What is the world outside our solar system like?

What is a star? Stars are gas celestial bodies, relying on the energy generated by their internal nuclear reactions to maintain life.

Just as the sun moves in the sky during the day, the stars cross the sky at night. Every day, the sun seems to rise in the east and set in the west. Of course, this is just a phenomenon, which is actually caused by the rotation of the earth. Of course, the stars behave like this at night. It's like being on a giant carousel. You feel that you are not moving, but that everything around you revolves around you. This illusion made many ancient people believe that the earth is motionless and the universe revolves around it.

The apparent motion of stars at night seems to be more complicated than that of the sun during the day. Go outdoors on a clear night and find a star near the eastern horizon. 1 hour or so, go out and have a look. The stars have risen (just as the sun rises in the east in the morning). In this 1 hour, the stars in the west will fall lower, and the stars in the south will also cross the sky from left to right. The motion of this independent star is the apparent motion of the star caused by the rotation of the earth. Because the earth revolves around an axis near Polaris, all the stars in the sky seem to revolve around Polaris.

All you need is a 35mm camera and a tripod to capture the apparent motion of the stars on Sunday. You just need to point the camera in any direction in the sky, but for the best effect, please point to the North Star. Use cheap photographic film (ASA or ISO 200 is enough) and choose a clear, cloudless and windy night. Fix the camera firmly, increase the aperture, set the lens to the maximum, set the shutter to "timing", and then expose it for 1 ~ 2 hours. After washing out, you will see that every star in the photo has a trace of a curve. Every trajectory is the trajectory swept by the stars in the sky when the earth rotates. If you aim your camera at the horizon in the south or east or west, you can also take pictures of the stars moving. If you use color photos, you can also capture bright stars of different colors.

How many stars can you see with the naked eye at night? It depends on how clear and dark the sky is where you observe it. In the center of new york or Tokyo, you are lucky to see dozens of stars. But on a clear and cloudless night in the countryside, people with good eyesight can see more than 3000 stars with the naked eye.

Since the Neolithic Age, people have tried to understand the nature of Heaven. At first glance, the stars all over the sky are at sixes and sevens, and they all cross the sky in a panic. Your first reaction is probably to know how astronomers find their way to the stars and know everything. Looking at it again, the situation is not so bad. Your eyes and thoughts have been matched together, subconsciously connecting patterns between stars, and the result is a simple intellectual game of "connecting points into maps". People began to do this before writing. Today, we have divided constellations (from Latin "cums" and "stella", which mean "together" and "stars" respectively) according to these patterns or star groups.

For many early residents, the patterns of constellations have special significance. The ancestors soon noticed that the stars were constantly moving in the sky, and the position of the same constellation in the sky was constant at the same time every year. So the starry sky became the earliest clocks and calendars. It tells people who can recognize constellations when they can sow, harvest and catch migrating animals. It is no exaggeration to say that for our ancestors, astronomical knowledge is a matter of life and death.

In some civilizations, having astronomical knowledge means having power. Most of the economy of ancient Egypt depended on the annual flood of the Nile and the fertile soil left after the flood receded. Every year, the prophet of Egypt goes back to visit the Pharaoh and accurately predicts when such an important flood will happen. They seem to enjoy the Oracle conveyed by the wives of the gods. In fact, they are just some careful sky observers. They noticed that Sirius rose before sunrise, and the flood of the Nile was coming soon after that day. So they closely monitor the sky before dawn every day. In this way, they make people believe that they have the magic power to master the lifeline of the country, even surpassing the Pharaoh.

Modern astronomers divide the sky into 88 constellations. Now the whole day is divided into 88 regions, called constellations. Many people draw constellations as short lines with stars as their endpoints (instead of figures with connecting points). For astronomers, constellations are more like national boundaries. Just as the United States is divided into 48 states, any town can be described by its state. So the whole day is divided into 88 constellations, and any star can be described by its constellation. Constellations themselves do not contain scientific knowledge, but are artificially imposed boundaries. If an astronomer says that his research object belongs to a certain constellation, other astronomers can get a general picture of the sky area under discussion.

The name of the constellation is not what you usually think. When asked to name a constellation, a big spoon may be his first choice. It may surprise many people to say it, but there are no big spoons in 88 constellations. They are all part of the constellation. The "big spoon" is a part of Ursa major and the "small spoon" is a part of Ursa minor. There is no constellation consisting of spoons alone. These recognized shapes in the sky are called constellations. In ancient China, the sky was not divided into 88 constellations, but into more than 300 constellations. Some are small stars, and some are 1 pairs or 1 bright stars.

Zodiac constellation is one of the more famous constellations. In western tradition, the zodiac is a group of *** 12 constellations around the celestial sphere. The zodiac includes Pisces, Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn and Aquarius. The word Zodiac in English comes from Greek, which means "Zodiac". Zodiacs are mostly animals, but Gemini, Virgo, Libra and Aquarius are not animals. Sagittarius is usually painted as half man and half beast.

The zodiac is of great significance to astronomers and astrologers. The zodiac is famous because the sun, the moon and the visible planets all move in this area. This area is very important for astrologers, because they regard the appearance of these sacred objects in a constellation as an influence on this constellation. For astronomers, this area provides a perspective to understand the shape and physical properties of the solar system. Zodiac constellation occupies a relatively narrow area in the sky, providing a lot of information about the shape of the solar system. It means that the solar system must be relatively flat. On the other hand, it means that the orbits of all planets in the solar system and the orbits of the moon are roughly in the same plane. In fact, except Pluto, the angles between the orbital planes of other planets are very small. In other words, the shape of the solar system is like a pancake centered on the sun. This is the result of the law of conservation of angular momentum. When we observe the formation of similar solar system structures around other stars, we will also see similar disk structures.

Some constellations are ancient and some are modern. Some constellations, such as Leo, can be traced back to the Pharaoh's time in ancient Egypt. Other constellations were named by two Dutch travelers Peter Caesar and Frederic de houtman around 1600. These constellations are mainly distributed in the southern hemisphere. At that time, they were traveling around the world and saw the starry sky that Europe had never seen before. Then they created a series of imaginative animal names to name these constellations. 1 Centuries later, in order to commemorate some tools invented in the industrial revolution, Nicolas de Imcaille formed some scattered stars in the southern sky into new constellations: stove base, pump base and microscope base. Of course, a long time ago, the natives in the southern hemisphere also had their own imaginary patterns for the starry sky overhead, and that was their constellation.

Among the inhabitants of the Andes, some constellations are dark rather than bright. In the Andes of South America, at a certain moment, the Milky Way seems to be a bright belt across the top of the head, criss-crossing with dark holes or stripes, which is caused by dark dust blocking the starlight in the universe. The inhabitants of the Andes not only created constellation patterns composed of connected stars, but also specially created dark constellations imagined by the shapes of these dark areas. So we can see such "dark constellations" in some places: foxes and hens. There is a constellation called alpaca, which consists of 1 dark area and two bright stars. Alpha and Beta Centauri are regarded as the eyes of alpaca.

Sometimes the pattern of the same star is different in the eyes of different people. The big spoon in the eyes of non-indigenous North American residents was called a plow by the British, but it was imagined by China as a three-horse carriage. In some Native American tribes, the bucket of a big spoon is imagined as a bear, while the handle of the spoon is imagined as a hunter chasing prey. People with good eyesight can see that the stars in the middle of the spoon handle are actually two. They look too close in the sky, so these two fuzzy stars are regarded as a hunter with a pot. In the eyes of westerners, the curve composed of stars in the sky is Scorpio; In the eyes of Polynesian aborigines, it was a big hook thrown into the air by Maui. Maui used this hook to fish out the soil from the deep sea and formed a beautiful island in the Pacific Ocean.

When asked about the brightest star in the sky, many people will answer "North Star". This is a common conceptual mistake. Polaris barely ranks in the top 50 in the list of bright stars. Polaris is famous not because it is surprisingly bright, but because of its unique position in the sky. At present, Polaris is the closest star to the north celestial pole. The north celestial pole is at the north pole of the earth's axis, so as the earth rotates, all the stars seem to be slowly rotating around the north celestial pole. As a result, it seems that all the stars are orbiting the Polaris, which is basically in the same position in the sky and always points to the north.

Polaris is not near the north celestial pole and will not be there forever. Polaris is about the point indicated by the earth's rotation axis. As time goes on, the earth's axis will swing slowly, just like a spinning top. This movement is called precession. The precession changes slowly, with a period of 26,000 years. It was the earth's axis that drew a big circle in the sky during these 26,000 years. At present, the earth axis points to Polaris, but in the past and in the future, our Polaris will not be the present star, but a star in or near the precession circle. During the reign of Pharaoh in Egypt, Tuban in the constellation Draco was the North Star at that time. In the year 14000, Vega will become our north star. It is now a bright blue and white star in the summer sky near our zenith.

If Polaris is the star of the north celestial pole, which one is the star of the south celestial pole? The earth's axis extends from the center of the earth to the North Pole, to the vicinity of Polaris, from the South Pole to the south, and can also point to the sky. But when you go to the South Pole, you won't find invivo, because there are no bright or semi-bright stars in that sky. Residents of Australia and South America can see many beautiful stars in the southern sky, but there is no invivo.

In the northern hemisphere, as long as there is Polaris and your fist, you can estimate the latitude of your position. Because the earth's axis almost reaches Polaris, the horizon height of Polaris is also the geographical latitude of the earth. Take new york as an example, it is about Polaris 41n, and it is also about 41above the northern horizon. Reaching out one arm away, the clenched fist is about 10 in your opinion, so as far as new york is concerned, Polaris is about "four fists" above the northern horizon. In contrast, in Miami, the latitude is 26 N, and the height of Polaris is only about 26, which can also be said to be "two fists and a half" above the horizon. At the north latitude of 90 N, Polaris is at the zenith; On the equator, Polaris is located on the northern horizon; South of the equator, Polaris is below the horizon and will never be seen.

People at the same latitude can see the same stars. Because the height of Polaris is determined by the latitude of the observation site, people at the same latitude will see the same starry sky no matter where they are in the world and in the same place at the same night. So people in new york, Madrid, Ankara and Peking (generally at the same latitude) see the same starry sky on the same night of the year, although they are far apart.

People living in different latitudes see different starry sky at night. For example, when a person from new york goes to Rio de Janeiro or Australia for a holiday, he can't see the big spoon, small spoon and other constellations near the North Star, because these constellations are always below the horizon. However, constellations like the Southern Cross, which he has never seen before, will be very common. When he is in new york, other constellations he sees in the south will appear upside down in the northern sky.

Observing the universe from the earth, there will be some "cheap seats". The role of the observatory on the earth is different. Take the north pole as an example. Polaris always hangs at the zenith, because the apparent motion of all stars revolves around Polaris, so every star can be seen at its height all year round. In short, in the arctic sky, the stars don't rise or fall. The same is true of Antarctica, but the stars in the Antarctic sky are completely different from those in the North Pole. In other words, at the two poles of the earth, we all see only half of the universe. Two o'clock in the south, only half of the day. They are "cheap seats".

Where is the best place to observe the stars? The best place to observe the stars is on the equator. Because Polaris is on the horizon, all the year round, the stars visible in both hemispheres will slowly come into view. As long as a star is visible to the naked eye on the equator, it can be seen that no star will fall below the horizon.

Imagine putting a lamp in the center of the room as the sun, and you revolve around it yourself, just like the revolution of the earth. At some point, at any point, half of your body will be illuminated and the other half will be in the shadow. In this way, you simulate the state that the earth is always half day and half night. If you draw a star on the wall, when the light is very bright, you can only see half of the star at a certain moment, because the dazzling light makes you unable to see the direction of the star. Similarly, the stars seen in the night hemisphere in winter and summer are different, and so are the stars in spring and autumn. So, we see different constellations at different times of the year, and the constellations we usually see at the same season every year are the same.

Some constellations are always in the sky. Because all the stars in the sky seem to revolve around the Polaris. So there are some stars in the sky all year round. Take new york as an example, the latitude is 41n, and the height of Polaris above the northern horizon is almost motionless. Therefore, all the stars within Polaris 4 1 will never reach the horizon when they revolve around the north celestial pole. They can be seen all year round in new york, and they are called circumpolar stars (from Latin meaning "around the pole"). In Miami's 26 N, only the stars whose Polaris is within 26 are Polaris. Pushing to the limit, all the stars in the North Pole are arch stars, but at the equator, no star is always above the horizon, and all the stars rise and fall.

Many bright stars in the sky actually have unique names. Many of these names came from Arabia 1000 years ago, when Arab astronomers made great contributions to astronomy and made the most exquisite star map at that time. Some Arabic names have been preserved intact by us, while others have been baptized for centuries and integrated into western culture. Both of these situations make the names of many bright stars strange and can even be recognized as foreign words. For example, Deneb (cygnus α) means "tail or feathers on the tail" in Arabic, which indicates a part of the body structure of a swan. Pisces has a star called Alrischa, which means "knot" in Arabic, referring to the knot on the rope that binds two fish together in the starry sky. The names of some stars still sound very rhythmic. From left to right, the three stars on Orion's belt all have their own beautiful names: Betelgeuse, Betelgeuse and mintaka.

There are not so many foreign words in the other directory. Both professional and amateur astronomers like this more comprehensive catalogue. The rules are simple and logical. The brightest star in each constellation is represented by the first letter α of the Greek alphabet, followed by the adjective form of the Latin name of the constellation. For example, the brightest star in Taurus, Bisuwu, is named αtTauri (which accurately expresses "the brightest star in Taurus") in this catalogue. Next to it, the brightest star in Orion has an interesting name Betetgeuse, but it is the brightest star in Orion, so it is called Aurora. The second brightest star in each constellation is represented by the second letter β of the Greek alphabet, followed by the adjective form of the Latin name of the constellation. For example, Orion's bright left foot Betelgeuse is also called βOrionis (meaning "the second star of Orion").

Unfortunately, the Greek alphabet has only 24 letters, and there are far more than 24 stars in each constellation. Sometimes when two or more stars are close together in the sky, they all use the same Greek letter, but they should be marked. Therefore, the binary stars of Lyra are called ε 1Lyrae and ε2Lyrae. Variable stars are represented by other letters, usually ordinary letters, such as RRLyrea. But the telescope is getting bigger and bigger, and we see more and more stars. The current catalogue is far from enough. One way is to simply give each star a number when establishing a catalog. A star may be called HD2 13468, which is No.213468 in the catalogue compiled by Henry draper of Harvard University. Another star will be called SA034798 1 in the catalogue of the Smithsonian Astrophysics Observatory. Actually, there are too many directories. Most stars only have numbers, and the same star will have different numbers in different catalogs. This may be inhuman, but it solves a big problem.

In recent years, some companies and some research institutions have made a lot of money by naming stars after people. In many cases, you will spend a lot of money to get a certificate that looks beautiful and a photo or star map of the sky where your star is. That may be a good gesture and a "best gift", but will astronomers quote this name in their research and academic papers in the future? The answer is no doubt, a piece of paper with your name on it can be kept in the safe of a Swiss bank, but it will never be included in the scientific research catalogue or publication of an observatory or university. If you want to leave your name in the sky, go out and find a comet. Many amateur and professional astronomers have achieved success. If you find a comet, the professional astronomical union will really be named after you. But if you are a star, you can't just buy a name.

When we look up at the starry sky, we will strongly feel that the stars are like points attached to or protruding from the top of a ball that hides our heads. In fact, this kind of imagination exists in many ancient cultures, and the realistic artificial starry sky in modern astronomy is also used in this way. In fact, the distance between the star and the earth is different, but distributed in three-dimensional space. In addition, the time for starlight to reach the earth is limited, and observing in the sky also means observing the fourth dimension, that is, time.

On earth, we sometimes see the present object and hear the sound it made in the past. If you sit in the stands and watch the baseball game carefully, you will find that you hear the batter's voice after seeing him hit the ball. Similarly, you see lightning ahead of time, and then you hear thunder. In both cases, the speed of sound propagation is much less than the speed of light. At room temperature, the speed of sound is 335 m/s, while the speed of light in vacuum is about 300 thousand km/s (similar to the speed in air). This means that you hear distant sounds after it happens, but you can see it as soon as it happens, at least on earth.

When we look at the universe, we see the way it used to exist. Compared with what we see on earth, the celestial bodies in the universe are too far away from us, and even light takes a long time to reach us. So the different celestial bodies we see are their states in the past. For example, it takes about 1.5 seconds for light to travel from the moon, which is about 400,000 kilometers away from us, to the earth. So the moon we see is not now, but 1.5 seconds ago. 1.500 million kilometers of the sun, what we see is its state 8 minutes and 20 seconds ago. If the sun mysteriously disappears, it will take us 8 minutes and 20 seconds to know. In our view, different planets were in a state a few minutes or even hours ago, while the stars we saw were in a state a few years ago, and galaxies were in a state millions or even billions of years ago. Therefore, when we look up at the starry sky, we are also reviewing history!