The first of two Titan shadow transits this month occurs this morning — can you catch the big, black shadow crossing Saturn’s cloud tops?
Titan’s shadow transits Saturn’s northern hemisphere Aug. 2/3, reaching nearly halfway across by 4:30 AM EDT on the 3rd. Note that Epimetheus, Janus, Pandora may not be visible due to their faintness. Credit: Stellarium/Oleg Pluton/Magenta Meteorite
- Observers in the U.S. can witness the transit of Titan’s shadow across Saturn’s northeastern limb, beginning approximately 2:03 A.M. EDT on the specified date.
- The shadow’s transit will last roughly an hour and fifty minutes, traversing Saturn’s disk from east to west, concluding around 5:12 A.M. MDT.
- Concurrently, the moons Enceladus and Tethys will also be transiting Saturn’s rings, observable primarily through imaging due to their faint magnitudes (11.8 and 10.3, respectively).
- Saturn’s rings, spanning 40″ end-to-end and only 2.5″ in thickness, will provide a striking backdrop to the celestial event; Saturn itself can be readily located in Pisces, below the Circlet asterism.
U.S. observers can catch the first of two transits of Titan’s shadow across Saturn this month — and one of the last few of the year, before cosmic alignment that allows the shadow to cross the cloud tops comes to an end.
Saturn now rises shortly after 10 P.M. local daylight time and is located in Pisces, hanging below the Circlet asterism. Shining at magnitude 0.8, it’s brighter than the nearby stars, making it easy to pick out in the sky. By local midnight, it is roughly 20° high in the east. Point your telescope at the ringed world, and you should also capture distant Neptune (magnitude 7.7) in your field of view. The ice giant is just over 1° north of Saturn, and will sit exactly due north of Saturn in just a few days.
Saturn’s rings are, as always, stunning. They are also quite thin, with the narrow axis spanning just 2.5”. They stretch more than 40” from end to end.
But today, our attention is on the northeastern limb of Saturn. Note that Titan, easily visible at mid-8th-magnitude, lies some 15” from the planet. But at 2:03 A.M. EDT — note this is just after midnight in the Mountain time zone and still late on the 2nd in the Pacific time zone — Titan’s shadow begins to appear on the northeastern limb, taking nearly 20 minutes to fully appear. The shadow slowly crosses from east to west, reaching roughly midway on the disk around 4:30 A.M. EDT. Titan is now 10” from the planet.
The shadow finally reaches the northwestern limb and begins to disappear around 5:12 A.M. MDT — after sunrise in the Midwest, leaving only the western half of the U.S. to view its exit. As with ingress, it takes about 20 minutes for the shadow to fully disappear.
There’s an added bonus for imagers: During this time, two of Saturn’s smaller, fainter moons are also transiting. Enceladus (magnitude 11.8) and Tethys (magnitude 10.3) appear just north of the rings for much of the shadow’s transit. Timing-wise, Enceladus begins to transit around 2:10 A.M. EDT, while Tethys’ transit begins around 2:33 A.M. EDT. They take 2.5 hours to cross the disk and will be difficult to see visually, but may be picked up by imaging.
Sunrise: 6:01 A.M.
Sunset: 8:11 P.M.
Moonrise: 4:09 P.M.
Moonset: 12:25 A.M.
Moon Phase: Waxing gibbous (70%)
*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.