Two of Jupiter’s Galilean moons cross the planet overnight, as their shadows race ahead. Which shadow will win?
By 9:30 P.M. EST, the shadows of Io and Callisto are roughly central on Jupiter’s disk, as Io prepares to transit. Europa and Ganymede lie to Jupiter’s west, outside this field of view. Credit: Alison Klesman (via TheSkyX)
- On November 19, Jupiter rises in Gemini at approximately 8:30 P.M. local time, where East Coast observers initially note Callisto’s and Io’s shadows near the planet’s southeastern limb.
- By 9:30 P.M. EST on November 19, both Io’s and Callisto’s shadows become roughly central on Jupiter’s disk, with Io commencing its transit across the disk at 9:37 P.M. EST.
- Io’s shadow completes its transit by 10:10 P.M. EST, followed by Callisto’s shadow disappearing before 11:30 P.M. EST, and Io’s full transit concluding prior to midnight EST.
- On November 21, Callisto is projected to begin its transit across Jupiter’s eastern limb at 5:53 A.M. EST, an event visible nationwide in the U.S.
Looking for a sky event this week? Check out our full Sky This Week column.
November 19: Venus rises in Libra
Tonight, all the action is over at Jupiter. The giant planet rises in Gemini around 8:30 P.M. local time; as soon as it’s visible above the horizon, East Coast observers will notice two dark shadows near the southeastern limb. The larger shadow closer to the planet’s center is Callisto’s, although that moon lies far to the planet’s east. Closer to the planet’s limb is Io’s shadow, which belongs to the small bright point that is also closer to the planet on the eastern side. Europa and Ganymede lie to Jupiter’s west.
By 9:30 P.M. EST, Io’s shadow has caught up to Callisto’s and both are roughly central on the disk, with Io’s shadow north of Callisto’s. Io is nearly at the limb — it begins a transit around 9:37 P.M. EST. Io’s shadow quickly overtakes Callisto’s, reaching the western limb first and exiting by 10:10 P.M. EST, with Io a little more than halfway in its journey across the disk from east to west. Callisto’s shadow is now nearing the southwestern limb, finally disappearing shortly before 11:30 P.M. EST. Io’s transit ends not long before midnight EST. Which of these events you will be able to see will depend on your time zone.
Tomorrow morning, starting at 5:53 A.M. EST on the 21st, Callisto will finally reach Jupiter’s eastern limb and begin to transit. Everyone across the U.S. will be able to catch the transit’s start, though the Sun will rise with Callisto still crossing the disk.
Sunrise: 6:51 A.M.
Sunset: 4:40 P.M.
Moonrise: 7:28 A.M.
Moonset: 4:33 P.M.
Moon Phase: Waxing 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 10 P.M. local time from the same location.
