Today, astrophysics is considered one of the most controversial and dynamically developing sciences. If classical and academic truths that have become statements and axioms dominate in physics and mathematics, then in astronomy scientists constantly have to deal with something new, proving the opposite for established statements. Current technological advances allow the scientific community to conduct a more detailed study and exploration of space, therefore, more and more often in modern science and there are situations similar to the one that has developed around Pluto.

Since 1930, since its discovery, for some time Pluto was considered a full-fledged planet, having the ninth serial number. However, the celestial body was in this status for a short time - only 76 years. In 2006, Pluto was excluded from the list of planets in the solar system, moving into the category of dwarf planets. This move by the scientific community disrupted the classical view of the solar system, setting a precedent in modern science. What was the reason for modern science to make such a radical decision and what can we face tomorrow, continuing to study the near space?

The main characteristics of the new dwarf planet

To come to a decision to transfer the ninth planet to the category of dwarf planets, humanity took a little time. A period of 76 years, even by earthly standards, is considered short enough for significant changes to occur in the astrophysical laboratory. However, the rapid development of science and technology over the past years has cast doubt on the seemingly indisputable fact that Pluto is a planet.

Even 15-20 years ago, in all school textbooks on astronomy, in all planetariums, Pluto was spoken of as a full-fledged planet in the solar system. Today, this celestial body has been downgraded and is considered a dwarf planet. What is the difference between these two categories? What does Pluto lack to be considered a full-fledged planet?

In terms of size, the ex-planet is really very small. The size of Pluto is 18% of the Earth's, 2360 km versus 12742 km. However, even with such a small size, Pluto had the status of a planet. This situation looked somewhat unusual, given the fact that there are many natural satellites in the solar system that have much big sizes. What are the giant satellites of Jupiter and Saturn - Ganymede and Titan - exceeding even Mercury in size. In terms of its physical parameters, Pluto is inferior even to our Moon, whose diameter is 3,474 km. It turns out that the size of a celestial body is not always the main criterion for determining its status in astrophysics.

The small size of Pluto did not prevent astronomers for a long time theoretically acknowledge its presence. Long before its discovery, this celestial object had a modest name - Planet X. In 1930, the American astronomer Clyde Tombaugh visually discovered that the star he observed in the night sky was moving in its own planetary orbit. Then scientists considered that in front of them was the ninth planet of the solar system, the orbit of which is the boundary of our solar system. The scientific community was not embarrassed by either the size of the newly discovered celestial body or its orbital parameters. To top it all, the new planet was given a solid name - Pluto, given in honor of the ancient Greek god, ruler of the underworld. The distance from the Sun to the ninth planet was 5.9 billion km. These parameters were then used for a long time to determine the scale of our solar system.

The one who discovered the planet did not have the technical ability to look deeper into space and put everything in its place. At that time, astrophysicists had limited knowledge and information about the border regions of our solar system. They did not know where near space ends and boundless outer space begins.

Why is Pluto not a planet?

Despite the fact that the former ninth planet was tiny in size, it was she who was considered the last and only large celestial body located beyond the orbit of Neptune. The emergence of more powerful optical telescopes in the second half of the 20th century completely changed the idea of ​​outer space surrounding our star system. In addition to the fact that scientists managed to find their own natural satellites in baby Pluto, the status of the ninth planet was shaken.

The main reason for the changed attitude of scientists to a small planet was the discovery at a distance of 55 AU. from the Sun a large cluster of celestial bodies of various sizes. This region extended just beyond the orbit of Neptune and became known as the Kuiper Belt. Subsequently, in this region of space, it was possible to detect numerous objects with a diameter exceeding 100 km, and similar in composition to Pluto. It turned out that the small planet is just one of many celestial bodies revolving in such a tight circle. This was the main argument in favor of the fact that Pluto is not the last large celestial body discovered beyond the orbit of Neptune. The discovery in the Kuiper belt of the small planet Makemake in 2005 was the first sign. Following her in the same year, astrophysicists discovered three more large celestial bodies in the Kuiper belt, which received the status of trans-Neptunian objects - Haumea and Sedna. In size, they were slightly inferior to Pluto.

For astrophysicists, 2005 was a turning point. The discovery of numerous objects outside the orbit of Neptune gave scientists reason to believe that Pluto is not the only large celestial body. It is possible that in this region of the solar system there are objects similar to or larger than the ninth planet. The received accurate information about Eris put an end to the disputes about the fate of Pluto. It turned out that Eris is not only larger than the planetary disk of Pluto (2600 km versus 2360 km), but also has a whole quarter more mass.

The availability of such information led to the fact that the scientific community had to urgently look for a way out of this situation. Among scientists and astrologers at international conferences, real battles unfolded over this occasion. After the very first speeches by scientists and astrologers, it became clear that Pluto could not be called a planet. They have accumulated great material in favor of the fact that in the Kuiper belt, along with Pluto, there are other objects with similar astrophysical parameters and characteristics. Proponents of the revision of the concept of the classical structure of the solar system suggested that all trans-Neptunian objects be separated into a separate class of celestial bodies in the solar system. According to this concept, Pluto became an ordinary trans-Neptunian object, finally losing its status as the ninth planet of our star system.

The members of the International Astronomical Union, who gathered in Prague for the XXVI General Assembly, put an end to this issue. In accordance with the decision of the General Assembly, Pluto was deprived of the status of a planet. On top of that, a new definition has appeared in astronomy: dwarf planets are celestial bodies that meet certain criteria. These included Pluto, Eris, Makemake and Haumeu and the largest Asteroid - Ceres.

It is believed that Pluto, unlike other large celestial bodies, does not meet one of the four criteria according to which a celestial body can be classified as a planet. For the former ninth planet, the following features are characteristic:

• the presence of a sufficiently large mass;
• Pluto is no one's moon, and itself has four natural satellites;
• the celestial body has own orbit which Pluto revolves around the sun.

The last fourth criterion that allows you to classify Pluto as a planet, in this case absent. The celestial body, neither before nor after, has been able to clear the orbital space around itself. This was the main argument in favor of the fact that Pluto is now a dwarf planet, a celestial body with a completely different status.

In support of this concept, a version is given about the formation of a planet when it becomes the dominant object in a certain orbit, subordinating all other bodies to its own gravitational field. Subsequently, a large celestial body must either absorb smaller objects, or push them beyond the boundaries of its own gravity. Judging by the size and mass of Pluto, nothing like this happened to the ex-planet. The small planet has a mass equal to only 0.07 of the mass of all space objects included in the Kuiper belt.

Basic information about Pluto

IN old time, when Pluto was a full member of the club of planets, he was ranked among the terrestrial planets. Unlike the gas giants Jupiter, Saturn, Uranus and Neptune, the former planet has a solid surface. It was only in 2018 that the surface of the most distant object in the solar system could be examined from a close distance, when the New Horizons space probe flew 12 thousand km from the underground god. With the help of this automatic probe, a person first saw the surface of a dwarf planet in detail and was able to draw short description this celestial body.

A small planet that is barely visible in the sky conspicuous star, runs around the Sun in 249 years. At perihelion, Pluto approaches it at a distance of 29-30 AU, at aphelion the dwarf planet moves away at a distance of 50-55 AU. Despite such vast distances, Pluto, unlike its neighbors Neptune and Uranus, is an icy world open to exploration. The baby rotates around its own axis at a speed of 6 days and 9 hours, although its orbital speed is quite small - only 4.6 km / s. For comparison, Mercury's orbital speed is 48 km/s.

The area of ​​the planet is 17.7 million square meters. kilometers. Almost over the entire area, the surface of the planetary disk is available for viewing and represents the kingdom eternal ice and cold. It is assumed that Pluto consists of frozen water ice, nitrogen and silicate rocks. In other words, this is a huge ice block, the density of which is 1.860 ± 0.013 g/cm3. Average temperatures on the planet are extreme: -223 degrees Celsius below zero. A weak gravitational field and low density have led to the fact that on Pluto the minimum value of acceleration free fall— 0.617 m/s2.

Judging by the images, there are depressions and mountains on Pluto, the height of which can reach 3-3.5 km. In addition to the solid surface, Pluto also has its own atmosphere. A weak gravitational field does not allow the planet to have an extensive air-gas layer. The thickness of the gas layer is only 60 km. These are mainly gases evaporating from the icy surface of Pluto under the influence of hard ultraviolet radiation.

New discoveries from the life of Pluto

In addition to all the information available about Pluto, an atmosphere has recently been discovered on Pluto's moon Charon. This satellite is slightly inferior in size main planet, and scientists have their own opinions on this matter.

The last fact is quite curious. There is a version that Pluto and Charon are a typical double planet. This is the only case in our solar system when the parent celestial body and its satellite are similar in many respects to each other. Whether this is so - time will tell, while humanity continues to collect Interesting Facts about the Kuiper belt, where, along with Pluto, there are many more curious space objects.

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Not so long ago, Pluto was excluded from the list of planets in the solar system and classified as a dwarf planet. Let's see why Pluto is not a planet.

Discovery history

The history of the discovery of the planet is unusual. Pluto seemed to be “hiding” from people for a long time, its existence was proved for more than 90 years, from 1840 to March 13, 1930 when Boston's Lowell Observatory obtained photographs confirming the existence of the ninth planet in the solar system. The name Pluto was given by the eleven-year-old schoolgirl Venetia Burney, who was interested in astronomy and classical mythology, and named the planet after the Greek god of the underworld.

Pluto is very far from the Earth, so its research is very difficult. Even when observed in very powerful telescopes, the planet appears star-shaped and blurry, only very high magnification makes it possible to see that Pluto has a light brown, with a faint tint yellow color. Conducting spectroscopic analysis showed that the structure of the dwarf planet consists mainly of nitrogen ice (98%) with traces of carbon monoxide and methane.

Pluto's surface is very uneven. The side of the planet that faces Charon is practically methane ice, and the opposite surface of the side actually does not contain this component, but it has a lot of Hubble monoxide, "suggest that the internal structure of Pluto consists of rocks (50-70%) and ice (30-50%).

Pluto is one of the most "elusive" and mysterious planets in the solar system. Like its existence, and its reliable mass, no one could determine for a long time. So, in 1955, scientists astronomers believed that the mass of Pluto is approximately equal to the mass of our planet. Since then, the estimated mass has changed many times, and at this time it is believed that Pluto has a mass of about 0.24% of the mass of the Earth. Almost exactly the same as with the mass of the planet, scientists for a long time could not decide on the diameter of Pluto. Until 1950, it was believed that the diameter of the dwarf planet is close to Mars and is approximately equal to 6700 km. However, to date, scientists have agreed that the diameter of Pluto is approximately 2390 kilometers. Pluto is not called a dwarf planet for nothing; it is inferior in size not only to the planets of the solar system, but even to some of their satellites. For example, such as Ganymede, Titan, Callisto, Io, Europa, Triton and the Moon.

What is the problem?

Over the past few decades, powerful new ground and space observatories have completely changed previous ideas about the outer regions of the solar system. Rather than being the only planet in its region like all the other planets in the solar system, Pluto and its moons are now known to be an example a large number objects called the Kuiper belt. This region extends from the orbit of Neptune to a distance of 55 astronomical units(the boundary of the belt is 55 times farther from the Sun than the Earth).

And in 2005, Mike Brown and his team broke the astonishing news. They found an object beyond the orbit of Pluto that was probably the same size, maybe even larger. Officially named 2003 UB313, the facility was later renamed Eridu. Astronomers later determined that Eris had a diameter of about 2600 km, plus it had a mass about 25% greater than that of Pluto.

With Eris, more massive than Pluto, made up of the same mixture of ice and rock, astronomers have been forced to rethink the concept that the solar system has nine planets. What is Eris - a planet or a Kuiper belt object? What is Pluto? final decision was to be adopted at the XXVI General Assembly of the International Astronomical Union, which was held from 14 to 25 August 2006 in Prague, Czech Republic.

Is Pluto no longer a planet?

Association astronomers were given the opportunity to vote for various options planet definitions. One of these options would increase the number of planets to 12: Pluto would continue to be considered a planet, Eris and even Ceres, which was previously considered as the largest asteroid, would be added to the number of planets. Various proposals supported the idea of ​​9 planets, and one of the options for determining the planet led to the deletion of Pluto from the list of the planetary club. But then how to classify Pluto? Do not consider it an asteroid.

Why is Pluto no longer a planet? The sensational decision was made on August 25, 2006 by 2.5 thousand participants of the Congress of the International Astronomical Union. Millions of astronomy students‚ thousands of star charts‚ hundreds of scientific works will be rewritten. From now on, Pluto will be removed from the list of planets in the solar system. In ten days of debate, the International Astronomical Union has stripped the most mysterious object of the solar system of the status that it had for only 76 years. However, over the past few decades, powerful new ground-based and space-based observatories have completely changed previous ideas about the outer regions of the solar system. Instead of being the only planet in its region, like all the other planets in the solar system, Pluto and its moons are now known to be an example of a large number of objects, united under the name of the Kuiper belt. This region extends from the orbit of Neptune to a distance of 55 astronomical units (the boundary of the belt is 55 times farther from the Sun than the Earth). According to the new rules for identifying planets, the fact that Pluto's orbit is inhabited by such objects is the main reason why Pluto is not a planet. Pluto is just one of many Kuiper belt objects. And his orbit is not a circle, but an ellipse, and he himself is very small, so he cannot be on the same list with such as the Earth and with such giants as the planet Jupiter. "It also has a different density, and the dimensions are small. It cannot be attributed to either the terrestrial planets, or to the giant planets, and it is not a satellite of the planets," explains Vladislav Shevchenko, professor at Moscow State University named after M.V. Lomonosov. The conference in Prague left only eight planets on the star maps instead of the usual nine. Since 1930, when Pluto was discovered, astronomers have found at least three more objects in space comparable to it in size and mass - Charon, Ceres and Xena. Pluto is six times smaller than the earth, Charon, its satellite, is ten times smaller. And Xena is bigger than Pluto. Could it be that these are all the planets? Yes, and the Moon was then undeservedly named "satellite". None of the contenders for planetary status could compare with its dimensions. "If we say that Pluto is a planet, then we should attribute to this class not one, but already at first several planets. And then the solar system should not consist of nine planets, but of 12, and a little later - 20 -30 and even hundreds of planets. Therefore, the decision is correct. It is both culturally correct‚ and physically correct," says Andrey Finkelstein, director of the Institute of Applied Astronomy of the Russian Academy of Sciences. In the end, astronomers voted for a rather controversial decision by the standards of that time and attributed Pluto (and other similar objects) to a new class of objects - to the "dwarf planets". What is a planet according to the new definition? Is Pluto a planet? Does it pass the classification? For an object in the solar system to be considered a planet, it must meet four requirements defined by the IAU: 1. The object must orbit the Sun - AND Pluto passes. 2. It has to be massive enough to be spherical with its gravitational force - And here everything seems to be all right with Pluto. 3. It must not be a satellite of another object. Pluto itself has 5 moons. 4. He must be able to clear the space around his orbit from other objects - Aha! This is the rule that Pluto breaks, it's main reason why Pluto is not a planet. What does it mean to "clear the space around your orbit from other objects"? At a time when the planet is just being formed, it becomes the dominant gravitational body in a given orbit. When it interacts with other, smaller objects, it either absorbs them or pushes them away with its gravity. Pluto is only 0.07 of the mass of all objects in its orbit. Compare with the Earth - its mass is 1.7 million times the mass of all other objects in its orbit combined. Any object that does not meet the fourth criterion is considered a dwarf planet. Therefore, Pluto is a dwarf planet. In the solar system, there are a lot of objects with similar sizes and masses that move in approximately the same orbit. And until Pluto collides with them and takes their mass to its hands, it will remain a dwarf planet. The same is true of Eris. But astrophysicists protest. If we classify objects by size and type of orbit, then any shapeless, but very large cosmic body that revolves around the Sun, is also a contender for the name of the planet. Planets‚ say opponents of astronomers‚ is a sphere‚ created by gravity. "Just the size does not mean anything. If the body is loose, then even a small one can only be supported by gravity and will have round shapes. That is small body may be a planet" - explains Vladimir Lipunov, astrophysicist, professor of Moscow State University named after M.V. Lomonosov. The results of this conference put an end to the long-term dispute of astronomers and answered the question why Pluto is not a planet in the Solar System. Pluto has always been the least studied planet. where the atmosphere appears only for a time when the cosmic body approaches the Sun - the ice melts from the heat. But they again tighten Pluto as soon as it moves away from the star. Now American scientists are upset. Not only does the United States own the discovery of 1930, so also the status of the greatest expedition of the already sent probe "New Horizons" is under threat. Nine years later, the Earth was supposed to see pictures of the planet farthest from us, and will receive only a photo of the asteroid. So, the most mysterious planet solar system. Pluto is beautiful, it is a very regular ball reflecting sunlight hundreds of times brighter than the moon. In motion, he is sedateness itself: one year on Pluto is 248 of ours. Finally, Pluto is so far from the Sun that the celestial body from its orbit is just a point. Hence the cold - minus 223 degrees Celsius. Enough reasons to be mysterious! Not even a hundred years have passed since the discovery of the planet. (Hence, in the ancient astrological forecasts Pluto was not taken into account.) Yes, and having opened it, they did not immediately figure out what it was. At first it was believed that it was much larger than now proved, and in textbooks it is called the ninth planet, although it moves in its orbit in such a way that sometimes it turns out to be the eighth planet from the sun! And for a long time it was considered a double planet, until it was found out that Charon, its satellite, has no atmosphere. But the controversy over Pluto led to the adoption (this is 400 years after Galileo pointed the first telescope at the stars) the following definition: only celestial bodies that revolve around the Sun, have sufficient gravity to have a shape close to a sphere and occupy its orbit alone. Although Pluto is now considered a dwarf planet, it is still a fascinating object to explore. And so NASA sent the New Horizons spacecraft to visit Pluto. New Horizons will reach Pluto in July 2015 and will take a close-up photo of Pluto for the first time in human history. Of course, it is worth noting that Nature, in general, does not care how a tiny civilization in one of the billions of star systems classifies the objects of this system. Earth, Mars, Pluto are just clumps of matter revolving around a much more massive body, and Pluto will always be just Pluto, no matter what category of objects we have invented, we refer to it. But there is no cause for concern, since nothing has changed. Pluto at least stays on his own same place.

Characteristics:

• Distance from the Sun: 5,900 million km
• Planet Diameter: 2,390 km*
• Days on the planet: 6 days 8 hours**
• Year on the planet: 247.7 years***
• t° on the surface: -230°C
• Atmosphere: Composed of nitrogen and methane
• Satellites: Charon

* diameter at the equator of the planet
** period of rotation around its own axis (in Earth days)
*** orbital period around the Sun (in Earth days)

Pluto is one of the farthest small objects in the solar system (since 2006, the status of the planet has been replaced by the status of a dwarf planet). This small dwarf planet is located 5900 million km from the Sun and makes one revolution around the celestial body in 247.7 years.

Presentation: planet Pluto

* Correction to presentation video: New Horizons spacecraft has already explored Pluto

The diameter of Pluto is relatively small, it is 2390 km. The approximate density of this celestial body is 1.5 - 2.0 g / cm³. In terms of its mass, Pluto is inferior to other planets, this figure is only 0.002 of the mass of our Earth. Astronomers have also found that one day on Pluto is equal to 6.9 Earth days.

Internal structure

Since Pluto remains a little-studied planet due to its considerable distance from the Earth, scientists and astronauts can only speculate about it. internal structure. Officially, it is believed that this planet consists entirely of frozen gases, in particular methane and nitrogen. Such an assumption was put forward on the basis of spectral analysis data carried out in the late 1980s. However, there is reason to believe that Pluto has a core, possibly with ice content, an icy mantle and crust. Main constituent elements Pluto water and methane.

atmosphere and surface

Pluto is the ninth largest planet in terms of size. solar system, has its own atmosphere, unsuitable for any living organisms to live on it. The atmosphere consists of carbon monoxide, methane gas, which is very light and poorly soluble in water, and a large amount of nitrogen. Pluto is a very cold planet (about -220 °C), and its approach to the sun, which occurs no more than once every 247 years, contributes to the transformation of part of the ice covering its surface into gas and a decrease in temperature by another 10 °C. At the same time, the temperature of the atmosphere of a celestial body fluctuates within - 180 ° C.

The surface of Pluto is covered with a thick layer of ice, the main component of which is nitrogen. It is also known that it has flat terrain and rocks made of hard rocks with an admixture of the same ice. The south and north poles of Pluto are covered with eternal snow.

Moons of the planet Pluto

For a long time it was known about one natural satellite of Pluto, its name is Charon, and it was discovered in 1978, but it turned out to be not the only satellite of a distant planet in the solar system. In a re-study of Hubble telescope images in 2005, two more satellites of Pluto, S/2005 P1 and S/2005 P2, were discovered, which soon received the names Hydra and Nix. To date, in 2013, 5 satellites of Pluto are known, the fourth discovered was the satellite with the temporary designation P4 in June 2011, and the fifth P5 in July 2012.

As for the main large satellite by Pluto's standards, Charon, its size is 1200 km in diameter, which is only half the size of Pluto itself. Their strong differences composition leads scientists to the hypothesis that the entire Pluto-Charon system was formed as a result of a powerful collision of the future planet with its future satellite during the stage of their independent formation from the proto-cloud.

It turns out that Charon was formed from the ejected fragments of the planet, and with it other much smaller small satellites of Pluto.

Pluto is considered a separate dwarf planet in the solar system, although some astronomers are willing to argue with this. This celestial body is located in the so-called Kuiper belt, which consists mainly of massive asteroids and dwarfs (minor planets), which include some volatile substances (for example, water) and certain rocks. Therefore, a number of scientists believe that it would be very appropriate to call Pluto not a planet, as everyone is used to, but an asteroid. Since 2006, Pluto has been classified as a dwarf planet.

Exploring the planet

Pluto was discovered by astronomers relatively recently (in 1930), its satellite Charon in 1978, and other satellites - Hydra, Nikta, P4 and P5 - even later, just a few years ago. Initially, the assumption of the existence of such a celestial object in the Kuiper belt was made by the American astronomer Percival Lovell back in 1906. However, the instruments used to observe the planets at the beginning of the 20th century did not allow us to determine its exact location. For the first time in the pictures, Pluto was captured in 1915, but its image was so subtle that scientists did not attach any importance to it.

Today, the discovery of the ninth planet is associated with the name of Clyde Tombaugh, an American who has been studying for for long years the study of asteroids. This astronomer was the first to take a high-quality image of Pluto, for which he received an award from the Astronomical Society of England.

For a long time, much less attention was paid to the study of Pluto than to other planets, although some attempts to send a spacecraft to a celestial body so far from the Sun (almost 40 times farther than from the Earth) were made. This planet is not of particular interest to scientists, since their attention is focused primarily on those celestial bodies on which the probability of the existence of any life is several times higher. One such object is Mars.

Nevertheless, on January 19, 2006, NASA launched the New Frontiers interplanetary automatic station to Pluto, which on June 14, 2015 made a flyby at the closest possible distance to Pluto (~ 12500 km) and within 9 days transmitted a lot of important for scientific mission images and data (~ 50GB of information).

(An image of the surface of Pluto taken by New Horizons at very close range. The picture clearly shows the plains and mountains.)

This is one of the longest space travels, the New Horizons mission is designed for 15 - 17 years. By the way, the New Frontiers spacecraft has the highest of all other automatic stations. Also, during its long flight, the spacecraft studied Jupiter, transmitting a lot of new images and successfully crossed the orbit of Uranus, and after studying the dwarf planet Pluto, continued on its way towards distant Kuiper belt objects.

And his orbit is not a circle, but an ellipse, and he himself is very small, so he cannot be on the same list with such as the Earth and with such giants as p.