The Sun in Equestria is not a star.

Ok, that's my point out of the way, now I can explain my blasphemous claims. I was thinking out physics in Equestria and something caught my attention. The Sun is not a star, in fact my theory suggests it's something else entirely. This is why:

Star's are huge and have a lot of mass, this means they have considerably powerful gravitational fields. And because they are not dense enough to be solid matter, they can be crushed by the force of their own gravity. To maintain themselves they provide an outward force in the form of nuclear fusion, this balances out the two forces and keeps the star from collapsing or exploding due to an unbalance in the forces. My problem with this universe and the Sun comes in the movement of the three bodies known to occupy the system Equestria is located in.

The sun and moon respectively both remain motionless high up in the sky for the most part of the Equestrian day/night until their respective princess moves it out of the way for the other to slowly take it's place in the sky where it will again stay for most of the day/night. I realised that if the sun really was a star then the planet Equestria is on would have been messed up a long time before the events of the show. Due to the sun and the planet being stationary relative to each other for such a long time, orbits would not be possible. This would cause the planet to accelerate toward the sun and roast into a big ball of magma before they collided. Now there is a flawed solution to this problem.

"But Night Fall!" I hear you scream. "Maybe the sun has the same mass of the planet and the moon! The balance keeps them in limbo!"

Now here's where I came to my realisation. Because it that were true, then the sun would have not have had enough fuel or mass to burn hot enough to ever become a star. It would have slowly cooled and condensed into a brown dwarf, a massive gas giant made of all the Hydrogen and Helium that would have been fused together if there had been enough fuel during the star's development. Equestria would never have been able to support life. Even if it were a miniscule star about the size of the planet, it would never last long enough to see the development of life on one of it's planets. That is before it melted it into the lava-ball I mentioned earlier.

The other option would be the sun in Equestria's system has one solar mass in the space of the planet... at which point it would be so dense it would collapse into a black hole. Basically, that's definitely not the solution.

A third option is that the sun has the size and mass of ours and the moon is massive enough to balance it. Here is another problem. A star sized solid moon would have FAR more gravity than the sun. It would have a stupendous amount of gravity. And it just had more mass but was normal sized it would also collapse into a singularity. Again, they'd be screwed.

So there we have it. The sun in MLP cannot be a star. It does not make sense in the terms of science. And don't just comment: "Magic! Deal with it!" Because if I'd have wanted to be able to accept that conclusion I would not have posted this to a group about discussing 'science in Equestria'. And besides, I'm not finished yet. I have two conclusions to make. These two theories would make the most sense physics and/or lore-wise, and are the best things I could come up with to explain it.

The Thaumatic Radiator Theory:
This theory implies the sun in MLP is not a star at all, and is instead the source of all magic in Equestria. It literally is a Thaumatic Radiator, shining down magic onto the land of Equestria, granting it's inhabitants the use of it's power. This also implies that the radiation of magic produces a waste energy: Heat. Enough so that it also warms the planet. This makes the most sense in canon terms, as Celestia is regarded as the most magical pony in the entirety of the land (Barring Twi of course). This also implies that the magic is actually coming from somewhere and will run dry at some point. Which means the sun is likely some sort of incredibly magical artifact or material that is so powerful it outclasses nearly every other being in existence.

The Proto-Star Theory:
This is my favorite option however it has the least credibility and is very far fetched. My personal theory is that the sun of Equestria is a Proto-Star in the early stages of late development. The planet of Equestria had been formed well before the creation of the proto-star and an extremely dense and/or large distant moon balances out the gravity. If the sun is still in development, an Accretion Disk could explain the purple tint in the night sky when they are able to see the hanging gasses in the surrounding space. The binary system will be spinning in a geostationary orbit relative to the planet, the sun and moon rotating in a circle on opposite sides of the planet.

Meaning the stars in the night sky would visibly move, giving the effect of some movement in the night, but the main celestial bodies still remaining completely still until moved by Celestia or the unicorns before Celestia and Luna arrived. This would imply that the balance may be broken when the sun gains enough mass, spelling the slow and painful end for Equestria as the planet is gradually pulled closer and closer to it's local newborn nuclear furnace.

Those are my theories, which imply the sun in MLP is not a star, at least not yet anyways. What do you think?

4698347
You neglected at least one other possibility: Celestia doesn't move the sun, but rather rotates the planet. Yes, if done in sudden jerks, this could result in flinging everything off of the world, but that's assuming that the sun does, in fact, spend most of the day overhead. "Lesson Zero," for example, suggested that the sun passed overhead relative to Ponyville as ours does relative to an observer on Earth. (The herky-jerk motions were likely a product of Twilight's rapidly decaying mental state.) Alternately, if Celestia's already turning the world in her magical grip, it seems like a small stretch to allow her telekinesis to do a little inertial dampening.

This option allows for Equestria to have a sun massive enough behave like the naturally occurring fusion reactors we're familiar with. An interesting side effect is that the resulting solar system is heliocentric rather than geocentric.

4698436
Sounds like it could work. Man, implementing physics where it was never meant to make sense is way too fun.

4698347
Thaumatic Radiator, but instead of the sun being an artifact that stores magic I believe it is a artifact that collects and distributes magic from a massive leyline node, and the moon does the same. It supplies Equestria with magic, enough that almost everything is magical in some way. The reason it is so hard to move the sun and moon is because you aren't just moving some small enchanted satellites, you are also moving rivers of magic coursing out from the center of the universe. There in the center of the universe, there is and intermultiversal breach that was formed from the space being destroyed during the first few picoseconds or so of the universe from the massive amount of energy there making it hit absolute heat. It reaches through to a universe of a multiverse where thermodynamics do not apply, so energy is infinite.

It is obvious that their cosmology works nothing like our own. Whatever the Sun and Moon are, they magically change the appearance of the sky, rather than simply shed light.

4698347
What if Equestria is tidally locked to the sun and Celestia spins the planet so the entire surface is habitable and not just a small ring around the planet?

Luna's role is self evident in this situation.

4698609
Your point kinda' makes mine moot...

4698609
It's like I said, using science to try and explain something that was never meant to make sense in the first place is fun. Simply saying "It's magic, it works differently!" is kinda' boring. Obvious as heck, but boring.

My story ,http://www.fimfiction.net/story/279183/twilight-explains-the-solar-system, can explain any strange movements of the Sun and Moon by stating that it is the result of organized reflection by dust in the atmosphere.

Of course, there is the question of how the dust got there, for if it was always there life could not have evolved without magic. Discord, perhaps?

4698347

In the Shadow Wars Storyverse, four thousand years ago the Cosmics Fusion, Gravity and Discord warped the Solar System into a Ptolemaric "toy cosmology" as part of their effort to save the Earth from being scoured clean of life in the Cataclysm. Unfortunately, the toy cosmology is breaking down.

4698347
Eh, if I was forced to pretend real-world stellar physics were involved, I would say that the sun is stationary, Celestia spins the Equestrian planet. Luna moves the moon, and that is actually mobile.

If I was feeling sufficient-technology-y, I would say that the sun isn't a sun, but instead is basically just a giant artificial reactor made to look like a sun. And it does orbit Equestria.

In reality though, neither of those explanations particularly satisfied what we see in the show. Especially given The Princess Twilight Sparkle, and that picture Titanium provided from it.

Clearly, however, Equestria isn't gravitationally balanced between the two. They've both been in the sky at the same time on dramatic occasion.

spelling the slow and painful end for Equestria as the planet is gradually pulled closer and closer to it's local newborn nuclear furnace.

Ahh, would it? If Equestria is in a stable orbit around this proto-star, and the associated gasses, why would the orbit change as the star pulled in said gas? The total mass of the system would remain the same. There'd probably be some minor perturbation as things shifted around some, but there's no real reason to think it would suddenly sent Equestria spiraling inward. It hasn't lost any of its orbital momentum.

4699767
The gasses are pulled in by the proto-star and it gradually gains mass, slowly increasing it's gravitational pull on the planet. This tightens the orbit's until they collide. Because the center of the system's mass converges on the 'sun' instead of being spread out. It also increases the proto-star's tidal forces acting on the planet.

4700001
Unless the gasses are massively diffuse, I imagine most of the gravity is already pulling the planet in toward the center of the system. If it's still so early in the system's life that the stars and planets haven't cleared most of their local space, then Equestria would probably be a volcanic hellhole, under constant bombardment from space, like young Earth.

Since the thing isn't a black hole or neutron star, and Equestria couldn't be that close and not be a cinder, tidal forces aren't likely to be some enormous problem.

4700011
That's why I mentioned that I expected the proto-star to never fully form and would likely cool down into a brown dwarf. There wouldn't be enough material and gas for it to gather in use as fuel. It was simply a far fetched theory I used science for. It's likely no proper answer actually exists, because you know, 'Magic!' But that's just boring.

4700021
FiM cosmology is one thing I really try to avoid even attempting to explain.

Whatever it is makes absolutely no sense, as we understand things. But then, Equestria is in some different dimension. So who even knows if the physics is the same?

The best answer I've ever read to this is "Days of wasp and spider" which manages to explain everything in cannon within the laws of physics. It's some of the bests sci-fi I've ever read , and I'm not speaking only of fimfiction.