The Sun is evidently not a sphere of hydrogen gas
"This wasn't known in my time," Kepler would continue, "but it is known now. It is known that almost all of the mass in the universe exists in the form of plasma, at least 99.999% of it does so. Now, while the Sun is evidently not a sphere of hydrogen gas, it is possible for the Sun to be a sphere of plasma that attracts plasma from surrounding space. In fact, plasma is focused onto the Sun in highly concentrated form. This plasma is literally forced onto it. It binds it up into bundles with the electric force, and creates tightly knit atomic elements with it, right at its surface, whereby the sunlight is created that thereby appears to be the Sun's surface."
Kepler might ask the girl, who would likely be smiling at this point, "Can you visualize with the power of your mind, such an atom-synthesizing process happening right at the surface on the Sun? If so, how would you know with certainty that what you see is true?"