But the point is, there is such a well-defined term, and the Sun isn’t one. “White hole” is just as defined as “black hole”, and answering a question about white holes by talking about the Sun is just as bad as answering a question about black holes by talking about the Chunnel during a power outage. Worse, actually, because the Chunnel is at least a hole.
But the OP fails to understand the definition of HYPOTHETICAL
So, i give him the sun, which is the opposite of a “black hole” as far as the simple words go.
White holes do exist. Every black hole is a time-reversed white hole. The question, then, is why we don’t have any memories or recordings of white holes spewing matter into the universe, and that’s because we only seem to remember the past, not the future, due to the mysterious arrow of time. The arrow of time is, apparently, because the universe as a whole is moving from a low-entropy to a high-entropy state. No one really knows why the universe started in a low-entropy state.
The “mysterious arrow of time” is entropy. The time of low entropy is the time we remember because it is low entropy.
And Weisshund, it’s possible enter the Sun from the outside, and therefore it is not a white hole. The fact that white holes are hypothetical is no excuse: One also wouldn’t say that the Sun is a unicorn.
An earlier thread of mine:
Imagine you’re a god observing our universe contained in a 4-dimensional box. The box is static, of course–what we perceive as time is just one of the dimensions.
You can see that 3 of the dimensions are very similar; if you take a 3D slice along those axes, you can see a distribution of stars and galaxies that are spread out fairly evenly.
However, the fourth axis is different. Everything in the box has a certain directionality to it, so that the parts that point to one side are simpler and more ordered, while the parts that point to the other side are more disordered. Singularities are one such object. You understand from the rules of the box that the disorder of a singularity grows in proportion to the surface area of its event horizon, and event horizons are always larger in area on the disordered side, and small on the ordered side. Eggs are another example; they are always broken on one side and intact on the other. You never spot an example where the ends are swapped.
You could reach in and flip one of these objects around yourself. The creatures in the box would see this as very unusual, but to you, almost nothing has changed. The 4D shape of the object is identical; it’s just oriented a bit differently than before. It’s hardly worth giving it a different name, just as a teakettle is still a teakettle if you rotate it 180 degrees. But to the creatures, black holes have turned to white holes and eggs start spontaneously reassembling themselves.
Ultimately, you conclude that the orientation is due to the constraints imposed on the far ends of the box. One side is set to maximum disorder and the other, a very low disorder. For consistency’s sake, the matter between the two sides “interpolates” between the two, and so everything in between the two ends will have a side that’s more disordered than the other. There are some fluctuations, but only very small ones; nothing as large as a singularity. And so singularities with their direction of disorder reversed are never observed naturally.
So, what is it?
But if a spacecraft flew too near to the sun it would be swallowed up so that seems to violate the definition you gave of a white hole.
Would you like to buy my toaster?
[QUOTE=Douglas Adams]
FORD:
Alright imagine this: you get a large round bath made of ebony.
ARTHUR:
Where from? Harrod’s was destroyed by the Vogons.
FORD:
Well it doesn’t matter -
ARTHUR:
So you keep saying!
FORD:
No, No listen. Just imagine that you’ve got this ebony bath, right? And it’s conical.
ARTHUR:
Conical? What kind of bath is -
FORD:
No, no, shh, shhh, it’s, it’s, it’s conical okay? So what you do, you fill it with fine white sand right? Or sugar, or anything like that. And when it’s full, you pull the plug out and it all just twirls down out of the plug hole… but the thing is…
ARTHUR:
Why?
FORD:
No, the clever thing is that you film it happening. You get a movie camera from somewhere and actually film it. But then you thread the film in the projector backwards.
ARTHUR:
Backwards?
FORD:
Yeah, neat you see. So what happens is you sit and you watch it and then everything appears to swirl upwards, out of the plug hole and fill the bath… amazing.
[/QUOTE]
And that’s a white hole … or a marvelous way to relax.
NB: IANATheoreticalPhysicist
A WHITE hole?
I can’t believe I’ve been playing the prat version of Rimmer all this time.
The simplest answer is there are no mechanism (aside from some speculative models) for the formation of a white hole. I think the most likely answer is that general relativity has a lot of solutions that are unphysical and solutions containing white holes are one of the most obvious examples.
Now I want a box like that, so that I can reach in and really mess with astronomers.
I suppose, and I am in no way a physicist, so this is probably wrong on a few levels…, but with space expanding, you could get a white whole if for some reason you ended up with a region of space that is expanding extremely rapidly, faster than C to an outside observer.
If the big rip is a thing, then there may be white holes at that time in the cosmological future history.
Okay, so white holes are theoretically possible according to Einstein’s equations but could only exist if we ran back time.
Thank you people. 
Couldn’t they also exist if we were to find a repulsive force with a strength so intense that the “capture velocity” exceeded the speed of light?
White holes are not repulsive, matter will still be attracted to them.
An observer observing a white hole from the outside can never see anything crossing the event horizon. The outside observer would consider the particles that they observe to have crossed the event horizon (from the inside to the outside) an infinite amount of coordinate time in the past.
What theoretical mechanism could create such a white hole? I suppose this goes beyond classical gravitation?
A black hole is known for being definitively local; if a white hole is the opposite, perhaps its defining characteristic is that it is extremely non-local?
There is only one white hole. It exists everywhere that a black hole doesn’t. 
When physicists use the word “classical”, they mean “non-quantum”, and white holes don’t emerge from quantum mechanics, so in that sense, they’re classical. What you might have meant was that they’re not Newtonian, being purely objects of general relativity.