Why is the sun yellow?

* The sun isn't actually yellow. It emits all colors of light, making it a white star.

* The Earth's atmosphere filters out some of the sun's light. The blue and violet wavelengths get scattered more by the air molecules, making the sky appear blue. This leaves more of the yellow and red wavelengths to reach our eyes, giving the sun a yellow appearance.

Why is the sun round?

* Gravity! The sun is a giant ball of gas held together by its own gravity. The force of gravity pulls everything in the sun towards its center, creating a sphere.

* Rotation. The sun spins on its axis, which also helps it maintain its round shape.

Fun fact: The sun actually appears reddish-orange during sunrise and sunset because the sunlight has to travel through more of the Earth's atmosphere, scattering even more blue light.