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On Earth, the planet has a single moon and a single sun. And as long as the moon stays within a certain proximity of Earth (apparently, it's slowly drifting further away), a total eclipse occurs at a point on Earth once every 400 years or so.

That's a long time. So I'm trying to devise a hypothetical system whereby a total eclipse at the same point on the planet can occur on a much more regular basis. Ideally, I'd like this to be on once per month basis.

Initially, I thought a binary-system would help -- more objects to obscure. However, it would seem that the more suns we include in the system, the more points of failure we have, since each would need to be blocked out to form a total solar eclipse. And as soon as we start relying on multiple moons covering up multiple suns at just the right time, the probabilities start to work against us, as I understand it. If this is the case, then we're back to square-one, a single sun.

Question

How can we maximize (greatly increase, not looking for perpetual total eclipse) the number of total solar eclipses that occur on a planet on a given point on a planet?

Further clarifications:

Can tweak anything about the solar system or planet, for example:

  • Number of stars
  • Number of moons
  • Orbital eccentricity

For the sake of simplicity, the goldilocks-zone-related habitability concerns can be out of the remit of this question. Instead, let's just zero in on what stellar / planetary configuration can maximize the number of total eclipses for a given point on the planet.

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  • $\begingroup$ What is your unit of time here? Per unit time or per lunar revolution? $\endgroup$
    – cms
    Commented Sep 10, 2021 at 12:27

2 Answers 2

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All you need is to flatten the orbits and make them circular

The reason total eclipses do not happen more often on Earth is that the orbit of Luna around Earth, and Earth around Sol, are elliptical and inclined.

enter image description here

All you need to make eclipses happen more frequently in this configuration is to...

  • Flatten the orbit, make Luna's orbit be in plan with Earth's orbit around Sol
  • Make the orbits be circular instead of elliptical
  • Move Luna a little bit closer, to ensure the shadow is large enough to cover the Earth

Note that the last two points work together, so you do not need a perfectly circular orbit, as long as the size of the shadow is large enough to cover the planet.

With this you will have a total eclipse once per orbit of the satellite around the main planet.

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    $\begingroup$ +1 for orbital inclination and "Move Luna a little bit closer, to ensure the shadow is large enough to cover the Earth" I think distance and size would be major factors ! The larger and nearer your moon is, the more chance you'll have a full solar eclipse. When your planet is farther away from the sun, same thing.. sun looks smaller, so it is covered more easily. $\endgroup$
    – Goodies
    Commented Sep 10, 2021 at 13:12
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    $\begingroup$ Equivalent to or in conjunction with making the moon closer: make it bigger. $\endgroup$ Commented Sep 10, 2021 at 21:14
  • $\begingroup$ How much more or less common are systems matching the one described in this answer (no inclination in the orbits of at least 1 planet and 1 moon as well as circular orbits) in real life? I'm guessing them to be very rare? $\endgroup$
    – Sixtyfive
    Commented Sep 11, 2021 at 20:50
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Gas Giant Moons

If your "planet" is actually a moon of a gas giant, the Jovian will cause many total eclipses.

Ganymede orbits Jupiter every 7 days, and Europa every 3.5, and every orbit will cause a total eclipse for whatever hemisphere of the moon is facing the sun. If you set the orbital period and rotational period right, every place on the moon could see an eclipse once a week.

Bonus Points

Potentially, you could get much more infrequent moon-moon eclipses, where one of the other moons aligns between your habitable moon and the sun. Since Jupiter has 4 moons that are roughly Luna size or larger, it seems reasonable to have a couple more good sized moons in your gas giant system.

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