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 Automatic translationAutomatic translation Category: Planets and dwarf planets
Updated June 01, 2013
  Pluton et Charon

Image: Composite photograph of Pluto and Charon photographed July 11, 2015 by the New Horizons probe. Image credit: NASA/JHUAPL/SWRI

 
    
 planetoids and dwarf planets

Image: Diameters compared, big dwarf planets, relative to that of the Moon and Earth. Earth (≈12756 km), Moon (≈3474 km), Eris (≈2300 km), Pluto (≈2300 km), Makemake (≈1600 km) and Haumea (≈1600 km).

 Pluto, Charon, Hydra et Nix

Image: The Pluto system, with three satellites seen by Hubble, 15 May 2005. In June 2011, another satellite was discovered by Hubble. The fourth is called Kerberos. The tiny moon Kerberos orbits Pluto in 32.1 days. The fifth, Styx, revolves in 20 days, it is between 10 and 25 km.

    
 

Image: Simulation rotations of Charon, Nix, Hydra, Kerberos and Styx around the icy dwarf planet Pluto. The tidal force of most of the inner solar system moons blocks the satellite, a side facing their central planet. This animation shows that this is not the case with small moons of Pluto, which behave like tops while Pluto and Charon are face to face. Pluto is shown in the center with, in order, from the smallest to the largest orbits Charon, Styx, Kerberos Nix and Hydra. The rotation of two nearby objects like Pluto and Charon (12% of the mass of Pluto) is around centroid or center of mass of the two objects, Pluto and Charon. The barycenter is located outside the main body, ie Pluto. Credits: NASA/JHUAPL/SwRI/M. Showalter

   
  Mountains of Pluto

Image: The surprising Pluto Mountains. Unlike the icy moons of the giant planets, Pluto can not be heated by gravitational interactions with a much larger planetary body. Another process of generating this mountainous landscape. Scientists suspect a geological activity, which would be very surprising.

Aphelion comes from the ancient Greek apo (distant) and Helios (sun). This is the furthest point from the Sun on heliocentric orbit of a planet or a solar system object (comet, asteroid).
The aphelion of the Earth is reached around July 4, when the Earth is at a distance of 152 097 701 km from the Sun.
This date shifts on average about twenty minutes a sidereal year, due to the precession of the equinoxes and gravitational disturbances caused by the other planets of the solar system.
The sidereal year is the time it takes for the Sun finds the same position relative to the fixed stars on the celestial sphere, it is 20 minutes and 24 seconds longer than the average tropical year (≈365,2422 days).
Aphelion comes from the ancient Greek peri (around) and Helios (Sun). It is the closest point to the Sun on the heliocentric orbit of a planet or a solar system object (comet, asteroid).
The perihelion of the Earth is reached on January 4, when the Earth is at a distance of 147 098 074 km from the sun.
This date shifts on average about twenty minutes a sidereal year, due to the precession of the equinoxes and gravitational disturbances caused by the other planets of the solar system.
The sidereal year is the time it takes for the Sun finds the same position relative to the fixed stars on the celestial sphere, it is 20 minutes and 24 seconds longer than the average tropical year (≈365,2422 days).
 
           
 
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