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elleng

(130,126 posts)
Wed Mar 31, 2021, 12:17 PM Mar 2021

Jupiter's equinox and mutual events of its 4 major moons

The king planet Jupiter reaches its equinox on May 2, 2021, an event that always causes mutual events of Jupiter’s 4 major moons. It’s an eclipse season of the moons.

The king planet Jupiter will reach an equinox – an event that happens twice in every 12-year orbit of Jupiter – on May 2, 2021. Around Jupiter’s equinoxes, we on Earth always have an opportunity to see a series of mutual events – or you might call them eclipses – of Jupiter’s four major moons. These are the four famous Galilean satellites, Io, Europa, Ganymede and Callisto. The eclipses are already happening. They’ll continue through August 2021. Experienced telescope users will be the ones seeing them; if you get an image, please submit it here. As the four large moons revolve around Jupiter, a moon shadow will sometimes eclipse (fall upon) a different moon. Or the body of one Jovian moon will occult (move directly in front) of another moon. For example, on April 4, Io’s shadow will fall upon Europa. The following day – April 5 – Io itself will occult the moon Ganymede.

It hasn’t happened (we haven’t had a Jupiter equinox) since February 4, 2015. The next eclipse season for Jupiter’s moons won’t come again until around Jupiter’s next equinox, on December 16, 2026.

These moons orbit in the plane of Jupiter’s equator. We see the shadows of Jupiter’s moons eclipsing other moons at or near a Jovian equinox, because that’s when the shadows of Jupiter’s moons align with Jupiter’s equatorial plane. At times other than near a Jovian equinox, the moon shadows slant relative to the Jovian equator; they angle north or south of the other moons, and no eclipses take place.

https://earthsky.org/astronomy-essentials/jupiter-equinox-mutual-events-moon-2021?

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