Friday, December 13
The bright gibbous Moon passes 4° north of Uranus at 5 A.M. EST. At that time, the Moon sits in Aries the Ram, while Uranus is just over the border in far western Taurus the Bull. The two set together around 5 A.M. local time.
You might have better luck spotting the ice giant in the evening sky, some 40° high in the east two hours after sunset and with the Moon farther away now, hanging nearly 11° above bright Aldebaran, Taurus’ red giant eye.
Uranus is located 7.5° southwest of the Pleiades, and about 2.4° south-southwest of the 5th-magnitude star 63 Arietis. The planet, at magnitude 5.6, is easy to spot in binoculars or any small scope, though the brighter background sky due to the still-nearby Moon may make it a bit more challenging than under darker conditions. Look for a small, “flat” star with a grayish-blue hue. You might also notice the planet’s 4”-wide disk looks like a tiny circle, rather than a pinpoint of light (as stars appear).
The Geminid meteor shower peaks this morning, though with the bright Moon in the sky, its usual stunning display will be quite muted. After darkness falls this evening, you can still keep an eye out for shower meteors, originating from the radiant near the heads of Gemini the Twins. However, again the bright Moon’s light will interfere, and by evening the Moon is even closer to Gemini, further diminishing prospects.
The Ursid meteor shower, which peaks a few days before Christmas, will take place under darker skies. So, stay tuned — we’ll make sure to highlight that event when it occurs.
Sunrise: 7:14 A.M.
Sunset: 4:35 P.M.
Moonrise: 2:54 P.M.
Moonset: 5:26 A.M.
Moon Phase: Waxing gibbous (96%)
*Times for sunrise, sunset, moonrise, and moonset are given in local time from 40° N 90° W. The Moon’s illumination is given at 12 P.M. local time from the same location.
Saturday, December 14
Asteroid 15 Eunomia reaches opposition in the constellation Auriga at 1 A.M. EST; unfortunately, the Moon again interferes, located nearby in northern Taurus. However, at 8th magnitude, Eunomia should still be visible to larger scopes even with the bright background light, although the stunning deep-sky objects it is passing in this region of sky will likely be washed out. Check out the chart above and make sure to revisit Auriga later in the month after the Moon has passed by; you’ll have better luck with both the asteroid and the star clusters and nebulae it’s near.
The Moon passes 5° north of Jupiter in Taurus at 3 P.M. EST; both are already above the eastern horizon at sunset and stand side by side as they rise, gaining altitude as darkness falls. The Moon is very nearly Full, a phase it will reach early tomorrow morning, but fortunately Jupiter is still at its brightest, so its magnitude –2.8 glow will still cut through the bright moonlight to reach your naked eye. The planet now stands as the middle point in a line drawn between the Moon and Aldebaran, a wonderful sight for all to see in the evening sky.
If you’ve got a telescope, you can zoom in further on Jupiter to examine the colored cloud bands visible on its 48”-wide disk and look for its four Galilean moons. For three hours, between about 6:35 P.M. and 9:35 P.M. EST, only three moons are visible: Io alone to the west and Ganymede (closer) and Callisto to the east. Shortly before 9:35 P.M. EST, Europa appears just off Jupiter’s northeastern limb, having crossed behind the planet and through its currently short, dark shadow, thanks to the geometry of opposition.
Sunrise: 7:15 A.M.
Sunset: 4:35 P.M.
Moonrise: 3:53 P.M.
Moonset: 6:43 A.M.
Moon Phase: Waxing gibbous (99%)
Sunday, December 15
The last Full Moon of 2024 occurs at 4:02 A.M. EST. December’s Full Moon is also called the Cold Moon, as it occurs when colder temperatures are falling across North America.
Even as the Full Moon is setting in the west in the hour before dawn, Mercury is reaching its stationary point against the background stars of Scorpius in the southeastern sky. An hour before sunrise, the tiny planet is nearly 5° high, glowing at magnitude 0.4. It’s the brightest point of light in this region of the sky, especially as the morning twilight grows. Through a telescope, the planet shows off an 8”-wide disk that is some 30 percent lit; it will reach 50 percent lit in just a few days, so we’ll return to see how it has changed.
Mercury officially reaches its stationary at 4 P.M. EST, ending its current retrograde (westward) motion and quickly moving east (prograde) again.
Sunrise: 7:15 A.M.
Sunset: 4:36 P.M.
Moonrise: 4:41 P.M.
Moonset: 7:54 A.M.
Moon Phase: Full
Monday, December 16
Double stars can provide the perfect opportunity to view contrasting star colors in one place. The most famous example is Albireo in Cygnus the Swan, but 145 Canis Majoris is another one — so like the former that it’s sometimes called the Winter Albireo.
Canis Major is one of the standout constellations in the winter sky, following its master, Orion the Hunter, up into the sky from the east toward the south as the evening progresses. Located near the hindquarters of the Big Dog, 145 Cma is some 25° high in the south around midnight. It’s just 3.6° northeast of magnitude 1.8 Wezen (Delta [δ] Cma), and about 10° east-southeast (to the lower left) of blazing Sirius.
Shining with a total magnitude of 4.8, 145 Cma consists of a cooler, golden star nestled near a hotter, bluish star, just as the “real” Albireo at the head of Cygnus the Swan. At some 27” apart, most instruments will find the pair relatively easy to split.
Sunrise: 7:16 A.M.
Sunset: 4:36 P.M.
Moonrise: 5:49 P.M.
Moonset: 8:53 A.M.
Moon Phase: Waning gibbous (97%)
Tuesday, December 17
Slowly setting toward the horizon as the evening progresses, Saturn now hangs some 40° high in the south an hour after sunset. Glowing at magnitude 1 through the end of the year, the ringed planet is the brightest point of light in Aquarius and the surrounding constellations, hanging below the Circlet of Pisces. Closer to the horizon, directly below Saturn in the early evening, is magnitude 1.2 Fomalhaut, Piscis Austrinus’ alpha star.
Through a telescope, Saturn’s 17”-wide disk is flanked by its stunning rings, now tilted just under 5° to our line of sight. Over the next few months, the rings will narrow until they virtually disappear as Earth passes through the plane of the rings, although the actual date of the ring-plane crossing occurs when Saturn is too close to the Sun to view. At present, those rings appear to stretch nearly 40” from end to end, offering an excellent target through a telescope even at the low viewing angle.
The planet’s brightest moon, 8th-magnitude Titan, lies nearly 2.5’ to the east, while several of its fainter, 10th-magnitude moons cluster closer to the disk. Tethys spends the early evening just north of the eastern portion of the rings, while Rhea and Dione stand to the west; Rhea is slightly closer to Saturn than Dione, and stands southeast of the latter moon.
Sunrise: 7:17 A.M.
Sunset: 4:36 P.M.
Moonrise: 6:59 P.M.
Moonset: 9:41 A.M.
Moon Phase: Waning gibbous (93%)
Wednesday, December 18
The Moon passes 0.9° north of Mars at 4 A.M. EST. You can easily catch the pair before sunrise this morning — an hour before local sunrise, they’re 40° high in the west in central Cancer, near the Beehive open cluster (M44). Of course, the Moon’s bright light will likely wash out the cluster itself, but Mars is glowing at magnitude –0.9, quickly brightening as it approaches opposition in about a month.
Mars sits just to the lower right of the waxing gibbous Moon this morning. Through a telescope, the Red Planet now appears 13” wide and 96 percent lit. Because this upcoming opposition will be an aphelic opposition, when Mars is around its farthest point from the Sun, the planet won’t grow much larger even at opposition, only stretching to 15” wide around that date early next year.
To the pair’s lower right as sunrise approaches are the bright stars Castor and Pollux, which mark the heads of Gemini the Twins. To those stars’ lower left is Procyon, the nose of Canis Minor the Little Dog, while to their lower right is Capella, the alpha star of Auriga. Bright Jupiter, which outshines all these suns, is just barely above the horizon, setting around 6:30 A.M. local time.
Sunrise: 7:17 A.M.
Sunset: 4:37 P.M.
Moonrise: 8:09 P.M.
Moonset: 10:17 A.M.
Moon Phase: Waning gibbous (87%)
Thursday, December 19
With no Moon in the evening sky, the stars of the Little Dipper will be discernible to the naked eye from a dark site tonight. Early in the evening, the dipper is swinging from west to east, hanging directly from its handle mid-evening.
Pinned in the north, this famous asterism is part of the larger constellation Ursa Minor the Little Bear. Its handle is anchored by the North Star, the only star in the northern sky that does not appear to move as Earth rotates on its axis. Also cataloged as Alpha (α) Ursae Minoris or Polaris, this 2nd-magnitude star is far from the brightest, but gets its notoriety from its current location above the North Celestial Pole.
From Polaris, the Little Dipper’s handle is composed of two more stars: 4th-magnitude Yildun (Delta Umi) and similarly bright Epsilon (ε) Umi. Epsilon connects the handle to the cup of the dipper at 4th-magnitude Zeta (ζ) Umi. Moving clockwise, the other stars in the cup are 2nd-magnitude Kochab (Beta [β] Umi), 3rd-magnitude Pherkad (Gamma [γ] Umi), and 5th-magnitude 19 Umi.
Sunrise: 7:18 A.M.
Sunset: 4:37 P.M.
Moonrise: 9:16 P.M.
Moonset: 10:47 A.M.
Moon Phase: Waning gibbous (79%)
Friday, December 20
Mercury reaches 50 percent lit today, an event you can observe in the early-morning sky in the hour before sunrise. The planet has brightened to magnitude 0 and stands near the border of Scorpius and Ophiuchus, already some 7° high an hour before sunrise.
Through a telescope, Mercury’s half-lit face has lost a bit of size, now spanning closer to 7” as its distance from Earth increases. It now stands some 0.9 astronomical unit away; one astronomical unit is the average distance between Earth and the Sun (93 million miles or 150 million kilometers). Do make sure to put away any optics you’re using well before sunrise from your location, which could differ from the time listed below.
High above Mercury in the early-morning sky, the slightly brighter (magnitude –0.1) star Arcturus rules the southeast, while 1st-magnitude Spica sits far to Mercury’s upper right and Arcturus’ lower left. As sunrise approaches, see if you can also spot 1st-magnitude Antares peek above the horizon to Mercury’s lower right, although it will be a battle between the star’s light and the approaching dawn.
Sunrise: 7:18 A.M.
Sunset: 4:38 P.M.
Moonrise: 10:19 P.M.
Moonset: 11:11 A.M.
Moon Phase: Waning gibbous (70%)
Sky This Week is brought to you in part by Celestron.