Which sphere is closest to the sun?

Answer 1

This is a very vauge question as it could refer to anything from the surface of the sun, to the Earth, to many things beyond the sun.

1) if by sphere you mean the sun, then the closest layer is that is not part of the sun is the plasma sphere.

2) if by sphere you men the Earth layers, then the Exosphere is the closest.

3) if by sphere you mean a body that is large enough to be considered a planet, the answer is Mercury, since the other bodies in the area maybe closer but they are not large enough to be sphere shaped.