As Iapetus approaches eastern elongation, several of Saturn’s moons stand in a line on either side of the ringed world overnight tonight.
Several of Saturn’s moons are visible overnight as they line up east and west of the ringed planet. Iapetus is farthest east, glowing faintly at 12th magnitude — challenge yourself to spot it. Credit: Stellarium/Oleg Pluton
Saturn’s moon Iapetus is now some 8’ east of the planet; although it is nearing 12th magnitude as it approaches its fainter eastern elongation in the first week of October, observers with larger scopes may find it easier to see farther from the “noise” of the several moons that cluster closer to the ringed planet.
By 10 P.M. local daylight time, Saturn is more than 30° high in the southeast. It is the brightest point of light in this region, hanging just beneath the Circlet of Pisces. Zoom in on Saturn with a telescope and you’ll easily spot Titan, its largest and brightest moon, about 3’ east of the planet. Iapetus lies 4’ farther in the same direction, but again, it is roughly 12th magnitude (Titan is mid-8th magnitude).
Tenth-magnitude Tethys lies just west of the western edge of the rings, while Rhea lies between Titan and the eastern tip of the rings. Over the course of the night, Dione moves progressively eastward, approaching Rhea’s position early on the morning of the 1st if you follow the planet as it sinks in the west.
Mid-11th-magnitude Enceladus starts the evening on the northeastern side of the planet and passes behind it in an occultation beginning just before midnight EDT. It reappears at the northwestern limb around 2:30 A.M. EDT on the 1st.
Sunrise: 6:56 A.M.
Sunset: 6:43 P.M.
Moonrise: 3:21 P.M.
Moonset: —
Moon Phase: Waxing gibbous (57%)
*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.
For a look ahead at more upcoming sky events, check out our full Sky This Week column.