Key Takeaways:
- The article details observational opportunities for deep-sky objects including the North America Nebula (NGC 7000) and Pelican Nebula (IC 5070) in Cygnus, and the Christmas Tree Cluster (NGC 2264) in Monoceros, noting conditions for enhanced visibility.
- Specific planetary and satellite phenomena are highlighted, such as the transit and shadow transit of Jupiter's moon Io, a close approach of dwarf planet 1 Ceres to star HD 3126, and a partial transit of Saturn's moon Titan, along with a lunar conjunction with Saturn.
- Annual celestial events covered include the winter solstice, marking the shortest day in the Northern Hemisphere, and the peak of the Ursid meteor shower, expected to yield approximately 10 meteors per hour under dark conditions.
- Further observations include Comet 24P/Schaumasse as it navigates the Virgo Cluster, and the star Fomalhaut, discussed in the context of its dusty protoplanetary disk and the reclassification of "Fomalhaut b" from a planet to an expanding debris cloud.
Sky This Week is brought to you in part by Celestron.
Friday, December 19
We’re getting ready to say goodbye to the summertime constellations, including Cygnus the Swan, now about 40° high in the west two hours after sunset. Before this famous star pattern disappears, however, let’s take a last look at some of its lovely deep-sky treasures, such as the North America Nebula (NGC 7000).
With no Moon in the sky tonight, darkness is on our side. NGC 7000 lies just 3° east of Deneb (Alpha [α] Cygni), the Swan’s brightest star. If your skies are free from light pollution, you may be able to spot its gentle glow in binoculars, while a mid-sized telescope (4 to 6 inches) should give you a spectacular close-up view even under slightly brighter conditions. This blob of glowing gas stretches over an area of sky about 10 times the size of the Full Moon. Its similarity to its namesake is perhaps most obvious along the “East Coast,” where a dark swath cuts through the region, separating NGC 7000 from the nearby Pelican Nebula (IC 5070) just to its west. That darkness is a cloud of cold dust known as a dark nebula; this one was cataloged by Beverly Lynds as L935.
If you’ve got one available, a UHC filter should really enhance the view.
Sunrise: 7:18 A.M.
Sunset: 4:37 P.M.
Moonrise: 7:19 A.M.
Moonset: 4:01 P.M.
Moon Phase: New
*Times for sunrise, sunset, moonrise, and moonset are given in local time from 40° N 90° W. The Moon’s illumination is given at 10 P.M. local time from the same location.
Saturday, December 20
Jupiter’s innermost Galilean moon, Io, crosses the gas giant along with its shadow this evening in an event visible across the U.S.
Jupiter rises around 6:30 P.M. local time, climbing above the eastern horizon in the constellation Gemini. The giant planet is approaching opposition, now shining at magnitude –2.6. It’s the brightest light in the Twins. It should be easy to center the planet in your telescope, where its 46”-wide disk will show off details such as alternating light and dark cloud bands. The Great Red Spot will make an appearance late in the evening as well, rotating into view a few hours before midnight EST.
Early in the evening, all four Galilean moons sit east of the planet. In order from closest to farthest, they are: Io, Europa, Ganymede, and Callisto. Io approaches the planet over the next few hours; shortly before it reaches the eastern limb, its shadow appears on the cloud tops at 10:35 p.m. EST. Io begins its transit 30 minutes later.
The two are visible together in front of Jupiter’s disk until shortly before midnight CST (now early on the 21st for those on Eastern time), when Io’s shadow slips off the western limb around 11:50 P.M. CST. The Great Red Spot should now be visible on the disk as well.
Io again follows suit about 30 minutes later, ending its transit around 12:20 CST (now early on the 21st in CST as well).
Sunrise: 7:18 A.M.
Sunset: 4:37 P.M.
Moonrise: 8:10 A.M.
Moonset: 4:57 P.M.
Moon Phase: Waxing crescent (1%)
Sunday, December 21
The winter solstice occurs today at 10:03 A.M. EST. This marks the beginning of astronomical winter in the Northern Hemisphere and astronomical summer in the Southern Hemisphere. (Note that meteorological winter began December 1st, so you may have already heard news outlets saying it is wintertime before this date.)
On the winter solstice, the Northern Hemisphere experiences its shortest duration of daylight. After this date, the Sun will begin to remain above the horizon for longer, although it may take a few days for sunrise and sunset times to change, depending on your location.
The solstice itself — at 10:03 A.M. EST — is the exact moment the Northern Hemisphere is tilted farthest from the Sun. On this date, the Sun makes its lowest arc through the Northern Hemisphere sky as well, while our star sits directly overhead at noon for those on the Tropic of Capricorn in the Southern Hemisphere.
Astronomical winter will last until the spring equinox, which will occur March 20, 2026, at 10:46 A.M. EDT.
Sunrise: 7:19 A.M.
Sunset: 4:38 P.M.
Moonrise: 8:54 A.M.
Moonset: 5:59 P.M.
Moon Phase: Waxing crescent (4%)
Monday, December 22
This morning offers a chance to catch the last major meteor shower of the year: the Ursids. This short-lived shower is active for only about a week and peaks this morning under dark, moonless skies.
Although the Ursids’ peak rate is just ⅒ that of the Geminids last week — meaning at its best, it will only produce about 10 meteors per hour — it’s still worth stepping outside before sunrise to see if you can catch a few shooting stars. In fact, the radiant in the north is visible all night for much of the Northern Hemisphere, meaning you can watch for meteors late on the 21st as well as again this evening.
The Ursids’ radiant is located just off the cup of the Little Dipper. It is nearly 50° high in the north by 5 A.M. local time, to the upper right of the North Star, Polaris. If you can find the Big Dipper in the northern sky — upside-down early this morning — look beneath its cup to find the matching, smaller cup of the Little Dipper. These cups always appear to pour into each other as the stars wheel around the North Celestial Pole, anchored by Polaris.
The Moon passes 0.6° north of Pluto at 4 P.M. EST during daylight hours.
Sunrise: 7:19 A.M.
Sunset: 4:38 P.M.
Moonrise: 9:32 A.M.
Moonset: 7:04 P.M.
Moon Phase: Waxing crescent (9%)
Tuesday, December 23
Rising around midnight and visible in the early-morning sky, Comet 24P/Schaumasse glows at roughly 11th magnitude as it prepares to enter the rich Virgo Cluster.
Now in far southwestern Coma Berenices, Schaumasse is just 1.7° northwest of M98, an edge-on spiral galaxy that, at magnitude 10.1, glows slightly brighter than the comet. Not far away are M99 (a little farther southeast of Schaumasse) and M100 (about 3.4° east of the comet). M99 is a face-on spiral that contrasts nicely with M98, glowing at roughly the same magnitude (9.9). M100 is brighter at magnitude 9.3 — in fact, it’s one of the brighter galaxies in the Virgo Cluster, offering a lovely example of what astronomers call a grand design spiral, with well-defined arms wrapping around its bright nucleus.
Take your time with this region, enjoying the scene as the faint, fuzzy comet approaches the galactic gaggle. Schaumasse will be passing through this rich region for the rest of the month — hang onto the chart provided above to help you identify both the comet and the galaxies it’s passing over time.
Sunrise: 7:20 A.M.
Sunset: 4:39 P.M.
Moonrise: 10:03 A.M.
Moonset: 8:10 P.M.
Moon Phase: Waxing crescent (15%)
Wednesday, December 24
Dominating the main belt, dwarf planet 1 Ceres now shines at 9th magnitude in Cetus the Whale. The small dot is passing close to a background star this evening, appearing as one component in a temporary double system you can enjoy for one night only.
Ceres is located about 4.4° northeast of magnitude 3.6 Iota (ι) Ceti, which itself stands to the upper right of brighter magnitude 2.0 Diphda (Beta [β] Cet) in the south around 8 P.M. local time. Once you’ve found Iota, skim slowly northeast with binoculars or a telescope, looking for a 7th-magnitude star. This is HD 3126 (also cataloged as HIP 2710) — it may even be in your go-to scope’s stellar library, allowing you to zoom right over with the push of a button. Once there, Ceres is the fainter spot just 2’ north of this star.
Earlier in the evening, Titan makes its last transit of Saturn for the year. This event is largely only visible for observers in Europe and the U.K. The transit begins at 16:58 UT (11:58 A.M. EST) and ends about six hours later, around 23:50 UT. Note that this is 5:50 P.M. EST, so quick observers on the U.S. East Coast might be able to catch the last few moments of the transit, as Titan slides off the ringed planet’s northwestern limb.
Sunrise: 7:20 A.M.
Sunset: 4:40 P.M.
Moonrise: 10:29 A.M.
Moonset: 9:17 P.M.
Moon Phase: Waxing crescent (24%)
Thursday, December 25
As Orion and Gemini rise in the east after dark, they carry between them the lesser-known constellation Monoceros. Within this star pattern is our target for tonight: the festive Christmas Tree Cluster.
Cataloged as NGC 2264, this pine tree-shaped group of stars is part of a combination open cluster and star-forming region. It lies near the Cone Nebula, which appears to reach toward the top of the tree as if to touch it.
To find the magnitude 3.9 cluster, wait until around 9 or 10 P.M. local time, when this region reaches 40° in altitude above the eastern horizon. Look with binoculars or a telescope toward the region between Orion and Gemini, about 6.5° south of 2nd-magnitude Gamma (γ) Geminorum or 11.5° east of magnitude 0.5 Betelgeuse in Orion. You’re looking for several bright stars in the rough shape of a triangle or arrowhead, pointing toward the south. (Note that this means the top of the tree might not be oriented up in your eyepiece.) The base of the tree, its trunk, is anchored by the cluster’s brightest star, magnitude 4.7 15 Monocerotis. Under magnifications of 50x, about a dozen stars will appear. Higher powers reveal more stars. The entire cluster stretches about 20’ on the sky.
Observers with larger scopes (on the order of 12 inches) will begin to pick up some of the nebulosity of the surrounding star-forming region. The adjacent Cone Nebula may start to appear as well, also visible only in large scopes.
Sunrise: 7:20 A.M.
Sunset: 4:40 P.M.
Moonrise: 10:53 A.M.
Moonset: 11:23 P.M.
Moon Phase: Waxing crescent (33%)
Friday, December 26
The Moon passes 4° north of Saturn at 11 P.M. EST. The pair is visible all evening, sinking toward the western horizon later on. Earlier in the evening, around 7 P.M. local time, the two worlds stand roughly 40° high in the southwest, with Saturn to the lower left of the nearly First Quarter Moon.
Saturn shines at magnitude 0.7, still easy to pick out with the naked eye. Through a telescope, its disk stretches 17” across, its rings some 39” from end to end. Those rings are tilted just 0.8° to our line of sight, appearing close to edge on. The planet’s brightest moon, Titan, lies just over 2’ west of the center of the planet. Far to the east, Iapetus is at its faintest (12th magnitude) nearly 8.5’ away. Closer to the ringed world are 10th-magnitude Tethys, Rhea, and Dione. These three moons cluster close to each other on Saturn’s western side tonight, inside the orbit of Titan.
Now drop your gaze far below Saturn toward the horizon. Do you see a similarly bright light, this one only about 13° high? That’s magnitude 1.2 Fomalhaut, the brightest star in Piscis Austrinus the Southern Fish. This young star is famous for the large, dusty disk of planet-forming material around it. Several years ago, astronomers found what they believed was a young planet orbiting within the disk, which they named Fomalhaut b. Yet in 2014, after 10 years of observations, it disappeared from view. Astronomers ultimately determined Fomalhaut b likely hadn’t been a planet at all, but a collection of debris from the previous smash-up of protoplanetary pieces within the disk. As that debris cloud expanded and spread out, it faded until it was no longer detectable from Earth.
Sunrise: 7:21 A.M.
Sunset: 4:41 P.M.
Moonrise: 11:15 A.M.
Moonset: 11:31 P.M.
Moon Phase: Waxing crescent (43%)
