Astronomical enlightenment, with the simplest language to take you to feel the vastest galaxy.

universe

The universe is thought to have been born in the Big Bang 654.38+03.7 billion years ago. A strong evidence is the ubiquitous microwave radiation all day, which is called the cosmic microwave background. After the Big Bang, the universe was stretched and expanded, and the early radiation wavelength was also lengthened, so the original high-energy short-wave radiation has now become low-energy long-wave radiation-microwave. The tiny fluctuations in the density of matter in the early universe, like seeds, made matter cluster and led to the formation of huge galaxy clusters.

The first stars are thought to have appeared 200 million years after BIGBANG. They are huge celestial bodies-maybe 100 to 1000 times that of our sun, and almost all of them are composed of hydrogen and helium.

The original galaxy was a collection of huge stars. It is believed that the first galaxies were formed 500 million years after the Big Bang. These early galaxies look different from today's galaxies, such as the Milky Way.

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planet

Before the telescope appeared, ancient astronomers noticed that some bright stars would run in the sky for many days. The ancient Greeks called these stars "planets", which means "walking" stars.

The solar system is centered on the sun, including the sun and all celestial bodies constrained by its gravity. It consists of eight planets, several dwarf planets and countless other small bodies, including comets and asteroids.

The sun itself accounts for 99.8% of the total matter in the solar system.

The celestial bodies around the sun are divided into three categories: planets, dwarf planets and small celestial bodies.

The sun and all other celestial bodies in the solar system are formed by a huge cloud of dust and gas, which is called the solar cloud.

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What is a star?

A star will go through a series of stages in its life, and the order and duration depend on the quality of the star.

In a typical night sky, about 90% of the stars we see are in the main sequence stage of their lives.

A star is a huge gas ball mainly composed of hydrogen. The mass of this constant ball is very large, and the pressure in its center can make hydrogen fusion, which will produce a lot of energy, including the starlight we see in the night sky. Stars polymerize hydrogen atoms in the core to become helium, and gradually become more important elements through further nuclear reactions-stars can create all elements heavier than helium in the universe K, such as oxygen, nitrogen and iron.

Stars are born in huge clouds of gas and dust called nebulae. The lower the temperature of the nebula, the more vulnerable it is to gravitational interference, such as shock waves from supernovae.

Although the mass of the sun is larger than the planets in the solar system, there are many stars in the Milky Way that are hundreds of times larger than it. The quality of a star is decisive because it determines how a star evolves in its lifetime. Massive stars will soon run out of hydrogen, and their life span will be shorter-maybe only a few million years, and they will soon die. When they die, the star about the size of the sun slowly expands into a red giant, and then collapses, leaving a white dwarf at the center of the planetary nebula. The scene of massive stars dying is very violent, exploding into supernovae, eventually becoming neutron stars, and massive stars finally becoming black holes.

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nebula

Most parts of the Milky Way are in an extreme vacuum, and only a small amount of hydrogen and helium mixed with dust are scattered in the space between stars, which is called interstellar medium. Denser gas and dust make up nebulae, most of which can be seen in the night sky.

There are emission nebula, dark nebula, reflection nebula and planetary nebula.

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beam splitter

Light is a form of electromagnetic radiation of energy, which propagates like waves and can pass through transparent materials, such as air, and of course, through vacuum. Due to different wavelengths, a beam of white light can be divided into various colors through a prism.

Amateur astronomers mainly study visible light with meat. However, for professional astronomers with complex observatories and telescopes, observing at different wavelengths is the key to studying the universe. The earth can receive seven kinds of electromagnetic radiation from the universe, namely: radio waves, ultraviolet rays, microwaves, X-rays, infrared rays, R-rays and visible light.

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constellation

The concept of "constellation" can be traced back to tens of thousands of years ago. The murals in Lascaux Cave in southern France are considered to be 16000 years old.

The constellations recognized by western astronomers today come from the work of early Greeks and the work of sailors, navigators and astronomers in this paper. However, many other civilizations in the world have their own constellations, including ancient China. The constellation of China also has four signs: the black dragon in the east (spring), the suzaku in the south (summer), the white tiger in the west (autumn) and the Xu Xuan in the north (winter), which are used to indicate the direction and the seasons all year round.

What constellation you can see depends on the latitude of your position on the earth. For example, the constellation in the extreme south is invisible in the northern latitude.

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solar system

The solar system consists of the sun and all the substances bound in its gravitational field, including several planets revolving around the sun, mixed zones of rocks and ice, and flying comets.

There is no doubt that the three planets in orbit are Mars, Jupiter and Saturn. There are eight planets in the solar system bound by the strong gravity of the sun. The earth is one of four rocky planets, whose orbits are located in the asteroid belt and closer to the sun. Outside the asteroid belt is Jupiter, which is the closest one of the four gas giants to the sun.

Most celestial bodies in the solar system are in orbits close to the same plane, so occasionally we can see that they are just in the same direction, and one of them passes in front of the other. When the sun, the earth, mercury or venus are in a straight line, we will see the transit phenomenon: mercury or venus passes in front of the sun. Other situations include the moon passing in front of the planet or the larger celestial body blocking the smaller celestial body, which is called occultation.

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Mercury and Venus

Mercury is a small rocky world, and its desolate surface is covered with craters due to the impact of meteorites for millions of years. Venus is much bigger than mercury and a little farther from the sun. Volcanoes and solidified lava constitute the main landforms. Venus' rotation speed is very slow, and the Venus day of 1 is actually longer than the Venus year of 1, which means that its revolution time around the sun is shorter than its rotation time.

Mercury always appears at a low altitude near the horizon and can only be observed through the hazy atmosphere. So mercury always looks like a fuzzy round surface, and its edges are always unclear.

Mercury itself is smaller. It is far from the earth, but close to the sun, which makes observation very challenging. It is possible to see mercury floating in the low sky with the naked eye in the early morning or evening. Mercury moves faster, and there are not many visible days, and a good observation window rarely exceeds one week.

Venus is brighter than any star except the moon for a period of time before and after its brightest. Sunlight is always reflected by the clouds on Venus, which is very close to us, between the east distance and the west distance, so Venus really matches the two special names "Morning Star" and "Gengxing Star". Venus is farther from the sun than mercury, so it doesn't move very fast. Compared with its inner neighbors, Venus can be seen for a long time. It may appear in the sky in the morning or at night for half a year. Because Venus is too bright, the best time to observe Venus with a telescope is not in the dark, but around sunset. At this time, the sky just began to turn black, and Venus's head was lower and the effect was better.

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Mars and Jupiter

Mars is only half the diameter of the earth, but it is the closest planet to the earth in the solar system. Its surface is desolate, dotted with volcanoes, craters and huge rift valleys, of which the longest "Sailor's Valley" stretches for 4,000 kilometers. Mars has two satellites-Phobos and Phobos. They may be small celestial bodies in the solar system, but for some reason, they were pulled into the gravitational field of Mars and captured.

When Mars approaches the earth, the most striking features on the surface of Mars-bright or dark marks-can also be seen with a small telescope, among which the polar cap composed of water ice and carbon dioxide dry ice is the easiest to see.

Jupiter is the largest planet in the solar system, and its diameter is 1 1 times that of the earth. It is a huge gaseous planet surrounded by powerful storms. Jupiter's huge gravitational field means that it has captured and owned a large number of satellites, and it also has a dim aura.

Jupiter is brighter than Sirius, the brightest star, even in the darkest time, so it is easy to find with the naked eye. It moves slowly in orbit and slowly in the sky, passing only one constellation a year. Jupiter has more than 60 known satellites, and the actual number may be close to 100. Most of them are just small rocks or ice cubes, and satellites other than the largest four Europa are unlikely to be seen with binoculars or small telescopes. Seen from a telescope, these satellites are light spots arranged on both sides of Jupiter, and their positions change as they rotate around Jupiter.

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Saturn

Saturn is the second largest planet in the solar system. To the naked eye, Saturn is a bright beige bright spot; It was not until the telescope pointed to the world that the halo was discovered.

All the giant planets-Jupiter, Saturn, Uranus and Neptune-have rings, but the rings of other planets are not as good as Saturn's rings: their rings are darker and less dense. Saturn's rings are wide, flat and thin, with a width of 280,000 kilometers between its inner and outer edges and an average thickness of only 1 km. Saturn also has at least 60 moons, of which Titan is bigger than Mercury and has its own atmosphere.

The interesting thing about Saturn's rings is its changing direction. In seven and a half years, the halo we see will change from an almost invisible front to a fully unfolded 27-degree inclination, and we can see as many details of the halo as possible during the eclipse.

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Uranus and Neptune

Deep in the dark and cold edge of the solar system are the last two planets-the cold and blue gas giants Uranus and Neptune.

These two exoplanets are like a pair of partners, with similar size, shape and composition. Uranus is a dark blue green sphere with no features on its surface. Neptune, on the other hand, is a translucent and pure blue world with strange spots, storms and white clouds formed by frozen methane.

The most unusual feature of Uranus is that its axis of rotation is so inclined that it moves like a ball rolling on the ground.

Uranus has an orbital period of 84 years, and Neptune has an orbital period of 165 years. These two planets collide with the sun basically every 1 year. I hope that because they are so far away, the brightness of the collision will only increase by several tenths of an order of magnitude. Uranus can reach 5.5 at its brightest, just visible to the naked eye. Neptune's brightest magnitude is only 7.8, which is invisible to the naked eye.

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Dwarfs and asteroids

In addition to the eight planets, there are countless small celestial bodies around the sun, the largest of which are classified as dwarf planets and asteroids.

Dwarf planet

Pluto has been the ninth largest planet in the solar system since it was discovered at 1930 until 2006. However, at the end of the 20th century, it was obvious that Pluto was not the only celestial body in the marginal zone outside Neptune. In fact, Pluto is a member of a distant belt of small celestial bodies, some of which are similar to Pluto, even if they are not bigger than Pluto. In order to limit the number of celestial bodies classified as planets, the International Astronomical Union redefined the characteristics of planets and defined dwarf planets and asteroids. The two most important dwarf planets Pluto and Venus are very far away, and Ceres, once the largest asteroid, is now classified as a dwarf planet, located in the rocky celestial belt around the sun between Mars and Jupiter.

Outside Neptune, there is a large group of icy celestial bodies orbiting the sun, and this area is collectively called the Kuiper Belt. The small celestial bodies in the asteroid belt are mainly composed of rocks and metals, while the Kuiper Belt is a frozen world, because it is too far away from the sun and will never melt.

Astronomers have detected more than 1000 celestial bodies belonging to the Kuiper Belt, among which Pluto is the brightest. An overseas celestial body recognized as a dwarf planet is called Pluto.

To see Pluto, you need to use a large telescope, because its brightest light can only reach dim 13.6. This dwarf planet is very small and far away from the earth, so it will only look like a star. However, seeing the edge of the solar system that we thought before can still bring people satisfaction.

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sun

Located at the center of the solar system is a truly fascinating celestial body-the sun.

The sun is the closest star to us, a huge balloon of hydrogen and helium, and an example of the balance of forces: if there is no constraint of gravity, hot gas will expand into space; Under the action of strategy, layers of gas are compressed inward.

The middle-aged sun will eventually expand into a red giant, but it will take billions of years for the sun to age and have a major impact on the earth.

This huge dazzling celestial sphere is extremely bright at -26.7. If you look directly at it with the naked eye, too bright light will damage the retina.

Never observe the sun directly with naked eyes, binoculars or binoculars. The light gathered through the eyepiece will immediately lead to blindness! ! !

Observing the sun after taking appropriate protective measures, we actually see the photosphere of the sun, and its temperature is slightly lower than 550℃. There are sunspots on the photosphere, which is a low temperature area. They appear and disappear periodically for days to weeks. The sun is around 1 month, so we can see that sunspots are constantly moving.

Sunspots are black spots on the surface of the sun. Sunspots are signs of solar activity, and the solar magnetic field is disturbed where sunspots appear.

A solar eclipse occurs when the moon blocks sunlight from reaching the earth. It is caused by the special arrangement of the earth, the moon and the sun. Of the three, the sun is of course the biggest, 400 times bigger than the moon. But the strange coincidence is that the distance between the sun and the moon is 400 times that of the moon, so the sun and the moon look almost the same size in the sky, which also makes the moon block the sun just within a few minutes of the total solar eclipse, showing a magnificent corona scene.

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moon

The moon is the only natural satellite of the earth. The orbit of the moon is quite close to the earth, only 384400 kilometers. The size of the moon is about 1/4 of that of the earth, which is enough to make people think that the earth and the moon are twin planets. Like all planets and satellites, the moon itself does not shine. The so-called moonlight is reflected sunlight.

During the movement of the moon, we can see its phase change. At the new moon, the moon lies between the earth and the sun. If they line up in a straight line, there will be a solar eclipse. But the orbital plane of the moon is inclined, so most of the time the moon passes silently above or below the sun. A few days after the new moon, a thin Emei moon can be seen in the western night sky after sunset. The moon moves eastward day by day, getting farther and farther away from the sun, and its phase also goes through the first quarter moon and the full moon, and finally becomes a full moon after the new moon 14.5 days.

The sun always illuminates half the moon. In the illuminated part of the moon, the size of the area we can see depends on the orbital position of the moon around the earth.

When there is a total lunar eclipse, there is no direct sunlight on the moon, but the surface of the moon is not completely black, but red. This is because sunlight scattered through the earth's atmosphere can still reach the moon indirectly.

How is the moon formed? A widely accepted theory holds that a Mars-sized celestial body collided with the young earth and produced a large amount of molten material. Some of these melts came from the earth's surface and some from the impactor itself, and were thrown into orbit around the earth. Gravity slowly brought these substances together and finally formed the moon. Since then, the moon has left us at a speed of 4 cm per year, which is the gravitational tide effect-the energy collected by the moon from earth-moon system makes it slowly move away, and it also slows down the rotation of the earth. However, this change is not drastic, and the length of a day will increase by 2.2 seconds every 654.38+ million years.

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Comets and meteors

Comets are formed when dust particles released by frozen comets collide with the earth's atmosphere.

Comets are huge masses of ice and dust that move around the sun. Comets usually travel a long way, as far as interstellar space. When the comet approached the sun, it began to be heated and evaporated, which produced a dramatic scene. During the journey around the sun, comets constantly emit tiny particles of rock dust to form meteoroids. They form meteors when they enter the earth's atmosphere. Thousands of tons of dust from interplanetary space enter the earth's atmosphere every year.

The size of the comet nucleus is 1 to 50 kilometers, which is the legacy of the formation of the solar system. When the sun begins to shine, its radiation blows lighter matter out of the planetary orbit and reaches the Kuiper Belt, which is the home base of short-period comets with orbital periods less than 200 years. Any short-period or long-period comet may be pulled by the gravity of the planet or nearby stars, making it turn to the sun, and a coma and a tail will grow from the nucleus and cross the night sky.

Meteors can be seen on any clear night. Every small particle that produces this phenomenon is a fragment that moves in space and happens to meet the earth. Accidental meteors are called "accidental" and are formed by floating meteoroids. They may have been left behind by comets a long time ago, so they may appear in any direction in the sky at any time.

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Deep in the dark and cold edge of the solar system are the last two planets-the cold and blue gas giants Uranus and Neptune.

These two exoplanets are like a pair of partners, with similar size, shape and composition. Uranus is a dark blue green sphere with no features on its surface. Neptune, on the other hand, is a translucent and pure blue world with strange spots, storms and white clouds formed by frozen methane.

The most unusual feature of Uranus is that its axis of rotation is so inclined that it moves like a ball rolling on the ground.

Uranus has an orbital period of 84 years, and Neptune has an orbital period of 165 years. These two planets collide with the sun basically every 1 year. I hope that because they are so far away, the brightness of the collision will only increase by several tenths of an order of magnitude. Uranus can reach 5.5 at its brightest, just visible to the naked eye. Neptune's brightest magnitude is only 7.8, which is invisible to the naked eye.

atmospheric phenomenon

When light rays or charged particles from the sun reach the earth's atmosphere directly or indirectly, under certain conditions, observers on the ground can see some wonderful scenes. Some of these phenomena, such as aurora, can only be seen in a specific area or at a specific time, some need perfect weather conditions, but some can appear anywhere and at any time.

The lunar halo is a bright circle, which is formed by the moonlight diffracted by hexagonal ice crystals in the atmosphere at a certain distance from the moon 22.

The magic sun is a bright spot that usually appears in pairs on both sides of the sun, which is caused by the diffraction of sunlight by hexagonal ice crystals arranged neatly in cirrus clouds. This is very common. If the arrangement of ice crystals is not particularly consistent, then the magical sun may appear next to the halo around the sun. It is rarely possible to see a ring of light around the sun in the horizontal direction at the same time, and it also passes through the magic sun, which is called the magic sun ring.

When particles from the sun explode and disturb the earth's magnetic field, charged particles gather in the polar regions of the earth, creating this strange spectacle. Aurora can last for hours. Usually, it starts with a soft green arc, then the brightness increases, the range is expanded, until there are red and green lights, and finally it is extended to the long practice across the sky.