Natural Satellite


The Solar System has eight planets, five mini-planets (dwarfs), comets, and asteroids. The solid celestial bodies that revolve around them are called natural satellites, since they are not created by man. The natural satellite of the Earth is the Moon, but there are other celestial bodies that have been given their own names. They come in different sizes and shapes, they are solid and have no atmosphere. Generally, they move around bodies larger than themselves. Among its functions is the stabilization of the orbit of the planets, so as not to modify their direction.


What is a natural satellite?

A natural satellite is a solid celestial body that does not have an atmosphere and revolves around planets, comets and asteroids larger than them. They are gravitationally attracted. There is still no certainty about their composition, it is thought that some are made of ice and rocks. Earth’s Moon is known to be made up of potassium, helium, sodium, and argon. Its shape and dimension varies. Currently 146 natural satellites are known.


Characteristics of a natural satellite

  • Solid in its constitution
  • Most have no atmosphere
  • Orbit around bodies larger than themselves
  • They maintain their position by gravitational effect
  • They are opaque, of various sizes and shapes.
  • They are inhospitable


The formation or origin of natural satellites is not conclusive.However, there are several theories about it.

  • They were created at the same time as the planet they orbit
  • They are a part that was detached from the planet in the course of its formation
  • The planet attracted them with its force of gravity


There are no completely accurate data on the composition of natural satellites. Scientists believe that much of it contains ice and rocks. Samples collected on Earth’s Moon determined that it is made up of Sodium, Helium, Potassium, and Argon. Internally it is structured similar to Earth and externally it is rocky.

Shape and size

Not all natural satellites have the appearance of our Moon, that is, with a spherical shape. They are irregular, elliptical, round and even flattened . Its dimensions also vary remarkably. The largest discovered is Ganymede, which has 5,262 km and is one of the 50 natural satellites that Jupiter has. The Earth’s moon is 3,474 km long and the fifth largest in the solar system. The smallest is Phobos, one of the two moons of Mars (Deimos is the other), which barely reaches a radius of 11 millimeters.


Natural satellites are classified into two types based on how they orbit. The periods it takes to do so are variable. For example, it takes the Earth’s Moon 27 days to make a complete revolution and the Ganymede of Jupiter does it in almost 7 days. The types are:

  • Regular natural satellites: They orbit around a body following the direction in which it revolves around the Sun. For example, if the planet rotates from east to west the moon will also. So it is Regular. Among these are: Oberon, Ganymede, Tethys and Titan.
  • Irregular natural satellites: They orbit very far from their planets, inclined and elliptical. These satellites are thought to have been comets before being attracted to the planet. Among them are: Leda, Febe, Nereida and Himalia.

Function of a natural satellite

Basically, a natural satellite fulfills the function of a “counterweight” or directional stabilizer with the planet that it accompanies. Its presence full of gravitational force and inertia, ensure that the same direction is always maintained. For example, thanks to the Moon, the Earth is not drawn towards the Sun (it would cause it to burn) or to move away (which would freeze us). The effect of the tides is another example of the important function or action of the Earth’s Moon. Mercury and Venus do not have natural satellites.

Earth’s natural satellites

The Moon is the only natural satellite that the Earth has. It is 3,474 km long and is the largest when compared to the primitive planet, but in terms of its surface it is the fifth largest, below Ganymede (Jupiter, 5,262 km), Titan ( Saturn , 5,150 km), Callisto ( Jupiter, 4,820 km) and Io (Jupiter, 3,643 km). It has a huge and important influence. Although it does not have the conditions for human life, its gravitational force generates enough light time for photosynthesis to take place, the seasons, the tides and we have a suitable atmosphere to breathe. In addition, its beauty and shape has inspired artists, cultists, and provides guidance to farmers.

Natural satellites of Mars

It has two moons, Deimos and Phobos. Both are small, Phobos is the smallest in the Solar System so far discovered, about 11 kilometers in radius. Scientists found them in the 19th century. It is estimated that they were not generated with the red planet, but were attracted by its force of gravity. Both orbit very close to Mars, especially Phobos (up to less than 3,000 km) so they predict that one day it will end up crashing into the planet.

Saturn’s natural satellites

Saturn is the planet with the largest number of natural satellites. Named there are 53, but they calculate that it has 82. Its moons are Enceladus, Mimas, Tethys, Rhea, Dione, Titan, Iapetus, Hyperion, Erriapo, Janus, Phoebe, Epimetheus, Telesto, Helena, Calypso, Atlas, Kiviuq, Prometheus, Pan , Pandora, Ymir, Tarvos, Paaliaq, Ijiraq, Suttungr, Albiorix, Mundilfari, Skadi, Thrymr, Siarnaq, Narvi, Palene, Metone, Pollux, Aegir, Dafne, Bebhionn, Bestla, Bergelmir, Farbauti, Fornjot, Fenrir , Hati, Kari , Hyrokkin, Loge, Surtur, Skoll, Greip, Tarqeq, Jarnsaxa, Egeón and Antea. Titan stands out because it has an atmosphere and is the second largest in the solar system.

Jupiter’s natural satellites

There are also many natural satellites of Jupiter. There are about 79. The 50 best known are: Io, Ganymede, Kore, Europa , Amalthea, Elara, Himalia, Pasiphae, Lisitea, Sinope, Carme, Ananké, Tebe, Leda, Adrastea, Calírroe, Metis, Themisto, Táigete, Megaclite , Caldona, Cálice, Harpálice, Jocasta, Isonoé, Erínome, Praxídice, Tione, Autónoe, Hermipé, Eurídome, Aitné, Euante, Ortosia, Euporia, Espondé, Pasítea, Calé, Hegémone, Aedea, Mnemea, Telxikénoe, Arborce , Eukélade, Cilene, Carpo, Herse and Callisto. Its four largest moons discovered by Galileo stand out (Io, Europa, Ganymede and Callisto).

Natural satellites of Uranus

Uranus has 27 moons and none have an atmosphere . These are: Ofelia, Bianca, Cordelia, Crésida, Julieta, Desdemona, Porcia, Mab, Rosalinda, Belinda, Puck, Perdita, Cupido, Francisco, Miranda, Ariel, Titania, Umbriel, Oberón, Stefano, Calibán, Sicorax, Trínculo, Ferdinando , Margarita, Prospero and Setebos. The most prominent satellite is Miranda, due to its impressive cracked exterior that appears to have suffered multiple impacts.

Neptune’s natural satellites

Neptune has 13 natural satellites : Nereida, Naiad, Triton, Thalassa, Despina, Larisa, Galatea, Proteus, Psámate, Halimede, Sao, Neso and Laomedeia. The most prominent is Triton, due to its beautiful spherical shape compared to the rest of its companions. There are also incredible data about how cold the place is, since it is estimated that it has temperatures that reach -236 degrees.

Pluto’s natural satellites

Plato has five moons: Nix, Cerberus , Styx, Hydra, and Charon. The latter is the most prominent, as it is almost the same size as its parent planet, so some do not consider it a satellite but a “binary system” . Pluto and Charon orbit synchronously.

Differences between natural and artificial satellite

As its name indicates, the most notable difference between natural and artificial satellites is that the latter are created on Earth by men and the former arose naturally by various processes in the Solar System. That is why the trajectory of the artificial ones can be modified and that of the natural ones not. There are a large number of artificial satellites that surround the Earth and other planets. These can be classified according to their function or the mission they fulfill:

  • Weather satellites: record the climate and weather of the Earth’s atmosphere.
  • Astronomical satellites: They are used to observe galaxies, planets and other space bodies.
  • Communications satellites: They are used for telecommunications services.
  • Navigation satellites: They send signals to identify a precise position of receivers on Earth.
  • Biosatellites: They are what living organisms contain for scientific study purposes.
  • Solar energy satellites: They send solar energy to terrestrial antennas.
  • Earth observation satellites: They monitor environmental, meteorological and cartographic conditions without a military purpose.
  • Spy satellites: They have military purposes. They carry out observation and / or communications work.
  • Killer satellites: They are equipped with weapons for the destruction of enemy satellites, dangerous targets or other weapons orbiting in space.
  • Space stations: They are those that are designed so that humans can live in space. They do not have propulsion or system to land. The stations are reached by other transport devices.

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