How many planets in the solar system ?The characteristics of the planets and the number of satellites.

Not long ago, any educated person to a question about how many planets in the solar system, would answer without hesitation - nine.And it would have been right.If you do not particularly follow the developments in the world of astronomy and are not a permanent spectator Discovery Channel, today the question you answer the same way.However, it would be wrong at this time.

And here's the thing.In 2006, namely, 26 August, 2.5 thousand participants of the Congress of the International Astronomical Union took a sensational decision and actually crossed Pluto from the list of planets in the solar system, because after 76 years after the discovery he had ceased to satisfy the requirements of scientists to the planets.

Let's understand first that such a planet as well - how many planets in the solar system, astronomers have left us, and look at each of them separately.

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stories Previously, the planet is any body that is in orbit around a star, shines by reflected light from her and has a size greate
r than that of the asteroid.

Even in ancient Greece referred to the seven luminous bodies that move across the sky against the background of fixed stars.These celestial bodies are: Sun, Mercury, Venus, the Moon, Mars, Jupiter and Saturn.The land in this list are not included, as the ancient Greeks believed the Earth was the center of all things.And only in the XVI century, Nicolaus Copernicus in his scientific work entitled "On the Revolutions of the Celestial Spheres" came to the conclusion that it is not the Earth, namely, the sun must be at the center of planetary systems.Therefore removed from the list of Sun and Moon, and made it Earth.But after the appearance of telescopes added Uranus and Neptune, in 1781 and 1846 respectively.
latest discovery planet of the solar system since 1930. Until recently, Pluto was considered.

And now, after almost 400 years since the creation of the telescope by Galileo Galilei first in the world to observe the stars, astronomers, scientists have come to the following definition of a planet.

Planet - a celestial body that must satisfy four conditions:
• body must revolve around the star (eg, around the sun);
• body must possess sufficient gravity, or to have a spherical shape close to it;
• the body should not be near its orbit of other large bodies;

• the body should not be a star.

In turn star - this cosmic body that emits light and a powerful source of energy.This is because, firstly, it occurring in thermonuclear reactions, and secondly, the gravitational compression processes, which resulted in a huge amount of energy is released.

Planets of the Solar System today

solar system - a planetary system, which consists of a central star - the Sun - and all natural cosmic objects circulating around it.

So today solar system consists of eight planets : four internal, so-called terrestrial planets and the four outer planets called gas giants.
For terrestrial planets are Earth, Mercury, Venus and Mars.All of them are composed mainly of metal silicates.

outer planets - a Jupiter, Saturn, Uranus and Neptune.The composition of the gas giants consists mainly of hydrogen and helium.

sizes of the planets of the solar system differ both within groups and between groups.Thus, the gas giants are much larger and more massive than the terrestrial planets.
closest to the Sun is Mercury, then with distance: Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

It would be wrong to consider the characteristics of the planets of the solar system, not paying attention to its main components: the Sun itself.Therefore, we will start with it.

Sun

sun - a star that gave rise to all living things in the solar system.Around him turning planets, dwarf planets and their moons, asteroids, comets, meteorites and cosmic dust.

sun emerged around 5 billion. Years ago, it is a spherical, red-hot plasma ball and has a mass that is more than 300 thousand. Times the mass of the Earth.The temperature at the surface is over 5000 degrees Kelvin, and the core temperature -. More than 13 million K.

Sun is one of the biggest and brightest stars in our galaxy, which is called the Milky Way galaxy.The sun is at a distance of about 26 thousand. Light-years from the galactic center, and makes a complete revolution around it in about 230-250 mln. Years!For comparison, the Earth makes a complete revolution around the Sun in 1 year.



Mercury Mercury - is the smallest planet in the system, which is closest to the sun.Mercury has no satellites.

the planet's surface is covered with craters, emerged about 3.5 billion. Years ago as a result of massive bombardment by meteorites.The diameter of the crater can range from a few meters to more than 1000 km.

Mercury's atmosphere is deeply discharged, consists mainly of helium and is inflated by the solar wind.Since the planet is very close to the Sun and has an atmosphere that would retain heat at night, on the surface temperature ranges from -180 to 440 degrees Celsius.

By earthly standards, a complete revolution around the Sun, Mercury makes for 88 days.But Mercurian day equals 176 earth.

Venus

Venus - the second planet close to the Sun, the solar system.With its dimensions of Venus is only slightly smaller than Earth, so it is sometimes called "Earth's sister planet."Companions are not allowed.

atmosphere consists of carbon dioxide with admixtures of nitrogen and oxygen.The air pressure in the world more than 90 atmospheres, which is 35 times larger than the Earth.

carbon dioxide and as a result, the greenhouse effect, dense atmosphere and proximity to the Sun, Venus, allow to wear the title of "the hottest planet."The temperature on the surface can reach 460 ° C.


Venus - one of the brightest object in Earth's sky after the Sun and the Moon.

Earth

Earth - this is the only presently known planet in the universe, where there is life.Land has the greatest size, mass and density among the so-called inner planets of the solar system.

Age of the Earth is about 4.5 billion. Years, and life appeared on the planet about 3.5 billion. Years ago.Moon - a natural satellite, the largest of the satellites of the terrestrial planets.

The Earth's atmosphere is radically different from the atmospheres of other planets due to the presence of life.Most of the atmosphere consists of nitrogen, and it is composed of oxygen, argon, carbon dioxide and water vapor.Ozone layer and Earth's magnetic field, in turn, weaken the life-threatening impact of solar and cosmic radiation.

Because carbon dioxide contained in the atmosphere in the world there is also a greenhouse effect.It manifests itself not so much as on Venus, but without it the temperature would be about 40 ° C lower.Without the atmosphere and temperature variations would be very significant: according to scientists, from -100 ° C at night and + 160 ° C during the day.

About 71% of the Earth's surface holds the world's oceans, the remaining 29% - this is the continents and islands.

Mars

Mars - seventh the size of a planet in the solar system."Red Planet", as it is called because of the presence of large amounts of iron oxide in the soil.Mars has two moons: Phobos and Deimos.
The atmosphere of Mars is strongly discharged, and the distance to the Sun is almost one and a half times larger than the Earth.Therefore, the annual average temperature on the planet is equal to -60 ° C, and the temperature drops in some places up to 40 degrees during the day.

distinctive features of the Martian surface are impact craters and volcanoes, valleys and deserts, icy polar caps like Earth.Mars is the highest mountain in the solar system: extinct volcano Olympus, whose height - 27 km!As well as the largest canyon: Valles Marineris, the depth of which reaches 11 km, and the length - 4,500 km.



Jupiter Jupiter - is the largest planet in the solar system.It is 318 times heavier than Earth and about 2.5 times more massive than all the planets of our system together.The composition of Jupiter resembles the Sun - it is composed mainly of hydrogen and helium - and emits a tremendous amount of heat equal to 4 * 1017 Watts.However, in order to become a star like the Sun, Jupiter is to be back in 70-80 times heavier.

Jupiter entire 63 satellite, list of which has a meaning only the largest - Callisto, Ganymede, Io and Europa.Ganymede is the largest satellite in the solar system, it is superior in size even Mercury.

Because of certain processes in the inner atmosphere of Jupiter, its outer atmosphere there is a set of vortex structures, such as cloud bands brown-red shades, as well as the Great Red Spot - a giant storm, known from the XVII century.


Saturn

Saturn - the second largest planet in the solar system.Saturn Business Card - this, of course, its ring system, which consists mainly of ice particles of different size (from a few tenths of a millimeter to a few meters), as well as rocks and dust.

Saturn 62 satellites, the largest of which - Titan and Enceladus.
The composition of Saturn resembles Jupiter, but it is inferior in density even ordinary water.
outer atmosphere of the planet looks calm and smooth, due to a very dense layer of fog.However, the wind speed in some places can reach 1,800 km / h.



Uranus Uranus - the first planet discovered with a telescope, and the only planet in the solar system, which turns around the sun, "lying on its side."
Uranus 27 satellites, which are named after Shakespearean characters.The largest of them - Oberon, Titania and Umbriel.

composition of the planet is different from gas giants to the large number of high-temperature modifications of ice.Therefore, along with Neptune, Uranus, scientists have identified the category of "ice giants".And if Venus has the title of "the hottest planet" solar system, Uranus - the planet is the coldest with a minimum temperature of about -224 ° C.



Neptune Neptune - the most distant from the center of the planet of the solar system.The history of its discovery: before watching the planet through a telescope, scientists with the help of mathematical calculations calculated its position in the sky.It happened after the discovery of unexplained changes in the motion of Uranus on its own orbit.

Today science knows 13 satellites of Neptune.The largest of them - Triton - a single satellite, which moves in the opposite direction to the rotation of the planet.Against the rotation of the planet and blow the fastest winds in the solar system: their speed of 2200 km / h.

In composition is very similar to Neptune to Uranus, so is the second "ice giant".However, like Jupiter and Saturn, Neptune has an internal heat source and radiates 2.5 times more energy than it receives from the sun.
Blue planet impart traces of methane in the outer layers of the atmosphere.

Conclusion
Pluto, unfortunately, did not have time to get into our parade of planets in the solar system.But worry about it is absolutely not necessary, because all the planets are still in place, despite the changes in scientific views and concepts.

So we answer the question how many planets in the solar system.There are only 8 .