Even in ancient Greece, mentioned seven luminous bodies that move across the sky against the background of fixed stars. These cosmic bodies were: the Sun, Mercury, Venus, the Moon, Mars, Jupiter and Saturn. The earth was not included in this list, since the ancient Greeks considered the Earth to be the center of everything. And only in the XVI century, Nicolaus Copernicus in his scientific work entitled "On the conversion of the heavenly spheres" came to the conclusion that it is not the Earth, namely the Sun should be at the center of the system of planets. Therefore, the Sun and the Moon were removed from the list, and the Earth was added to it. And after the appearance of telescopes, Uranus and Neptune were added, in 1781 and 1846 respectively. The last open planet of the solar system since 1930 until recently was Pluto.
And now, almost 400 years after the creation of the world's first telescope for observing the stars by Galileo Galilei, astronomers have come to the next definition of the planet.
The planet is a celestial body that must satisfy four conditions: • the body must turn around the star( for example, around the Sun); • the body must have sufficient gravity to be spherical or close to it; • the body should not have other large bodies near its orbit; • The body should not be a star.
star is a cosmic body that emits light and is a powerful source of energy. This is due, first, to the thermonuclear reactions occurring in it, and secondly, to the processes of gravitational compression, which result in the release of a huge amount of energy.
Planets of the Solar System today
The solar system is a planetary system that consists of a central star - the Sun - and all natural cosmic objects circulating around it.
So, for today the Solar system consists of from eight planets : four internal, so-called terrestrial planets, and four outer planets called gas giants. The planets of the terrestrial group include the Earth, Mercury, Venus and Mars. All of them consist mainly of silicates and metals.
The outer planets are Jupiter, Saturn, Uranus and Neptune. The gas giants consist mainly of hydrogen and helium.
The dimensions of the planets of the solar system vary both within groups and between groups. Thus, gas giants are much larger and more massive than the terrestrial planets. The closest to the Sun is Mercury, then as we move away: Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
It would be wrong to consider the characteristics of the planets of the solar system without paying attention to its main component: the Sun itself. Therefore, we will begin with it.
The sun
The sun is the star that gave birth to all living things in the solar system. Around him are planets, dwarf planets and their satellites, asteroids, comets, meteorites and cosmic dust.
The sun arose about 5 billion years ago, 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 on the surface is more than 5000 degrees Kelvin, and the core temperature is more than 13 million K.
The sun is one of the biggest and brightest stars in our galaxy, which is called the Milky Way galaxy. The sun is located about 26 thousand light-years from the center of the Galaxy and makes a complete revolution around it for about 230-250 million years! For comparison, the Earth makes a complete revolution around the Sun for 1 year.
Mercury
Mercury is the smallest planet in the system that is closest to the Sun. Mercury does not have satellites.
The surface of the planet is covered by craters that arose about 3.5 billion years ago due to massive bombardment by meteorites. The diameter of the craters can range from several meters to more than 1000 km.
The atmosphere of Mercury is very discharged, consists mainly of helium and is blown by a solar wind. Since the planet is very close to the Sun and does not have an atmosphere that keeps the heat at night, the temperature on the surface varies from -180 to +440 degrees Celsius.
By terrestrial standards, Mercury completes a complete revolution around the Sun in 88 days. But the Mercurian day is equal to 176 terrestrial.
Venus
Venus is the second closest planet to the Sun of the solar system. By its size, Venus is only slightly inferior to Earth, so it is sometimes called the "sister of the Earth."He has no companions.
The atmosphere consists of carbon dioxide with nitrogen and oxygen impurities. The air pressure on the planet is more than 90 atmospheres, which is 35 times greater than the earth's.
Carbon dioxide and, as a consequence, the greenhouse effect, a dense atmosphere, and proximity to the Sun, allow Venus to be the title of "the hottest planet".The temperature on its surface can reach 460 ° C.
Venus is one of the brightest objects on the earth's sky after the Sun and the Moon.
Earth
Earth is the only known planet in the universe today, on which there is life. The earth has the largest dimensions, mass and density among the so-called inner planets of the solar system.
The age of the Earth is about 4.5 billion years, and life appeared on the planet about 3.5 billion years ago. The moon is a natural satellite, the largest of the satellites of the terrestrial planets.
Earth's atmosphere is fundamentally different from the atmospheres of other planets due to the presence of life. Most of the atmosphere consists of nitrogen, and also includes oxygen, argon, carbon dioxide and water vapor. The ozone layer and the Earth's magnetic field, in turn, weaken the life-threatening effect of solar and cosmic radiation.
Because of the carbon dioxide contained in the atmosphere, there is also a greenhouse effect on the Earth. It does not manifest as much as on Venus, but without it, the air temperature would be about 40 ° C lower. Without atmosphere and temperature fluctuations would be very significant: according to scientists, from -100 ° C at night to + 160 ° C in the afternoon.
About 71% of the Earth's surface is occupied by the world's oceans, the remaining 29% are continents and islands.
Mars
Mars is the seventh largest planet in the solar system."Red planet", as it is also called due to the presence of a large amount of iron oxide in the ground. Mars has two satellites: Deimos and Phobos. The atmosphere of Mars is very discharged, and the distance to the Sun is almost one and a half times greater than that of the Earth. Therefore, the average annual temperature on the planet is -60 ° C, and the temperature drops in some places reach 40 degrees during the day.
Distinctive features of the surface of Mars are impact craters and volcanoes, valleys and deserts, ice polar caps like earthly ones. On Mars is the highest mountain in the solar system: the extinct volcano Olympus, whose height is 27 km! And also the largest canyon: the Mariner Valley, whose depth is 11 km, and the length is 4,500 km.
Jupiter
Jupiter is the largest planet in the solar system. It is 318 times heavier than the Earth, and almost 2.5 times more massive than all the planets of our system combined. In its composition, Jupiter resembles the Sun - it consists predominantly of helium and hydrogen - and emits a huge amount of heat, equal to 4 * 1017 watts. However, in order to become a star like the Sun, Jupiter must be even 70-80 times heavier.
Jupiter has as many as 63 satellites, of which only the largest are relevant - Callisto, Ganymede, Io and Europe. Ganymede is the largest companion in the solar system, it surpasses in size even Mercury.
Due to certain processes in the inner atmosphere of Jupiter, a lot of vortex structures appear in its external atmosphere, for example, stripes of clouds of brownish-red hues, as well as the Great red spot - a giant storm known since the XVII century.
Saturn
Saturn is the second largest planet in the solar system. Saturn's business card is, of course, his system of rings, which consists mainly of ice particles of different sizes( from tenths of a millimeter to several meters), as well as rocks and dust.
Saturn has 62 satellites, the largest of which are Titan and Enceladus. In its composition, Saturn resembles Jupiter, but in density it is inferior even to ordinary water. The outer atmosphere of the planet looks calm and homogeneous, which is explained by a very dense layer of fog. However, the wind speed in some places can reach 1800 km / h.
Uranus
Uranus is the first planet discovered by a telescope, and also the only planet in the solar system that wraps around the sun, "lying on its side." Uranus has 27 satellites, which are named after Shakespeare's heroes. The largest of them - Oberon, Titania and Umbriel.
The composition of the planet differs from gas giants by the presence of a large number of high-temperature modifications of ice. Therefore, along with Neptune, scientists have identified Uranus in the category of "ice giants".And if Venus has the title of "the hottest planet" of the solar system, then Uranus is the coldest planet with a minimum temperature of about -224 ° C.
Neptune
Neptune is the most distant planet from the center of the solar system. The history of his discovery is interesting: before observing the planet in a telescope, scientists using mathematical calculations calculated its position in the sky. This happened after the discovery of unexplained changes in the movement of Uranus in its own orbit.
Today, 13 satellites of Neptune are known in science. The largest of them - Triton - the only satellite that moves in the direction opposite to the rotation of the planet. Against the rotation of the planet, the fastest winds in the solar system are also blowing: their speed reaches 2200 km / h.
By composition, Neptune is very similar to Uranus, therefore it is the second "ice giant".However, like Jupiter and Saturn, Neptune has an internal heat source and emits 2.5 times more energy than it receives from the Sun. The blue color of the planet gives traces of methane in the outer layers of the atmosphere.
Conclusion Pluto, unfortunately, did not manage to get to our parade of the planets of the solar system. But to worry about this is absolutely not necessary, because all the planets remain in their places, despite the changes in scientific views and concepts.
So, we answered the question how many entire planets in the solar system. There are only 8 .
