Sunday, December 26
Mars passes 5° due north of Antares at 1 P.M. EST. Although daylight will hide them at that time, you can catch them again early this morning, about 10° above the horizon 30 minutes before sunrise.
Meanwhile, evening observers should zero in on Jupiter after sunset, where the Galilean moons are putting on a show. As darkness falls, you’ll see just three of the four moons: Callisto closest to the planet’s eastern limb, with Io and then Ganymede farther east. But keep an eye on things over the next few hours: By 8:24 P.M. EST, Europa is just poised to emerge from Jupiter’s long, dark shadow. It will reappear roughly 26" from the eastern limb — farther from the limb than Callisto now sits. That’s because the planet’s shadow stretches far out behind it, while Callisto is approaching from the front. It will begin transiting the disk at 8:53 P.M. EST and should be visible as a bright spot against the cloud tops alongside the Great Red Spot, also rotating across the visible face of the planet at the same time. Jupiter will set around 9 P.M. local time with Callisto still crossing its 36"-wide disk.
Last Quarter Moon also occurs tonight, with our satellite reaching this phase at 9:24 P.M. EST
Sunrise: 7:21 A.M.
Sunset: 4:41 P.M.
Moonrise: —
Moonset: 12:01 P.M.
Moon Phase: Waning gibbous (54%)
Monday, December 27
The constellation Lynx is climbing above the horizon at sunset tonight. Wait a few hours and then take advantage of the moonless sky before midnight to catch a glimpse of NGC 2419, the Intergalactic Wanderer.
This globular cluster earned is strange name thanks to its distance — some 300,000 light-years away. That’s nearly twice the distance to the Milky Way’s largest satellite galaxy, the Large Magellanic Cloud. Initially, astronomers weren’t sure this cluster orbited the Milky Way at all, but have since discovered that it does. Nonetheless, that vast distance is the reason NGC 2419 appears so faint (roughly magnitude 9, so opt for a 4-inch scope or larger), as it is physically quite large and intrinsically bright.
To find this compact cluster, it’s actually easier to use a guidepost in nearby Gemini: The bright star Castor sits 7° due south of the Intergalactic Wanderer. While you’re in the area, perhaps take some time to enjoy Castor itself, whose bright (2nd and 3rd magnitude, respectively) A and B components are just a few arcseconds apart. Castor C lies 1.2' to their south — see if you can also spot this 9th-magnitude star. Each of these three stars is a binary, bringing the total number of stars in this system to six.
Sunrise: 7:21 A.M.
Sunset: 4:42 P.M.
Moonrise: 12:08 A.M.
Moonset: 12:25 P.M.
Moon Phase: Waning crescent (43%)
Tuesday, December 28
Mercury has finally emerged from the Sun’s glare and is visible in the evening. Tonight, the solar system’s smallest planet passes 4° south of Venus at 8 P.M. EST. The two planets are below the horizon then, so instead catch them just after sunset, when they’re 4.2° apart and about 7° high in the southwest 30 minutes after the Sun disappears.
Venus is much brighter — magnitude –4.5 — while tiny Mercury still glows at a decent magnitude –0.8. It should be easy to catch both in binoculars or zoom in on one at a time with a telescope. Mercury’s face spans just 6" and is 84 percent lit; Venus is a much wider 59" but only 4 percent lit.
In the coming days, Mercury will continue to track higher in the sky each evening, becoming easier to catch for longer after sunset.
Sunrise: 7:21 A.M.
Sunset: 4:42 P.M.
Moonrise: 1:17 A.M.
Moonset: 12:51 P.M.
Moon Phase: Waning crescent (32%)
Wednesday, December 29
Rising with Gemini the Twins after sunset tonight is the open cluster Collinder 89. According to Astronomy columnist Stephen James O’Meara, this cluster could also be called the Peek-a-Boo Cluster because so many people see it without realizing!
The 20 or so stars of Collinder 89 shine with a total apparent magnitude of 5.7. They’re located in the 0.7°-wide space between the two brighter stars 9 and 12 Geminorum, which are magnitude 6 and 7, respectively. If you need a brighter signpost, start at Mu (μ) Gem, which shines at magnitude 2.9, and look 1.5° northwest. The best way to see this target is with binoculars or a low-power telescope eyepiece.
Take your time and enjoy this loose elliptical cluster — and then look (without changing your field of view) closer at 12 Gem to note that it is veiled in a 30'-wide reflection nebula: IC 444. If you can’t see it, make note of the field and bump up your aperture or power to try again. Visual observers will likely only see the brightest 10' of this nebula, but astroimagers will be able to pick up the full extent of its glow.
Sunrise: 7:22 A.M.
Sunset: 4:43 P.M.
Moonrise: 2:28 A.M.
Moonset: 1:21 P.M.
Moon Phase: Waning crescent (22%)
Thursday, December 30
Andromeda the Princess is high in the northern sky after sunset tonight — the perfect opportunity to hunt down the appropriately wintry themed Blue Snowball. Also cataloged as NGC 7662, this object is a planetary nebula created by a dying Sun-like star. As the star has aged, it’s blown off its outer layers into a spherical shell, subsequently lighting up this tenuous gas.
The Blue Snowball is about 2,200 light-years away. At that distance, it spans about 30" on the sky and glows at magnitude 8.3 — easy for binoculars or a small telescope. You’ll find it about 4.5° due east of magnitude 3.6 Omicron (ο) Andromedae, situated near this long constellation’s western border. Take a look for yourself and enjoy this nebula’s namesake bright blue color.
Sunrise: 7:22 A.M.
Sunset: 4:44 P.M.
Moonrise: 3:44 A.M.
Moonset: 1:56 P.M.
Moon Phase: Waning crescent (13%)