Plutonian system

Pluton is bound by gravity to three other objects: largest is Charon. Two other satellites of definitely lower size, Hydra and Nix, were discovered in 2005.

Contrary to the majority of the known couples which have to them Center of gravity or barycentre inside the main object (kind couples Ground - the Moon), the couple Pluton/Charon form a Binary system whose barycentre is apart from same dimensions of Pluto. This characteristic is due to the difference of gravitational Masse between the two bodies which are relatively weak, the gravitational mass of Charon being worth approximately 12 % of that of Pluto. For certain astronomers, rather than speaking about planets and satellites, it would be advisable in this precise case to retain the concept of “double planet”. Associated with Hydra and Nix, which on the other hand are 300 times lighter than Charon, therefore keep a statute of “satellites”, one speaks then about “Plutonian system”.

Plutonian system

The satellite nearest to Pluto, Charon was discovered by James Christy on June 22nd, 1978, almost 50 years after Pluton. The two other satellites, Hydra and Nix, were photographed by the Space telescope Hubble and were discovered by the team of the Pluto Companion Search in May 2005. Because of sensitivity of the telescope and that all the area of the space where the gravitational field of Pluto east dominating was photographed, it does not seem that the star has another satellite of more than 20 km in diameter.

Pluto and Charon were sometimes called a planet doubles, Charon being larger compared to Pluton (half of its diameter, the eighth of its mass) that any other satellite compared to its planet. Pluto orbits besides around the Barycentre of the system, which is located in-outside its surface. Charon and Pluton are also synchronous and always present the same face one compared to the other.

Nix and Hydra are very close to a orbital Résonance 1:4: 6 with the orbital period of the couple Pluto-Charon: Nix is to 2,7% of this resonance, Hydra with 0,3%. This proximity is probably not a chance.

It was emitted the assumption of the formation of the Plutonian system by a massive collision. However, Pluto east one of the reddest objects of the solar system, while Charon is rather gray. Nix is even redder than Pluton and Hydra slightly grayer than Charon. These colors are current at the objects of the Ceinture of Kuiper, but their mixture makes not easily explainable the creation of the system starting from one only impact.

The Plutonian sytème was not visited yet by a space probe, but an overflight by the probe New Horizons is planned for 2015.

List

Here the list of the known satellites of Pluto, classified by Equatorial radius growing. Pluto was added to this list, because it orbits around a point located apart from itself.

Source: New Constraints one Additional Satellites off the Pluto System and Orbits and photometry off Pluto' S satellites: Charon, S/2005 P1 and S/2005 P2 .

See too

Internal bonds

Pluto (dwarf planet)
Natural satellite
Natural satellite of Jupiter
Natural satellite of Natural satellite Saturn
of Uranus
Natural satellite of Neptune

External bonds

'' Pluto Fact Sheet ''
'' Hubble Spots Possible New Moons Around Pluto '' (NASA)
Animation of the Plutonian system (file .mpg)

References

Random links: