Friday, December 9
Jupiter’s moons open this week with an alternating disappearing and reappearing act. Look southwest late this night to search out magnitude –2.5 Jupiter standing left (southeast) of the Circlet of Pisces. Zero in on the planet with a telescope and round 10 P.M. EST, you’ll discover solely three moons are seen: Callisto to the east, and Europa (nearer to the planet) and Ganymede to the west.
However preserve watching. Europa is inching nearer to Jupiter’s western limb. Simply after 10:40 P.M. EST, Europa disappears behind the gas giant in an occultation. Not a lot later, shortly after 11 P.M. EST, look off to the planet’s east, the place Io pops again into view because it slides out of Jupiter’s darkish shadow. That shadow stretches fairly far — Io will reappear some 25″ off the planet’s limb.
Additionally seen round this time is Jupiter’s well-known Nice Crimson Spot. Round 9 P.M. EST, it ought to seem roughly halfway throughout the disk, simply south of the equator. It’s shifting from east to west because the planet rotates and needs to be seen for an additional two hours or so earlier than it slides across the seen limb.
Dawn: 7:10 A.M.
Sundown: 4:34 P.M.
Moonrise: 5:38 P.M.
Moonset: 8:44 A.M.
Moon Section: Waning gibbous (98%)
*Occasions for dawn, sundown, moonrise, and moonset are given in native time from 40° N 90° W. The Moon’s illumination is given at 12 P.M. native time from the identical location.
Saturday, December 10
Saturn’s largest moon, Titan, sits due north of the planet tonight. To search out it, look southwest an hour or two after sundown, the place Saturn glows at magnitude 0.7 in Capricornus the Sea Goat. The planet now sits 3.5° west of Deneb Algedi.
By way of a telescope, Saturn’s disk stretches 16″ throughout, whereas its rings are barely greater than double that width. These rings are slowly getting narrower because the planet’s tilt adjustments with respect to our line of sight, dropping beneath 14° by the top of the month.
Along with Titan immediately north, Saturn is accompanied by a number of smaller and fainter moons. Tenth-magnitude Tethys, Dione, and Rhea sit to the planet’s west and south — Tethys is due west, Dione is southwest, and Rhea is due south. You’ll want a bigger scope to choose up these moons, as they’re dimmer than magnitude 8.5 Titan. If you wish to see them, decide to look earlier within the night fairly than later, because the turbulent air close to the horizon will make these satellites more durable to identify because the planet sinks. Saturn units round 9:30 P.M. native time.
Dawn: 7:11 A.M.
Sundown: 4:34 P.M.
Moonrise: 6:33 P.M.
Moonset: 9:35 A.M.
Moon Section: Waning gibbous (94%)
