Orbital dominance – Wikipedia
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The orbital dominance It is one of the distinctive characteristics of the planets compared to the other objects of the Solar System. In particular, according to the definition of planet approved during the XXV General Assembly of the International Astronomical Union is the characteristic that distinguishes the planets from the Nani planets [first] .
In the final phase of the planetary training process, a planet will have become gravitationally dominant, that is will have cleaned up their orbital nearby (reporting the words used in the definition of the IAU), if in their orbital area they will not orbit other bodies of dimensions comparable to those of the planet who are not either its satellites or in any case gravitationally linked to it.
The definition does not provide numerical indications or equations that allow you to measure how gravitation is an object of the sun system, above all it does not indicate a limit that distinguishes the planets from the dwarf planets. However, it provides examples, separating the 8 planets – Mercury, Venus, the earth, Mars, Jupiter, Saturn, Uranus and Neptune – from the three major dwarf planets: Ceres, Pluto and Eris.
A first proposal to distinguish the planetoids in orbit around a star in gravitation and non -dominant objects, was made by Alan Stern and Harold F. Levison in their article presented at the XXIV General Assembly of IAU, held in 2000 in Manchester in Manchester [2] . It is probably from this article that IAU has drawn the expression used in the definition finally approved. In 2007 Steven Soter proposed the use of a parameter, called ” planetary discriminant “, To describe the concept of orbital dominance with mathematical formulation. [3]
The ability to distinguish the “planets” from the “dwarf planets” and the other minor bodies of the sun system has become necessary because the IAU adopts different rules for the name of the new planets discovered compared to those for the other new bodies discovered. The denomination process stalled in 2005 for Eris and other objects with similar characteristics, precisely because it was necessary to clarify their subsequent classification. [4] [5]
We can define the orbital area Like the region occupied by two bodies whose orbits cross a common distance from the sun, if their orbital periods differ less than an order of magnitude. In other words, two bodies are in the same orbital area:
- If they occupy the same distance from the sun in a point of their orbits,
- If the two orbits are of comparable size, rather than, as it could be in the case of a comet, one could extend the dimensions of the other several times. [3] The mass of the comets is negligible in any case compared to that of the other minor bodies of the Solar System.
After a high number of orbital cycles, a larger body will influence the orbits of the minor bodies that occupy its orbital area in two ways: it will attract them to itself, feeding its according process, or will determine their transfer to orbits that are not disturbed from one’s gravitational action. Consequently, a gravitationally dominant object does not share the region in which it orbit with other bodies of dimensions comparable to its own which are not either its satellites or in any case gravitationally linked to it. A clear example of objects gravitatedly linked to the planet of which the orbital area occupy are the Trojan asteroids of Jupiter and Neptune, which occupy an unstable balance position in the system consisting of the corresponding planet and the sun. Other examples are 3753 Cruthne, linked to the Earth, and the plutini, asteroids that have an orbital resonance 2: 3 with Neptune and that can pass through the orbit, but do not clash with the planet, thanks to the resonance established during the formation of the Solar System. [2]
Stern and Levison in their 2000 article suggest that they label all substellar objects in hydrostatic equilibrium as “planets” and to distinguish these in turn in ” überplanets ” It is ” sub -planet “Based on a mathematical analysis of the planet’s ability to remove other objects from one’s orbit in a long period of time. The two scholars derive from Ernst Öpik’s theory (1951) [7] A parameter, λ (Lambda), which measures the probability that a celestial body deviates other objects from his orbit following a more or less close encounter and that essentially expresses a measure of the ability to remove other objects from his orbital area. A body that present a value of λ above 1 will have substantially cleaned up its orbital area. Mathematically λ is defined as: [3]
Where k it is approximately constant and M It is P They are respectively the mass and orbital period of the Planet candidate. Stern and Levison found a jump of five orders of magnitude in L Among the smallest terrestrial planets and the largest asteroids and objects of the Kuiper band (Kbo). [2]
Soter proposed a second parameter, which called “planetary discriminant”, indicated with the μ (Mi) symbol, which represents an experimental measure of the degree of ‘cleanliness’ of the orbital area reached by each planet. μ is calculated by dividing the mass of the planet candidate for the total mass of the other objects that share its orbital area. Soter proposes that a body is classified between the planets if μ> 100. [3]
A prospectus of the planets and dwarf planets of the Solar System for which both the planetary discriminant μ proposed by Soter are calculated, defined as the relationship between the mass of the body and the total mass of the other objects that share its orbital area, both The parameter λ proposed by Stern and Levinson, defined as the ratio of the square of the mass on the orbital period, normalized with the value calculated for the earth (λ/λ AND ).
(Note that λ AND ~ 1.5 × 10 5 , so that the values not normalized for the eight planets indicated by the IAU are different orders of magnitude greater than 1, while the values not normalized for the dwarf planets are different orders of magnitude lower than 1.) [3]
| Range | Name | parameter λ / λ AND (Stern-Levinson) |
Discriminating Planetario μ |
Mass (kg) | Classification |
|---|---|---|---|---|---|
| first | Earth | 1.00 | 1.7 × 10 6 | 5,9736 × 10 24 | 3º planet |
| 2 | Venus | 1.08 | 1.35 × 10 6 | 4,8685 × 10 24 | 2º planet |
| 3 | Jupiter | 8510 | 6.25 × 10 5 | 1.8986 × 10 27 | 5º planet |
| 4 | Saturn | 308 | 1.9 × 10 5 | 5,6846 × 10 26 | 6º planet |
| 5 | Marte | 0.0061 | 1.8 × 10 5 | 6,4185 × 10 23 | 4º planet |
| 6 | Mercury | 0.0126 | 9.1 × 10 4 | 3,3022 × 10 23 | 1º planet |
| 7 | Uranus | 2.51 | 2.9 × 10 4 | 8,6832 × 10 25 | 7º planet |
| 8 | Neptune | 1.79 | 2.4 × 10 4 | 1,0243 × 10 26 | 8º planet |
| 9 | application | 8.7 × 10 −9 | 0.33 | 9.43 × 10 20 | 1º Pianeta nano |
| ten | Eris | 3.5 × 10 −8 | 0.10 | 1.67 × 10 22 | 3º Pianeta nano |
| 11 | Pluto | 1.95 × 10 −8 | 0.077 | 1.29 × 10 22 ± 10% | 2º Pianeta nano |
| twelfth | Would like | 1.45 × 10 −9 | 0.02 [8] | ~ 4 × 10 21 | 4º Pianeta nano |
| 13 | Haumea | 1.72 × 10 −9 | 0.02 [8] | 4.2 ± 0.1 × 10 21 | 5º Pianeta nano |
- ^ ( IN ) Definition of a Planet in the Solar System: Resolutions 5 and 6 ( PDF ), are IAU 2006 General Assembly , International Astronomical Union, 24 agosto 2006. URL consulted on November 25, 2008 .
- ^ a b c Alan Stern; Harold F. Levison (2000)
- ^ a b c d It is Stevan Soter (2006)
- ^ ( IN ) Wm. Robert Johnston, Names of Solar System objects and features . are Johnstonsarchive.net , Johnston’s Archive, 24 August URL consulted on May 5, 2011 .
- ^ ( IN ) Daniel W.e. Green, (134340) PLUTO, (136199) ERIS, AND (136199) ERIS I (DYSNOMIA) ( PDF ), are Circular No. 8747 , Central Bureau for Astronomical Telegrams, 13 settembre 2006. URL consulted on May 5, 2011 .
- ^ The mass of Trojan asteroids is estimated at 10 -4 times the mass of the earth from Jewitt, Trujillo, Luu (2000); The mass of the earth is equal to about 3.15 × 10 -3 times the mass of Jupiter.
David C. Jewitt, Trujillo, Chadwick A.; Luu, Jane X., Population and size distribution of small Jovian Trojan asteroids , in The Astronomical journal , vol. 120, 2000, pp. 1140–7, two: 10.1086/301453 . - ^ Ernst Julius Öpik, Collision probability with the planets and the distribution of planetary matter , in Proc. R. Irish Acad. Sect , 54a, December 1951, pp. 165-199. URL consulted on November 26, 2008 .
- ^ a b Calculated using the estimate for the masses of the objects of the Kuiper band present in Iorio (2007) of 0.033 terrestrial masses
- S. Alan Stern, Levison, Harold F., Regarding the criteria for planethood and proposed planetary classification schemes ( PDF ), in Highlights of Astronomy , vol. 12, 2002, pp. 205–213, as presented at the XXIV General Assembly of IAU -2000 [Manchester, UK, 7–18 August 2000].
- Steven Soter, What Is a Planet? , in Astronomical Journal , vol. 132, n. 6, December 2006, pp. 2513-2519. URL consulted on November 23, 2008 .
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