The solar system is a system of planets in which we can find the Earth and a series of astronomical objects that are rotating either directly or indirectly in an orbit around the only star called the sun . In this huge solar system it is the place where we find the planets , which are rotating and forming different orbits around the sun.


What are planets?

A planet is a body of solid consistency that is revolving around a star, which in this case is the sun and that manages to become visible thanks to the light that it reflects from it.



The definition of the word planet has been the subject of intense debate among scientists for some time . Although the word dates back thousands of years, no officially decreed scientific definition of “planet” existed before the 21st century.  According to scientists, there are three requirements paramount for a body in space is considered a planet, the first is found in orbit around the Sun and not another object; It must be an object that has a sufficient amount of gravity to turn round ; and also must have clearedtheir way orbital of rubble.



The main characteristics that we can observe in the planets are the following:

  • All the planets that exist are revolving around the sun , which functions as the center of the system.
  • The planets do not have their own light but reflect the light that comes from the sun.
  • They have the same translational and rotational movement .
  • Its shape is practically spherical and a bit flattened on the pole side .
  • Planets are made up of a nucleus and are made up of a series of compact materials and gases that make up the atmosphere.
  • The size and characteristics of planets can vary from one to another.
  • There are the giant terrestrial planets and the gas giants .
  • They have orbital inclination and axial inclination.
  • They also have a sidereal orbital period and a sidonic orbital period.

How the planets were formed

Scientific studies agree that planets were formed from the dust and gas material that make up the stars known as nebulae . Gravity is responsible for attracting this material to a common point where its temperature and density are compressed and increased, shaping a star . Then, around the star a disk of dust forms that is rotating and that little by little is flattened . These disks that are full of dust begin to form larger pieces and gravityis responsible for bringing them together and giving rise to the birth of a planet.


The evolution of the planets have gone from being in many cases chaotic and unstable places to habitable places as in the case of the Earth. During their first steps of evolution after they are formed, the planets suffer in many cases of migrations being able to even evolve to outer or inner orbits .

Types of planets

There are several types of planets among which we mention the following:

  • Terrestrial or Telluric : they are the planets closest to the sun and are also called internal planets . They are rocky and solid places , small, with a high density and they have almost no moons or ring systems .
  • Jovians : they are the giant planets far from the sun or outer planets . They are planets made of helium or hydrogen , they have a low density , they have many moons and ring systems and they are larger than normal, which is why they are also called gas giants .
  • Ice giants: they  have characteristics of Jovian planets but they also have a large amount of rocks and ice on their surface so they would be in an intermediate category.
  • Extrasolar : it is a planet that orbits a star other than the Sun and does not belong to the solar system. They are also known as gaseous planets .
  • Interstellar : it is also called as a wandering or wandering planet . It has a mass equal to that of a planet but is not gravitationally attached to any star and moves in space as an independent object .
  • Dwarfs : larger than an asteroid but smaller than a real planet. These planets have the mass that allows them to reach hydrostatic equilibrium and become a sphere.

How many planets are there

At present we can find a total of  planets in the solar system, this because after 2006 , Pluto was relegated as a dwarf planet and, for this reason, it ceased to be part of the list that until that date had been taught in schools.

What are the main

The main planets of the solar system are:

  • The earth : it is the only planet that has water in liquid form giving it a blue color and clouds in the atmosphere, which in turn has a low amount of carbon dioxide . It has an earth’s crust formed by layers that are pushed and that collide with each other, producing earthquakes.
  • Mars : it is one of the planets best known for its red colorand for the uncertainty they cause in men. There have been many studies to determine whether on this planet can be possible the life . It has an atmosphere made up of carbon dioxide .
  • Jupiter : it is the largest planetin the solar system and has a ring . Its force of gravity is very great and can affect the movement of other planets . It is made up mainly of hydrogen in a liquid state .
  • Saturn : it has huge rings and can be seen from Earth. In size it is very similar to the earth and has a low density , so much that it could float in a swimming pool.


The size of the planets is as follows:

Mercury 4,880 km.
Venus 12,104 km.
The earth 12,756 km.
Mars 6,794 km.
Jupiter 142,984 km.
Saturn 108,728 km.
Uranus 51,118 km.
Neptune 49,532 km.
Pluto 2,320 km.


Gravity is the force that planets have, which includes their density and size . It is the matter that exists on the planet that is in charge of realizing the gravitational power . The gravity that exists on planets is as follows:

  • Mercury : has a surface gravity of 3.7 m / s2.
  • Venus : the force of gravity is also 8.87 m / s2.
  • Mars : it is similar to that of the earth and is 3.7 m / s2.
  • Jupiter : gravity is usually 24.8 m / s2; in short, almost three times the gravity of the earth.
  • Saturn : its gravity is equivalent to 10.44 m / s2.
  • Uranus : has a gravity of 7 m / s2; it can be said that it is very minimal since its size is 4 times larger.
  • Neptune : its gravity is 11.15 m / s2.

Life on other planets

In relation to the presence of life on other planets, a theory that is complete and accurate that describes its formation in other planetary systems has not yet been created . Nowadays, thanks to the different advances in biology , biochemistry and planetary sciences , new expectations have been formulated that make scientists think that there is life beyond planet earth. Several discoveries have been made to prove this. For life to exist on other planets, scientists agree on four necessary aspects: the presence of liquid water , the presence of organic matter, a powerful source of available energy and a stable environment so that organic molecules can develop properly to shape life.


Some of the planets can be observed through a telescope and others with the naked eye . One of the most difficult planets to observe is Mercury since it never moves away from the sun, it can be observed under specific conditions and at certain times of the year. Venus is the easiest planet to observe with the naked eye , and if you look at the sky it is the third brightest object in the sky, it alternates between sunrise and sunset . Another planet that we can see is Mars, Uranus and Saturn . Neptune cannot be observed with the naked eye.


Planets are important because through them scientists manage to carry out a large number of experiments and expeditions in search of new life and new horizons. It should be noted that among them we have the planet Earth which is fundamental for life.

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