Solar System

Solar System

The Solar System is the gravitationally bound system of the Sun and the objects that orbit it, either directly or indirectly. Of the objects that orbit the Sun directly, the largest are the eight planets, with the remainder being smaller objects, such as the five dwarf planets and small Solar System bodies.

Structure and Composition

The Solar System is composed primarily of the Sun, eight planets, five dwarf planets, and small Solar System bodies. The four smaller inner planets, Mercury, Venus, Earth, and Mars, are terrestrial planets, being primarily composed of rock and metal. The four outer planets are giant planets, being substantially more massive than the terrestrials.

Formation and Evolution

The Solar System formed 4.6 billion years ago from the gravitational collapse of a giant interstellar molecular cloud. The vast majority of the system's mass is in the Sun, with the majority of the remaining mass contained in Jupiter.

Exploration

The exploration of the Solar System is carried out both by human spaceflight and robotic spacecraft. While the first form of human exploration was the Apollo program, the exploration of the Solar System is primarily performed by unmanned robotic spacecraft.

See Also

• List of gravitationally rounded objects of the Solar System
• Formation and evolution of the Solar System
• Astronomical object
• Planetary system

External Links

• NASA's Solar System Exploration

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