I am working on a world where an event, like a celebration, occurs during every lunar eclipse.
I would like to have lunar eclipses occurring more frequently--maybe even once a month--in order for this ceremony to be a fairly regular phenomenon. However, my limited knowledge of astrophysics is holding me back in the process of envisioning if something like this could be realistically accomplished.
Could such a solar system exist and sustain life similar to our own?
Take Earth and Moon, and make the orbital plane of the Moon around the Earth to be in the orbital plane of the Earth around the Sun.
In this way each lunar month you will get a solar eclipse and a lunar eclipse.
The price would be that you would never get a full moon.
In my answer to this question:
What kind of lunar orbit would cause a total solar eclipse to happen once a day?1
I suggested that a habitable planet could have a ring of 7 to 42 identical moons sharing a single orbit. They would be identically sized and evenly spaced 8.57 to 54.428 degrees apart along the shared orbit. Thus there could be solar and/or lunar eclipses much more often than if a single moon orbited the planet.
If the moons orbited the planet in the same plane as the planet orbited its star, there would be solar eclipses every time a moon came between the planet and the star, and lunar eclipses every time a moon passed exactly on the far side of the planet from the star.
If the Moon’s orbit around the Earth was in the plane of the ecliptic and the Moon’s orbit was circular, there could be a lunar eclipse every night.
If the Moon’s orbit was suitably elliptical there could be a lunar eclipse once a month at the Moon’s closest approach.
In brief, I see no reason why this this couldn't work...with a few caveats.
Eclipses are very localized events, usually clear from only small portion of the Earth. Eclipse cycles also run on cycles, but these cycles are not monthly because the near monthly lunar cycle is one rotation of the moon around the Earth.
Eclipses result from specific alignments of the Sun-Moon-Earth and this cycle is about 18 years. Multiple eclipses can occur over this time period, but the Eclipses will not be in the same location, nor at the exact same time in the cycle. This is because of two factors; the eccentricity of orbit (orbits are not circular and predicting the alignment of elliptical paths is more complicated than predicting the alignment of circular paths), and the precession of the Earth-Moon system. This means changing these two things in the right way could get the desired effects.
In summary if the Earth's orbit about the sun, and the Moons orbit about the Earth were more circular, and if the Earth-Moon system did not precess, you could in theory get a system were an eclipse happened at consistent intervals and even perhaps with the eclipse happening once in a lunar cycle. But then come the caveats...lunar eclipses would only be view-able from one side of the Earth, and Solar eclipses only view-able from a specific locality on Earth, everyone else would not experience these events, so they would have to be cultural significant based upon locality. Also a lack of precession in both the Earth and Moon and a circular lunar orbit would affect climate, and rather severely. A lack of seasons and no tide cycle would become a problem and uneven temperatures would result in rather extreme weather. Of course, this could all be downplayed, but the climate differences would be an important consequence of having getting the desired eclipse cycle.
