Key Takeaways:
- On September 20th, beginning around 12:30 A.M. EDT, Titan, a moon of Saturn, will transit across the planet's disk, accompanied by its shadow.
- The transit will be visible telescopically, with Titan's crossing commencing approximately 12:33 A.M. EDT, followed by its shadow at 12:37 A.M. EDT. The event concludes with the shadow's departure at 4:04 A.M. EDT and Titan at 4:37 A.M. EDT.
- Other Saturnian moons, including Tethys, Rhea, and Dione, will be observable during this event, though Enceladus' transit may be obscured.
- This Titan shadow transit is a relatively rare occurrence, with the next similar event not expected for over a decade.
Shortly after September 20 begins in the Eastern time zone, Saturn’s moon Titan transits the ringed world alongside its shadow — the second-to-last shadow transit we will see for more than a decade.
The event starts around 12:30 A.M. EDT on September 20 — note this is early Saturday for those on Eastern time, but late Friday night for U.S. time zones farther west. At that time, Saturn stands some 40° high in the southeast, located to the lower left of the Circlet in Pisces. The planet is the brightest point of light in that region of the sky, shining at magnitude 0.6.
Zoom in on Saturn with a telescope and you’ll see mid-8th-magnitude Titan approaching the planet’s northeastern limb shortly before 12:30 A.M. EDT. It crosses in front of the disk starting around 12:33 A.M. EDT, taking several minutes to fully cross the limb. Five minutes later, around 12:37 A.M. EDT, the moon’s shadow begins to appear, slightly farther north on the limb.
The two cross the disk of Saturn together, reaching roughly halfway in their journey around 2:30 AM EDT (now the 20th in all time zones but Pacific). About 90 minutes later, the shadow slips off the disk first, disappearing by 4:04 A.M. EDT. Titan’s transit ends half an hour later, at 4:37 A.M. EDT.
Several other moons are visible during the transit as well, including 10th-magnitude Tethys, Rhea, and Dione. Check the chart above for their locations. Enceladus is transiting with its shadow around the same time as Titan, but closer to the rings, just north of them. This moon is much smaller and fainter than Titan, and will likely be lost in the glare.
Sunrise: 6:46 A.M.
Sunset: 7:00 P.M.
Moonrise: 5:30 A.M.
Moonset: 6:32 P.M.
Moon Phase: Waning crescent (1%)
*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.
