The Planets

Next to the sun, the most important members of the solar system are the planets. The planets in the solar system are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Pluto which is once called a planet is now considered by astronomers as a dwarf planet because of its very low mass. It is a member of the Kuiper belt, a region of icy bodies that lies beyond the orbit of Neptune. These celestial bodies all revolve around the sun at different periods, distances, and speed while they spin on their own axes.

All planets have their own distinctive characteristics. These characteristics are related to their distances from the sun. The nearer the planet is to the sun, the shorter is the planet's period of revolution. Also, the planet nearest the sun receives more heat than those far from it; hence, it has a higher temperature. Each planet follows an orbit or a path in moving around the sun. The orbit of the inner planets are almost circular but those of the outer planets are highly elliptical.

The gravitational attraction between the sun and each planet makes the planet stay in its own orbit as it moves around the sun. The sun having a bigger mass and size than the planets, has a stronger force of attraction for planets to move around. The specific planetary orbit is determined by the relation of the mass of the planets and the gravitation of the sun.

Most of the planets have moons that move around them as they revolved around the sun. As of 2008, there are 176 moons in the solar system.