1. Some stars are bigger than others, some are different colors or temperatures. It all really depends on the age of the star.
2. Four differences could be:
1) Outer planets are much farther away from the sun, so they get less sunlight than inner planets.
2) Also, the outer planets are all gas giants (excluding Pluto), while inner planets are all rocky planets.
3) Inner planets also have a much higher density than outer planets.
4) Outer planets also tend to have many more moons than inner planets (such as Jupiter, with 63 known moons).
3. The barrier that separates the inner from the outer planets is a ring of space rocks known as the Asteroid Belt.
A comet is a ball of ice that orbits a star in a wide elliptical orbit.
An asteroid is a large rocky body that orbits a star, and could be anywhere in size from 600 miles across to tiny dust particles.
A meteoroid is a small object floating through space freely (not necessarily bound in any orbit) that is usually made of a rocky or metallic material.
4. Day and night are caused by the earth's rotation on its axis. Night is relative to the observer, and occurs when the observer is on the side opposite that on which the sun is shining.
Hope that helped =)
