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Astronomy Picture of the Day - The Mutual Occultation of Ganymede and Io
NASA ^ | 28 Oct, 2026 | Credit & Copyright: Michael Wong

Posted on 10/28/2026 12:58:25 PM PDT by MtnClimber

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. This occurs once every 6 years when Jupiter reaches its equinox and appears less “tilted”. Ganymede is also casting its shadow on Jupiter’s right side. Any fictional Jovian species within the shadow would experience a solar eclipse!


TOPICS: Astronomy; Astronomy Picture of the Day; Science
KEYWORDS: apod; nasa

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Today's image is a short video at the source link.

1 posted on 10/28/2026 12:58:25 PM PDT by MtnClimber
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To: 21stCenturion; 21twelve; 31R1O; 4everontheRight; A Navy Vet; A_perfect_lady; abb; AFB-XYZ; ...
Pinging the APOD list

🪐 🌟 🌌 🍔

Today's image is a short video at the source link.

2 posted on 10/28/2026 12:59:05 PM PDT by MtnClimber (For photos of scenery, wildlife and climbing, click on my screen name for my FR home page.)
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To: MtnClimber

“mutual occultation” — frisky planets getting kinky!


3 posted on 10/28/2026 1:12:58 PM PDT by ProtectOurFreedom
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To: MtnClimber

Darn, I missed it.It would’ve been really cool to see it through the eyepiece, to watch both moons merge into one and separate back into two again.


4 posted on 10/28/2026 3:22:21 PM PDT by telescope115 (Ad Astra, Ad Deum…)
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To: ProtectOurFreedom
“mutual occultation” — frisky planets getting kinky!

In case anyone is interested:

A mutual occultation is an occultation between two bodies of the same type — planet–planet or satellite–satellite — where the nearer body appears larger in angular size and partially or fully hides the farther one. The "mutual" signals that both bodies are of comparable status, not that each one simultaneously hides the other.

A "non-mutual occultation" is not a standard term — it would simply be what everyone calls a regular occultation: one body (typically much larger in apparent size, or of a different category) passing in front of another. Examples:

* The Moon occulting a star (the most common type)

* The Moon occulting the Sun (a total solar eclipse)

* A planet occulting a background star

The distinction is purely taxonomic
Regards,
5 posted on 10/29/2026 1:17:59 AM PDT by alexander_busek (Extraordinary claims require extraordinary evidence.)
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