The smallest planet
It is widely believed that there from school, what in the Solar system smallest planet is Pluto. But is it right today?
A bit of history
Pluto was opened in 1930. Its distance from Earth is about 5,913 million km, and at first his weight was on par with our planet. But further studies showed that its mass is approximately equal to the Month, or even less. The development of the science of astronomy and the means of surveillance allowed the examination of distant parts of our system to detect the Kuiper belt, which includes a variety of relatively small cosmic bodies. Some of them were of similar mass to Pluto. The question arose about the classification of these bodies and assigning them a certain status. Before astronomers faced the question: «What to call a planet and you can assign such a status to reopened bodies mass similar to Pluto?» At a meeting of the MASSES in 2006, scientists have discussed this topic.
Scientists have given a clear definition of what can be called a planet. It was determined that the earth – body, which is orbit around the Sun, round shape, and it has hydrostatic equilibrium. It must have such a mass, which gives it the opportunity to have a clean orbit free from other cosmic bodies.
The whole number of known planets in the Solar system from mercury to Neptune meets the requirements of the definition of «planet». But Pluto, which has in its orbit of foreign cosmic body, the definition is not suitable. Was given the new name «dwarf planet», which Pluto received and a number of objects. They began to take Ceres, which is located in the Main asteroid belt, Eris and some other objects in the Kuiper belt, despite the fact that the Eris for the mass of Pluto more. In accordance with this definition, it was found that the smallest planet in the Solar system at this time was mercury.
Some facts about mercury – the smallest planet
Your name planet got during the heyday of the Empire of Rome in honor of the God, the patron of the enterprise trade – mercury.
In its landscape, the surface of the planet looks like the moon. A big part of it is desert, but there are craters and hills 4 km In the atmosphere of mercury is observed in the presence of oxygen, carbon, helium, carbon dioxide, neon, argon, but it is weak.
The radius of the planet — 2439,7 with an accuracy of 1 km, which is less than that of Saturn’s moon Titan, but it decreases. The data of scientific observations showed that the radius was reduced to 1.5 km away. This happens due to the fact that the planet cools. The mass of mercury is 3.3 x 1023 kg
Mercury is from the Sun at a distance of 45.9 million km. because it is closer to the sun of all the planets, heat from the Sun, he gets 7 times more than the Earth.
Moving in an orbit around the Sun, mercury rotates simultaneously around its axis, whereby it is turned towards the Sun is always on one side. This implies that one side of the planet immersed in the eternal day, and on the other the endless night. On the day half the temperature reaches 400 degrees or more. According to scientists, the region of the poles of the planet never sees sunlight. The temperature there can be 200-250 degrees below zero. With this cold, it is possible that at the poles is water ice. Pluto undergoes a complete revolution around the Sun in 88 days at a speed of 47.8 km/s.
Mercury is still poorly studied by scientists. It is difficult to see in the sky. To the surface of the planet was launched only two research apparatus. First flew to mercury in 1973 and was called Mariner 10. The robot circled the planet three times and took pictures, which formed the basis for the map. It reflects only 45% of the planet’s surface. Then Sputnik went further in the direction of Venus.
In the 2004 study mercury was sent, the satellite Messenger. He gave the Ground a huge number of images, around 75 thousand units, which will significantly fill in the blank spots of knowledge about mercury and its surface.
But the planet holds many unsolved mysteries. For example, the component of sulphur in the soil is significantly more intense than on Earth, although it would seem that under such high temperatures, the material should just disappear. It remains a mystery, and density, consistency of soil components. The soil composition of mercury, under the weight of its weight should spresovuyetsya and compacted. But such direct relation can not be traced. The force of gravity on the planet is much weaker than on Earth, about 3 times. The question requires their response. Or where the planet has a huge core and magnetic field. It is not yet clear, the magnetic field is present on the entire planet, or only in some places. These mysteries require clues for further research.