The best way would be using either a Point or an Area light.
A Point light is how an astronomer would see the sun: a big hot ball of ultraviolet radiation and scorching fire. Point lights emit light in all directions.
A Sun light is how someone on the ground would experience the Sun: something really high up that shines down on the ground. The sphere object would have gotten in the way.
A Spot light is a flat Sun light. It projects a two-dimensional circle onto a three-dimensional world, sometimes bending to scale with the objects.
A Hemi light has the nasty habit of affecting all planes equally, even if a Sun or Spot light cannot reach because they are being blocked by another object/plane.
An Area light is a Point light with gamma controls and the ability to choose the bounds and direction of the light.