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1.5. The Solar System and its components

The solar system

The Solar System is a set of stars formed by the Sun, and other astronomical objects (planets, their satellites, cometsasteroids) that rotate directly or indirectly in an orbit around the Sun.

The Solar System was formed from an interstellar cloud of gas and dust, which was concentrated by gravity on the Sun, and began to rotate on itself. In the process matter was released, which continued to rotate, giving rise to the planets.

Although the Solar System is the best known, there are also other planetary systems in which planets revolve around a star.

The components of the Solar System are:


The Sun is the star of our planetary system. It is located about 40,000 light years from the core of the Milky WayAND It is a yellow , medium-sized star that contains 99.75% of the mass of the entire Solar System. Most of the rest of the mass is concentrated in eight planets whose orbits are practically circular and transit within an almost flat disk called the ecliptic plane . The Sun is very important to us because it has allowed life to exist on Earth.

The Sun is the only celestial body in the solar system that emits its own light (like all stars), due to the thermonuclear fusion of hydrogen and its transformation into helium in its nucleus, which is why it emits a large amount of light and energy. It has a surface temperature of about 5500 ºC.

The planets

The planets are planets orbiting a star. They do not emit their own light. Almost all planets in the Solar System have satellites that orbit them.

Tiny planets

There are some celestial bodies that do not meet the conditions to be called a planet , and they are called dwarf planets. They are too small and their orbits are not clear of smaller bodies. Some examples of dwarf planets are Pluto (before it was considered a planet) and Ceres (in the asteroid belt, between the orbit of Mars and that of Jupiter.


The asteroids  are solid fragments orbiting the sun from residues forming rocky planets.

The Solar System formed about 4.6 billion years ago from a large cloud of gas and dust. Most of the matter accumulated in the center forming the Sun, but other materials condensed to form the planets. The bodies of the asteroid belt never became part of a planet.

The asteroids have spherical (or near) as the planets, but are irregularly shaped.

There are thousands of asteroids in our solar system. Its size is very varied, from hundreds of kilometers in diameter to similar to a stone.

Most asteroids are found between the orbits of Mars and Jupiter, in an area called the asteroid belt, although there may also be other places, such as in the orbit of the planets. Thus, some asteroid follows the same path as a planet around the Sun, as happens in the case of Earth and other planets. It may be the case that they are pulled by gravity towards the planet and fall in the form of a meteorite. If their mass is small, they disintegrate when they come into contact with the atmosphere by friction and form a shooting star. If they are large, they can fall on the planet and leave craters, like those that exist on the Moon or on other planets.

The most famous meteorite that has fallen on Earth did it about 60 million years ago in the Yucatan peninsula, and was the cause of the extinction of the dinosaurs.

Cinturón de asteroides entre la órbita de Marte y la de Júpiter

y Asteroid Belt PT.svg: Diogo Sergio (talk · contribs)derivative work: Rowanwindwhistler (talk) work: Rowanwindwhistler (Asteroid Belt PT.svg) [CC BY-SA 4.0 ], via Wikimedia Commons

Brillante bólido sobre Marruecos en la noche del 8 de Julio de 2016. (s. f.). Recuperado 13 de julio de 2016, a partir de

Answer in your notebook

Why, unlike Earth, does the Moon have so many meteorite impact craters?


The Comets are celestial bodies made up of ice, dust and rock that orbit the Sun along different elliptic, parabolic or hyperbolic, highly eccentric trajectories. Most comets are in the Kuiper belt, located beyond the orbit of Pluto.

The kites are solid bodies formed of materials which sublimate in the vicinity of the sun. They have a gas zone which surrounds the core, called a coma or hair, formed by gas and dust. When they approach the Sun, at high speed, the friction of the solar wind causes them to lose matter, generating the characteristic tail, formed by dust and ionized gas.

The best known comet is Halley's Comet, discovered by Edmun Halley in 1705. It is a large, bright comet that orbits the Sun every 75 years on average. It is a comet visible to the naked eye, and although it could be seen on Earth in 1996, we will have to wait until 2061 to see it again near our planet. 

Cola y cabellera de un cometaBy Юкатан [CC BY-SA 4.0 ], from Wikimedia Commons