Hua Feng understood that even so, first of all, the dangerous asteroid was under the supervision of astronomical experts, and he was able to accurately predict the asteroid's flight trajectory. In the event of an imminent impact, the asteroid's orbit can also be changed accordingly.

There are several specific schemes. The first is to change the orbit with mechanical force, that is, after launching an artificial celestial body into space, adjust it to be parallel to the asteroid, and make the relative velocity of the two zero, and then push the asteroid with mechanical force, and it will change its orbit.

Secondly, it is also possible to change the asteroid's orbit by changing the color. If the asteroid turns out to be gray, it can be turned black, and the color of the object can determine how much heat it absorbs, and its orbit will change accordingly.

Thirdly, the explosion method can also achieve a change in the orbit of an asteroid. For planets with iron elements and strong structures, they can be attacked with ** or nuclear devices, ideally by blowing it up into two parts, so that the mass changes and the orbit changes.

Finally, by installing a "solar sail" on the asteroid, that is, installing a large rocket engine or a "solar sail" on the surface of the asteroid body, the planet is pushed away from the Earth's orbit.

If a near-Earth asteroid collides with Earth, scientists can use nuclear weapons to contain it. The purpose of using a nuclear bomb to attack an incoming asteroid is not to destroy it, but to change the asteroid's orbit. If it were destroyed, the deadly fragments of the incoming asteroid would still fall to Earth, causing disaster for humanity. The intense radiation from a nuclear explosion is capable of vaporizing part of the asteroid's surface, causing it to eject surface material into space. This jet is like installing an infinite number of miniature rockets on an asteroid to change its orbit.

Some scientists consider the use of nuclear weapons to prevent an asteroid from hitting the Earth as an "overreaction" and that it is also possible to change the orbit of an asteroid by hitting it.

NASA has come up with what it calls "kinetics", which is like firing a spinning bowling ball with a projectile gun, and using the impact to deflect the asteroid from its collision trajectory. According to the Space Network, if the "bowling ball" were launched 20 years before the predicted impact, a 1 mile per hour (1.6 kilometers per hour) impact would be enough to deflect the asteroid 170,000 miles (273,500 kilometers) from its original orbit.

"Painting" an asteroid is also a way to cope, although it sounds a little ridiculous. This method makes use of solar orbital mechanics. During the hot summer months, you will definitely choose a white shirt over a black shirt because white reflects more solar radiation, while black absorbs more radiation. The "lacquering method" uses this principle.

If parts of the asteroid's surface are painted white, these areas will receive more "thrust" from solar radiation, gradually pushing the asteroid out of its original orbit and saying "goodbye" to Earth. The "lacquer" used in the "lacquer method" can be light-colored dust, chalk, or any other material that alters the proportion of radiation reflected and absorbed by the asteroid.

"Painting" an asteroid may not catch everyone's eye, but solar wind will play a crucial role in the many ways in which an asteroid impact can be responded to by changing its orbit. For example, scientists could send a spacecraft to install giant "solar sails" on an asteroid, using the powerful solar wind to deflect the asteroid from its original orbit and prevent it from hitting Earth.

In some of the scenarios proposed by scientists, the solar sail could even be adjusted, allowing it to be remotely manipulated to a certain extent. However, many experts have questioned the strategy of "installing solar sails on asteroids", because asteroids are constantly tumbling and spinning, and even if we can send an unmanned spacecraft to land on an asteroid, it will be difficult to erect solar sails that can change its orbit.

NASA scientists believe that a carbon fiber web weighing about 550 pounds (249 kilograms) would be enough to change the orbit of an incoming asteroid like Apophis. The material used in this "Skynet" can act as a solar sail, increasing the amount of solar radiation absorbed and emitted by the asteroid.

Until 2029, Destroyer will not have a dangerous close encounter with Earth. In 2036, the asteroid will return to Earth. Scientists believe that even if the planet is trapped in the net for only 18 years, it will be enough to keep this "space demon" away from Earth.

To stop an asteroid from hitting the Earth, we don't have to use nuclear weapons in a big way, we just need mirrors to achieve the same effect. The role of the mirror is to gather sunlight and heat a small area of the asteroid's surface, causing it to eject steam outward. This ejection of material creates a thrust that changes the asteroid's orbit.

Early ideas suggested the use of so-called "single giant space mirrors," but as research progressed, scientists decided that deploying a multi-mirror system would produce more desirable results. Some scientists refer to the mirror method as "laser sublimation".

In that case, it takes a long time for both the solar sail and the space mirror to change the orbit of an incoming asteroid, so why not just put a giant rocket on the asteroid and use the huge thrust generated by the rocket to change its orbit? Some scientists agree with the giant rocket method. According to their idea, a spacecraft could be sent to land on an asteroid, then dig a hole in it, place a heavy rocket powered by chemical fuel, and finally ignite the rocket, using the thrust generated by the rocket to "kick away" the asteroid that would try to destroy the Earth.

To many, gravitational drag sounds like a technique imagined by the writers of Star Trek with astonishing complexity, but in fact it is quite the opposite. Gravitational drag is generated by everything in the universe, including asteroids and man-made spaceships. Gravity may be one of the weakest forces in the universe, but it's also one of the easiest to harness because all you need is a little mass.

Quality here refers to the device responsible for the tow. Theoretically, a heavy robot flying near an asteroid would be enough to use gravitational drag to change the asteroid's orbit. However, not everyone supports this approach. To prevent the spacecraft from hitting the asteroid, the thrusters must be aligned with the direction in which the asteroid is traveling. In addition, the cost of this way is also astronomical.

Under the vision of the NASA-funded Modular Asteroid Offset Mission (MADMEN), scientists could send nuclear-powered robots to attack asteroids that threaten Earth. Once they landed, they excavated on the asteroid, figuratively devouring the material on the asteroid's surface and using electromagnets to eject debris into space at high speeds. This injection of material produces the same thrust as a rocket without the need for any chemical fuel. However, scientists need to conduct in-depth research to determine if this approach works.

If all nine of these ways to change the asteroid's orbit end up failing, humanity will be largely powerless in the face of an incoming asteroid, even if the threat was foreseen hundreds of years in advance. In this case, we can only choose to accept that in horror and chaos we will witness the eventual extinction of humanity, the ruler of the Earth, by the immense power of nature.

The moon is the most obvious example of a natural satellite. In the solar system, except for Mercury and Venus, all other planets have natural satellites. The total number of known natural satellites in the solar system (including the larger fragments that make up the planetary rings) is at least 160.

A natural satellite is a planet that orbits a planet, which in turn orbits a star. For example, in the solar system, the sun is a star, our earth and other planets orbit the sun, and the moon, Enceladus, Celeladus and other planets orbit our earth and other planets, and these planets are called natural satellites of the planets. Saturn has the second most natural satellites, with 62 known. Jupiter has the most natural satellites, of which 63 have been confirmed and at least 6 have yet to be confirmed.

Natural satellites vary in size and vary greatly from each other. Some of them are only a few kilometers in diameter, for example, the two small moons of Mars, and some small moons on the periphery of Jupiter, Saturn, and Uranus. Others are larger than Mercury, such as Titan, Ganymede and Callisto, all of which are more than 5,200 kilometers in diameter.

The largest moons in the solar system (more than 3,000 km) include Earth's moon moon, Jupiter's Galileo moons Europa (Io), Europa, Europa (Ganymede), Ganymede (Callisto), Saturn's moon Titan (Titan), and Neptune's captured moon Triton (Triton). Smaller moons are listed in the respective planetary entries.

Here is a classification of the solar system's satellites by diameter and the stars they orbit, and the rightmost column also lists some of the asteroids, planets, and Kuiper Belt objects for comparison. Due to the limited space in the table, all satellites with more than three characters in Chinese names are represented by numbers, and those with three characters or less in Chinese names are listed according to their official names.

Jupiter's satellites of Jupite

Jupiter's other moons are much darker than Galileo's moons and can only be seen with larger telescopes. American astronomer Barnard discovered with a telescope in 1892 that Ganymede moves within the orbit of Europa.

In March 1979, the Voyager 1 space probe found that Calliste was light gray, with a reddish area about 130 kilometers long and 200~220 kilometers wide. Jupiter's other moons have been photographed since 1904, moving in orbits beyond Callisto. Some of Jupiter's 13 moons have a radius of more than 2,000 kilometers, while others have a radius of only a few kilometers or a dozen kilometers.