NASA posted an Astronomy Picture of the Day video showing a rare mutual occultation between Jupiter’s moons Ganymede and Io, with Ganymede briefly blocking Io from view, according to NASA’s explanation. The video is credited to Michael Wong. The APOD entry is dated Oct. 28, 2026.
NASA said the meeting of the two Galilean moons took place on Oct. 20, 2026. The agency described a mutual occultation as an event in which one astronomical object passes in front of another and either completely or partially blocks it.
The agency said such occultations among the Galilean moons are rare to witness because they require Earth’s edge-on view of their orbits. According to the explanation, that viewing geometry occurs once every six years when Jupiter reaches its equinox and appears less “tilted”.
The video also shows Ganymede casting its shadow on Jupiter’s right side, NASA said. The explanation adds that any fictional Jovian species within the shadow would experience a solar eclipse.
NASA’s explanation also notes the scale of Jupiter’s satellite system. It says 115 moons have been discovered orbiting Jupiter so far. It adds that Saturn has the most with 293.
Astronomy Picture of the Day features a different image or video of space each day, along with a brief explanation written by a professional astronomer, according to the page. The APOD entry credits authors and editors Keighley Rockcliffe, Robert Nemiroff, Jerry Bonnell and Cecilia Chirenti.