Sky This Month: December 2022

Saturn is over 30° excessive within the south at nightfall in early December. However catch it early, because the ringed planet units by 10 P.M. native time on Dec. 1 and at 8 P.M. by Dec. 31. Saturn lies in jap Capricornus and begins the month at magnitude 0.7, dropping to magnitude 0.8 by the twenty third. Its disk spans 16″ and the rings stretch an impressive 36″.

The rings’ obvious tilt to our line of sight drops beneath 14° late in December. A waxing crescent Moon stands 5° southeast of the planet on Dec. 26.

Titan, Saturn’s largest moon, is magnitude 8.5 — a simple goal for small scopes. Discover it north of Saturn Dec. 10 and 26, and due south Dec. 2 and 18. Fainter Tethys, Dione, and Rhea shine at magnitude 10 and lie inside Titan’s orbit. They grow to be more and more troublesome to identify because the planet’s altitude drops later within the night.

Search for Eleventh-magnitude Iapetus Dec. 22 and 23. It reaches inferior conjunction early on the twenty third and U.S. observers on the night of the twenty second may spot the faint moon passing in entrance of the rings. Iapetus will seem darkish towards the brighter B ring. The transit is underway as darkness falls alongside the jap seaboard.

On the twenty third, Iapetus passes briefly very near Tethys, beginning round 6:23 P.M. EST. The pair will seem to merge in a telescope. An hour later, as darkness falls throughout the Midwest, they’re 3″ aside.

Good Jupiter is a helpful information to search out distant Neptune in Aquarius these winter evenings. In early December, Neptune stands 6° west of Jupiter. That distance extends to eight° by the thirty first, due largely to Jupiter’s easterly movement alongside the ecliptic. Neptune shines at magnitude 7.9, requiring at the least binoculars to identify.

Neptune is positioned conveniently between two Seventh-magnitude stars all month. The planet is retracing its steps from November because it turns eastward on Dec. 4. The 2 stars are the easternmost pair of a parallelogram of 4 stars every about 1° aside, situated 5° northeast of Phi (ϕ) Aquarii and simply recognized with binoculars.

Catch Neptune early, because it units by 1 A.M. Dec. 1st and shortly earlier than 11 P.M. on the thirty first. Telescopes reveal a dim bluish disk spanning 2″. The waxing crescent Moon lies 3° south of Neptune on Dec. 28.

Jupiter is tough to overlook because the brightest planet within the sky after Venus units. It’s excessive in Pisces within the south after sundown. The large planet dims from magnitude –2.6 to –2.4 throughout the month. It’s transferring east, deeper into Pisces and away from Aquarius.

Jupiter’s disk slims from 43″ to 39″, however stays a powerful sight with a wealth of atmospheric particulars. Start observing Jupiter in late twilight for the perfect views, when its brilliance is tempered by the brighter sky and the darkish pair of equatorial belts leap out. Finer particulars seem with affected person consideration. Each different evening or so, the Nice Purple Spot makes a grand look.

Io, Europa, Ganymede, and Callisto often change place and transit Jupiter, casting their accompanying shadows. Io begins the month with a transit Dec. 1 at 8:25 P.M. EST. Its shadow follows 77 minutes later. Watch as Jupiter sinks within the west; Io leaves the disk at 10:39 P.M. EST, adopted by the shadow’s egress at 11:54 P.M. EST. The occasion repeats the night of Dec. 8, starting at 10:19 P.M. EST.

Io and Europa placed on a present Dec. 9, beginning as Europa passes behind the planet’s western limb at 10:43 P.M. EST. After Europa disappears, look to the jap limb to look at Io come out of eclipse about 25″ from the planet at 11:01 P.M. EST.

Callisto skims due south of Jupiter early on the night of Dec. 13. Its orbital airplane is such that the moon misses transiting or being eclipsed, however this move is de facto near a transit. Are you able to make out any darkish space between the planet and moon?

Dec. 15 finds the massive shadow of Ganymede transiting Jupiter. It exhibits up on the southern temperate belt beginning at 7:41 P.M. EST, however the shadow is so massive that you could be see it start to look a couple of minutes earlier. The shadow takes almost two hours and 40 minutes to transit. And you may spherical out the 12 months by observing the Dec. 29 transit of Ganymede beginning at 10:11 P.M. EST and lasting almost three hours. The Royal Astronomical Society of Canada’s Observer’s Handbook provides a whole listing of occasions.

Uranus lies in southern Aries as a simple binocular goal at magnitude 5.7. It’s seen all evening and is highest within the hour or two earlier than native midnight. Its 4″-wide bluish disk is a problem in a telescope.

Uranus lies about 6° north-northeast of Mu (μ) Ceti. The simplest technique to discover it’s to look north of Mu for Fifth-magnitude Sigma (σ) Arietis, adopted 3° farther alongside the identical line by Rho (ρ) Arietis. Uranus begins the month halfway between these two stars, transferring slowly southwest and passing 1° due north of Sigma on Dec. 13. Each match simply inside the sphere of view of 7×50 binoculars or a low-power telescope. That very same evening, Pi (≠) Arietis stands 1.5° northwest of Uranus.