We explain what the planets are, how they originated, and their classification. Also, what are its characteristics and its movements?
Planets (from the Greek planëtes , which translates as "wanderer" or "wanderer") are called certain natural astronomical bodies, of relatively large size , that move on an orbit around a star (such as the Sun ).
Unlike stars, they lack their own light and energy emissions from nuclear reactions inside them.
In other words, planets are large, opaque bodies that orbit stars. In turn, they can be orbited by moons or other natural (and artificial) satellites, being the dominant object throughout their orbit.
Specialists impose other requirements on astronomical bodies that meet these basic conditions to distinguish them from asteroids and other space objects:
There is no consensus regarding the exact origin of the planets.
However, the most accepted theory is that they were part of the disk of gas and dust from which stars are formed , which by attracting heavy elements ends up becoming a planetesimal.
This first formation merges with others due to the effect of gravity until it forms a larger element.
The gravity of this larger object manages to capture gaseous elements in the form of an atmosphere around it.
The planets can be classified according to various criteria, such as their spatial location (within our Solar System , within some other or without any system), but above all according to their size.
Thus, we can talk about:
Not all the planets do it at the same speed , nor do they have orbits of the same size: the further away they are from their axis of translation, the longer and slower this movement is.
Since the Earth 's axis is tilted, there are sectors of the orbit where the southern hemisphere points more directly towards the Sun, and other sectors where the northern hemisphere is more exposed. This is due to the change of seasons.
On the other hand, the planets also rotate on their own axis , in what is known as rotational movement, and which can occur at different speeds. In the case of Earth this produces day and night and takes 24 hours to occur; but on other planets it can be much faster or much slower.
So far we know that it is made up of eight main planets : four inner and four outer, each with their respective natural satellites . In addition, it includes two asteroid fields and four dwarf planets.
These planets have a similar size, a higher density and a clearly differentiated structure , with solid surfaces and atmospheres. The inner planets are Mercury , Venus , Earth, and Mars .
They are gigantic and gaseous planets , with no defined surface, with very fast rotation periods and strong magnetic fields . In some cases, they have ring systems surrounding them.
The outer planets are Jupiter , Saturn , Uranus, and Neptune .
The latter were defined as those celestial bodies whose masses are too small to prevail over their orbits and force other bodies to orbit around them as moons. But at the same time they are too big (and their very spherical and regular shapes) to think that they are asteroids.
The dwarf planets in the Solar System are Ceres, Pluto , Charon, and Eris .
To them could be added other planetoids often referred to as "Trans-Neptunian Objects" , being beyond the orbit of Neptune. Among them are Makemake, Orcus, Quaoar, Varuna, Ixion, and others.
It is very possible that each star in the universe has its own planetary system, but until 1992 it had not been possible to prove its existence. The vast majority of these planets are Jupiter-like gas giants .
Therefore, these planets move through space as independent objects, adrift.
However, in our search for a future new home, we have already identified 57 potentially habitable extrasolar planets , judging by their similarity to Earth. The closest of them is 305.09 light-years away.
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