Any astronomers/cosmologists/planetary scientists in the house?

[AJ Stevens]

I'd like to offer the flip side of the argument for a shorter year. It doesn't necessarily mean that your planet is closer to the star. A more massive star means more gravity means the planet has to orbit faster means a shorter year. I'm not too hot on the knock-on effects of such an occurrence however.

 

[Duncan M]

Hello! Aspiring Astrophysicist here. I'm certainly no expert, but when it comes to moons I'll say the sky is the limit (bad).

Since you're looking for a (relatively) large moon orbiting a smaller planet, you may want to consider a tidally-locked planet-moon system, where the moon and planet are close enough that both perpetually face one side towards the other. Thus, the planet rotates once per lunar orbit, which could potentially be shorter than a day. From the surface, the Moon would never appear to move across the sky, instead just wobbling back-and-forth predictably.

This would result in a world where only one side of the planet receives moonlight. Additionally, tides on this planet would be interesting: the moon would cause a kind of perpetual "high-tide" on the regions facing directly towards it (and opposite), intensified when the Sun is high in the sky and lessened during the dawn and dusk when the Sun pulls as counterweight.

Pluto and Charon are a great example of this. The tidal forces between the two are so strong that bits of Pluto's upper atmosphere have been found bridging the gap to Charon, and Charon is massive enough that their center of mass is outside Pluto, and the two just spin about each-other.

Since you also mentioned an axial tilt, there will (as stated by ThinkerX) be severe seasons. With a 60° axial tilt, your arctic and antarctic circles will be about three times as wide as Earth's. They'll begin at around 30° N and 30° S respectively. Much of these areas will experience perpetual sunlight for half the year and none for the other half, which means that for half of your planet the Moon may be the only source of natural light for that Wintry season. Between those regions and around the equator you'll have a kind of temperate zone, but the sun's position in the sky will be low for most of the year.

Should you decide against a tidally-locked system, then the moon's motions will remain interesting given the axial tilt. The Earth's Sun and Moon follow a similar path across the sky, but if your planet has a 60° tilt, the Moon's location will be much harder to predict, with it often crossing or coinciding the Sun.

I hope some of this proved interesting or helpful. Cheers.

 

[Trick]

Hello! Aspiring Astrophysicist here. I'm certainly no expert, but when it comes to moons I'll say the sky is the limit (bad).

Sounds like you know more than me about this, which is the only qualification I'm looking for

The sky being the limit is actually pretty good news. If that's the case, I'm basically able to place the moon in the sky where and when I need it for the story, within reason.

Since you also mentioned an axial tilt, there will (as stated by ThinkerX) be severe seasons. With a 60° axial tilt, your arctic and antarctic circles will be about three times as wide as Earth's. They'll begin at around 30° N and 30° S respectively. Much of these areas will experience perpetual sunlight for half the year and none for the other half, which means that for half of your planet the Moon may be the only source of natural light for that Wintry season. Between those regions and around the equator you'll have a kind of temperate zone, but the sun's position in the sky will be low for most of the year.

The reason I chose a 60 degree axial tilt was from this video.

Seasonbuilding 101: Axial Tilt | Worldbuilding - YouTube

According to Artifexian, at 60 degrees, the arctic circles and equator switch places and the center of the planet becomes an unlivable barren waste of ice. If the tilt would also lead to severe weather in that area, it would be even better for the book. I need no one to travel from one side of the planet to the other and a ring of ice/wasteland with unpredictable and deadly weather is quite the deterrent.

In your estimation, if Artifexian is right about the arctic circles and equator switching, what kind of climates am I looking at for land masses where the arctic and Antarctica are on Earth? I'm hoping for a place very similar to Venezuela.

Should you decide against a tidally-locked system, then the moon's motions will remain interesting given the axial tilt. The Earth's Sun and Moon follow a similar path across the sky, but if your planet has a 60° tilt, the Moon's location will be much harder to predict, with it often crossing or coinciding the Sun.

Tidally locked won't work unfortunately. I need month-based seasons like earth. I need the phases of the moon (months) to be 26 days long, with 13 months per year.

Is that an impossibility with a 60 degree axial tilt?