What is the Solar System? Solar system is Sun and everything that travels around it. The Solar System is elliptical in shape. That means it is shaped like an egg. The Sun is in the center of the Solar System and always in motion. The Solar System consists of the Sun and its planetary system of eight planets, their moons, and other non-stellar objects. It formed approximately 4.6 billion years ago from the collapse of a giant molecular cloud.
The smaller inner planets, Mercury, Venus, Earth and Mars, also called the terrestrial planets, are primarily composed of rock and metal. The four outer planets, called the gas giant, 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, Neptune and Pluto are composed largely of ices, such as water, ammonia and methane, and are often reffered to separately as "ice giants".
Mercury (0.4 AU from the Sun) is the closest planet to the Sun and the smallest planet in the Solar System (0.055 Earth masses). Mercury has no natural satellites, and its only known geological features besides impacts craters are lobed ridge or rupes, probably produced by a period of contraction early in its history. Mercury is too close to the Sun and its temperature is too hot to support life.
Venus (0.7 AU from the Sun) is close in size to Earth (0.815 Earth masses), and has a thick silicate mantle around an iron core, a substantial atmosphere and evidence of internal geological activity. However, it is much drier than Earth. Venus has no natural satellites, and is the hottest planet with over 400°C because a great amount of heat from the Sun is trapped in its atmosphere.
Earth (1 AU from the Sun) is the largest and densest of the inner planets, known as an ocean planet, is the only one known to have current geological activity and is the only place in the Solar System where life is known to exist. Earth's atmosphere is radically different from those of the other planets, have been altered by the presence of the life to contain 21% free oxygen.
Mars (1.5 AU from the Sun) is smaller than Earth and Venus (0.017 Earth masses). Mars is a cold desert world. It is half the diameter of Earth and has the Same amount of dry land, like Earth. Mars has seasons, polar ice caps, volcanoes, canyons and weather, but its atmosphere is too thin for liquid water to exist for long on the surface.
Jupiter (5.2 AU from the Sun), at 318 Earth masses, is 2.5 times the mass of all the other planets put together. It is composed largely of hydrogen and helium. Jupiter has 67 known satellites. The four largest, Ganymede, Callisto, Io and Europa, show similarities to the terrestrial planets, such as volcanism and internal heating.
Saturn (9.5 AU from the Sun), distinguished by its extensive ring system, has several similarities to Jupiter, such as its atmospheric composition and magnetosphere. Although Saturn has 60% of Jupiter's volume, it is less than a third massive, at 95 Earth masses, making it the least dense planet in the Solar System. The rings of Saturn are made up of small ice and rock particles. Saturn has 62 confirmed satellites; two of which, Titan and Enceladus, show signs of geological activity, through they are largely made of ice.
Uranus (19.6 AU from the Sun), at 14 Earth masses, is the lightest of the outer planets. Uniquely among the planets, it orbits the Sun on its side; its axial tilt is over ninety degrees to the ecliptic. It has much colder core than the other gas giants, and radiates very little heat into space. Uranus has 27 known satellites, the largest ones being Titania, Oberon, Umbriel, Ariel, and Miranda.
Neptune ( 30AU from the Sun ), through slightly smaller than Uranus, is more massive (equivalent to 17 Earth masses) and therefore more dense. It radiates more internal heat, but not as much as Jupiter or Saturn. Neptune has 13 Known satellites. The largest, Triton, is geologically active, with Geysers of liquid nitrogen. Neptune is covered with blue ocean of the liquid methane.
Pluto (32.1 AU from the Sun ) is the second-most-massive known dwarf planet in the solar system (after Eris) and the tenth-massive body observed directly orbiting the Sun. Originally classified as the ninth planet from the Sun. Pluto is very cold because it is far from the Sun.