Celestial Highlights

By Robert C. Victor, Staff Astronomer (now retired), Abrams Planetarium, Michigan State University

Bright stars and a lone bright planet visible at dusk as December begins include the Summer Triangle of Vega, Altair, and Deneb well up in west and getting lower as month progresses; Saturn halfway up in SE to SSE, with Fomalhaut, Mouth of the Southern Fish, to its lower right -- and be sure to arrange for telescopic views of Saturn’s rings, tipped only 0.4° to 1.0° from edge-on this month; Capella, the “Mother Goat” star, in NE; and reddish-orange Aldebaran low in ENE, to lower right of Capella. Aldebaran, the eye of Taurus, the Bull, is at opposition to the Sun on Dec. 1. so, that night, you can also spot the star highest in the south in the middle of the night, and low in WNW as dawn brightens. The Arabic name Aldebaran means “the Follower”, and you can find the pursued, beautiful Pleiades or Seven Sisters star cluster 14° above Aldebaran in deepening evening twilight, and 31° lower left of a bright, 88-percent waxing gibbous Moon.

Winter begins on Dec. 21 at 7:03 a.m. PST, as the Sun reaches the southernmost point of its annual journey, directly above the Tropic of Capricorn. The Moon will return to the early evening sky later that day, as a thin 4-percent crescent low in SW at dusk. By Dec. 26, the Moon is a gravid 42-percent crescent, 3° upper right of Saturn well up in the south.

Watch the waxing gibbous Moon hopscotch over the Pleiades from one night to the next, December 30 to 31, while its phase increases from 84-to 92 percent. At dusk on Dec. 31, the Moon appears 10° north (upper left) of Aldebaran, while Jupiter is just rising 43° to Moon’s lower left. Majestic Orion now rises in twilight at year’s end, to the Moon's lower right. Two or so hours later, watch for the rising of Sirius in ESE, in line with Orion’s belt, extended downward. If you’re in a place with unobstructed views toward west and ESE, both the Winter Triangle, Betelgeuse-Procyon-Sirius, and the Summer Triangle, Deneb-Vega-Altair, can be seen simultaneously. On subsequent nights, find the stars in the same positions 4 minutes earlier each evening, or two hours earlier per month.

At this time of year, the entire Winter Hexagon is visible for 8½ consecutive hours, taking up most of the night. Its stars of first magnitude or brighter, in clockwise order, are Sirius; Procyon; Jupiter (a temporary visitor, not really a star, but a planet or “wandering star”); Pollux; Castor (of mag. 1.6, so not really of first magnitude, but listed anyway, because it’s only 4.5° from Pollux and helps identify it); Capella; Aldebaran; Rigel; and back to Sirius. That makes a Hexagon of half a dozen stars of first magnitude or brighter, with Jupiter and Castor added to its perimeter. Betelgeuse, another first-magnitude star, lies inside the polygon. From the Coachella Valley on December 1, the Hexagon is in good view from 9:00 p.m. until 5:30 a.m., and on December 31, two hours earlier, or 7:00 p.m. until 3:30 a.m.

In morning twilight, within the hour before sunrise (see our morning twilight sky map included), Jupiter is in the west with the “Twin” stars Pollux and Castor to its upper right. Capella is in NW, to the lower right of the Twins. The “Dog Stars”, Procyon and Sirius – the latter, the brightest of all nighttime stars but not as bright as Jupiter, appear to the lower left of Jupiter and the Twins.

Below Jupiter, find red Betelgeuse, with Orion’s 3-star belt farther down. Setting in WNW, far to the lower right of Jupiter and Betelgeuse, is another reddish star, Aldebaran, eye of Taurus. Rigel, Orion’s foot, is already gone from the morning mid-twilight sky at the start of December, but you can still catch it, by looking earlier in the morning. After Rigel, the stars Aldebaran, Sirius, and Betelgeuse will all disappear below the western horizon. Remaining in the western sky at dawn through month’s end will be the “Spring Arch” of Procyon, Jupiter (the very bright, temporary visitor), Pollux, Castor, and Capella.

Regulus, highest of the first mag. stars in the SW quadrant of the sky on December mornings, marks the heart of Leo, the Lion. Look for Regulus 36° to 39° upper left of Jupiter.

In eastern half of the sky on December mornings, golden-orange Arcturus climbs high in E to SE, with Spica of Virgo 33° to its lower right, in SE to S. Blue-white Vega is in NE to ENE, nearly 60° to lower left of Arcturus. Deneb rises in the far NE, to the lower left of Vega.

Mercury puts on its year’s best morning showing low in the SE sky in the first three weeks of December, and sinks to the horizon at mid-twilight by month’s end. Watch for fainter, first-mag. Antares emerges in the last two weeks of the month. It’s 6° lower right of Mercury Dec. 17-21, moving to the upper right of Mercury thereafter, to 10° on Christmas morning, to 18° on Dec.  31.

Welcome the New Year in a Sirius way. In the middle of the night of December 31 to January 1, the brightest star, Sirius (mag –1.45), passes directly south almost exactly 12 hours after the Sun’s midday passage through its highest point, solar midday, on Dec. 31, 2025, at 11:49 a.m. in Palm Springs, or at different times, depending on the longitude of your location within your time zone. On the night of Dec. 31, find the Dog Star well up in the southern sky as the New Year begins. Observers in southern California have an added bonus: The second brightest star, Canopus (mag. –0.72), reaches its high point in the south just 22 minutes before Sirius does. Observers in the Coachella Valley will find it 3° to 4° up due south when it’s highest, provided mountains don’t block the view.

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