The Sun  The sun is the star of the planetary system in which the Earth is found, therefore, it is the closest to the Earth and, thus, the shiniest star apparent to the Earth. Its presence or absence in the sky determines day and night. The energy radiated by the sun is used by photosynthetic beings which constitutes the base of the food chain, making it the main source of energy for life. It also provides the energy that keeps the climate processes going. The Sun is found in the so-called main sequence with a spectral type G2, which was formed some 5 billion years ago and will remain in the main sequence approximately 5 billion years more. The Sun, and the Earth and all the celestial bodies orbiting around it, form the Solar System.
Despite being a medium-sized star, it is the only one you can see with the naked eye. It has an angular diameter of 32'35" arc perihelion and 3131" aphelion, which gives an average diameter of 32'03". Because of some strange coincidence, the combination of sizes and distances from the Sun and Moon are such that they are, approximately, the same apparent size in the sky. This allows a wide range of different solar eclipses (total , annular or partial).
The Sun was formed some 4500 million years ago from gas clouds and dust that contained residues of previous generations of stars. Thanks to the metallicity of this gas, the planets, asteroids and comets in the Solar System later emerged from its circumstelar disk. In the Sun, fusion reactions are produced in which hydrogen atoms are converted into helium, producing the energy it radiates. Currently, the Sun is in the main sequence, phase in which it will continue to burn hydrogen constantly for another 5000 million years. When the hydrogen nucleus becomes much less abundant it will shrink and the adjacent layer of hydrogen will start to burn, but it will not be enough to stop its collapse. It wll continue to contract until its temperature is high enough to fuse the helium nucleus (MK 100). At the same time, the outer layers of the wrapping will steadily expand, so much that, despite the increase of brightness of the star, its effective temperature will decrease, putting its light in the red spectrum zone. The Sun will have become a red giant. The radius of the Sun, then will be so great that it will have engulfed Mercury, Venus and possibly the Earth. During its time as a red giant (about 1000 million years), the Sun will expel gases with increasing intensity. In the last moments of its life, the solar winds will intensify and the sun will release its entire wrapping, which will, over time, form a planetary nebula. The nucleus and its surroundings will be more compressed until they form a very concentrated state of matter, in which the quantum repulsions between the extremely close electrons (degenerated) will slow down the collapse. What will be left is, a white, tiny star of carbon and oxygen gradually cooling down.
Most of the energy used by living things comes from the sun. The plants absorb it directly and carry out photosynthesis. Herbivores indirectly absorb a small amount of this energy by eating plants, and carnivores indirectly absorb a smaller amount by eating the herbivores.
Most of the energy used by humans derives indirectly from the sun. Fuel fossils preserve solar energy captured millions of years ago through photosynthesis. Hydroelectric energy uses the potential energy of water that condenses in altitude, after being evaporated because of the heat from the sun, etc..
However, the direct use of solar power for energy is not yet widespread, due to the fact that the current mechanisms are not sufficiently effective. The Planets 
A planet, according to the definition adopted by the International Astronomical Union on August 24, 2006, is a celestial body that:
Orbits around the Sun
It has enough mass so that its gravity can overcome the forces of the rigid bodies, and it acquires a shape in hydrostatic equilibrium (nearly spherical).
It has cleared the area of its orbit of planetesimals.
According to this definition, the Solar System has eight planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Pluto, which, until 2006, was considered a planet, has been classified as a dwarf planet, along with other similar objects in the Solar System. Certainly since the 70's there has been an extensive debate on the concept “planet”. With the enlightment of new data concerning the size of Pluto (it is smaller than estimated at the beginning), this debate grew in the following years after discovering new objects with similar sizes. This way, the new definition of “planet” introduces the concept of “dwarf planet”, a denomination which, besides Pluto, includes Ceres, previously considered an asteroid, and the transneptunian object, Eris. A dwarf planet is the difference of definition (c), since it has not cleared the area of its orbit and it is not a satellite of another body.
The bodies that revolve around other stars are generally called extrasolar planets or exoplanets. The condition requierements necesary to be considered an extrasolar planet, are the same as what we find in the definition of planet to the solar system, even if they orbit their respective stars. They also include a condition regarding the limit of size, not exceeding the 13 Jovian which constitutes the mass threshold that prevents nuclear fusion of deuterium [2].
Etymologically, the word planet comes from Latin who took it from the Greek πλαν? Της plane-te-s (“vagabond, wanderer), and planaö (" I vagabond "). The origin of this word comes from the apparent movement of the planets respecting the fixed background of stars, that despite moving through the sky according to different seasons, maintain their relative positions.
Thus, the word planet was used in the ancient geocentric theory which describes the seven stars that are visible to the naked eye and move with respect to the stars in the sky. These stars are the Sun, Moon, Mercury, Venus, Mars, Jupiter and Saturn.
With the new heliocentric theory of Copernicus, based on the theory of Aristarchus of Samos, the Earth was considered a planet (1543), and the Sun and the Moon were erased from the list. Therefore, the number of planets dropped to six.
Dwarf Planets  Dwarf planet is the term created by the International Astronomical Union (IAU) to define a new category of celestial bodies, different from "planet" (or "classical planet"). They are "smaller bodies of the Solar System." It was introduced in the IAU resolution of August 24, 2006. According to this definition, a dwarf planet is a celestial body that:
Orbits around the Sun
It has enough mass so that its gravity can overcome the forces of the rigid bodies, and it acquires a shape in hydrostatic equilibrium (nearly spherical).
It is not a satellite of a planet nor another non-stellar body.
It has not cleared the area of its orbit.
According to these characteristics, the difference between the classical planets and dwarf planets is that the dwarf planets have not cleared the area of their orbits.
The most immediate consequences of this new definition were the loss of Pluto as a "planet" (classical) and its renaming as (134340) Pluto, and the upgrading of Ceres, previously considered an asteroid, and Eris, formerly known as Xena (informally) or as 2003 UB313 (provisionally). Minor bodies
Among the minor bodies, we have the minor planets, which have enough mass to round off their surfaces. Before the discovery of 2060 Chiron and the first transneptunian objects, the term "minor planet" was a synonymous of asteroid. However, the term asteroid is often reserved for the small rocky bodies of the inner Solar System. Most transneptunian objects are frozen bodies like comets, although most objects possible to find at these distances are much larger than the comets.
The largest transneptunian objects are much bigger than the largest asteroids. The natural satellites of planets have a greater range of sizes and surfaces, the largest of them being much bigger than the largest asteroids.
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