Hua Feng knows that everything must be down-to-earth and move forward step by step in order to get out of a solid future, until today, the radius of human activity has been able to sail freely in the solar system, but there is still some distance to reach the voyage outside the galaxy.

In early 1979, Jewitt and Danielson of the California Institute of Technology announced the discovery of a new moon of Jupiter, Europa, based on the results of the Voyager 2 probe.

In 1980, the discovery of Europa XV and XVI was announced, but this has yet to be confirmed.

The reason why there are hydrogen clouds and sodium clouds near Io is because atoms escape from the weak gravitational field of the moon and drift into the surrounding space, but they are bound by Jupiter's huge gravitational field. Atomic clouds spread out in the "Jupiter space", concentrated near the birthplace of Europa. As for the ionosphere, it is caused by the ionization of atoms in Io's outer atmosphere by the sun's ultraviolet rays.

In March 1979, the Voyager 1 space probe discovered that Io's surface was relatively flat, unlike the many craters that ordinary celestial bodies do. The space probe also discovered at least six active volcanoes on Europa, erupting gases and solids at speeds of up to 450 kilometers per hour. Volcanic activity zones can be up to 200 kilometers in diameter, and volcanic eruptions are much stronger than those on Earth.

In addition, Io has a red polar crest, which increases in brightness for up to 15 minutes when Io emerges from Jupiter's shadow cone. Radio astronomers have also observed a close correlation between the intensity of Jupiter's radio noise storm and Io's position in orbit.

Voyager 1 found Europa to be a bright sphere with a few broad black stripes and yellowish dark areas on the surface. This indicates that Europa is covered in ice, which may be rocky underneath, and black streaks may be cracks on its surface. Voyager 1 found very clear signs of ridges and canyons on the surface of Europa, indicating that there is a fault on the surface of Europa.

Photographs taken by Voyager 1 also show that Callisto has some large basins surrounded by concentric rings, with little undulation. The basin of concentric rings emits a strange glow, indicating that there is ice on the surface of Callisto. In addition, it has been found that there are more craters on Ganymede than on Europa, indicating that Callisto's geological age is greater than that of Europa.

On July 17, 2018, U.S. researchers said they had discovered 12 new moons of Jupiter, bringing the total number of known Ganymede to 79. One of the newly discovered satellites is at risk of colliding head-on with the other satellites.

Jupiter's regular moons are thought to have formed on the ring planetary disk, a ring of gas and solid debris similar to the protoplanetary disk. These materials may be remnants of a moon formed early in Jupiter's history and with a mass similar to that of Galileo's moons.

Simulations show that the circumferential disk has a relatively low mass at all times, and every once in a while, a small portion of Jupiter's mass captured from the solar nebula passes through the circumferential disk. However, existing moons only need the mass of Jupiter's circumferential disk at 2 percent of Jupiter's mass to explain this.

This indicates that in Jupiter's early history, there may have been several generations of moons with similar masses to Galileo's moons. Each generation of moons descends into Jupiter due to the drag of the circumplanetary disk, and the captured fragments of the solar nebula form a new generation of moons.

By the time today's generation (possibly the fifth) was formed, the ring disk was too thin to affect the orbit of the satellite. Now the moon Galileo is still affected and is approaching Jupiter. Only Europa, Europa, and Europa are protected by orbital resonance. And the greater mass of Ganymede means that it will get closer to Jupiter faster than Europa and Europa.

It is believed that the irregular moons of the outer ring are captured passing asteroids. At that time, the mass of the original satellite ring was still enough to absorb the power of the asteroid and bring it into orbit. Many of them were torn apart by sudden decelerations, and some were later scattered by other satellites, forming the various groups we see today.

The physical and orbital properties of Jupiter's moons vary widely. The four Galilean moons are more than 3,000 kilometers in diameter, and Ganymede is even the largest object in the solar system after the Sun and the eight planets. The rest of the satellites are less than 250 kilometers in diameter, and the smallest is just over 5 kilometers. Even Europa, the smallest of Galileo's moons, is 5,000 times larger than the other moons (excluding Galileo) combined.

The shape of the orbit also varies greatly: from nearly perfect circle to high eccentricity. In addition, some orbits are in the opposite direction to Jupiter's rotation (retrograde). The orbital period also ranges from 7 hours (shorter than Jupiter's rotational period) to about 3 years.

In 1610, shortly after the discovery of Jupiter's Galileo moon, Simon Marius named Io (Europa), Europa (Europa), and Callisto (Callisto).

Before the 20th century, these names were not popular, and instead they were called "Europa", "Europa", or "Jupiter's first moon" and the like. These names were not widely used until the 20th century, while the remaining newly discovered moons remained to be named, and were called after their Roman numeral numbers V (5) to XII (12).

Discovered in 1892, Callisto, first known as Amandia by the French astronomer Frimparian, was unofficial, but popular.

In the 1970s, astronomy and literature used the Roman numeral numbering of satellites directly.

In 1975, the International Astronomical Union (IAU) named Europa to XIII and provided a formal naming procedure for the satellites discovered later. The rule is that the name of the newly discovered moon must be the lover and favorite of the god Jupiter (Zeus).

In 2004, the naming convention was extended to the descendants of the above figures. Moons after Callista were named after the daughters of Jupiter or Zeus.

Some asteroids have the same name as Jupiter's moons: Asteroid 9, Asteroid 38, Asteroid 52, Asteroid 85, Asteroid 113, and Asteroid 239. The International Astronomical Union permanently renamed two asteroids (Asteroid 1036 and Asteroid 204) to avoid conflict.

In fact, Ganymede was discovered by Gander, an astronomer from the Warring States period in China, who wrote two books, "The Book of Stars of the Year" and "Astronomical Astrological Horoscope", but unfortunately they have been lost. There is such a record in the twenty-third volume of the "Kaiyuan Zhanjing" compiled by the Tang Dynasty astronomer Qu Tan Siddha: "Gan said: The age of the single cast, the setig is in the mao, the year star is in the son, and the bearded woman, the void, the danger of the morning and the evening in, its shape is very large and bright, if there is a small red star attached to its side, it is called an alliance."

Gander discovered Ganymede as early as 346 BC, almost 2,000 years before Galileo.

Jupiter's 13 moons are divided into three groups. The closest group to Jupiter, Ganymede and the four Galilean moons, have very small orbital eccentricities (≦0.01), and the angle of intersection between the orbital plane and the equatorial plane of Jupiter is also very small (≦05), that is, they all move in circular orbits on the equatorial plane of Jupiter, and the orbital plane of these moons is about 2°~4° of the orbital plane of Jupiter.

The rest of the satellites are irregular, but they can be divided into two groups. A group of moons slightly farther away from Jupiter, Callisto, Callisto, and Ganymede have an angle of 24°~29° between the orbital plane and the equatorial plane, and are anterograde, with an orbital eccentricity of 0.13~0.21. The farthest group of Jupiter, Callisto, Callisto, and Europa have a fairly large orbital eccentricity (0.17~0.38), and their orbital planes are at an angle of 145°~164° to Jupiter's equatorial planes, and they are all retrograde moons. Some believe they may be asteroids captured by Jupiter.

The following phenomena will occur in the operation of Jupiter's moons: Jupiter has a shadow cone in the direction of the sun under the sun, and when the moon of Jupiter enters the shadow cone, the moon cannot reflect the sun's light and becomes invisible, which is called a Ganymede eclipse. When Jupiter's moons enter the back of Jupiter's circle, our view of Jupiter's moons from Earth is blocked by Jupiter, which is called a Callisto occultation.

Jupiter's moons pass in front of Jupiter's circle and cast a circular spot on Jupiter's apparent circle as seen from Earth, called Callis. When the shadow of one of Jupiter's moons is cast on Jupiter's apparent circle and it is not itself on Jupiter's apparent circle, it is called Ganymede. When seen from Earth, when one of Jupiter's moons blocks the other, it is called a Ganymede occultation, and when one Ganymede enters another Ganymede's shadow cone, it is called a Europa eclipse.

Jupiter's four larger moons, the Galilean moons, are listed from the inside to the outside as Io and Europa (Eu).

opa), Ganymede (Ga

ymede), Callisto, which, together with Jupiter, form a small "solar system". The motion of Galileo's moons around Jupiter has been of great concern to astronomers. The orbital models of these satellites can be improved through continuous observations, thus providing the necessary support for in-depth exploration of Jupiter and its surrounding space environment. In recent years, Jupiter and its moons will have multiple occultation and eclipses.

Mutual occultation can occur when the Earth and Galileo satellites are in the same orbital plane, and similarly, mutual eclipse can occur when the Sun and Galileo satellites are in the same orbital plane. For Galileo's moons, this occultation occurs once every 6 years, Saturn's moons every 15 years, and Uranus's moons only once every 42 years.

During the mutual occultation and eclipse of the satellites, the photometric results of the two related objects show that the light flow of the occlusion object decreases, as shown in the figure (CCD(cha

gecoupleddevice) observations). The optical flow can be divided into three parts, namely the skylight background and the current Da

k (darkfield) value, the value of the change in occult starlight flow and occluded starlight flow.

In the processing and analysis of observations, we use the occultation star as the reference star to measure the change of the light flow of the occultated star. Point A in the figure is the beginning moment of the occultation phenomenon, at this time, the occlusion of the occult star begins to decrease due to the occlusion of the occult star, point B is the intermediate moment, at this time, the occlusion degree of the occultated star reaches the maximum, and the light flow is the smallest, and point C is the end time, at this time, the occultation of the satellite ends, and the occlusion star flow value returns to the value before the occultation begins.

The huge screen in the classroom holographically projects the trajectories of various celestial bodies. Hua Feng, Yun Meng, Bai Feng, and most of them all felt as if they had come to outer space across the heavens.

What an amazing feeling! Hua Feng couldn't help but think.