A solar system refers to a star and all the objects that travel in orbit around it. Our solar system consists of the sun – our star – eight planets and their natural satellites (such as our moon), dwarf planets, asteroids and comets. Our solar system is located in an outward spiral of the Milky Way galaxy.
Everything in the Solar System orbits or revolves around the Sun. The Sun contains around 98% of all the material in the Solar System. The larger an object is, the more gravity it has. Because the Sun is so large, its powerful gravity attracts all the other objects in the Solar System towards it. At the same time, these objects, which are moving very rapidly, try to fly away from the Sun, outward into the emptiness of outer space. The result of the planets trying to fly away, at the same time that the Sun is trying to pull them inward is that they become trapped half-way in between. Balanced between flying towards the Sun, and escaping into space, they spend eternity orbiting around their parent star.
The Solar System formed 4.6 billion years ago from the gravitational collapse of a giant molecular cloud. The vast majority of the system’s mass is in the Sun, with most of the remaining mass contained in Jupiter. 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, called the gas giants, are substantially more massive than the terrestrials (Mercury, Venus, Earth and Mars). The two largest, Jupiter and Saturn, are composed mainly of hydrogen and helium. The two outermost planets, Uranus and Neptune, are composed largely of substances with relatively high melting points (compared with hydrogen and helium) called ices, such as water, ammonia and methane and are often referred to separately as “ice giants”. All planets have almost circular orbits that lie within a nearly flat disc called the ecliptic plane.
The Solar System also contains regions populated by objects. The asteroid belt , which lies between Mars and Jupiter. It is made up of thousands of objects too small to be considered planets. Some of them no larger than a grain of dust, while others, like Eros can be more than 100 miles across. A few, like Ida(heavily cratered, irregularly shaped asteroid), even have their own moons.Beyond the gas giant Neptune lies a region of space filled with icy bodies. Known as the Kuiper Belt. The belt is similar to the asteroid belt found between Mars and Jupiter, although the objects in the Kuiper Belt tend more to be icy rather than rocky. The region also contains several dwarf planets, round worlds too large to be considered asteroids and yet not qualifying as planets because they’re too small, on an odd orbit, and don’t clear out the space around them the way the 8 planets do. Identified dwarf planets include the asteroid Ceres and the trans-Neptunian objects Pluto and Eris. In addition to these two regions, various other small-body populations including comets, centaurs and interplanetary dust freely travel between regions. Six of the planets, at least three of the dwarf planets, and many of the smaller bodies are orbited by natural satellites, usually termed “moons” after Earth’s Moon. Each of the outer planets is encircled by planetary rings of dust and other small objects. There are four planets in our Solar System with rings, although some of the ring systems are so faint that they are hard to spot. These planets – Jupiter, Saturn, Uranus, and Neptune – are all gas giants. Jupiter is the largest planet in our Solar System, but its rings are faint. Saturn has the brightest ring system of any planet in our Solar System. Earth, our home planet, is the only planet in our solar system known to harbor life – life that is incredibly diverse. Our solar system is full of surprises, whose are wait to be discovered.
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