Brandon (who has an excellent and praiseworthy internet residence called Siris) asks whether "Does writing [a fiction about a planet) miraculously create a fictional object the size of Jupiter?" should not really be "Does this describe a fictional miraculously created object the size of Jupiter?"
A good and Brandonesque objection. Well, the question is whether fictional statements (as opposed to merely false ones) 'bestow' properties on fictional objects. If so fictional statements have to be true.
(1) The statement that A is B 'bestows' B upon the fictional A, according to the theory.
(2) So A now has B.
(3) Since the fictional statement 'A is B' now corresponds to the fictional reality, the statement 'A is B' is true as a result.
This raises the question of when the fictional A begins to exist. I suppose it could coherently be held that A always existed, because the author was going to write about A, but that doesn't altogether make sense. What if the world were to turn out otherwise? What happens to the fictional object in a possible world where no one wrote about 'it'?
More plausible (plausibility being relative) is that the fictional object is created just as soon as I talk or write about it. It doesn't possess any properties until I 'bestow' them by making the fictional claim. So why shouldn't we suppose that the existence of the object is also bestowed at the point of writing. Another argument for this is that it is absurd for the the object to exist before it has any properties 'bestowed' upon it, so that there exists an object without any properties whatsoever (except perhaps of existence). Another problem is that this view requires existence being a property, so does it possess this property before the author has said that exists, i.e. bestows existence upon it?