The most distant celestial body in the solar system is the dwarf planet Pluto. More recently, school textbooks stated that Pluto is the ninth planet. However, the facts that were obtained during the study of this celestial body at the turn of the millennium forced the scientific community to doubt whether Pluto is a planet. Despite this and many other controversial issues, the small and distant world continues to excite the minds of astronomers, astrophysicists and a huge army of amateurs.

History of the planet Pluto

Back in the 80s of the 19th century, many astronomers tried unsuccessfully to find a certain Planet-X, which, through its behavior, influenced the orbital characteristics of Uranus. The searches were carried out in the most isolated areas of our space, approximately at a distance of 50-100 AU. from the center of the solar system. American Percival Lowell spent more than fourteen years unsuccessfully searching for a mysterious object that continued to excite the minds of scientists.

It will be half a century before the world receives proof of the existence of another planet in the solar system. The discovery of the planet was carried out by Clyde Tombaugh, an astronomer from the Flagstaff Observatory, which was founded by the same restless Lowell. In March 1930, Clyde Tombaugh, observing through a telescope the area of ​​space in which Lowell assumed the existence of a large celestial body, discovered a new fairly large space object.

Subsequently, it turned out that due to its small size and low mass, Pluto is not able to influence the larger Uranus. Oscillations and interaction of the orbits of Uranus and Neptune have a different nature, associated with the special physical parameters of the two planets.

The discovered planet was named Pluto, thereby continuing the tradition of naming the celestial bodies of the Solar System in honor of the gods of the ancient Pantheon. There is another version in the history of the name of the new planet. It is believed that Pluto received its name in honor of Percival Lowell because Tombaugh suggested choosing a name in accordance with the initials of the restless scientist.

Until the end of the 20th century, Pluto firmly occupied a place in the planetary series of the Solar family. Changes in the status of the planet occurred at the turn of the millennium. Scientists have been able to identify a number of other massive objects in the Kuiper belt, which has cast doubt on Pluto's exceptional position. This prompted the scientific world to revise the position of the ninth planet and answer the question of why Pluto is not a planet. In accordance with the new formal definition of the term “planet,” Pluto fell out of the general ensemble. The result of long debates and discussions was the decision of the International Astronomical Union in 2006 to transfer the object to the category of dwarf planets, putting Pluto on a par with Ceres and Eris. A little later, the status of the former ninth planet of the solar system was further lowered, including it in the category of small planets with tail number 134,340.

What do we know about Pluto?

The former ninth planet is considered the most distant of all large celestial bodies known to this day. Such a distant object can only be observed using powerful telescopes or photographs. It is quite difficult to fix a dim small point on the sky, since the planet’s orbit has specific parameters. Periods have been noted when Pluto is at its maximum brightness and its luminosity is 14m. However, in general, the distant wanderer does not differ in bright behavior, and the rest of the time he is practically invisible, and only during the period of oppositions the planet opens itself to observation.

One of the best periods for studying and researching Pluto occurred in the 90s of the 20th century. The farthest planet was at a minimum distance from the Sun, closer than its neighbor Neptune.

According to astronomical parameters, the object stands out among the celestial bodies of the Solar System. The baby has the highest orbital eccentricity and inclination. Pluto completes its stellar journey around the main luminary in 250 Earth years. The average orbital speed is the slowest in the Solar System, only 4.7 kilometers per second. In this case, the period of rotation of the small planet around its own axis is 132 hours (6 days and 8 hours).

At perihelion, the object is located at a distance of 4 billion 425 million km from the Sun, and at aphelion it runs away to almost 7.5 billion km. (to be precise - 7375 million km). At such enormous distances, the Sun gives Pluto 1600 times less heat than we, earthlings, receive.

The axis deviation is 122.5⁰, the deviation of Pluto’s orbital path from the ecliptic plane has an angle of 17.15⁰. In simple terms, the planet lies on its side, rolling as it moves around its orbit.

The physical parameters of the dwarf planet are as follows:

• equatorial diameter is 2930 km;
• Pluto's mass is 1.3 × 10²² kg, which is 0.002 Earth's mass;
• the density of the dwarf planet is 1.860 ± 0.013 g/cm³;
• the acceleration of gravity on Pluto is only 0.617 m/s².

The size of the former ninth planet is 2/3 of the diameter of the Moon. Of all the known dwarf planets, only Eris has a larger diameter. The mass of this celestial body is also small, which is six times less than the mass of our satellite.

Dwarf planet retinue

However, despite such a small size, Pluto bothered to get five natural satellites: Charon, Styx, Nikta, Kerberos and Hydra. All of them are listed in order of distance from the mother planet. Charon's size forces it to have the same pressure center as Pluto, around which both celestial bodies revolve. In this regard, scientists consider Pluto-Charon a double planetary system.

The satellites of this celestial body are of different nature. If Charon has a spherical shape, then all the others are huge and shapeless giant stones. It is likely that these objects were captured by Pluto's gravitational field from among the asteroids traveling in the Kuiper belt.

Charon is Pluto's largest moon, which was discovered only in 1978. The distance between the two objects is 19640 km. At the same time, the diameter of the largest moon of the dwarf planet is 2 times smaller - 1205 km. The ratio of the masses of both celestial bodies is 1:8.

Pluto's other satellites - Niktas and Hydra - are approximately the same in size, but are much inferior in this parameter to Charon. Styx and Nyx are generally barely noticeable objects with dimensions of 100-150 km. Unlike Charon, the remaining four satellites of Pluto are located at a considerable distance from the mother planet.

When observing with the Hubble telescope, scientists were interested in the fact that Pluto and Charon have significantly different colors. Charon's surface appears darker than Pluto's. Presumably, the surface of the dwarf planet's largest satellite is covered with a thick layer of cosmic ice, consisting of frozen ammonia, methane, ethane and water vapor.

Atmosphere and brief description of the structure of a dwarf planet

With the presence of natural satellites, Pluto can be considered a planet, albeit a dwarf one. To a large extent, this is facilitated by the presence of Pluto’s atmosphere. Of course, this is not an earthly paradise with a high content of nitrogen and oxygen, but Pluto still has an air blanket. The atmospheric density of this celestial object varies depending on its distance from the Sun.

People first started talking about Pluto's atmosphere in 1988, when the planet passed through the solar disk. Scientists admit the idea that the dwarf’s air-gas shell appears only during the period of maximum approach to the Sun. When Pluto moves significantly away from the center of the solar system, its atmosphere freezes. Judging by spectral images obtained from the Hubble Space Telescope, the composition of Pluto's atmosphere is approximately the following:

• nitrogen 90%;
• carbon monoxide 5%;
• methane 4%.

The remaining one percent comes from organic compounds of nitrogen and carbon. The strong rarefaction of the planet's air-gas shell is evidenced by data on atmospheric pressure. On Pluto it varies from 1-3 to 10-20 microbars.

The surface of the planet has a characteristic slightly reddish tint, which is caused by the presence of organic compounds in the atmosphere. After studying the resulting images, polar caps were discovered on Pluto. It is possible that we are dealing with frozen nitrogen. Where the planet is covered in dark spots, there are likely vast fields of frozen methane that are darkened by sunlight and cosmic radiation. The alternation of light and dark spots on the surface of the dwarf indicates the presence of seasons. Like Mercury, which also has a very thin atmosphere, Pluto is covered with craters of cosmic origin.

The temperatures in this distant and dark world are very low and incompatible with life. On the surface of Pluto there is eternal cosmic cold with a temperature of 230-260⁰С below zero. Due to the planet's recumbent position, the planet's poles are considered the warmest areas. While vast areas of Pluto's surface are a permafrost zone.

As for the internal structure of this distant celestial body, a typical picture is possible here, characteristic of the terrestrial planets. Pluto has a fairly large and massive core consisting of silicates. Its diameter is estimated at 885 km, which explains the rather high density of the planet.

Interesting facts about the research of the former ninth planet

The huge distances that separate Earth and Pluto make it very difficult to study and research using technical means. Earthlings will have to wait about ten Earth years for the spacecraft to reach Pluto. Launched in January 2006, the New Horizons space probe was able to reach this region of the solar system only in July 2015.

For five months, as the automatic station “New Horizons” approached Pluto, photometric studies of this region of space were actively carried out.

Flight of the New Horizons probe

This device was the first to fly in close proximity to a distant planet. The previously launched American Voyager probes, the first and second, focused on studying larger objects - Jupiter, Saturn and its moons.

The flight of the New Horizons probe made it possible to obtain detailed images of the surface of the dwarf planet numbered 134,340. The study of the object was carried out from a distance of 12 thousand km. Not only detailed photographs of the surface of a distant planet, but also photographs of all five of Pluto’s moons were received on Earth. Until now, work is underway in NASA laboratories to detail the information received from the spacecraft, as a result of which in the future we will receive a clearer picture of that world distant from us.

Kudlanov Daniil

Research work based on a plan drawn up independently by the student in the form of a presentation. The work was presented at the interschool student research conference “Creativity, Search, Discovery” and was awarded a certificate for the best research work.

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Research work on the topic: “Why is Pluto not a planet of the solar system?”
Completed by: student of class 3B of MBOU “School No. 32” Kudlanov Daniil Supervisor: Golovashkina I. S.
Plan
1) scientific basis of the problem2) planets of the solar system3) characteristics of Pluto4) experiment 5) Pluto relative to other planets6) conclusion
Scientific basis of the problem
Once, during a lesson on the surrounding world, my neighbor at my desk had a picture in my textbook that depicted 9 planets of the solar system. There was the same picture in my textbook, but there were 8 of them. I became very interested. It turned out that his textbook was an old edition, and my teacher explained that Pluto had been excluded from the list of planets of the solar system. I became interested in this fact and began to look for an answer to this question in additional sources of information. This is precisely what served as the theme for my work.
Planets of the Solar System
Currently, there are 8 planets belonging to the planets of the solar system:
1. Mercury
Mercury is the planet closest to the Sun. On the surface of the planet, the temperature rises to 400 degrees Celsius. Mercury revolves around the Sun in 88 Earth days. Mercury's iron core makes up 80% of its mass. It is now recognized as the smallest of the planets. Mercury has no satellites.
2. Venus
Venus is the second planet from the Sun, with an orbital period of 224.7 Earth days. It passes closer to Earth than any other planet. The atmosphere, which is a thick blanket of carbon dioxide, traps heat coming from the Sun. Venus can be observed an hour after sunset or an hour before sunrise. Venus has no satellites.
3. Earth
Earth is the third planet from the Sun, with an orbital period of 365 days. About 71% of the Earth's surface is occupied by the World Ocean. About 3 - 3.5 billion years ago, life arose on Earth, and the development of the biosphere began. The planet's satellite is the Moon.
4. Mars
Mars is the fourth planet from the Sun, similar to Earth, but smaller and cooler. Has a rarefied atmosphere. There are two small moons flying around the Red Planet, as Mars is also called, the satellites Phobos and Deimos.
5. Jupiter
Jupiter is the fifth planet from the Sun, the largest planet in the Solar System. The planet is classified as a gas giant. Unlike the four rocky planets closest to the Sun, Jupiter has 67 satellites, as well as a ring 20,000 km wide, almost closely adjacent to the planet.
6. Saturn
Saturn, the sixth planet from the Sun, has an amazing ring system. Due to the rapid rotation around its axis, Saturn's ball is, as it were, flattened at the poles and inflated along the equator. It belongs to the category of gas giants. The radius of the planet's equator is more than 60 thousand km, the polar radius is 54 thousand km. Saturn has 62 known satellites.
7. Uranus
Uranus is the seventh planet from the Sun. Uranus has 27 moons and a ring system. The atmosphere of Uranus is based on helium and hydrogen. At the center of Uranus is a core made of rock and iron.
8. Neptune
Neptune is the last planet in the solar system. Its orbit intersects with Pluto's orbit in some places. Neptune is not visible to the naked eye. Has 13 satellites (Triton, Nereid, Naiad, Thalassa, Despina, Galatea, Larissa, Proteus, Halimeda, Psamapha, Sao, Laomedia, Neso.)
Characteristics of Pluto
Pluto (134340 Pluto) is the largest dwarf planet in the Solar System and the ninth largest celestial body orbiting the Sun by mass (excluding satellites).
From the day of its discovery in 1930 until 2006, Pluto was considered the ninth planet of the solar system. In August 2006, at the General Assembly of the III Division of the International Astronomical Union, it was deprived of planet status.
Pluto's magnitude averages 15.1. Pluto appears star-shaped and blurry.
Among the objects of the Solar System, Pluto is not only smaller in size and mass in comparison with the other planets, it is even inferior to some of their satellites.
Pluto's atmosphere is a thin shell of nitrogen, methane and carbon monoxide evaporating from the surface ice.
The temperature of Pluto's atmosphere is significantly higher than the temperature of its surface and is equal to −180 °C.
There are five known natural satellites of Pluto; three of them currently have names: Charon, discovered in 1978 by astronomer James Christie, and two small satellites, Nix and Hydra, discovered in 2005. The fourth satellite was discovered using the Hubble telescope; a message about the discovery was published on July 20, 2011 on the telescope’s website. It was temporarily named S/2011 P 1 (P4); its dimensions range from 13 to 34 km. On July 11, 2012, the discovery of Pluto's fifth moon was announced.
Experiment
I assumed that Pluto was excluded from the list of planets in the solar system because it is smaller in size. In this regard, I decided to conduct an experiment and try to represent all these planets according to their sizes. To do this, I sculpted all the planets out of plasticine and compared them. Here are the results:
Noticing that Pluto is not so different from some planets (for example, from Mercury), I realized that size is not the reason why it is no longer a planet in the solar system. It turned out that my assumptions were wrong, which means we need to look for other reasons why how Pluto differs from other planets. For this, I have compiled a visual table with the characteristics of all the planets. I'll try to compare them and find the differences.
Pluto compared to other planets
Atmospheric composition
Surface area
Equator radius
Weight
Mercury
42% oxygen, 29% sodium, 22% hydrogen, 6% helium, 0.5% potassium 0.5% (water, nitrogen, argon, etc.)
88 earth days
7.48·107 km²
2439.7 km
3.33022·1023 kg
Venus
96.5% carbon dioxide, 3.5 nitrogen
224.7 Earth days
4.60·108 km²
6051 km
48.685 1023 kg
Earth
78.08% nitrogen, 20.95 oxygen, 0.93 argon, 0.039 carbon dioxide, about 1% water vapor
365 earth days
510,072,000 km/148,940,000 km/land (29.2%) 361,132,000 km/water (70.8%)
6378.1 km
59.736 1023 kg
Mars
95.32 carbon dioxide, 2.7 nitrogen, 1.6 argon, 0.38% (oxygen, carbon monoxide, etc.)
687 Earth days
144,371,391 km²
3396.2 km
6.4185 1023 kg
Atmospheric composition
Period of revolution around the Sun
Surface area
Equator radius
Weight
Jupiter
89% hydrogen, 10% helium, 1% (methane, water, ethane, etc.)
11.86 Earth years
6.21796·1010 km²
71492 km
18986·1023 kg
Saturn
96% hydrogen, 3% helium, 1% (methane, ammonia, etc.)
29.46 Earth years
4.27·1010 km²
60270 km
5684.6 1023 kg
Uranus
83% hydrogen, 15% helium, 2% methane
84 earth years
8.1156·109 km²
25559 km
868.32 1023
Neptune
80% hydrogen, 18% helium, 1.5 methane, 0.5% (ethane, hydrogen deuteride)
164,491 Earth years
7.6408·109 km²
24764 km
1024.3 1023 kg
Pluto
99% nitrogen, 0.1 methane, 0.99% carbon monoxide
247.69 Earth years
1.795·107 km²
1195 km
0.1305·1023 kg
The table shows: each planet has its own atmospheric composition, the farther the planet is, the longer the time it takes to orbit the Sun, the surface area and radius of the equator are also different for each planet, but it is worth noting that these data are the smallest for Pluto. And the most important indicator is the mass of Pluto is very different from the masses of other planets. I assumed that this characteristic is the reason that Pluto is no longer a planet. In order to make sure of this, I decided to study in more detail the data according to which any celestial body can be consider it a planet. In one of the encyclopedias I found the following criteria: 1) orbits the Sun2) has sufficient mass to achieve a hydrostatically equilibrium form due to its own gravity. 3) dominates its orbit
I was right. Pluto does not have enough mass to be considered a planet. “It does not meet one of the criteria for defining a planet: the mass of non-moon objects in its orbit is too large compared to the mass of Pluto to consider it dominant” (I Know the World Encyclopedia). It is for this reason that it was classified to the dwarf planets of our solar system.
Conclusion
Bibliography:
1. Large series of knowledge. Universe / Team of authors. - M: World of Books LLC, 2004.2. “Universe” series “Life of the Planet” Nicholson Yang. – ROSMEN-IZDAT LLC, 1999.3. “Universe”: Popular scientific publication for children / Galpershtein L.Ya-M: LLC Publishing House “Rosman-Press”, 2002.4. “Planets” - Alexander Volkov, Vladimir Surdin - M: SLOVO, 2000.5. "Planet Earth" / Comp. A.M. Berlyant: - M: Book World LLC, 2004.6. Encyclopedia for children. Volume 8. Astronomy - Avanta+, 2004.7. I'm exploring the world. Space / Gontaruk T. I. - M.: AST, Khranitel, 2008. 8. ru.wikipedia.org/wiki9. ugorka.ivakorin.ru/planeta%20Zemlya.html

Pluto was discovered in 1930 by astronomer Clyde Tombaugh at the Lowell Observatory in Arizona. The search for it lasted 15 years, since the existence of a trans-Neptunian planet was predicted by Percival Lowell based on disturbances in the movement of Uranus and Neptune. These calculations turned out to be erroneous, but by pure chance Pluto was discovered not far from the predicted location.

Pluto is the only planet that has never been visited by spacecraft. Therefore, the characteristics of this planet are known only approximately: diameter is about 2200 km, surface temperature is 35-55 K (about -210 ° C). Pluto is made of a mixture of rocks and ice, and the atmosphere is made of nitrogen and methane.

The largest of Pluto's moons, Charon, which received its name from the mythological carrier of the dead across the river of the dead - Styx to the gates of Hades, was discovered in 1978 by Jim Chrisley. Charon has a diameter of about 1200 km and orbits with a period of 6.4 days around a common center of gravity with Pluto, which lies between them. Pluto and Charon always face each other with the same side. In 2005, the Hubble Space Telescope discovered two more very small satellites (61 and 46 km) near Pluto, which a year later were named Hydra and Nix. The words in the name of the first interplanetary probe, New Horizons, begin with the same letters, which in the same year set off on a 10-year journey to Pluto.

Since the end of the 20th century, celestial bodies with a diameter of several hundred to several thousand kilometers, which have come to be called trans-Neptunian objects, have increasingly been found beyond the orbit of Neptune. Collectively they are sometimes called the Kuiper Belt. As his research progressed, it became increasingly clear that Pluto was an ordinary trans-Neptunian object. In 2003, an object larger than Pluto, UB 313, was found on the outskirts of the solar system.

As a result, in August 2006, the International Astronomical Union decided to deprive Pluto of its planet status and introduce a new category of dwarf planets, which initially included Pluto, UB 313 and the “promoted” asteroid Ceres from the main asteroid belt between Mars and Jupiter. Thus, Pluto remained in the status of a planet for 76 years and became the first celestial body to lose this status.

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

History of discovery

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

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

The surface of Pluto is very heterogeneous. The side of the planet that faces Charon consists almost of methane ice, and the opposite surface of the side does not actually contain this component, but it contains a lot of monoxide. “Hubble” suggests 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. For a long time, no one could determine both its existence and its reliable mass. So, in 1955, astronomers believed that the mass of Pluto was approximately equal to the mass of our planet. Since then, the estimated mass has changed several times, and at this time it is believed that Pluto has a mass of about 0.24% of the Earth's mass. 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 was close to Mars and was approximately 6,700 km. However, today, scientists agree that Pluto's diameter is approximately 2,390 kilometers. Pluto is not called a dwarf planet for nothing; it is smaller in size not only than the planets of the Solar System, but even 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-based and space-based observatories have completely changed previous understanding of 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, collectively called the Kuiper belt. This region extends from the orbit of Neptune to a distance of 55 astronomical units (the belt boundary is 55 times farther from the Sun than Earth).

And in 2005, Mike Brown and his team delivered some amazing news. They discovered an object beyond Pluto's orbit that was likely the same size, perhaps even larger.

Officially named 2003 UB313, the object was later renamed Eris. Astronomers later determined that Eris is about 2,600 km in diameter, plus it has a mass about 25% greater than Pluto.

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

The association's astronomers were given the opportunity to vote on various options for defining the planet. One of these options would increase the number of planets to 12: Pluto would continue to be considered a planet; in addition, Eris and even Ceres, which was previously considered the largest asteroid, would be included in the number of planets. Various proposals supported the idea of ​​9 planets, and one of the definitions of a planet led to Pluto being removed from the planet club list. But then how to classify Pluto? Don't consider it an asteroid.