Information about the moon

The moon is commonly known as the moon, also known as the Moon. It is the only natural satellite of the earth in the solar system. The moon is the most obvious example of a natural satellite. In the solar system, except Mercury and Venus, all other planets are natural satellites. The moon is about 4.6 billion years old. The moon has a layered structure such as shell, mantle and core. The average thickness of the outermost lunar shell is about 60-65 kilometers. Below the lunar crust 1000 km is the lunar mantle, which occupies most of the moon's volume. Below the moon's mantle is the moon's core, whose temperature is about 1000 degrees, which is likely to be in a molten state. The moon is about 3476 kilometers in diameter, which is 3/ 1 1 of the earth. The volume is only 1/49 of the earth's, and the mass is about 735 billion tons, which is equivalent to 1/8 1 of the earth's mass. The gravity on the surface of the moon is almost equal to 1/6 of the gravity of the earth.

There are dark parts and bright areas on the moon. When early astronomers observed the moon, they thought that the dark area was covered by seawater, so they called it "sea". The more famous ones are the sea of clouds, the wet sea and the sea of tranquility. The bright part is the mountains, where mountains are stacked and criss-crossed, and craters are dotted. Bailey Crater is located near the South Pole, with a diameter of 295 kilometers, which can hold the whole Hainan Island. The deepest mountain is Newton crater, which is 8788 meters deep. Besides craters, there are ordinary mountains on the moon. Mountains and valleys overlap, giving you a unique perspective.

The front of the moon always faces the earth. On the other hand, except for the area near the edge of the moon, which is visible in the middle due to Libra movement, most areas on the back of the moon are invisible from the earth. In the era without detectors, the back of the moon has always been an unknown world.

A major feature of the back of the moon is that there are almost no dark lunar surface features such as the moon and the sea. When the probe runs to the back of the moon, it will not be able to communicate directly with the earth.

The moon revolves around the earth for about one lunar month, and moves half a degree relative to the background starry sky every hour, which is similar to the apparent diameter of the moon. Unlike other satellites, the orbital plane of the moon is closer to the ecliptic plane than the equatorial plane of the earth.

Relative to the background starry sky, the time required for the moon to go around the earth (the moon makes one revolution) is called sidereal month; The time between the new moon and the next one (or the time between two identical moon phases) is called the new moon. The reason why Wang Shuo's moon is longer than that of the star moon is that during the earth's operation on the moon, it moved forward a certain distance in its orbit around the sun.

Because the rotation period of the moon is exactly the same as its period of revolution, we can only see that the moon always faces the earth with the same face. From the early days of the moon's formation, the moon was influenced by a certain moment, which led to the slow rotation speed. This process is called tidal locking. Therefore, part of the angular momentum of the earth's rotation is converted into the angular momentum of the moon's revolution around the earth. As a result, the moon is far away from the earth at a speed of about 38 mm per year. At the same time, the earth's rotation is getting slower and slower, and the length of a day is getting longer every year 15 microsecond.

The gravity exerted by the moon on the earth is one of the reasons for the tidal phenomenon. The orbit of the moon around the earth is synchronous, and the so-called synchronous rotation is not strict. Because the orbit of the moon is elliptical, when the moon is at perihelion, its rotation speed can't keep up with the revolution speed, so we can see that the eastern part of the moon reaches 98 degrees east longitude. On the contrary, when the moon is at apohelion, its rotation speed is faster than its revolution speed, so we can see that the western part of the moon passes through 98 degrees Darcy. This phenomenon is called Libra movement. Because the orbit of the moon is inclined to the equator of the earth, when the moon moves in the starry sky, the polar regions will shake about 7 degrees, which is called Libra movement. Furthermore, since the distance between the earth and the moon is only 60 times that of radius of the earth, if the observer observes the moon from sunrise to sunset, the observation point will have the displacement of the diameter of the earth, which can be seen in the area with the longitude of 1 degree. This phenomenon is called Libra movement.

Strictly speaking, the earth and the moon revolve around a concentric center, which is 4,700 kilometers away from the center of the earth (2/3 of radius of the earth's). Because the center of homogeneity is below the surface, the movement of the earth around the center of homogeneity seems to be "shaking". Seen from above the North Pole of the Earth, both the Earth and the Moon rotate clockwise. Moreover, the moon is also clockwise around the earth; Even the earth moves clockwise around the sun.

Many people don't understand why the inclination of the moon's orbit and the inclination of the moon from the axis change so much. In fact, the orbital inclination is relative to the central celestial body (the earth), from the axial inclination to the satellite.

The orbit plane of the moon (ecliptic plane) keeps an included angle of 5. 145396 with the ecliptic plane (earth's orbit plane), while the rotation axis of the moon forms an included angle of 1.5424 with the normal of the ecliptic plane. Because the earth is not a perfect sphere, but bulges at the equator, the white road surface keeps precessing (that is, the intersection with the ecliptic rotates clockwise) and completes one week every 6793.5 days (18.5966). During this period, the angle between the white plane and the equatorial plane of the earth (the equatorial plane of the earth inclines to the ecliptic plane at 23.45) will change from 28.60 (i.e. 23.45+5. 15) to18.30 (i.e. 23.45-5. 15). Similarly, the angle between the rotation axis of the moon and the white plane will be between 6.69 (that is, 5. 15+ 1.54) and 3.60 (that is, 5. 15- 1.54). These changes in the lunar orbit will in turn affect the inclination of the earth's rotation axis, making it swing by 0.002 56, which is called nutation.

The two intersections between the ecliptic plane and the ecliptic plane are called the lunar intersection-the ascending intersection (north point) refers to the point where the moon passes to the north of the ecliptic plane; Descending node (South Point) refers to the point where the moon passes south of the ecliptic. When the new moon is just at the intersection of the moon, a solar eclipse will occur; An eclipse occurs when the full moon is just at the intersection of the moons.

The structure on the back of the moon is quite different from that on the front. The Moon Sea occupies less land and there are many craters. The terrain is uneven, and the longest and shortest radius of the moon are located on the back. Some places are 4 kilometers longer than the average radius of the moon, and some places are 5 kilometers shorter (such as Van der Graf depression). No "lump" was found on the back. The moon shell on the back is thicker than that on the front, with the thickest point reaching 150km, while the thickness of the moon shell on the front is only about 60km.

The moon itself does not shine, but reflects sunlight. The brightness of the moon varies with the angular distance between the sun and the moon and the distance between the earth and the moon. The average brightness is 1/465000 of the brightness of the sun, and the brightness varies from 1/630000 to 1/375000. At the full moon, the average brightness is-12.7 (see). Its average illumination to the earth is 0.22 lux, which is equivalent to the illumination of 100 watt electric lamp at a distance of 2 1 meter. The surface of the moon is not a good reflector. Its average albedo is only 7%, and the other 93% is absorbed by the moon. The albedo of Guangdong Sea is even lower, about 6%. The albedo of the lunar highlands and craters is 17%, and it seems that the mountains are brighter than the moon sea. The brightness of the moon also changes. The following table [] lists the brightness values of different months with full moon brightness of 100. It can be seen that the brightness of the full moon is more than ten times that of the upper and lower chords.

Because there is no atmosphere on the moon, the heat capacity and thermal conductivity of lunar materials are very low, so the temperature difference between day and night on the surface of the moon is very large. During the day, the temperature where the sun shines vertically is as high as+127℃; The temperature can be reduced to-183℃ at night. These values only represent the temperature on the surface of the moon. The temperature in the lunar soil can be measured by radio observation. The longer the wavelength of radio waves used, the deeper the temperature in the lunar soil can be detected. This measurement shows that the temperature in the deep soil on the surface of the moon rarely changes, which is precisely because of the low thermal conductivity of the material on the surface of the moon.

From the propagation of lunar seismic waves, we know that the moon also has layered structures such as shell, mantle and core. The outermost lunar shell is 60 ~ 65km thick. Under the lunar crust to the depth of 1000 km is the lunar mantle, which accounts for most of the lunar volume. Below the lunar mantle is the lunar core. The temperature of the lunar nucleus is about 1000℃, which is probably in a molten state. It is speculated that it may be composed of iron, nickel, sulfur and eclogite.

Lunar data

The average orbital radius is 384,400 kilometers.

Track eccentricity is 0.0549.

Perigee distance is 363,300 kilometers.

The apogee is 405500 kilometers away.

The average revolution period is 27 days, 7 hours and 43 minutes 1 1.559 seconds.

The average speed is1.023km/s.

The inclination of the track varies from 28.58 to 18.28.

(The intersection angle with the ecliptic plane is 5. 145).

Ascending intersection right ascension 125.08.

The perigee angle is 3 18. 15.

Repeat stage/day 19.

The average distance between the moon and the earth is about 384,400 kilometers.

The retrogression period of intersection is 18.438+0 years.

The perigee movement period is 8.85 years.

The annual food consumption was 346.6 days.

Repeated lunar eclipse)181011day.

The average inclination of track and ecliptic is 5 9'

The average inclination between the equator and the ecliptic of the moon is132'

The equatorial diameter is 3476.2 kilometers.

The diameter of the pole is 3472.0km.

Flatness 0.00 12

The surface area is 3.976×10.7 square kilometers.

Flatness 0.00 12

The volume is 2.199×1010 cubic kilometer.

The mass is 7.349× 10 22kg.

3.350 times the average density of water.

Equatorial gravity acceleration1.62m/s2

1/6 of the earth

The escape speed is 2.38km/s.

The rotation period is 27 days, 7 hours and 43 minutes 1 1.559 seconds.

(synchronous rotation)

Rotational speed16.655m/s (on the equator)

The axial inclination varies between 3.60 and 6.69.

(The intersection angle with the ecliptic is 1.5424)

Albedo 0. 12

Apparent magnitude at full moon-12.74

Surface temperature (t) -233~ 123℃ (average -23℃)

Atmospheric pressure 1.3× 10- 10 kPa

Monthly cycle

Name value (d) definition

The moon and the moon are 27.32 1 66 1

The moon is 29.530 588 relative to the sun (moon phase).

The equinox 27.32 1.582 is relative to the vernal equinox.

Perigee month 27.554 550 relative to perigee

The node month 27.2 12 220 is relative to the rising node.