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Ephemeris: 10/09/2025 – Eclipses and occultations of Jupiter’s satellites by each other

October 9, 2025

This is Ephemeris for Thursday, October 9th. Today the Sun will be up for 11 hours and 17 minutes, setting at 7:08, and it will rise tomorrow at 7:52. The Moon, 3 days past full, will rise at 8:16 this evening.

To astronomers the word occult doesn’t mean what you think it means. It’s not a mysterious thing, but the word occult simply means hidden, when one body hides behind another. For example, a solar eclipse isn’t really an eclipse by astronomical standards it is an occultation: the Sun hides behind the Moon. But, a lunar eclipse is really an eclipse where the Moon enters the Earth’s shadow. There is a period for the next 2½ years when Jupiter’s satellites will be both occulting and eclipsing each other. This can easily be seen in a small telescope or even binoculars. Satellites will slowly seem to merge in occultations and disappear, for some minutes, being eclipsed in another satellite’s shadow. The main show starts in May next year and ends in August 2028.

The astronomical event times given in this blog are for the Traverse City/Interlochen area of Michigan (Lat 44.7° N, Long 85.7° W; EDT, UT – 4 hours) unless stated otherwise. Times will be different for other locations.

Addendum

Example of a deep total occultation of Europa
Example of a deep occultation of Europa, by Io on September 8, 2026. Diagram created by the Occult app by the International Occultation Timing Association (IOTA).
Example of an eclipse of Europa in Io's shadow
Example of an eclipse of Europa in Io’s shadow on October 14, 2026. Diagram created by the Occult app by the International Occultation Timing Association (IOTA).

IOTA’s website is occultations.org. Occult is free software. Besides occultations, it can be used to investigate historical and future solar and lunar eclipses, and transits of Mercury and Venus across the face of the Sun. And more.

Categories: Eclipses, Ephemeris Program, Observing, Occultation