Dwarf Planet

In Astronomy, a dwarf planet is a type of Celestial object Solar system, intermediary between a Planet and a small body.

The term was adopted in 2006 by the international astronomical Union in order to clarify the classification of the objects turning around the Sun.

Apart from this new classification, the other terms such those of Asteroid or object of the Ceinture of Kuiper continue to apply. These terms are based on the situation of the object in the solar system or its composition. Cérès continues to be the largest asteroid and Pluton is always an object of the belt of Kuiper in spite of their classification like dwarf planets.

Characteristics

Dimensions

The higher and lower limits in the face and mass of dwarf planets are not specified in the 5A resolution of the international astronomical Union. Strictly speaking, there does not exist any higher limit and a larger object and more solid mass that Mercure and who “did not clean its vicinity around its orbit” can be categorized like a dwarf planet.

The lower limit is determined by the concept of “hydrostatic balance”, but dimensions to which an object reaches such a state are not given; empirical observations suggest that they vary according to the composition and the history of the object. The initial version of resolution 5 defined hydrostatic balance as applying “to the objects whose mass exceeds 5 {{x10 20}} kg (either 500 million billion tons) and the diameter 800 km”, but this was not retained in the final resolution.

Vicinity

The definition of a dwarf planet supposes that it “did not make clear place in its vicinity”, but does not clarify more this concept.

Alan Stern and Harold F. Levison defined a criterion making it possible to make the distinction between a planet and a dwarf planet, expressing the probability of a meeting between an object and a smaller body following a deviation of the orbit of this last. According to its authors, this criterion makes it possible to estimate the capacity of a body to clean its vicinity. Stern and Levison found a variation of five orders of magnitude between its value for Mars and that of the largest asteroids and transneptuniens. By using this work, Steven Soter proposed a parameter named planetary discriminant, making it possible to make the distinction between dwarf planets and the eight planets of the solar system, on the basis of their capacity to clean the smaller bodies by collision, captures or gravitational disturbance.

List

Recognized dwarf planets

Summary

The 26e general meeting of the international astronomical Union allotted to Éris, Pluton, and Cérès the dwarf planet statute.

The second larger asteroid, Vesta, seems also about spherical, but has a significant plane face however. Pallas and Hygée more irregular, but nevertheless is partially rounded by their own gravity. Potentially, all the three could fill the criteria defined by the UAI. Just like Cérès, these objects were regarded as planets since their discovery until the years 1850.

The statute of Charon, currently regarded as a satellite of Pluto, is dubious. Indeed, there does not exist clear definition of what constitutes a satellite system or a binary system. Charon is largely larger than the other satellites compared to Pluto and Pluton and Charon rather orbits both around a point located in space than inside Pluton. Consequently, the system could be indicated in the future like a planetary system doubles, making of Charon a dwarf planet.

The following table gathers the known objects of more than 800 km in diameter which could be included in the list of dwarf planets:

See too

Internal bonds

Other types of bodies defined by the UAI:

Other types of objects:

Asteroid
Object of the brown category of Pluto
Object transneptunien
Dwarf
Oph 162225-240515 (example of dwarf brown doubles)

External bonds

References

Be-X-old: Карлікаваяплянэта Simple: Dwarf planet Zh-min-nan: E-he̍k-chheⁿ

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