In our solar system, the primary star is called the Sun. The Sun is a G-type main-sequence star, commonly referred to as a yellow dwarf. It is at the center of our solar system and provides heat, light, and energy to all the planets and other celestial objects within its gravitational influence.
The other objects in our solar system that are not stars but are commonly referred to as planets include Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. These are all considered planets because they meet the criteria defined by the International Astronomical Union (IAU) for a celestial body to be classified as a planet.
According to the IAU's definition, a planet must satisfy three criteria:
It orbits the Sun: All the planets in our solar system orbit the Sun, rather than being independent sources of light like stars.
It is spherical in shape: Planets are generally rounded by their own gravity, assuming a nearly spherical shape. This is due to the balance between the planet's gravity pulling it inward and its internal forces pushing outward.
It has cleared its orbit: A planet has cleared its orbit of other debris and smaller objects by virtue of its gravitational dominance. In other words, a planet has become the most dominant gravitational body in its immediate orbital vicinity.
Objects like Venus, Mars, and the other planets in our solar system satisfy these criteria and are thus considered planets. The reason stars are not referred to as planets is because they are fundamentally different in nature. Stars are massive, luminous celestial bodies that generate energy through nuclear fusion in their cores. They emit light and heat, whereas planets do not produce their own light but reflect the light they receive from their star, in our case, the Sun.
While stars and planets have distinct characteristics and roles within a solar system, they are both important components of the larger cosmic tapestry, each with its own unique properties and contributions.