APOD

Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

To view this video please enable JavaScript, and consider upgrading to a web browser that supports HTML5 video

Explanation: Jupiter is one of the least lonely planets in the Solar System, at least when it comes to natural satellites . 115 moons have been discovered orbiting Jupiter so far! ( Saturn has the most with 293, but who’s counting . ) Ganymede and Io , two of Jupiter’s Galilean moons , met in the sky on October 20th, 2026. Today’s video captures the meeting, with Ganymede briefly blocking Io from view. This event, when an astronomical object passes in front of another and either completely or partially blocks it, is called a mutual occultation. The mutual occultations of Galilean moons are rare to witness because they require Earth’s edge-on view of their orbits.…