Callisto. Galileo's satellite and its heavenly neighbors

Man has always been interested in what is happening in the sky. The planets of the solar system seem particularly attractive, because they are relatively close to us. Now, when the research apparatus of Juno set off for Jupiter, the world community is looking forward to the results of his observations. At first the device sent clear pictures of Io, Europe and Ganymede. Callisto, satellite number two from the Galilee group, did not enter the field of view of the device. In anticipation of new data on the planet and its moons, it is worth remembering what we know about them at the moment.

Satellites

At present, about one hundred satellites of this giant are open. Four of them are quite large, the rest are much smaller.

All the moons of Jupiter are divided into internal and external groups.

The group of internal satellites includes eight objects. They all rotate in the plane of the planet, their orbits are circular. These satellites, in turn, are divided into subgroups:

• One of them includes Metis, Adrastei, Amalthea and Teba. These small bodies, from 20 to 250 km in diameter, call them the "Amalthea group".
• The second subgroup includes four Galilean satellites.

External satellites are bodies that do not exceed several kilometers. The largest of these objects is the Himalaya. Its diameter is only 170 km. External they are named for the reason that they rotate at a considerable distance from the planet, their orbits are elliptical and are located at a large angle to Jupiter. It is interesting that, unlike the satellites of the inner group, these rotate in the direction opposite to the rotation of the giant. This orbit is called retrograde. In science, it is customary to give names to such bodies that end in "e", regardless of whose name is given their honor. The outer satellites are so small that they can only be viewed in the most powerful telescopes.

Most of the satellites are open in the last couple of decades, because their dimensions did not allow them to be observed with the help of devices of previous years. However, scientists do not exclude that in the coming years will be found a few more satellites of this giant planet.

Galilean satellites

This group was discovered in 1610 by Galileo Galilei. He observed them in one of the first telescopes. These moons are so great that you can see them even in a telescope.

Ganymede

The largest is not only among the objects near Jupiter, but also among all the satellites of the solar system. Yes there satellites - its size exceeds the diameter of Mercury. To avoid doubts, it is worth turning to the figures: the diameter of Ganymede - 5262 km, the Moon - 3474.2, Mercury - 4880. Thus, if this object independently rotated around our luminary, it would be considered a planet! However, despite its impressive size, the weight of Ganymede is half that of Mercury. Which nevertheless makes him the heaviest companion in the solar system. The core of Ganymede is melted, it has a magnetosphere, a kind of atmosphere with residual traces of oxygen. The planet is covered with a column of water ice. Presumably, this layer hides the ocean of water. If it were not for the incredible radiation streams from Jupiter, the scientists would do their best to study this satellite.

Callisto

A bit smaller in diameter - 4820.6 km - Callisto. The satellite, the photo of which the Yunona apparatus has already sent, is covered with ice. The thickness of this layer is about 200 km. In the dimensional row of moons in our star system, the third place is occupied by Callisto (satellite). Mercury in this rating is not, because it is a planet. Nevertheless, their dimensions are quite comparable, although in weight the moon of the giant planet loses greatly.

The tidal forces of Jupiter are so great that Callisto is a satellite that rotates around itself as much as around the planet.

This object attracts special interest of scientists for the reason that it seems most suitable for the equipment on it base in the future. This seems possible for the following reasons:

- Callisto is a satellite whose orbit passes beyond the boundary of the strong radiation of Jupiter.

- Its surface is water ice, which means that there will not be a lack of water there.

- The satellite of Jupiter Callisto was formed about 4 billion years ago, which almost guarantees its geological stability.

Europe

Is the smallest of this group of satellites. Its size is 3138 km. The core of the planet is metallic. Like Ganymede and Callisto, the satellite Europe is covered with water ice. Scientists believe that under it are also hidden oceans. It is likely salty. It is these water spaces that attract the attention of scientists. The fact is that the ice here is the thinnest - only 10-30 kilometers. This is very small in order to create high blood pressure. Therefore, experts suggest that water is a liquid due to a positive temperature. What is so important? Scientists hope that warm water can be a source of life. These facts make Europe such a desirable object for study in a variety of space agencies. The only negative is radiation, because Europe is inside the radiation field of Jupiter.

And about

The satellite closest to the planet. A nucleus of metal, a liquid mantle and a bark. The main feature is geological instability. On this satellite there are more than 400 volcanoes, each of which is active.

The satellites of Jupiter Io, Europe, Ganymede and Callisto in the next twenty months will be carefully studied along with the planet itself. Scientists hope that by the end of this period they will have a lot of new information, thanks to which they can realize their old dream - to begin a closer study of satellites to detect life in any form.