Here's why:
* 1 AU (Astronomical Unit) is the average distance between the Earth and the Sun.
* Mercury is the closest planet to the Sun. Its average distance is about 0.39 AU.
Other planets in our solar system orbit further out:
* Venus: 0.72 AU
* Earth: 1.00 AU
* Mars: 1.52 AU
* Jupiter: 5.20 AU
* Saturn: 9.58 AU
* Uranus: 19.22 AU
* Neptune: 30.06 AU
The reason Mercury orbits so close to the Sun is likely due to its formation. During the early stages of our solar system, the planets formed from a disk of gas and dust. Mercury's location in this disk, closer to the Sun, meant it was exposed to higher temperatures and denser material. This led to its smaller size and rocky composition.
