Solar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago.
Of the many objects that orbit the Sun, most of the mass is contained within eight relatively solitary planets whose orbits are almost circular and lie within a nearly flat disc called the ecliptic plane.
The classifications
a) interstellar or cosmic dust: Particles in the space
b) Meteoroid: between 0.1 mm and 10 m wide. Ranking by importance of meteoroids falling to Earth.
c) Planets: A celestial body orbiting the Sun that has enough mass to be rounded by its gravity and that has cleared the neighborhood around its orbit. There are 8, ordered from smallest to largest: Mercury, Mars, Venus, Earth, Uranus, Neptune, Saturn and Jupiter.
d) Sun: Contains the 99'8% of the mass of the solar system.
e) Star is a massive, luminous sphere of plasma held together by gravity.
e) The Moon is the only natural satellite of a planet in the Solar System.
f) The orbit of a planet around the center of a solar system.
The four smaller inner planets, Mercury, Venus, Earth and Mars, also called the terrestrial planets, are primarily composed of rock and metal. The four outer planets, the gas giants, are substantially more massive than the terrestrials. The two largest, Jupiter and Saturn, are composed mainly of hydrogen and helium; the two outermost planets, Uranus and Neptune, are composed largely of ices, such as water, ammonia and methane, and are often referred to separately as "ice giants".
