Wyoming Skies: Bright planets light up December skies

December marks the approach of the winter solstice on December 21, bringing a stretch of cold and snowy weather to Wyoming. Despite the chill, the night sky features 15 objects shining at first magnitude or brighter. In order of brightness, these include: Jupiter, Sirius, Mars, Vega, Capella, Rigel, Procyon, Betelgeuse, Altair, Aldebaran, Saturn, Pollux, Fomalhaut, and Deneb.

As night falls, the stars forming the Summer Triangle Altair, Vega, and Deneb remain visible midway in the western sky. A few hours later, Cygnus appears upright above the western horizon, highlighting its Northern Cross asterism. The lowest star of this cross, Alberio, is a striking telescopic double star displaying gold and blue colors.

High overhead, the distinctive W or M shape of Cassiopeia is easy to spot, along with the four moderately bright stars forming the Great Square of Pegasus. Nearby, the Andromeda Galaxy (M31) can be seen. Under dark skies, it is visible to the naked eye, lying over two million light-years away. Binoculars reveal more of its spiral structure.

Turning eastward, winter constellations and stars dominate the sky. The brightest object in this direction is Jupiter. Leading the winter display, the Pleiades star cluster glimmers like a tiny dipper. Below them lies Aldebaran, the fiery red eye of Taurus, with Capella shining in the constellation Auriga.

As the night progresses, Gemini and Orion rise in the east. Orion is notable for its three-star belt along the eastern horizon, with Betelgeuse marking the hunters shoulder. Nearby, Geminis twin stars, Castor and Pollux, shine brightly, while Jupiter stands out as a steady, brilliant light close to Gemini.

December evenings offer the opportunity to see two planets. Jupiter rises after sunset and remains visible until dawn, with the Moon near it on December 7. Saturn glows in the southwest as darkness falls, with the Moon nearby on December 26. In the morning sky, Jupiter appears in the western sky before dawn, and Mercury is visible in the eastern morning twilight around December 25.

The Geminid meteor shower peaks overnight on December 13-14. This reliable and bright shower is unaffected by the gibbous waning crescent Moon this year and can produce up to 120 meteors per hour under dark skies. The showers radiant rises in mid-evening and peaks around 2 a.m., allowing early evening observers to catch meteors, including long-lasting earthgrazers traveling horizontally across the sky. Geminid meteors originate from debris left by an asteroid rather than a comet.

The Ursid meteor shower reaches its peak before dawn on December 22. With a new moon two days prior, dark skies may reveal around 10 meteors per hour.

December 4 features the last supermoon of 2025, known as the Cold Moon, visible all night. Near the horizon, the Moon appears larger due to the moon illusion, though it looks smaller through a straw. The next supermoon occurs in January 2026. While supermoons do not appear larger, they do shine brighter in the sky.

Analysis: December Night Skies and Celestial Events

As December rolls in, Wyoming residents can look forward to a series of celestial events, despite the biting cold of the approaching winter solstice. The clear winter nights present an excellent opportunity for stargazing, with multiple bright celestial bodies gracing the night sky. The alignment of planets, meteors, and distant galaxies promises a spectacular visual display for observers throughout the month.

The Winter Solstice on December 21 is the shortest day of the year, marking the official start of winter. However, the early nights provide ample time to observe the beauty above. In addition to the usual constellations, a particularly bright set of celestial objects will be visible. Among the brightest are Jupiter, Sirius, and Mars, alongside the easily recognizable Summer Triangle. The Winter Triangle, featuring stars like Betelgeuse, Capella, and Aldebaran, will also be prominent.

However, the highlight for many skywatchers this month is the Geminid Meteor Shower. Peaking on December 13-14, this meteor shower offers the opportunity to witness up to 120 meteors per hour, showcasing bright meteors that can be observed from both early evening and the early morning. Unlike other meteor showers, the Geminids originate from asteroid debris, providing a different kind of celestial spectacle.

Additionally, the Cold Moon, the last supermoon of 2025, will rise on December 4, offering a larger-than-usual lunar sight due to the 'moon illusion.' While not truly larger in size, it will appear brighter and more striking in the night sky. This will set the stage for the next supermoon, expected in January 2026.

Looking to the east, winter constellations like Gemini and Orion will rise steadily through the night. The signature three-star belt of Orion, combined with the bright stars of Gemini, such as Castor and Pollux, will dominate the horizon. Jupiter’s brilliance near Gemini adds to the overall wonder of the season's night skies.

As December progresses, the combination of celestial events, meteor showers, and planetary alignments provides a unique opportunity for both amateur and seasoned astronomers to witness the beauty of the universe. With the arrival of the Ursid Meteor Shower on December 22 and the chance to observe Mercury and Saturn, it’s clear that December offers a rich variety of celestial phenomena that should not be missed.

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• Wyoming Skies: December skies may be dark, but two planets shine bright