Waning moon meets Zubenelgenubi morning of December 2

Waning moon meets Zubenelgenubi: Chart showing moon and Zubenelgenubi on December 2, 2021.
If you’re up and around on the morning of December 2, 2021, watch for the waning crescent moon very near the star Zubenelgenubi, the constellation Libra’s alpha star. Very pretty early morning scene!

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Waning moon meets Zubenelgenubi

Throughout the month, the moon passes near planets and stars, creating interesting scenes in the sky.

The moon starts December 2021 as a waning crescent, positioned in the early morning sky low in the southeast. December 2 finds it floating very near an interesting, moderately-bright star with a strange sounding name: Zubenelgenubi. The name rhymes with Obi-Wan Kenobi of the Star Wars franchise.

Many see Zubenelgenubi as a single star. People with clear dark skies and good eyesight can see two separate points of light in this star. One of the two is dimmer than the other. Binoculars easily reveal the dual nature of Zubenelgenubi. Using spectroscopy, astronomers have found that both stars are themselves double, making at least four stars in this system!

Interested in double stars you can see with the eye, binoculars or a small telescope? Try our double star observing guide.

We in the Northern Hemisphere usually consider Zubenelgenubi as a summer star. Summer is when you’ll see this star – and its brother star Zubeneschamali in the constellation Libra the Scales – in the evening.

Every year in December, though, Zubenelgenubi returns from being behind the sun from our earthly vantage point. It’s just now beginning another cycle of visibility in Earth’s sky… a pretty sight near the waning moon on December 2!

Libra, a diamond-shaped constellation, with its 2 brightest stars labeled.
Zubenelgenubi is nearly always shown with its brother star in Libra, Zubeneschamali. Here’s the view on June evenings, when you’ll notice them between 2 brighter stars: Antares in the constellation Scorpius and Spica in the constellation Virgo. This chart faces south around 10 p.m. in mid- to late June. Libra is a faint, diamond-shaped pattern of stars. Map created with Stellarium by AstroBob. Used with permission.

Bottom line: Watch for the waning crescent moon near Libra’s bright star Zubenelgenubi on the morning of December 2, 2021.

November 30, 2021

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John Jardine Goss

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