Some astronomical knowledge about the moon, stars, meteors, comets, five stars and the sun.

The sun is 5 billion years old and is in the middle of its life. As the center of the solar system, the growth of all living things on earth directly or indirectly needs the light and heat it provides.

2. Venus

Venus appears in the sky in the morning and at dusk respectively. Ancient astrologers always thought that there were two such planets, so they were called "morning star" and "evening star" respectively. In English, Venus is the goddess of ancient Rome, symbolizing love and beauty. Venus has been shrouded in a mysterious veil by curly clouds.

Venus is the second farthest planet from the sun. It is very similar to the earth in volume, mass, density and weight, and can be regarded as the sister star of the earth. In fact, Venus is very different from the Earth. A day on Venus is equivalent to 243 days on Earth, but its year is only 225 days. Venus' rotation from east to west also makes the sun rise in the west and set in the east on Venus. Venus has a thick carbon dioxide atmosphere and no water. Its cloud is made up of sulfuric acid drops. Its surface atmospheric pressure is more than 90 times that of the earth. Venus' thick carbon dioxide atmosphere has a strong "greenhouse effect". Sunlight can bake the surface of Venus through the atmosphere, but the surface radiation is blocked by the atmosphere and the heat cannot be released, resulting in the surface temperature exceeding 480 degrees Celsius. Such a high temperature melts the metal.

3. the moon

Mass 7.349e+22kg

Equatorial radius1.2298e-02km.

The average density is 3.34 g/cm3.

The average distance to the ground is 384,400 kilometers.

The rotation period is 27.32 166 days.

Period of revolution 27.3 166 days

The average orbital speed is1.03km/s.

Equatorial surface gravity1.62m/s2

The equatorial escape velocity is 2.38 km/s.

The average surface temperature during the day is 107℃

Average surface temperature at night-153℃

The maximum surface temperature is123 C.

Minimum surface temperature -233 degrees Celsius.

The moon is commonly known as the moon, also known as the Moon. The moon is also about 4.6 billion years old and is closely related to the earth. The moon also has layered structures such as shell, mantle and core. The average thickness of the outermost lunar shell is about 60-65 kilometers. Below the lunar crust to the depth of 1000 km is the lunar mantle, which occupies most of the volume of the moon. 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, most of the back of the moon can't be seen from the earth, except the area near the edge of the moon, which can be seen occasionally due to the movement of Libra. 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 moon 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.

4. Meteors and related contents

Meteor is a light trail produced by dust particles and solid blocks (meteoroids) in interplanetary space breaking into the earth's atmosphere and rubbing with the atmosphere. If they are not completely burned in the atmosphere, they are called "meteorites" or "meteorites" after falling to the ground. Meteorites originally moved around the sun, and when passing near the earth, they changed their orbits under the action of the earth's gravity, thus entering the earth's atmosphere. There are several kinds of meteors: single meteor, fireball and meteor shower. The appearance time and direction of a single meteor are irregular, which is also called accidental meteor. Fireball is also an occasional meteor, but when it appears, it is very bright, like a fire dragon and may be accompanied by explosion, and some can even be seen during the day. Many meteors radiate from a certain point (radiation point) in the starry sky, which is a meteor shower. Meteorite is the remaining part of the larger meteoroid in the solar system that has not completely burned after it broke into the earth's atmosphere. It brings us rich information about the formation and evolution of celestial bodies in the solar system, and it is a welcome uninvited guest. Generally speaking, the density of meteoroids is extremely low, about 1/20 of that of water. Billions of meteoroids enter the earth's atmosphere every day, and their total mass can reach 20 tons.

bolide

The fireball looks very bright, like a huge sparkling dragon, making a rustling sound and sometimes exploding. Some fireballs can see it even during the day. The fireball appears because its meteoroid has a large mass (more than several hundred grams). After entering the earth's atmosphere, it was too late to burn out at high altitude, and continued to break into the dense lower atmosphere, rubbing violently with the earth's atmosphere at a very high speed, producing dazzling light. After the fireball disappears, it will leave a long cloud-like belt on its path, which is called "meteor trail"; Some traces disappear quickly, while others can last for several seconds to several minutes, or even as long as several tens of minutes.

meteor shower

Among all kinds of meteor phenomena, the most beautiful and spectacular is the meteor shower. When it appears, thousands of meteors radiate from a certain point (radiation point) in the sky like flashing ribbons. Meteor showers are named after the constellations where the radiant points are located, such as andromedids and Leonid meteor showers. There have been many famous meteor showers in history: Lyra meteor shower, Aquarius meteor shower, Leonid meteor shower and andromedids. China recorded the Lyra meteor shower in 687 BC, which is the earliest meteor shower record in the world.

Meteor showers appear regularly, and they often appear repeatedly on roughly the same day every year, so they are also called "periodic meteors".

5. Comets

Comet is a small cloud-like celestial body with low mass, which orbits the sun in a flat orbit (very few in a near-circular orbit).

There are three kinds of orbits of comets: ellipse, parabola and hyperbola. Comets with elliptical orbits are also called periodic comets, and comets with other two orbits are also called aperiodic comets. Periodic comets are divided into short-period comets and long-period comets. Generally speaking, a comet consists of a head and a tail. The comet head includes two parts: the nucleus and the coma, and some have comet clouds. Not all comets have structures such as nucleus, coma and tail. In ancient China, the shape of comets has been studied a lot. There are 29 pictures of comets on the silk book unearthed from Mawangdui ancient tomb in Changsha. It is clearly stated in Tian Wenzhi in the Book of Jin that comets don't shine because they reflect sunlight and are seen by us. Their tails are facing away from the sun. Comets are huge, but their mass is pitifully small, even the mass of big comets is less than one tenth of that of the earth. Because a comet is composed of frozen impurities and dust, it is only a small cloud-like spot when it is far away from the sun; When it is close to the sun, the comet tail is produced because of the evaporation, gasification, expansion and eruption of the solidified body. The tail is huge, hundreds of millions of kilometers long. It has different shapes, some more than one, and generally extends away from the sun, and the closer it is to the tail of the sun, the longer it is. There are many comets in the universe, but only about 1600 has been observed so far.

The orbit of a comet

The orbit of a comet is very different from that of a planet. It is an extremely flat ellipse, and some even have parabolic or hyperbolic orbits. Comets with elliptical orbits can return to the sun regularly, and such comets are called periodic comets. A comet with a parabolic or hyperbolic orbit can only approach the sun once in its life, and once it leaves, it will never come back. They are called aperiodic comets. These comets may not be members of the solar system, but passers-by from outside the solar system, inadvertently broke into the solar system, and then returned to the depths of the vast universe without hesitation. Periodic comets can be divided into short-period comets (period of revolution around the sun is less than 200 years) and long-period comets (period of revolution around the sun is more than 200 years). The orbits of more than 600 comets have been calculated so far. The orbit of a comet may be affected by planets and changes. When the comet is accelerated by the influence of the planet, its orbit will flatten, even become a parabola or hyperbola, thus making the comet leave the solar system; When the comet slows down, the eccentricity of the orbit will become smaller, which will make the long-period comet become a short-period comet, or even change from an aperiodic comet to a periodic comet and be "captured".

Structure of comet

Comets have no fixed volume. They are very small when they are far away from the sun. When approaching the sun, the coma becomes bigger and bigger, the tail becomes longer and the volume becomes very huge. The longest tail can reach more than 200 million kilometers. The mass of comets is very small, and most of them are concentrated in the nucleus. The average density of the nucleus is per cubic centimeter1g. The material in coma and tail is extremely thin, accounting for only 1%-5% of the total mass, or even less. Comet material is mainly composed of water, ammonia, methane, cyanide, nitrogen, carbon dioxide and so on. The comet nucleus is a "dirty snowball" composed of water, carbon dioxide (dry ice), ammonia and dust particles condensed into ice.

The origin of comets

The origin of comets is an unsolved mystery. It has been suggested that there is a large comet area outside the solar system, where there are about 654.38+000 billion comets, called Oort Cloud. Due to the gravity of other stars, some comets enter the solar system. Due to the influence of Jupiter, some comets escape from the solar system, while others are "captured" as short-period comets. Others believe that comets are formed near Jupiter or other planets; Others believe that comets formed in remote areas of the solar system; Some people even think that comets are visitors from outside the solar system.

The source of life.

6. Mercury and other planets

Mercury, the closest to the sun, is the second asteroid in the solar system. Mercury is smaller in diameter than Ganymede and Titan, but it is heavier. Magic five-star Julian

The temperature difference on Mercury is the largest in the whole solar system, ranging from 90 to 700. In contrast, the temperature of Venus is slightly higher, but it is more stable.

Mercury is similar to the moon in many ways. There are many craters on its surface, which is very old. It also has no plate movement. On the other hand, the density of mercury is much larger than that of the moon (5.43g/cm3 for mercury and 3.34g/cm3 for the moon). Mercury is the second largest celestial body in the solar system in density after the earth. In fact, the high density of the earth is partly due to the compression of gravity; Otherwise, the density of Mercury will be greater than that of the Earth, indicating that the iron core of Mercury is relatively larger than that of the Earth, and it is likely to constitute most of the planets. So relatively speaking, Mercury has only a thin silicate mantle and crust.

The huge iron core has a radius of 1800 to 1900 km, and is the dominator inside Mercury. The silicate shell is only 500 to 600 kilometers thick, and at least part of the inner core may be molten.

In fact, Mercury's atmosphere is very thin, made up of destroyed atoms brought by the solar wind. The temperature of mercury is so high that these atoms quickly escape into space, so compared with the stable atmosphere of the earth and Venus, the atmosphere of mercury is frequently replaced.

The surface of Mercury presents huge steep slopes, some of which are hundreds of kilometers long and as high as three kilometers. Some cross the outer ring of the crater, while others are compressed by steep slopes. It is estimated that the surface of Mercury has shrunk by about 0. 1% (or by about 1 km in the radius of the planet).

One of the largest landforms on Mercury is the Callaris Basin (right), with a diameter of about 1300 km, which is considered to be similar to Maria, the largest basin on the moon. Like the moon's basin, the Carolis basin was probably formed in the early collision of the solar system, which probably caused the strange terrain that the other side of the planet faced the basin at the same time.

In addition to the terrain covered with craters, Mercury has relatively flat plains, some of which may be the result of ancient volcanic movements, but others are probably the result of the deposition of ejecta formed by meteorites.

launch

Mars is one of the nine planets in the solar system, ranking fourth in the order from near to far from the sun and seventh in volume in the solar system. Because the rocks, sand and sky on Mars are red or pink, this planet is usually called "red planet". Its distance from the earth is constantly changing, so is its brightness: the apparent magnitude at the darkest time is about+1.5, etc. At the brightest time, it reaches -2.9, which is much brighter than the brightest Sirius. Its apparent position in the star is also constantly changing, sometimes forward and sometimes backward. Mars is smaller than the Earth, with an equatorial radius of 3,395km, accounting for 53% of the Earth, volume 15%, mass 10.8%, and surface gravity acceleration of 38% of the Earth. This red planet is extremely cold and dry. Nevertheless, Mars is still the most similar planet to Earth in the solar system. It is smaller than the earth, and the atmosphere is thinner than the earth.

The southern hemisphere of Mars is an ancient plateau, full of craters similar to the moon, while the northern hemisphere is mostly composed of young plains. Mount Olympus, 24 kilometers high on Mars, is the highest mountain range in the solar system. About tens of thousands of kilometers away from Mars, there are two very small stars, which are satellites of Mars. Namely Phobos and Phobos.

Jupiter:

Jupiter is the fifth farthest planet from the sun and the largest planet in the solar system.

If Jupiter is empty inside, it can hold more than a thousand earths. Jupiter's success

Some of them are more complicated than others. Its weight is1.9x1027kg,

The equatorial diameter is 142800 km. 1979, Voyager 1 discovered wood.

This star also has a halo, but it is too dark to be seen on earth. The size of Jupiter

The gas is very thick, maybe it is a gas ball like the sun. Jupiter's atmosphere

The main components are hydrogen and helium, and a small amount of methane, ammonia, water vapor and other chemicals.

Compound. Inside Jupiter, electrons in hydrogen atoms are trapped due to great pressure.

Released, leaving only bare protons. Make hydrogen look like metal.

Bright stripes in latitude, rolling clouds and storms symbolize Jupiter.

Changing weather system. Cloud patterns change every hour and every day. "Great Red Spot"

This is a complicated storm moving clockwise. Its outer edge is once every four to six days.

Rotate once, but near the center, the movement is small and the direction is uncertain. On the long street

A series of small storms and eddies can be found on the clouds. The average temperature of Jupiter's atmosphere

The temperature is-12 1 celsius.

At the poles of Jupiter, aurora very similar to that on earth was found. It seems that

It is related to the matter that enters Jupiter's atmosphere along Io's spiral magnetic field line. exist

At the top of Jupiter's clouds, high-altitude lightning similar to that on earth was also found.

Jupiter is a planet with more satellites in the solar system. So far, I have

Scientists have found that Jupiter has 16 satellites, four of which (Callisto, Europa,

Ganymede and io were discovered by Galileo as early as 16 10 years ago. They are related to wood.

Stars form a family: the Jupiter system.

Saturn:

Saturn

China, one of the nine planets in the solar system, was called Zhenxing or Buxing in ancient times, and was named after the ancient western Saturnalia. The semimajor axis of Saturn's orbit is 9. 539 astronomical units; The track eccentricity is 0.055 and the inclination angle is 2.5. Saturn is the second largest planet in the solar system after Jupiter, with a mass of 5688×1029g, 95. 18 times the mass of the earth, an equatorial radius of 60,000km, a oblateness of 0. 108, a volume of 755 times that of the earth and an average density of 0.7/kloc-0. The surface gravity is 1. 15 times that of the earth, and that of period of revolution is 10759.2 days, or 29.46 years. The rendezvous period is 378.09 days, the average revolution speed is 9.64 km/s, the rotation period is 10 hour, the equator is 14 minute, and the poles are 65434. Saturn's most striking feature is that it has a bright ring. The halo plane does not coincide with Saturn's orbital plane, and the direction of the halo plane remains unchanged during its revolution around the sun. So from the earth, the apparent area of the halo is not fixed, which affects the brightness of Saturn. The difference between the brightest and the darkest is about 3 times. Saturn has 23 moons.

7.stars

I remember that there is no such thing as a star in astronomy. The star you mentioned should be visible to the naked eye at night.

A spherical or quasi-spherical object composed of hot gas, which can emit light by itself. The nearest star to the earth is the sun. Followed by proxima centauri Centauri, whose light takes 4.22 years to reach the earth. On a clear moonless night, most people can see about 3000 stars with the naked eye somewhere. With the help of a telescope, you can see hundreds of thousands or even millions. It is estimated that there are about 200 billion stars in the Milky Way. The stars are not motionless, just because they are too far away from us, and it is difficult to find their position changes in the sky without special tools and methods. So the ancients regarded them as fixed stars and called them stars.

The most basic method for measuring the distance between stars is the triangular parallax method. Firstly, the opening angle of the earth's orbit at the stars (called annual parallax) is measured, and then the distance between the stars can be obtained through simple operation. This is the most direct way to measure the distance. But for most stars, this opening angle is too small to be accurately measured. Therefore, some indirect methods are often used to determine the distance between stars, such as spectral parallax method, cluster parallax method, statistical parallax method, parallax determined by Cepheid variable period-luminosity relationship and so on. (see celestial distance). These indirect methods are based on the triangular parallax method.

The brightness of a star is usually expressed in magnitude. The brighter the star, the smaller the magnitude. The magnitude measured on the earth is called apparent magnitude; The magnitude reduced from the earth to 10 parsec is called absolute magnitude. The magnitude of the same star measured by detection elements sensitive to different bands is generally unequal. At present, one of the most commonly used magnitude systems is the three-color system of U (ultraviolet), B (blue) and V (yellow) (see photometry system). Photometric system); B and v are close to photographic magnitude and visual magnitude, respectively. The difference between them lies in the commonly used color index. The sun's V=-26.74, absolute apparent magnitude M=+4.83, color index B-V=0.63, U-B=0. 12. The color temperature can be determined by the color index.

The temperature on the surface of a star is generally expressed by the effective temperature, which is equal to the temperature of an absolute black body with the same diameter and the same total radiation. The spectral energy distribution of stars is related to the effective temperature, from which it can be determined that the larger the volume of stars with the same spectral type (also known as temperature type) such as O, B, A, F, G, K and M, the greater the total radiation flux (i.e. luminosity) and the smaller the absolute magnitude. The luminosity levels of stars can be divided into Ⅰ, Ⅱ, Ⅲ, Ⅳ, Ⅴ, ⅶ, which are called Supergiant star, bright giant, giant, sub-giant, main sequence star (or dwarf), sub-dwarf and white dwarf in turn. The light spectrum of the sun is G2V, the color is yellow, and the effective temperature is about 5,770 K. The average color index of A0V star is zero, and the temperature is about10000 K. The effective surface temperature of the star varies greatly, from tens of thousands of degrees in the early O type to thousands of degrees in the late M type.

According to the apparent diameter (angular diameter) and distance of the star, the true diameter of the star can be calculated. The commonly used interferometer or lunar occultation method can measure the angular diameter of stars as small as 000 1. Smaller stars are not easy to measure accurately, and the measurement distance error makes the true diameter of stars less reliable. According to the orbital data of eclipsing binary stars and splitting binary stars, the diameters of some stars can also be obtained. For some stars, the true diameter can also be calculated according to the absolute magnitude and effective temperature. The diameters of different stars calculated by various methods are as small as several kilometers and as large as 10 kilometers.