When and why Pluto was excluded from the list of planets?

Pluto — one of the most studied objects in the Solar system. Because of the large distance from Earth it is difficult to observe in telescopes. His appearance is more like a small star than a planet. But until 2006 it was considered the ninth planet known to us the Solar system. Why is Pluto excluded from the list of planets that have led to this? Consider everything in order.

The Unknown of science "planet X"

In the late nineteenth century, astronomers assumed that our Solar system would have to be another planet. Assumptions were based on scientific data. The fact that watching the Uranium, scientists have discovered a strong influence on its orbit foreign bodies. So, after a while opened the Neptune, but the impact was much stronger and started the search for another planet. It was called "planet X". The search continued until 1930 and was a success — was opened Pluto.

The Motion of Pluto noticed on photos taken within two weeks. Observation and confirmation of the existence of the object over the known limits of the galaxy have one planet took more than a year. Clyde Tombaugh, a young astronomer at the Lowell Observatory, initiated the study in March 1930 announced the opening of the world. So, in our Solar system for 76 years there was a ninth planet. Why exclude Pluto from the Solar system? What was wrong with this mysterious planet?

New openings

At One time Pluto are considered planets, were considered the last of the objects in the Solar system. According to preliminary data, its weight was considered equal to the mass of our Earth. But the development of astronomy is constantly changing this parameter. Today the mass of Pluto is less than 0.24% the mass of Earth, and its diameter is — less than 2400 km, and These figures became one of the reasons why Pluto was excluded from the list of planets. He's more of a dwarf than a full-fledged planet of the Solar system.

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He also has a lot of features, not inherent to conventional Solar system planets. Orbit, its small satellites and the atmosphere unique in themselves.

An Unusual orbit

The Usual eight planets of the Solar system's orbit is almost circular with a small inclination on the Ecliptic. But Pluto's orbit — highly elongated ellipse and has a tilt angle of more than 17 degrees. If the present model of the Solar system, eight planets would be uniformly rotated around the Sun, and Pluto — to cross the orbit of Neptune due to its angle.

In such an orbit rotates around the Sun in 248 earth years. And the global temperature does not rise above minus 240 degrees. Interestingly, Pluto rotates in the opposite direction from our Earth like Venus and Uranus. This unusual orbit of the planet was another reason why Pluto was removed from planets list.

Satellites

Today's five known moons of Pluto: Charon, nix, Hydra, Cerberus and Styx. All of them, except Charon, are very small, and their orbits too close to the planet. This is one of the differences from the officially recognized planets.

In Addition, the Charon, opened in 1978, less than half the size of Pluto. But for satellite it is too large. Interestingly, the center of gravity is outside Pluto, so it's like rocking from side to side. For these reasons, some scientists consider this object a double planet. But it also serves as a response to the question of why excluded Pluto from the list of planets.

Sights

Very difficult to study the object at a virtually inaccessible distance. It is assumed that Pluto is composed of rock and ice. Atmosphere it was discovered in 1985. It consists mainly of nitrogen, methane and carbon monoxide. Its presence was able to identify in the study of the planet as she closed the star. Having no atmosphere, the objects close stars dramatically, and having — gradually.

Due to a very low temperature and the elliptical orbits of the melting ice produces antipenkova effect that leads to a further lowering of the temperature on the planet. After studies carried out in 2015, the researchers came to the conclusion that atmospheric pressure depends on the proximity of the planet to the Sun.

Latest technology

Create a new powerful telescopes marked the beginning of further discoveries beyond the known planets. So, over time, was discovered space objects within the orbit of Pluto. In the middle of the last century this ring is called the Kuiper belt. Nowadays there are hundreds of bodies with a diameter of not less than 100 km and composition similar to Pluto. Found the belt was the main reason why Pluto was removed from planets.

Create the space telescope "Hubble" gave the opportunity to more thoroughly explore the outer space, especially the distant galactic objects. The result was the opened object, called Eris, which turned out to be on Pluto, and eventually — and two celestial bodies that diameter and mass was similar.

The spacecraft AMC “New horizons” sent tostudy Pluto in 2006, confirmed many of the scientific data. Scientists have raised the question of what to do with open objects. To classify them into the category of planets? And then in the Solar system is not 9 but 12 planets, or the exclusion of Pluto from the list of planets will solve this issue.

Revision status

When Pluto was removed from the list of planets? 25 Aug 2006 the participants of the Congress of the International Astronomical Union, composed of 2.5 thousand people took a sensational decision — to exclude Pluto from the list of planets in the Solar system. This meant that it was necessary to revise and rewrite a lot of textbooks as well as maps of the night sky and scientific works in this field.

Why was this decision made? Scientists had to revise the criteria by which classified the planet. A long debate led to the conclusion that the planet must meet all the parameters.

First, the object must rotate around the Sun in its orbit. Pluto according to this parameter choice. Although its orbit is highly elongated, it orbits the Sun.

Second, he must not be a satellite of another planet. This point also corresponds to Pluto. At one time it was thought that he was a moon of Neptune, but this assumption was discarded with the advent of new discoveries, and especially his own satellites.

Third time — have sufficient mass to acquire a spherical shape. Pluto, though small in weight, but is round, and this is confirmed by photographs.

And finally, the fourth requirement — to have a strong gravitational field to clear its orbit from other bodies in space. On this one point Pluto and not suited to the role of the planet. It is located in the Kuiper belt and is not the biggest object in it. His mass is not enough to clear a path for orbit.

Now I understand why Pluto was removed from planets list. But where to classify such objects? For such bodies was introduced by the definition of “dwarf planet”. They began to relate all objects that do not correspond to the last item. So the Pluto-still a planet, albeit a dwarf.