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The planets, most satellites and asteroids orbit the Sun in the same direction following elliptical orbits in a counterclockwise direction when viewed from above the north pole of the Sun. The plane where all these bodies are rotating is called ecliptic. Some objects orbiting with a particularly high degree of inclination, like Pluto with a 18-degree tilt, as well as an important part of the objects in the Kuiper belt. According to their characteristics, the bodies that make up the Solar System are classified as following:
- Sun: A spectral type G2 star containing more than 99% of the mass of the system.
- Planets: They can be divided into inner planets, also known as terrestrial or telluric planets, and giant or external planets. Among the latter, Jupiter and Saturn are called gas giants while Uranus and Neptune are often named as cold giants. All giant planets have rings around them.
- Dwarf Planets: This new category, inferior to planets, was created by the International Astronomical Union in August 2006. These are bodies whose masses allow them to have a round shape, but not enough to have attracted or expelled other bodies. For example, Pluto, Ceres and Eris can be found in this category.
- Satellites: Larger bodies orbiting the planets, some very large, like the Moon, Earth, Ganymede in Jupiter or Titan, in Saturn.
- Asteroids: Smaller bodies concentrated mostly in the asteroid belt between the orbits of Mars and Jupiter. Their low mass do not allow them to have a regular shape.
- Kuiper Belt Objects: Exterior frozen objects in stable orbits, the largest of which are Sedna and Quaoar.
- Comets: Small frozen objects from the Oort cloud.
The interplanetary space around the Sun contains material dispersed from the evaporation of comets and the escape of material from the different massive bodies. Interplanetary dust (a sort of interstellar dust) consists of solid microscopic particles. Interplanetary gas is a tenuous flow of gas and charged particles forming a plasma that is ejected by the Sun in the solar wind. The outer limit of the Solar System is defined by the interactive zone between the solar wind and the interstellar environment resulted from the interaction with other stars. The interactive zone is called heliopause and it determines the influential limits of the sun. The heliopause can be found about 100 AU (15,000 million kms. from the Sun). The different planetary systems observed around other stars seem remarkably different from the solar system, although there are observational challenges in detecting the presence of low-mass planets in other stars. Therefore, it is not possible to determine how unique or unusual the solar system really is among the planetary systems of the Universe. |
Solar System 
