Planets are celestial bodies made out of different materials that orbit around a common center, usually a star. There are many planets in the universe, but the most familiar ones are the planets in out solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto. Planets, like stars are also born, but unlike stars, they do no die. Planets can be thought of as large rocks wandering throughout the cosmos.
Our nine planets, however, were not always the way they appear to be today. Our solar system is very old, about 4.5 billion years is its age. The formation of this system began when a large cloud of gas and dust began to compress. Pockets of this cloud began to separate and fall under their own gravity. This formed the Nebula our sun and the planets formed from. As the process continued, a clear, dense center began to form: the sun. The remnants of the nebula, mostly gas
and dust, began to orbit around this massive center, creating a disk. Atoms and molecules began to combine and form larger substances. Since the solar heat from the sun prevented any gases from condensing, only rocks and metals combined to
form the first 4 inner planets: Mercury, Venus, Earth and Mars. Mercury is the smallest, quickest and closest planet to the sun. Due to its lack of an atmosphere, temperatures ranges from 350 degrees Celsius in the day to –180 degrees Celsius
during the night. Mercury is dense, its surface resembles that of the moon, and its core is most likely composed of nickel and iron. Mercury is approximately 58 million kilometers from the sun and its year is equal to 88 days on Earth.