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Pluto is one of the farthest small objects in the solar system (since 2006, the status of the planet has been replaced by the status of a dwarf planet).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, which occupies the ninth place in size among the planets of the solar system, has its own atmosphere, unsuitable for any living organisms to live on it. The atmosphere consists of carbon monoxide, a very light and slightly soluble gas in water, methane and a large number nitrogen. Pluto is very cold planet(about - 220 ° C), and its approach to the sun, which occurs no more than 1 time in 247 years, contributes to the transformation of part of the ice covering its surface into gas and lowering the 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. Southern and north pole Pluto is covered with eternal snows.

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 in composition lead 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 volatiles(e.g. 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 it. exact location 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 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 spacecraft to a celestial body so far from the Sun (almost 40 times farther than from the Earth) were undertaken. 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 with a 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.

In August 2006, incredible news thundered: the solar system lost one of the planets! Here you will really be on your guard: today one planet has disappeared, tomorrow another, and there, you see, the turn will reach the Earth!

However, there was no reason to panic then, nor now. It was only about the decision of the International Astronomical Union, which, after long disputes, deprived Pluto of the status of a full-fledged planet. And, contrary to misconceptions, on that day the solar system did not shrink, but, on the contrary, expanded unimaginably.

Briefly:
Pluto is too small for the planet. There are celestial bodies that were previously considered asteroids, although they are the same size, or even larger, than Pluto. Now both they and Pluto are called dwarf planets.

Search for wanderers

The discovery of Pluto for a long time was considered the ninth planet of the solar system, has a prehistory.

Before the advent of telescopes, mankind knew five celestial bodies called planets (translated from Greek - "wanderers"): Mercury, Venus, Mars, Jupiter, Saturn. In four centuries, two more have been discovered major planets: Uranus and Neptune.

The discovery of Uranus is remarkable in that it was made by an amateur music teacher William Herschel. On March 13, 1781, he was surveying the sky and suddenly noticed a small yellow-green disk in the constellation Gemini. At first, Herschel thought he had discovered a comet, but observations by other astronomers confirmed that a real planet had been discovered with a stable elliptical orbit.

Herschel wanted to name the planet Georgia after King George III. But the astronomical community has decided that the name of any new planet must match the others, that is, come from classical mythology. As a result, the planet was named Uranus in honor of ancient greek god heaven.

Observations of Uranus revealed an anomaly: the planet stubbornly refused to follow the laws of celestial mechanics, deviating from the calculated orbit. Twice astronomers calculated models of the motion of Uranus, adjusted for the gravity of other planets, and twice he “deceived” them. Then there was an assumption that Uranus is influenced by another planet located beyond its orbit.

On June 1, 1846, an article by the mathematician Urbain Le Verrier appeared in the journal of the French Academy of Sciences, where he described the expected position of a hypothetical celestial body. On the night of September 24, 1846, at his prompting, the German astronomers Johann Galle and Heinrich d'Arre, without spending much time searching, discovered an unknown object, which turned out to be big planet and was named Neptune.

Planet X

The discovery of the seventh and eighth planets in just half a century has tripled the boundaries of the solar system. Satellites were discovered near Uranus and Neptune, which made it possible to accurately calculate the masses of the planets and their mutual gravitational influence. Based on these data, Urbain Le Verrier built the most accurate model of orbits at that time. And again, reality diverged from the calculations! New riddle inspired astronomers to search for a trans-Neptunian object, which became conventionally called "planet X".

The glory of the discoverer went to the young astronomer Clyde Tombaugh, who abandoned mathematical models and began to study the sky with the help of a photographic refractor. On February 18, 1930, comparing photographic plates in January, Tombaugh discovered the displacement of a faint star-shaped object - it turned out to be Pluto.

Astronomers soon determined that Pluto was a very small planet, smaller than the Moon. And its mass is clearly not enough to influence the movement of the huge Neptune. Then Clyde Tombaugh launched a powerful search program for another "planet X", but, despite all efforts, it was not possible to find it.

We know a lot more about Pluto today than we did in the 1930s. Thanks to many years of observations and orbiting telescopes, it was possible to find out that it has a very elongated orbit, which is inclined to the plane of the ecliptic (Earth's orbit) at a significant angle - 17.1 °. This unusual property has allowed speculation as to whether Pluto is home planet The solar system or it is accidentally attracted by the gravity of the Sun (for example, this hypothesis is considered by Ivan Efremov in the novel "The Andromeda Nebula").

Pluto has small satellites, and many of them have been discovered quite recently. There are five of them: Charon (discovered in 1978), Hydra (2005), Nikta (2005), P4 (2011) and P5 (2012). The presence of such a complex system of satellites suggested that Pluto has rarefied rings of debris - such are always formed when small bodies collide in orbits around planets.

Data maps orbiting telescope Hubble showed that Pluto's surface is not uniform. The part facing Charon contains predominantly methane ice, while on the opposite side more ice from nitrogen and carbon monoxide. At the end of 2011, complex hydrocarbons were discovered on Pluto - this allowed scientists to assume that the simplest forms of life exist there. In addition, Pluto's rarefied atmosphere, consisting of methane and nitrogen, last years noticeably "swollen", which means that there are climate changes on the planet.

What was Pluto called?

Pluto was named on March 24, 1930. Astronomers voted on a shortlist containing three final options: Minerva, Kronos and Pluto.

The third option turned out to be the most suitable - the name of the ancient god of the kingdom of the dead, also known as Hades and Hades. It was proposed by Venetia Burney, an eleven-year-old schoolgirl from Oxford. She was interested not only in astronomy, but also in classical mythology, and decided that the name Pluto best suits the dark and cold world. The name came up in a conversation with her grandfather Falconer Meidan, who had read about the planet's discovery in a magazine. He conveyed Venice's proposal to Professor Herbert Turner, who, in turn, telegraphed his colleagues in the United States. For her contribution to the history of astronomy, Venetia Burney received a prize of five pounds sterling.

Interestingly, Venice survived until the moment when Pluto lost its status as a planet. When asked about her attitude to this "downgrade", she replied: "At my age, there is no such debate anymore, but I would like Pluto to remain a planet."

Edgeworth-Kuiper Belt

By all indications, Pluto is a normal planet, albeit a small one. Why did astronomers react so unfavorably to him?

The search for a hypothetical "Planet X" continued for decades, which led to many interesting discoveries. In 1992, a large cluster of small bodies, similar to asteroids and comet nuclei, was discovered beyond the orbit of Neptune. The existence of a belt of debris left over from the formation of the solar system was predicted long before by the Irish engineer Kenneth Edgeworth (in 1943) and the American astronomer Gerard Kuiper (in 1951).

The first trans-Neptunian object belonging to the Kuiper belt was discovered by astronomers David Jewitt and Jane Lu, observing the sky with the latest technologies. On August 30, 1992, they announced the discovery of the body 1992 QB1, which they named Smiley after the hero of the popular detective John Le Carré. However, this name is not officially used, since there is already an asteroid Smiley.

By 1995, seventeen more bodies had been discovered beyond the orbit of Neptune, eight of them beyond the orbit of Pluto. By 1999 total registered objects of the Edgeworth-Kuiper belt has exceeded a hundred, by now - over a thousand. Scientists believe that in the foreseeable future it will be possible to identify more than seventy thousand (!) Objects larger than 100 km. It is known that all these bodies move in elliptical orbits, like real planets, and a third of them have the same orbital period as Pluto (they are called “plutinos” - “plutons”). The objects of the belt are still very difficult to classify - it is only known that they have sizes from 100 to 1000 km, and their surface is dark with a reddish tint, which indicates an ancient composition and the presence of organic compounds.

By itself, the confirmation of the Edgeworth-Kuiper hypothesis could not cause a revolution in astronomy. Yes, now we know that Pluto is not a lonely wanderer, but the neighboring bodies are not able to compete with it in size, and besides, they have no atmosphere and satellites. scientific world could continue to sleep peacefully. And then something terrible happened!

Dozens of Plutos

Mike Brown - "the man who killed Pluto"

Astronomer Mike Brown, in his memoirs, claims that even as a child, through observations, he independently discovered the planets, unaware of their existence. When he became a specialist, he dreamed of the greatest discovery - "Planet X". And he opened it. And not even one, but sixteen!

The first trans-Neptunian object, designated 2001 YH140, was discovered by Mike Brown with Chadwick Trujillo in December 2001. It was a standard celestial body of the Edgeworth-Kuiper belt with a diameter of about 300 km. Astronomers continued their vigorous search, and on June 4, 2002, the team discovered the much larger object 2002 LM60, 850 km in diameter (now estimated to be 1,170 km in diameter). That is, the size of 2002 LM60 is comparable to the size of Pluto (2302 km). Later, this body, which looks like a full-fledged planet, was called Quaoar - after the creator god worshiped by the Tongva Indians of Southern California.

Further more! November 14, 2003 Brown's group discovers the trans-Neptunian object 2003 VB12, which is named Sedna - in honor of the Eskimo goddess of the sea, who lives at the bottom of the North Arctic Ocean. At first, the diameter of this celestial body was estimated at 1800 km; additional observations with the Spitzer Orbital Telescope reduced the estimate to 1,600 km; on the this moment it is believed that the size of Sedna is 995 km. Spectroscopic analysis has shown that Sedna's surface is similar to some other trans-Neptunian objects. Sedna moves in a very elongated orbit - scientists believe that it was once influenced by a star that passed by the solar system.

On February 17, 2004, Mike discovers an object 2004 DW, named Orc (deity of the underworld in Etruscan and Roman mythology), with a diameter of 946 km. Spectral analysis of Ork showed that he is covered water ice. Most of all, Orc is similar to Charon - a satellite of Pluto.

On December 28, 2004, Brown discovers object 2003 EL61, named Haumea (Hawaiian Goddess of Fertility), about 1300 km in diameter. Later it turned out that Haumea rotates very quickly, making one revolution around its axis in four hours. Hence, its shape must be strongly elongated. Modeling showed that in this case, the longitudinal size of Haumea should be close to the diameter of Pluto, and the transverse size - half as much. Perhaps Haumea appeared as a result of the collision of two celestial bodies. Upon impact, some of the light components evaporated and were ejected into space, subsequently forming two satellites: Hiiaka and Namaka.

goddess of discord

Mike Brown's finest hour struck on January 5, 2005, when his team discovered a trans-Neptunian object estimated to be 3000 km in diameter (later measurements gave a diameter of 2326 km). Thus, in the Edgeworth-Kuiper belt, a celestial body was found that is definitely larger than Pluto in size. Scientists made a noise: finally, the tenth planet is open!

Astronomers gave the new planet the unofficial name Xena in honor of the heroine. And when Xena found a companion, they immediately named him Gabriel - that was the name of Xena's companion. The International Astronomical Union could not accept such "frivolous" names, so Xena was renamed Eridu ( Greek goddess discord), and Gabriel - in Dysnomia (the Greek goddess of lawlessness).

Eris has indeed caused discord among astronomers. Logically, Xena-Eris should have been immediately recognized as the tenth planet, and the Michael Brown group should have been entered into the annals of history as its discoverers. But it was not there! Previous discoveries have indicated that perhaps dozens more objects comparable in size to Pluto are hiding in the Edgeworth-Kuiper Belt. What is easier - multiplying the number of planets, rewriting astronomy textbooks every couple of years, or throwing out Pluto from the list, and with it all the newly discovered celestial bodies?

The verdict was passed by Mike Brown himself, having discovered on March 31, 2005 the object 2005 FY9 with a diameter of 1500 km, named Makemake (the creator god of mankind in the mythology of the Rapanui people, the inhabitants of Easter Island). The patience of the colleagues ran out, and they gathered at the conference of the International Astronomical Union in Prague to determine once and for all what a planet is.

Previously, a planet could be considered a celestial body that revolves around the Sun, is not a satellite of another planet and has sufficient mass to acquire a spherical shape. As a result of the debate, astronomers added another requirement: that the body "clear" the surroundings of its orbit from bodies of comparable size. Pluto did not meet the last requirement and was deprived of the status of a planet.

He migrated to the list of "dwarf planets" (from the English "dwarf planet", literally - "dwarf planet") at number 134340.

This decision drew criticism and ridicule. Pluto scientist Alan Stern said that if this definition were applied to Earth, Mars, Jupiter and Neptune, in whose orbits asteroids were found, then they should also be stripped of the title of planets. In addition, according to him, less than 5% of astronomers voted for the decision, so their opinion cannot be considered universal.

However, Mike Brown himself accepted the definition of the International Astronomical Union, content that the discussion had finally ended to everyone's satisfaction. And indeed - the storm subsided, the astronomers went to their observatories.

Deprived of the status of a planet, Pluto has become an inexhaustible source for Internet creativity

Society reacted differently to the decision of the International Astronomical Union: someone did not attach importance, but someone was convinced that scientists were fooling around. AT English language the verb “to pluto” (“to pluto”) appeared, recognized as the word of 2006 according to the American Dialectological Society. The word means "decrease in value or value."

The authorities of the states of New Mexico and Illinois, where Clyde Tombo lived and worked, decided by law to retain the status of a planet for Pluto and declared March 13 the annual Day of the planet Pluto. Ordinary citizens responded with both online petitions and street protests. It was difficult for people who had considered Pluto a planet all their lives to get used to the decision of astronomers. In addition, Pluto was the only planet discovered by an American.

Who benefits?

Pluto is the only one who lost in status. The rest of the dwarf planets were previously classified as asteroids. Among them is Ceres (named after the Roman goddess of fertility), discovered back in 1801 by the Italian astronomer Giuseppe Piazzi. For some time, Ceres was considered the very missing planet between Mars and Jupiter, but later it was attributed to asteroids (by the way, this term was specially introduced precisely after the discovery of Ceres and neighboring large facilities). By the decision of the astronomical union in 2006, Ceres began to be considered a dwarf planet.

Ceres, whose diameter reaches 950 km, is located in the asteroid belt, which seriously complicates its observation. It is hypothesized to have an icy mantle or even oceans of liquid water below the surface. A qualitative step in the study of Ceres was the mission of the Dawn interplanetary apparatus, which reached the dwarf planet in the fall of 2015.

We won't be found!

The Pioneer 10 and Pioneer 11 interplanetary spacecraft, launched in the early 1970s, carried aluminum plates with a message to aliens. In addition to images of a man, a woman and an indication of where to look for us in the galaxy, there was a diagram of the solar system. And it consisted of nine planets, including Pluto.

It turns out that if someday the "brothers in mind", guided by the "Pioneers" scheme, want to find us, they are very likely to pass by, confused in the number of planets. However, if they are evil alien invaders, you can always say that we deliberately confused them.

∗∗∗

Today it seems unlikely that the classification of Pluto, Eris, Sedna, Haumea and Quaoar will ever be revised. And only Mike Brown is not discouraged - he is sure that in the coming years, a celestial body the size of Mars will be discovered at the far edge of the Edgeworth-Kuiper belt. It's terrible to imagine what will happen then!

• Michael Brown "How I Killed Pluto and Why It Was Inevitable"
• David A. Weintraub “Is Pluto a planet? Journey through the Solar System (Is Pluto a Planet?: A Historical Journey through the Solar System)
• Elayne Scott When Is a Planet Not a Planet?: The Story of Pluto
• David Aguilar Thirteen Planets. A Modern View of the Solar System (13 Planets: The Latest View of the Solar System)

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.