An Earth with 3 suns & 3 moons?

I read about Sun dogs a while ago, and got an idea for one of my worlds. I wonder what the effects would be on an Earth-like planet if it was circling a tripple-star system (if such an star-system would even be possible)?

Also, what happens if we throw in three moons into the calculation? I guess the sum would be that tides and tectonics would be quite messed up to say the least, along with a wierd day-night cycle and a strange calendre.

http://en.wikipedia.org/wiki/Sun_dogs

Since physicists throw up their hands in despair when asked to solve the interaction of three bodies of similar size (the dreaded three-body problem), I'm not sure anyone can give you a definite answer.

I kind of guessed it before as I said and what you wrote about the three-body-problem kind of confirms it.

I guess it maybe leaves the moons...?

One solution would be to have one moon be much larger than the other, and place the two others at Lagrange points.

Orbital resonances might be another solution to simplify matters. Jupiter's smaller Galilean sattelites are forced into a variety of orbital resonances by Ganymede (the largest of them).

You could make it work with high tech level-class gravity control, perhaps beyond the scope of anyone actually living on those worlds and only requiring minor adjustments every couple of thousand years. I think that's how Ringworld worked.

Simply put...a system with one sun, one planet and one moon is already potentially very unstable (which is actually a good thing if you're looking for the development of higher lifeforms...Earth would look quite different without its moon). Each additional satellite increases said instability exponentially. There are very, very few stable configurations for something like what you're suggesting, potentially making this a one-in-several-galaxies kind of thing.

On further thought, oribtal resonances might make some interesting calendars. One big outer moon, a small inner moon and a medium moon between the two in a 1:2:4 orbital resonance would make a very natural breakdown of a week, fortnight, month (or something similar depending on the exact resonance pattern).

Here are some multi-star system configurations. Note that multi-star systems outnumber single-star systems in our galaxy, but the way we find extra-solar planets is much easier to use if the system has only one star.

http://www.atlasoftheuniverse.com/orbits.html

AFAIK multi-stars planetary systems can exist in two configurations :

• Two (or more) close stars orbited by one (or more) distant planet.
• One big star orbited by one (or more) close planet and a distant star.

Basically, the three-body problem can be solved if two of the bodies are close enough to appear as one for the third.

Also, consider luminosity. If one sun is brighter (and hotter) than the other by some margin, then your ecosystem will be... erratic, to say the least.

I just remembered something that can be of use here. It's really Mind Screw-y stuff but I swear I'm not making this up.

So, I know this Hungarian sci-fi novel from 1983 about a weird planet that appears from freakin' nowhere, immediately draws a beeline towards Earth but shortly before collision, it suddenly enters a stable orbit around the Sun, close enough to Earth that the two planets can be seen from each other with the naked eye.

What is so Mind Screw-y here? It's that the planet also brings its suns with it. Two suns, to be exact. And they orbit the planet, not the other way around; none of the scientist characters in the story know how the heck is this possible, especially as the suns are moon-sized and thus faaaaar too small for a natural fusion reaction to occur (one of the characters theorize exotic matter might be involved). One of the suns is green and behaves like a normal star... but the other, a vivid violet one, makes everyone on the surface go completely crazy with Space Madness for as long as it's above the horizon, even if they're in a hermetically sealed environment with zero exposure to the sun's light.

Most of the novel reads like it was written on hardcore hallucinogenic drugs: the same chemical elements as the ones on Earth have radically different physical properties here; despite the planet being ideal for life, it has no native life at all; seeds experimentally planted into the soil, once exposed to the violet sun, explosively germinate into tentacled monstrosities that barely resemble plants and seem to have a mind of their own, eventually spawning animal-like entities that are essentially winged eyeballs that communicate with laser beams; one of the characters get killed by another, only for time to suddenly reverse and bring the dead character back to life who cryptically remarks "Rivers sometimes flow backwards... the river of time too."; and finally, the cast decides they can't take it anymore and collectively swallow suicide pills... only for the tentacle-plants to suddenly release their spaceship which takes off on autopilot, followed by the cast members all waking up alive and well.

Depends on distance between bodies. Take the Sirius star system in the constellation Canis Major. It's a double star system with Sirius A being the big blue one that accounts for most of what we see on Earth and Sirius B being a dwarf star set about a dozen AU from Sirius A. A planet in the habitable band of Sirius A would never see Sirius B as more than a really bright night star or a second point of light during the day. At best it would provide a mild twilight type of lighting not unlike a full moon on Earth. (But less than an actual full moon on Earth.)

There's a couple of points where physics will throw you a bone, though.

1) Binary and trinary star systems tend to have the stars orbiting, roughly, a common barycenter. However, binary and trinary stars are still huge distances apart; as in, having three suns that appear the same size is statistically nigh-impossible.

Thus, you really only need to worry about one star when describing your planet.

2) More moons adds complexity, yes. However, most terrestrial-size worlds only have one, maybe two moons; their gravity just isn't powerful enough to drag others in. So, odds are, either a 3-moon terran world was engineered to have that... or its moons are actually fairly small (or is one moon, broken apart by an impact).

3) Unfortunately, a cool sky with 3 visible suns isn't a thing, really. Even with binaries, your patron star's twin is often just a brighter, slightly larger, more notable star than the rest.

Remember, "space is big. Really big. No, bigger than that. You can't even begin to comprehend how mind-bogglingly big it is. You may think it's a long way down the road to the chemist's, but that's just peanuts to space."

Basically, if you see something like the iconic binary sunset scene from Star Wars, you know that somebody rather higher on the old kardashev scale than you are has been messing around. Which works as a sci-fi theme all by itself, really (and hangs around the edges of the Big Dumb Object trope).

Really ? Tatooine's suns are not very far apart, couldn't the planet have a stable orbit at that distance ?

Probably. If they're a close binary, the planet would orbit the barycentre of the two stars rather than either star directly. That said it would probably introduce some interesting eccentricities into the orbit as the stars themselves shift position relative to their orbit.

If those suns are close enough to each other to not cause an insanely unstable orbit for any planet even remotely near their goldilocks zone, they'd probably interfere with each other's orbits to the point of destabilizing that.

Re: Twin Suns a la Tatooine.

It Exists.

No really. Two stars orbiting a common barycenter and a planet orbiting both in a stable elliptical orbit around both.

With three stars, would it be a planet that never experiences night time, like Namek?

It would depend on the exact configuration. A close binary orbited by a planet with a third companion rendered dim by size and/or distance would probably have a normal day/night cycle like Earth's but with a very bright (up to full moon bright) night for decent portions of the year. But when it's orbit takes it on the opposite side of the twin primaries from the third companion it would just be a normal night.

Actually thinking it through, I can't think of any really stable configuration where the entire planet would be equally illuminated constantly.

A planet without night, while sounds cool, won't be cool at all for Earthlike habitat. And that's not counting the effect of constant radiation on atmosphere.

I'm not sure that's possible. AFAIK there are two stable configurations for a two-suns planet :

• The stars are close to each other and the planet is far away. Obviously both suns will always be on the same side of the planet.
• The stars are far from each other and the planet closely orbit one of them. The other star probably wouldn't be bright enough to qualify as "day" (and anyway there would be a clear luminosity drop).