Moons of the solar system

Large moons of the solar system

Solar system objects are carefully observed by our space telescopes, especially the moons of the planets, because each is unique and of great scientific interest.
The moons are linked to their planet by the tidal forces, and therefore, always present the same face to their planet, like the Moon from Earth.
But the moons of the solar system do not look like our moon.
Certainly one of them, we reserve one day a big surprise. The cameras of our space telescopes, more powerful and sophisticated robots bring our Earth showing stunning images of deep space dotted with rocks more or less large.
Jupiter, the largest planet in the solar system is surrounded by more than 60 moons. Ganymede with a diameter of 5262 km, is larger than our moon which is only 3 474.6 kilometers in diameter.
Besides, this is not the only, to be larger than our moon, Titan Saturn's moon, Io and Callisto, the moons of Jupiter, are larger than the moon that lights our nights.

Image: photo of the Moon lit by the sun in the foreground and the bright planet Venus, in the lower left.

Moons of the Hill sphere

In 2007 scientists discovered 20 additional moons of Jupiter, one of Saturn and three of Neptune.
The number of moons is growing gradually as the sensitivity of the onboard cameras. In 2011, over 150 moons revolve around their planet. In this cosmic broom, scientists classify moons 2 large groups.
The regular moons revolve in a circular orbit around the equator of their planet. These moons were formed by accretion of matter that existed around their planet, and that was not captured by it. This surplus of material has accumulated to form the moon. The first regular moons of Jupiter were discovered in 1610. Galileo Galilei discovered at that time the four largest Jovian satellites system Io, Europa, Ganymede and Callisto.
The irregular moons revolve in an elliptical orbit, highly inclined to the equator of their planet.
Moreover, most moves in a retrograde manner from the material of the solar system. These moons, at birth, were independent, were captured by their planet, on their cosmic journey around the Sun. All the moons orbit within the area of gravitational influence of their planet, this area is called the Hill sphere or the sphere of Roche.

Concept of the American astronomer George William Hill (1838-1914), based on the work of the French astronomer Edouard Roche (1820-1883).
More the planets are distant from the Sun and their area of influence is large and therefore they have more moons.

NB: the Hill sphere of an object (planet) in orbit around another object (Sun), more massive, is an area of gravitational influence of the object world, that is to say the space where the orbit of a third object (moon) of negligible mass compared to the other two, is possible around the object world, without being captured by the Sun.

Image: Europa is one of the four Galilean moons, subject to huge gravitational forces of Jupiter.
The Galileo spacecraft has revealed the presence of crystals on the surface of magnesium sulfate, which on Earth are in the dry lakes. Surface ice several kilometers thick hides an ocean kept liquid by heat generated by tidal forces due to its proximity to Jupiter.