Dwarf planets Pluto, Haumea, Makemake, Eris and other large trans-Neptunian objects compared by size, albedo and color. Their satellites are also shown.

A dwarf planet, as defined by the International Astronomical Union, is a celestial body that:

orbits around ;
has sufficient mass to maintain hydrostatic equilibrium under the influence of gravity and have a close to spherical shape;
is not ;
cannot clear the area of ​​its orbit from other objects.

The term "dwarf planet" was adopted in 2006 as part of the classification of bodies orbiting the Sun and other bodies into three categories. Bodies large enough to clear space in the band of their orbit are defined as planets, and bodies not large enough to achieve even hydrostatic equilibrium are defined as or. Dwarf planets occupy an intermediate position between these two categories. This definition met with both approval and criticism, and is still disputed by some scientists. For example, as the simplest alternative, they propose a conditional division between planets and dwarf planets by size, or even: if larger, then it’s a planet, if smaller, then it’s a planetoid.

The International Astronomical Union officially recognizes 5 dwarf planets: the largest asteroid and -,; however, it is possible that at least 40 more of the known objects in the world belong to this category. According to various estimates by scientists, up to 200 dwarf planets can be discovered in and up to 2000 dwarf planets beyond.

The classification of bodies with the characteristics of dwarf planets in other planetary systems has not been determined.

List of dwarf planets

In 2006, the IAU officially named three bodies that immediately received the classification of dwarf planets - former planet Pluto, considered the largest trans-Neptunian object, Eris and the largest asteroid Ceres. Later, two more trans-Neptunian objects were declared dwarf planets. The term "dwarf planet" should be distinguished from the concept " minor planet", which historically also refers to asteroids.

*Value in comparison with Earth.

From this list, only Pluto was “demoted”, becoming a dwarf planet and losing its status as a planet, while the rest, on the contrary, were “promoted”, ceasing to be just one of the asteroids.

Other candidates

Several dozen bodies are already known that could potentially qualify as dwarf planets.

The status of Charon, which is now considered to be a moon of Pluto, remains inconclusive, as there is currently no precise definition on distinguishing planets with a satellite from binary planetary systems. The draft resolution published by the IAU indicates that Charon can be considered a planet because:

Charon itself meets the size and shape criteria for planet status (in terms of the latest resolution, for dwarf planet status).

The status of Charon, which is now considered to be a satellite of Pluto, remains inconclusive, since there is currently no precise definition for distinguishing planets with a satellite from binary planetary systems. Draft Resolution (5) published by the IAU indicates that Charon can be considered a planet because:

1. Charon itself meets the size and shape criteria for dwarf planet status.
2. Charon, due to its large mass compared to Pluto, orbits Pluto general center mass located in space between Pluto and Charon, and not around a point located inside Pluto.

This definition, however, is not included in the final decision of the IAC. It is also unknown whether it will appear in the future. If such a definition is approved, Charon will be considered a dwarf (double) planet. To quickly resolve this issue, we are currently discussing the adoption of tidal interlocking or synchronous rotation of both components of the binary system as an additional criterion.

Besides Charon and all other candidate trans-Neptunian objects, three large objects in the asteroid belt (Vesta, Pallas and Hygeia) would have to be classified as dwarf planets if their shape is found to be determined by hydrostatic equilibrium. To date, this has not been convincingly proven.

Size and mass of dwarf planets

The lower and upper limits for the size and mass of dwarf planets are not specified in the IAU decision. There are no strict restrictions on the upper limits, and an object larger or more massive than Mercury with an unrefined orbital neighborhood can be classified as a dwarf planet.

The lower limit is determined by the concept of a hydrostatically equilibrium shape, but the size and mass of the object that has achieved this shape is unknown. Empirical observations suggest that they may vary greatly depending on the composition and history of the object. The original IAU preliminary decision defining hydrostatic equilibrium applied “to objects with a mass greater than 5 x 1020 kg and a diameter greater than 800 km,” but this was not included in the final decision 5A, which was approved.

According to some astronomers, the new definition means the addition of up to 45 new dwarf planets.

For example, bodies made of hard silicates (like rocky asteroids) should reach hydrostatic equilibrium with a diameter of about 600 kilometers and a mass of 3.4 x 10^20 kg. For a less rigid body from water ice such a limit would be closer to 320 km and 10^19 kg. As a result, to date there is no specific standard for defining a dwarf planet based on its size or mass, but instead it is usually defined based on its shape.

Orbital position

In addition to hydrostatic equilibrium, many astronomers have insisted on drawing a line between planets and dwarf planets based on their inability to "clear the environs of their orbit." In short, planets can remove smaller bodies near their orbits through collision, capture, or gravitational perturbation, whereas dwarf planets do not have the necessary mass to achieve this.

To calculate the likelihood that a planet will clear its orbit, planetary scientists Alan Stern and Harold Levinson introduced a parameter they call lambda.

This parameter expresses the probability of a collision as a function of a given deviation in the object's orbit. The value of this parameter in the Stern model is proportional to the square of the mass and inversely proportional to time and can be used to estimate the potential of a body to clear the vicinity of its orbit.

Astronomers like Steven Sauter, a scientist at New York University and research fellow The American Museum of Natural History suggests using this parameter to draw a line between planets and dwarf planets. Sauter also proposed a parameter he calls the planetary discriminant - denoted by the letter "mu" - which is calculated by dividing the mass of a body by the total mass of the bodies of other objects in the same orbit.

Recognized and possible dwarf planets

There are currently five dwarf planets: Pluto, Eris, Makemake, Haumea and Ceres. Only Ceres and Pluto have been observed enough to be unquestionably placed in this category. The IAU has ruled that unnamed trans-Neptunian objects (TNOs) with an absolute magnitude brighter than +1 (and mathematically limited to a minimum diameter of 838 km) should be classified as dwarf planets.

Possible candidates currently under consideration include Orcus, 2002 MS4, Salacia, Quaoar, 2007 OR10 and Sedna. All of these objects are located in the Kuiper Belt; with the exception of Sedna, which is considered separately - a separate class of dynamic TNOs in the outer Solar system.

It is possible that there are another 40 objects in the solar system that could fairly be designated dwarf planets. It is estimated that up to 200 dwarf planets could be found in the Kuiper belt once it is explored, and the number could exceed 10,000 outside the belt.

Disagreements

Immediately after the IAU decision regarding the definition of the planet, a number of scientists expressed their disagreement. Mike Brown (leader of the Caltech team that discovered Eris) agrees with reducing the number of planets to eight. However, a number of astronomers like Alan Stern regarding the IAU definition.

Stern argues that, like Pluto, Earth, Mars, and Neptune also do not completely clear their orbital zones. The Earth orbits the Sun with 10,000 near-Earth asteroids, which Stern estimates runs counter to the clearing of Earth's orbit. Jupiter, meanwhile, is accompanied by 100,000 Trojan asteroids on its orbital path.

In 2011, Stern referred to Pluto as a planet and considered other dwarf planets like Ceres and Eris, as well as large moons, as additional planets. However, other astronomers argue that although large planets do not clear their orbits, they completely control the orbits of other bodies within their orbital zone.

Another controversial application of the new definition of planets concerns planets outside the solar system. Methods for identifying extrasolar objects do not directly determine whether an object is “clearing its orbit,” only indirectly. As a result, in 2001, the IAU adopted separate “working” definitions for extrasolar planets, including this dubious criterion: “The minimum mass/size required to consider an extrasolar object as a planet must correspond to the parameters adopted for the Solar System.”

Although not all IAU members were in favor of adopting this definition of planets and dwarf planets, NASA recently announced that it would use the new guidelines established by the IAU. Nevertheless, the debate about the 2006 decision has not yet ceased, and we can well expect further development developments on this front as more "dwarf planets" are discovered and identified.

By IAU standards, it's fairly easy to identify a dwarf planet, but fitting the solar system into the three-tier classification system will become increasingly difficult as our understanding of the universe expands.

There are unusual bodies in the solar system called dwarf planets. These objects are in many ways similar to full-fledged planets, but in some respects they are still inferior to their “big brothers.” Little is known about them and this group is constantly updated with new objects. We will talk about the six currently known dwarf planets of the Solar System, their main features and differences from each other. We’ll also figure out why these celestial bodies cannot claim to be full-fledged planets.

Definition

According to the International Astronomical Union, dwarf planets are spherical celestial bodies revolving around the Sun. Their “dwarfism” is explained by their low mass and lack of gravitational dominance. The latter means that small celestial bodies are constantly present in the orbit of such an object.

How many dwarf planets are there in the solar system? This question is still very difficult to answer. Scientists have not yet fully explored the outskirts of our star system, and, according to their calculations, dozens and even hundreds of similar objects may be hiding there. But at the moment, only 6 are officially recognized - Pluto, Ceres, Eris, Haumea, Makemake and Sedna. At the same time, Pluto moved into this group from full-fledged planets, and all the rest - from asteroids of various classes.

Where are the dwarf planets located? The largest concentration of planetary dwarfs and candidates for this title is observed in the Kuiper belt. Only Sedna is located in the Oort cloud, and Ceres is located in an asteroid cluster between Mars and Jupiter. Due to the great distance from the Sun and the large number celestial bodies in the neighborhood, these objects are difficult to study. This explains the fact that most of them were discovered in the 21st century after the invention of powerful optical systems.

The definition of dwarf planets does not specify limits on the mass and size of an object falling into this group. Even if a body with suitable parameters is larger than Mercury, it will be considered a planetary dwarf. However, according to IAU experts, it must be at least 800 km in size and weigh more than 5 * 10 20 kg.

By chemical composition All dwarf planets are different from each other. But all representatives of this group are characterized by the presence of ice in the surface layer. It can cover the object with a continuous crust or be present in the form large number inclusions in rocks. Explore internal structure succeeded only at Ceres, because the remaining dwarfs are located too far from Earth.

Let us briefly examine the features of each of the dwarf planets

The largest Kuiper belt object was discovered in 1930. It received its official name in honor of the ancient Roman god of the kingdom of the dead. Until the early 2000s, Pluto had the status of the ninth and smallest planet in the solar system. But due to its weak gravity, which does not allow clearing the orbit of asteroids, it was transferred to the group of planetary dwarfs.

Among other objects of this group, it has largest size, and is second only to Eris in mass. Pluto's surface consists of rock and ice of methane and nitrogen origin. In addition, this shell contains many hydrocarbon impurities, which give the body a brownish tint. Pluto's atmosphere is thin and consists of evaporated ice.

The characteristics of the dwarf planet's orbit are quite interesting. Its trajectory around the Sun is a highly elongated ellipse, so at the perihelion point it is closer to the central star than Neptune. An orbital resonance occurs between the bodies in a ratio of 3:2. The average distance from the Sun to Pluto is 5.91 billion km.

Pluto has 5 natural satellites: Charon, Nyukta, Hydra, Cerberus and Styx. With the largest of them, Charon, the planet moves around a common center of mass. Therefore, today both bodies are considered components of a double planet. It is noteworthy that this Plutonian moon is one of the contenders for the title of a new dwarf planet in the solar system.

The celestial body, named after the ancient Greek goddess of discord, was discovered in 2005. To discover it, American astronomers had to study numerous images of the Kuiper belt taken over the past 50 years.

Eris is located in the Scattered Disk region, a remote part of the Solar System filled with icy bodies. It itself also consists of hydrocarbon ices, which, when evaporating, create a thin temporary gas shell.

Eris is the most massive dwarf planet. And in size it is only slightly inferior to Pluto. Its orbit has a high eccentricity coefficient and is also highly inclined to the ecliptic plane. Because of these orbital characteristics, Eris is classified as an isolated trans-Neptunian object. The celestial body is removed from the Sun by an average of 10 billion km. Because of this, its surface temperature does not rise above -253°C.

The dwarf planet Haumea was discovered in 2005. It is distinguished from the rest by its ovoid shape and incredible speed of rotation around its own axis. Another unique feature of Haumea is the presence of rings and a whole family of small bodies that resulted from the collision of a celestial body with a large asteroid.

The transverse and longitudinal diameters of planetary dwarfs vary greatly. At the equator, Haumea is almost equal to Pluto, while across it it is half its size.

Haumea is located in the Kuiper belt, 6.43 billion km from the Sun. Its movement is slightly affected by Neptune's gravity.

In composition, this dwarf is also an icy celestial body. Its surface is a thick layer of water ice mixed with minerals and hydrocarbons. Haumea has no atmosphere.

Another dwarf planet in the Kuiper Belt. It was discovered almost simultaneously with Eris. Named after the goddess of abundance, who is worshiped by the natives of Easter Island.

Due to its distance from the Sun, Makemake remains a poorly studied object. It is not yet possible to accurately establish its basic physical parameters, but according to preliminary calculations, it ranks fourth in size and fifth in mass among all dwarf planets. Its surface is covered with methane ice and polymer hydrocarbons. This Kuiper belt object does not have a permanent atmosphere.

Makemake has a tiny, very faint satellite. The weak brilliance of this moon makes it difficult to study thoroughly.

The only known dwarf planet in the Oort cloud was discovered in November 2003. Named after the goddess of sea animals in Eskimo mythology. It is considered one of the most distant bodies in the Solar System, which makes it very difficult to study.

It is known that among all the dwarf planets it is second only to Ceres in size and mass. The surface of Sedna is a layer of methane and water ice. The celestial body does not have a permanent atmosphere. It has not yet been possible to establish the exact temperature.

Due to the high eccentricity of the orbit and the great distance from the Sun, the year on Sedna is the longest among known objects in the Solar System. It lasts 11.5 thousand years.

It is the largest object and the only dwarf planet in the asteroid belt. At the same time, in terms of weight and size, it occupies last place among their group neighbors. It was discovered earlier than other dwarfs - in 1801. Ceres received its name in honor of the ancient Roman goddess of fertility.

Its surface consists of various clayey rocks with admixtures of ice. Beneath them lies a thick icy mantle and a shallow rocky core. The atmosphere of Ceres is thin water vapor. No satellites have been discovered for the smallest dwarf.

Mysterious dwarf planets

Astronomers around the world continue to search for new planetary dwarfs in the Solar System. In its outskirts, two trans-Neptunian objects were recently discovered, which in all respects fit the definition of dwarf planets. They are called Goblin and Farout.

Both planets are among the most distant objects in our star system. Goblin is 80 astronomical units away from the Sun, while Farout is 125. These bodies were found as part of the search mysterious planet Nibiru. Scientists have not yet been able to establish the exact size and mass of Goblin and Farout. It is only known that they are covered with ice of unknown chemical composition.

These mysterious celestial dwarfs only reveal a whole series of new space objects. It is quite possible that the IAU will again revise the criteria for various astronomical concepts and the list of planets, as well as planetary dwarfs, will expand significantly.

Municipal educational institution

Vnukovo secondary school

Conference

"Project of the Year"

Dwarf planets

solar system

Project work on the surrounding world

Completed:

student of 4th grade "B"

Zavyalov Vasily

Supervisor:

Dmitrov

2014

Purpose of work .. 3

Introduction. 4

Dwarf planet. 6

Examples of dwarf planets. 6

Planet Ceres. 6

Planet Pluto. 7

Planet Haumea. 8

Planet Makemake. 8

Planet Eris. 9

Comparison table. 10

Conclusion . 12

References.. 13

Application . 14

Purpose of the work

1. Get acquainted with new research on the planets of the solar system.

2. Find out whether there are changes in the solar system as a result of the latest astronomical discoveries.

Hypothesis:Using modern powerful telescopes and research work astronomical observatories may discover new cosmic bodies in our solar system and change the classification of planets.

Introduction

The term "dwarf planet" was adopted in2006 within the framework of the classification of bodies orbiting the Sun into three categories. Bodies large enough to clear the vicinity of their orbit are defined as planets , but not large enough to achieve even hydrostatic equilibrium - as small solar system body or asteroids. Dwarf planets occupy an intermediate position between these two categories. This definition has met with both approval and criticism, and is still disputed by some scientists. For example, as the simplest alternative, they propose a conditional division between planets and dwarf planets based on the size of Mercury or even the Moon: if larger, then a planet, if smaller, a planetoid.

What celestial bodies are called planets

A planet is a celestial body orbiting a star or its remnant that is massive enough to become rounded by its own gravity, but not massive enough to begin with thermonuclear reaction, and managed to clear the surroundings of its orbit.

Fig.1. Planet Earth

Dwarf planet

Bodies large enough to clear the vicinity of their orbit are defined asplanets , but not large enough to achieve even hydrostatic equilibrium - as small bodies of the solar system or asteroids. Dwarf planets occupy an intermediate position between these two categories. This definition has met with both approval and criticism, and is still disputed by some scientists.

Fig.2. Dwarf planet

Examples of dwarf planets

Planet Ceres

Ceres- a dwarf planet in the asteroid belt within the solar system. Ceres is the dwarf planet closest to Earth (the average distance between orbits is about 263 million km). Ceres was discovered on the evening of January 1, 1801 by the Italian astronomer Giuseppe Piazzi at the Palermo Astronomical Observatory. For some time, Ceres was considered as a full-fledged planet in the solar system; in 1802 it was classified as an asteroid, and based on the results of clarifying the concept of “planet” by the International Astronomical Union on August 24, 2006 at the XXVI General Assembly of the IAU, it was classified as a dwarf planet. It was named after the ancient Roman goddess of fertility, Ceres.

Fig.3. Planet Ceres

Planet Pluto

Pluto- the largest along withEris is the size of a dwarf planet in the Solar System, a trans-Neptunian object and the tenth most massive (excluding satellites) celestial body revolving around Sun . Pluto was originally classified as a classical planet , however, it is now considered a dwarf planet and one of the largest objects (possibly the largest) in Kuiper belt.Pluto lost its planetary status and was demoted to "dwarf planets". There are now only eight large planets and many dwarf planets in the solar system.

Fig.4. Planet Pluto

Planet Haumea.

Haumea, or Haumea- fourth largestdwarf planet of the solar system . Classified as plutoid, trans-Neptunian object . This is the fastest rotating body of all the studied objects in the Solar System, with a diameter of more than 100 km. Haumea has a highly elongated shape. She has 2 satellites discovered.

Fig.5. Planet Haumea

Planet Makemake

Fig.6. Planet Makemake

Planet Eris

Eris- the most massive ofdwarf planets of the solar system . Previously known as Xena. Refers to trans-Neptunian objects, plutoids. Until the XXVI Assembly of the International Astronomical Union Eris claimed the status of the tenth planets . However, on August 24, 2006 International Astronomical Union approved the definition of a classical planet, which Eris, like Pluto , does not match. Thus, although Pluto's status as a planet had long been disputed due to the discovery of other trans-Neptunian objects, it was the discovery of Eris that prompted the process of its revision instead of recognizing Eris as a planet. Eris has long been considered significantly larger than Pluto, but, according to the latest data, their sizes are so close that it is impossible to say with certainty which of these objects is larger.

Fig.7. Planet Eris

Comparison table

Fig.8. Comparison of planets

Similarities and differences between a classical planet and a dwarf planet.

Table 1. Comparison of planets

Conclusion

Now, according to the new classification, there will be four planets in the solar system terrestrial group(Mercury, Venus, Earth and Mars), the same number of giant planets (Jupiter, Saturn, Neptune and Uranus) and an unlimited number of dwarf planets. Russian scientists are against the removal of Pluto from a number of planets in the solar system. Therefore, we will wait for several more years of research for changes.

There are now only 5 dwarf planets - Ceres, Pluto, Haumea, Makemake and Eris. But this is just the beginning. Another 40 cosmic bodies are waiting for the time when they will also be given the status of dwarf planets.

References

1. Avanta+, Encyclopedia for children. Volume 8. Astronomy - Avanta+, 2004. - 688 p. - ISBN-040-1

2. , White spots of the Solar system - M.: Niola-Press, 2008. - 319 p. - ISBN 0363-6

3. Gontaruk T. I, I explore the world. Space. - M.: AST, Guardian, 2008. - 398 p. - ISBN -8, 2900-7.

4. , Migration of celestial bodies in the Solar System. - Editorial URSS. - 2000. - ISBN -

5. , Astronomy: Textbook. for 11th grade general education institutions/- 9th ed. - M.: Education, 2004. - 224 p.: ill. - ISBN -0.

6. , Sky of the Earth - L.: Children's literature, 1974. - 328 p.

7. http://ru. wikipedia. org/wiki

font-size:18.0pt;line-height:107%;font-family:" times new roman color:windowtext>Appendix

Fig.9. Solar system (my drawing)

Dwarf planets didn't actually exist until 2006. Then they were allocated to new class The purpose of this transformation was to introduce an intermediate link between the large planets and numerous asteroids to prevent confusion in the names and statuses of new bodies discovered beyond the orbit of Neptune.

Definition

Then, back in 2006, the next meeting of the IAU (International Astronomical Union) took place. On the agenda was the question of specifying the status of Pluto. During the discussions, it was decided to deprive him of the “title” of the ninth planet. The IAU has developed definitions for some space objects:

• A planet is a body orbiting the Sun that is massive enough to maintain hydrostatic equilibrium (that is, have a rounded shape) and clear its orbit of other objects.
• An asteroid is a body orbiting the Sun that has a low mass that does not allow it to achieve hydrostatic equilibrium.
• A dwarf planet is a body orbiting the Sun that maintains hydrostatic equilibrium, but is not massive enough to clear its orbit.

Pluto was included among the latter.

New status

Pluto is also classified as a Kuiper belt body. Like some other dwarf planets, it is classified as a Kuiper belt body. The impetus for revising the status of Pluto was the numerous discoveries of objects in this distant part of the solar system. Among them was Eris, which exceeds Pluto in mass by 27%. Logically, all these bodies should have been classified as planets. That is why it was decided to revise and specify the definitions of such space objects. This is how dwarf planets appeared.

Tenth

It wasn't just Pluto who was "demoted in rank." Eris, before the IAU meeting in 2006, claimed the “title” of the tenth planet. It surpasses Pluto in mass, but is inferior to it in size. Eris was discovered in 2005 by a group of American astronomers searching for trans-Neptunian objects. Initially she was called Xena or Zena, but later they began to use the modern name.

Eris, like other dwarf planets in the Solar System, has hydrostatic equilibrium, but is not able to clear its orbit of other cosmic bodies.

Third on the list

The next largest after Pluto and Eris is Makemake. This is a classic Kuiper belt object. Interesting story has the name of this body. As always, upon opening it was assigned the number 2005 FY 9. For a long time, the team of American astronomers that discovered Makemake called it among themselves the “Easter Bunny” (the discovery was made a few days after the holiday).

In 2006, when a new column “Dwarf planets of the Solar System” appeared in the classification, it was decided to call 2005 FY 9 differently. Traditionally, classical Kuiper Belt objects are named after deities associated with creation. Make-make is the creator of humanity in the mythology of the Rapanui people, the original inhabitants of Easter Island.

Haumea

The dwarf planets of the Solar System also include another trans-Neptunian object. This is Haumea. Its main feature is very fast rotation. In this parameter, Haumea is ahead of all known objects with a diameter of more than one hundred meters in our system. Among dwarf planets, the object ranks fourth in size.

Ceres

Another one belonging to this class is located in the Main, lying between the orbits of Jupiter and Mars. This is Ceres. It was opened at the beginning of 1801. For some time it was considered a full-fledged planet. And in 1802, Ceres was classified as an asteroid. Status cosmic body was revised in 2006.

Dwarf planets are mainly distinguished from their large neighbors by their inability to clear their own orbit of other bodies. It is difficult to say now how convenient such an innovation is to use - time will tell. In the meantime, the controversy over the downgrading of Pluto's status has only subsided a little. However, the value of the former ninth planet and similar bodies for science remains high regardless of what they are called.