In order to let the students learn more about the extraterrestrial stars, they put Hua Feng's group of students in the mimicry classroom.

At this moment, Hua Feng is like coming to the moon of Jupiter, the air and gravity are all real simulations. He came to know that a satellite eclipse occurs every time a moon enters Jupiter's shadow. If there is an observer on Jupiter who thinks that every once in a while t there will be a lunar eclipse, t is equal to the time it takes for the moon to make one revolution around Jupiter. If L is the distance from Jupiter to Earth, then it will take a period of time for this signal to reach Earth.

If let l denote the amount of change in distance L over the time it takes for the satellite to make one revolution, then the time interval between each adjacent satellite eclipse will appear slightly different to the observer on Earth, and it will be t+l/c

The time required for the lap is equal to t

=Nt+l

/C where I

It's on the satellite

The total amount of change in distance L over the time of the lap. Here are two unknowns t and c, which can be determined from two appropriately chosen observations.

First, the distance L between the Earth and Jupiter passes a certain time t

。 and then they were just as far apart. We can estimate this time interval t

。 The number of satellite eclipses that occur within N. Because Jupiter moves relatively slowly, it can be approximated that it depends only on the Earth's orbital position

。 Take the time it takes for the Earth to make one revolution around the Sun, i.e., one year. From this, t can be obtained.

Second, we start from the closest position of the Earth and Jupiter to each other, and count the number of lunar eclipses N' in a half-year period, where l'N is equal to the diameter of the Earth's orbit (i.e., about 3×108 km per astronomical unit). From this we can calculate t'N=N't+l'N/c. The observed delay time t'N-N't is 17 minutes, i.e. about 1000 seconds, and C = 300,000 km/s, which is very close to the exact value of the speed of light.

Discovered by Bradley in 1727. Another effect caused by the finite speed of light is the phenomenon of light travel. That is, all stars seem to be in a common annual motion, which clearly corresponds to the Earth's motion around the sun. It is easy to understand this phenomenon from the point of view of particles. If the Earth is stationary, then in order to observe a celestial body, we must point the telescope lens directly at that object, conversely, if the Earth is moving to the right, the telescope lens must be tilted at an angle as shown in B. The study of the propagation properties of light led to the emergence of the special theory of relativity.

According to Taiwan's "News Today" reported on the 23rd, American astronomers recently announced the latest news that Jupiter, the planet with the most moons in the solar system, has been discovered and has two new moons, which were discovered by Shepard of the Carnegie Institution in September 2011.

According to reports, the diameter of these two new moons is only 1 to 2 kilometers, which is smaller than the moon and irregular shape, one of them is about 2,000 kilometers away from Jupiter, and it orbits in about 582 days. The other is about 2,300 kilometers away from Jupiter and orbits for about 725 days.

Scientists say that 52 of Jupiter's 66 moons orbit in the opposite direction of Jupiter's rotation and are mostly located in the far outer regions, so scientists deduce that these moons are comets or asteroids captured by Jupiter's gravity and are not Jupiter's native moons.

It is understood that these two new satellites will be named by the International Astronomical Union (IAU) Solar System Celestial Nomenclature Committee, and in the future, they will also be named after the Greek god Zeus (Zeus), the Greek god Zeus with the last letter "e", and the total number of Jupiter moons has reached 66.

Titan

, also known as Titan) is a moon orbiting Saturn, the largest of Saturn's moons and the second largest in the solar system. It was discovered by Dutch physicist, astronomer and mathematician Christian Huygens on March 25, 1655, the first moon to be discovered in the solar system after Jupiter's Galilean moon.

Because it is the only moon in the solar system with a dense atmosphere, it is highly suspected of life, and scientists have speculated that methane in the atmosphere may be the basis for life. Titan can be seen as a time machine that helps us understand the earliest days of the Earth and unravel the mystery of how life came into being.

Titan's surface gravity is extremely low, comparable to that of the Moon, but it has a thick atmosphere with a surface pressure about 1.5 times that of the Earth, a strange phenomenon that is a good subject for studying planetary atmospheres. At the same time, the thick atmosphere combined with fairly low surface gravity makes landing and take-off easier.

Huygens simply called the satellite he discovered "Satu."

i Lu

a" ("Saturn's Moons"). Later, Giovanni Domenico Cassini named the four moons (Titan Thetis, Titan Diony, Titan Rhea and Iapetus Iapetus) Lodicea Side in honor of King Louis XIV

A (Louis Star). Astronomers routinely numbered the five satellites. The other moons were called Huygens moons or Saturn's sixth moon (from the time known to be near and far from Saturn, Enceladus Memas and Enceladus Enkladus were discovered in 1789).

Titan's English name is "Tita."

"And seven other moons of Saturn known at the time, whose names come from Sir John Herschel (John Herschel was the son of Sir William Herschel, who himself discovered Enceladus and Enceladus). In his 1847 book The Results of Astronomical Observations at the Cape of Good Hope, John Herschel named the new moon the Titan, a mythological term for Kronos (his Roman counterpart, Saturn) and his siblings.

Titan is Saturn's largest moon and the second largest moon in the solar system, larger than the planet Mercury (although not as massive as Mercury), and only smaller in the solar system than Jupiter's largest moon, Ganymede. But recent observations have also shown that the dense atmosphere may have led to an overestimation of Titan's diameter, which, like many other moons, is larger than the mass and volume of asteroid 134340 (pro-Pluto).

The average radius of Titan is 2575 km, the mass is 1.345×10²³ kg, and the average density is 1.880×10³ kg/m³. Titan's orbit around Saturn has a semi-major diameter of 1,221,850 km, an eccentricity of 0.0292, an angle of 0.33° between the orbital plane and Saturn's equatorial plane, and an orbital period of 15 days, 22 hours, 41 minutes and 24 seconds. Titan's rotation period is the same as its revolution, which is similar to that of the Moon. Titan has a dense atmosphere, the main component is nitrogen, a surface atmospheric pressure of 1.5×10⁵Pascal, and a surface temperature of -179.15°C.

Titan's mass is roughly similar to that of Ganymede, Ganymede, Triton, and the asteroid 134340 (Pluto). Titan is half water ice and half solid material. There is a solid core at 3400 meters below multiple different crystalline ice formations. The inside of the core should still be red-hot. While Titan and other moons of Saturn are similar, Titan's core is denser because of its sheer size, which causes gravity to compress its interior.

Atmospheric conditionsTitan is the only moon known to have a true atmosphere, and the rest of the satellites only have tracer gas at best. The presence of the atmosphere was first identified in 1944 by Ge Gilard Kuiper

a

d P. Kuipe

Using a spectroscopic telescope, he found that the local pressure of methane in Titan's atmosphere reached 100 millibars.

Later, observations by the Voyager spacecraft also confirmed that Titan has an atmosphere on it, and in fact, the atmospheric pressure on Titan is slightly greater than that of Earth, and the pressure on the planet's surface is 1.5 times that of Earth. Titan's surface is covered by dense clouds. It is generally believed that the surface of Titan is solid or liquid ethane. Radar measurements from the Earth have shown that there is no large ethane ocean, but it is still possible that small ethane lakes exist.

Later, scientists studied the photos sent back by the Cassini spacecraft and concluded that there may not be an ocean of liquid methane on Titan. Researchers who had observed Titan through ground-based telescopes believed that there were signs of a possible liquid ocean on Saturn's moon.

However, scientists still have doubts about the conclusions reached, because previous observations have shown that there is indeed a flickering reflection of liquid on the surface of Titan, especially from a large radio telescope a few years ago, which proves that a liquid ocean is highly likely.

Titan's atmosphere is 98.44% nitrogen, the only nitrogen-rich star in the solar system other than Earth, where there are large residues of different kinds of hydrocarbons (including methane, ethane, butylene, propyne, propynitrile, acetylene, propane, as well as carbon dioxide, cyanide, hydrogen cyanide, and helium).

These hydrocarbons are thought to come from methane in Titan's upper atmosphere. When methane reacts in response to solar radiation, it produces a dense cloud of orange-red smoke. The organic precipitate on the surface of Titan, which appears to be coated with a layer of tar, is called tholi

。 Titan is not protected by a magnetic field, so when it sometimes orbits outside Saturn's magnetosphere, it is directly exposed to the solar wind. This causes the atmosphere to ionize and release some molecules in the upper layers of the atmosphere.

Approaching the surface, Titan's temperature is approximately 94 K (-179.15 °C). Water ice sublimates at this temperature, so there is a small amount of water vapor in the atmosphere. Clouds may be made up of methane, ethane, or simple organic matter. Other rare complex chemicals are responsible for Titan's orange appearance in space.

In November 2004, Cassini flew past the bright and cloudy South Pole in the Titan photograph but did not find the desired methane to exist.

Cassini's 2004 observations of the atmosphere found that Titan's atmosphere "super-rotates", like Venus, and its atmosphere rotates much faster than the surface.