moon climb toward Pollux and Castor after sunset. By June 3, the moon will be above the brightest stars of Gemini.
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.
“I can sometimes see the moon in the daytime” was a cosmic revelation that John Jardine Goss first discovered through personal observations at age 6. It shook his young concept of the universe and launched his interest in astronomy and stargazing, a fascination he still holds today. John is past president of the Astronomical League, the largest U.S. federation of astronomical societies, with over 20,000 members. He's earned the title of Master Observer and has authored the celestial observing guides Exploring the Starry Realm and Carpe Lunam. John also writes a monthly stargazing column, Roanoke Skies, for the Roanoke Times, and a bimonthly column, Skywatch, for Blue Ridge Country magazine. He has contributed to Sky and Telescope magazine, the IDA Nightscape, the Astronomical League’s Reflector magazine, and the RASC Observer’s Handbook.
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