Why are the moon and sun not planets?
Answers
The sun and moon are not planets when you consider the objects in space they orbit. For the sun to be a planet, it would have to orbit another sun. Although the sun is in a orbit, it moves around the center of mass of the Milky Way galaxy, not another star. The sun fits the definition of a star, because it is a giant ball of gases consisting of hydrogen and helium, with nuclear reactions going on inside. The Earth’s moon is also not a planet because it orbits one. For the moon to be a planet, it would be in orbit directly around the sun.
A star is a sphere of hydrogen and helium held together by gravity. The pull of gravity would make the star collapse into itself if not for the pressure of nuclear fusion in its core. Heat and light energy are released by this process. That brightness is why you can see stars from such great distances. Astronomers cannot count the actual number of stars in Earth’s Milky Way galaxy. They do estimate, based on the amount of visible light and mass in the galaxy, about 100 billion stars shine there.