The Milky Way; galaxy refers to a milky white bright band across the sky.The Milky WayAquilaAndCelestial equatorIntersect, in the north halfcelestial sphere。The Milky Waycelestial sphereDraw a belt with different width, calledGalactic bandIts widest part is 30 °, and its narrowest part is only 4 °~5 °, with an average of about 20 °GalaxyPart of.[2]
The Milky Way is only visible on sunny nights, and is composed of numerousDark starCaused by the light of (a star).The Milky Way is not the Milky Way, but a part of the Milky Way.The Milky Way Galaxy (formerly called Milky Way, Tianhe, Xinghe, Tianhan, Yinhan, etc.)solar systemOfBarred spiral galaxy, with a diameter ranging from 100000 light years to 180000 light years.There are about 100 billion to 400 billion stars, and possibly 100 billion planets.[3]The solar system is about 26000 light-years away from the center of the Milky Way, with dense gas and dust, known asHunter armOfSpiral armThe inside edge of the.In the position of the sun,Revolution periodAbout 240 million years.Seen from the earthDiscoid structureThe Milky Way Galaxycelestial sphereA band that wraps around the top.
Chinese name
the galaxy
Foreign name
the Milky Way;galaxy
Alias
Tianhe、Hehan、Yinhan、Galaxy、Milky Way、Yunhan
Location
In the constellation Aquila and the skyequatorintersect
Diameter
About 1 ✕ 10seventeenTo 1.8 ✕ 10seventeenkm
Type
Barred spiral galaxy
Center thickness
12000 light years
Quality
About 4.1771 ✕ 10forty-onekg
Affiliated galaxy group
Local galaxy group
Belonging to galaxy cluster
Virgo supercluster
Mass of the central black hole of the Milky Way Galaxy
Since ancient times, the magnificent Milky Way has been the object of great attention and research.Thousands of years ago, people had various guesses about the Milky Way.In Chinese mythology, the Milky Way is a river in the sky;And ancientMYTHOSChinese people believe that the Milky Way is composed ofHeraIt is paved with milk.It was not until Galileo pointed the telescope at the Milky Way for the first time that he found that the Milky Way was actually composed of countless stars.[11]
Europeans imagine that the Milky Way is formed by the milk flowing from the queen of gods in the sky when feeding babies, and call it the Milky Way.This is how the Milky Way in English comes from.
In the early 17th century,ItalyThe scientist Galileo discovered that the Milky Way is formed by many stars gathered together.Because these stars are too far away from the earth, human eyes can't distinguish them clearly, and they regard them as a brightLight band。
The Milky Way in the sky varies in brightness and width.The narrowest is only 4 °~5 °, and the widest is about 30 °.[2]The white part of the Milky Way is composed of dense stars.The most dense stars in this "belt" sky area are because there are more than 100 billion stars forming a huge lenticular star system,solar systemIt is in this system.From the solar system, humans can see that the edge of the disk is a belt shaped sky area.The star projection in this area is the most intensive, which is the Milky Way seen.This huge star system is also named after the Milky WayGalaxy。
Centaur near the Silver Core
Naked eyeLimiting apparent magnitudeThe Milky Way can only be seen when the light pollution index is above 5.5 or below 5. If the Milky Way cannot be seen with the naked eye, it is difficult to see the Milky Way with the most advanced observation instruments.[5]Northern HemisphereIt is most obvious to see the Milky Way in summer (in Scorpio and Sagittarius extending toSummer Triangle, evenCassiopeia）, the Milky Way is very dim in winter (OrionAndCanis Major）。
In fact, the Milky Way is a part of the Milky Way, which is the galaxy of the solar system.Because its main part is projected oncelestial sphereOnBright bandIt is named after the Milky Way.Humans stand inside and look sidewaysGalaxyWhen you see it, it is full of stars.Because the light emitted by stars is far away from the earth, there are many, andInterstellar dustThe gas is mixed together, so it looks like a band of light surrounded by smoke, very beautiful.
The earth is one of the eight planets in the solar system. Compared with the sun, the earth is insignificant. The volume of the sun is one million times larger than the earth, and its mass is about 330000 times larger than the earth.Put the earth on the surface of the sun, just aSmall black spotJust not on the sunsunspot(sunspot) large.
But from the perspective of the universesunlightIt's just a very common star in the Milky Way. There are hundreds of billions of stars in the Milky Way, more thanSolar massThere are many stars dozens of times larger and one million times brighter than the sun.The breadth of the Milky Way is even more incredible. For example, if human beings want to think of the center of the Milky Way about 30000 light years away from the earth, the speed of light useTo travelIn the eyes of onlookers, it will take more than 30000 years becauseRelativistic effectThe people on the spaceship actually didn't spend time (so the stars seen in the distance are still the same as the scene at that time). Suppose there is such a starspacecraftWhen human beings set out at the speed of light and reached 30000 light years away, there were thousands of generations of descendants on the earth.
The sun and other stars in the Milky Way also rotate around the center of the Milky Way.earth rotationIt takes one day for the moon to circle the earth, one month for the earth to circle the sun, one year for the earth to circle the sunGalactic centerA week takes one galaxy year, and a galactic year equals 250 million years.
The Milky Way is very huge, but in the whole universe, there are three billion (3 billion) galaxies similar to the Milky WayLinear distanceThere is a spectrum of one billion light years.
The Milky Way of Capertine
Kant, the great philosopher of the 18th century, proposedScientific valueBy the end of the 18th century (1784), the British astronomer Herschel had made a systematicAstronomical observationBy counting the stars in the sky, we can get the observation results and confirm that the shape of the Milky Way Galaxy is flatMillstoneThe sun is in the axle hole of the millstone.At the end of the 19th century,NetherlandsAstronomer Kaibuting began to study the Milky Way again. He still used the method of Herschel counting stars. Because of the progress in measuring the distance of stars, his star counting technology was far ahead of Herschel. He used statistical methods to divide the Milky Way into several key areas, regardless of detailed observation and analysis. He spent 30 years, and finally published his Milky Way map before his eyes died,Later, it was called "Capertine Universe".
Arguing over the position of silver core
The stars of the Milky Way are located in a flat figure, and the sun is in the center of the figure. Using the observation technology at that time, Capertine determined that the diameter of the figure is 23000 light-years.At the beginning of the twentieth century, Kipoting's view of the Milky Way was unanimously agreed, because he discovered thatNumber of starsDecreasing with distance.This is a strong evidence that the sun must be in the center of the Milky Way.However, both Herschel and Caputine used a wrong hypothesis, they believed that interstellar light absorption could be completely ignored, which made his conclusion completely changed.Interstellar dust in the Milky Wayhydrogen atomGas operation, filled inGalactic planeThese interstellar dust can coverstarlightTherefore, people see stars in the Milky Way, which are actually stars close to the sun, while stars that are really far away in the plane of the Milky Way (about 15000 light-years or more) are difficult to see with the largest telescope.Because interstellar light absorption can only see stars near and to the left, and the number of stars decreases with distance because of light absorption, it is mistaken that the solar system is in the center of the Milky Way.
Bright Little Magellan Nebula
In 1917, Shevley began to criticize Caputine's view of the Milky Way.He claims that the center of the Milky Way isSagittariusIt is about 100000 light years away from the sun.However, it is not popular in the astronomical world. What is most obvious is that four years later, when Kipoting summarized his view of the Milky Way, he did not use Shepley's statement.Shevley did not lose heart in collecting more information, and continued to move towards his ideas. In the process of advancing, many academic debates were caused, the most famous one being the debate between Shevley and Curtis in 1926, which included two rounds and had a decisive impact on the understanding of the galaxy.[6]The first round is against the center and distance of the Milky Way.
The Milky Way consists of a number of stars, one of which is calledGlobular clusterEach cluster has a population of 100000 large and small stars.These stars are bound by gravity. Although they rush forward, they seldom escape from the cluster.A small number of stars can not form a climate. When they are clustered into a crowd of 100000, they form a force. There are more than 100 star clusters in the Milky Way. Shevley found that their distribution is as follows: (1) For the plane of the Milky Way, they are roughly symmetrical, that is, the number of stars above and below the plane is equal, and (2) these star clusters are concentrated in the direction of the Sagittarius constellation.The first point is to determine its relationship with the Milky Way (belonging to the Milky Way), so in 1926,American Astronomical SocietyThey were arranged to have an open debate at the Academy of Sciences in Washington.As a result, they stuck to their own words, but there was no result. This problem was not formally solved until 1930 when Ott and Lindbergh confirmed that the sun revolved around the constellation Sagittarius.The focus of the second round is on the vortex nebula.
Since the middle of the 19th century, many vortex nebulae have been discovered, and people have begun to study them;Whether these nebulae belong to the Milky Way or something outside the Milky Way, Shevley claimed that these nebulae belong to the Milky Way. Unfortunately, the observational evidence he cited was found to be faulty later.Curtis argues that vortex nebulae are extragalactic.His most important reasons are two (1) there are many vortex nebulae facing the solar system horizontally, and there is a dark and opaque shadow lying on the central plane. If the Milky Way is such a vortex nebula, people can see the Milky Way across the sky, which is just the lateral side of a Milky Way galaxy. Assuming that the vortex nebulae are located outside the Milky Way,The vortex nebula in the direction of the Milky Way is just behind the shadow and is hidden from view. In other directions, the vortex nebula will not be hidden from view.This is consistent with the observation that there are almost no vortex nebulae in the direction of the Milky Way, while other parts are full of vortex nebulae.（2） Line of sight of all vortex nebulaeSpeed ratioOrdinary stars are much higher, their own motion (i.e. perpendicular toDirection of sightBut very small.The second round dispute between Shevley and Curtis was gradually resolved when Herb saw the stars around the vortex nebula with a 100 inch telescope.
Galactic rotation
solar system
The relationship between the solar system and the center of the Milky Way was solved only when Ott and Lindbergh proved the rotation of the Milky Way.Ott is a Dutchman and Lindbergh is a Swede. They began to study the rotation of the Milky Way in 1926.Their method is to study the movement of stars near the solar system.The most important discovery isHigh-speed star(for the sunrelative velocity）Most of them are far away from the plane of the Milky Way, and their running directions are highly asymmetric and completely concentrated on one side.Lindbergh first saw this phenomenon clearly.He believes that the Milky Way stars can be divided into more systems according to their distribution, and the stars on the plane of the Milky Way rotate rapidly around the center of the Milky Way.Stars distributed at a considerable distance above and below the Milky Way rotate slowly.The sun belongs to the former system, so when looking at the stars in the latter system in the solar system, most of them go against the solar system, so there is this asymmetry. At the same time, only the stars close to the center of the Milky Way system rotate faster than the solar system, so we can also observe the position of the center of the Milky Way, which is in the direction of the Sagittarius constellation. For this reason, he supports Shapley's view of the Milky Way.
Otter further analyzed the stars belonging to a system of the solar system, and found that the solar system not onlySagittariusThe rotation of this system is faster inside and slower outside. The distance between the solar system and the center of the Milky Way is 10000Second gap(One second difference is 3.24 light years) The speed of the sun's revolution is 250 kilometers per second, that is, 900000 kilometers per hour. Although this is fast, it still takes 250 million years to circle the center of the Milky Way.Although Ott and Lindbergh established the relationship between the rotation of the Milky Way and thePoor autorotationHowever, how does it really rotate from the center of the Milky Way to the outside of the solar system, and how much faster it is inside than outside, is still unclear. It was not until twenty-two years later that Art and his assistant observed the movement of hydrogen atom gas in the Milky Way with a radio telescope that they found out.The Milky Way is mainly composed of stars, accounting for more than 95% of the total mass. The interstellar space is not vacuum, but filled with very thin hydrogen atomic gas, accounting for about 4% of the total masshydrogen atomBesides gas, there are interstellar dust, cosmic ray particle hydrogen ion gas and other substances.As mentioned earlier, interstellar dust can scatter starlight, so it caused the error of Capertine and the fact that Curtis sawSpiral galaxyThe shadow of.ordinaryOptical telescopeOnly 5000 angular differences (16000 light years) can be seen in the direction of the Milky Way, and the understanding of the whole Milky Way is only limited.howeverradio wavesOtherwise, because of its long wavelength, it can travel freely among stars, so Jansky discovered radio waves from the sky since 1937, making the whole astronomy a big step forward.Because an electron in the hydrogen atom rotates around a proton, both the electron and the proton are rotating.Changing the direction of rotation will emit radio waves with a wavelength of about 21 mm (cm).
Dutch astronomyphysical scientistVandahl was still fully used in 1944Theoretical predictionThis radio wave.But by 1951Harvard UniversityEvan and Pursey of Vandahl confirmed the prediction of Vandahl.With the full support of the Dutch government, Ott and Vandher built radio telescopes and devoted themselves to the study of the Milky Way. Their initial results were published successively in 1952, turning the Milky WayTotal massThe most important thing is that the structure of the Milky Way is gradually clarified.Galaxy rotation is directly related to mass,angular velocityThe closer to the center of the Milky Way, the faster. When the distance is half from the sun to the center of the Milky Way, the rotation will double. When the distance is close to the center of the Milky Way, the angular velocity will increase several times. According to this rotation rate, the height of the Milky Way mass is concentrated inside, and the density decreases outward.
It was discovered 100 years ago,AndromedaIt is suspected that the Milky Way has a similar structure. Later, it was found that the vortex nebula isExtragalactic galaxyLater, people determined that the Milky Way also has a vortex structure, and came up with a way to determine the vortex structure of the Milky Way. After the invention of the radio telescope, the structureProblem solvingPeople began to explore the vortex arm problem.German astronomer Bud first discovered the constellation Andromedathe magnitudeOb type ofNewborn star, concentrated in the vortex arm, which shows that the vortex arm is brighter than other parts of the galaxy, and proves that although the star system is tens of billions of years old, new stars are still emerging, and at the same time, people gradually believe that the stars areInterstellar gasIt is agglomerated.
The investigation of interstellar light absorption in the plane of the Milky Way is attributed to Jongborough. In 1930, he published the research results of the new group, which confirmed this phenomenon. By 1952, Morgan and his assistants had correctly corrected the light absorption effect, and their results clearly marked that newborn stars gathered in three regions.The outermost area is called the Perseid Vortex Arm, the middle is called the Hunter Vortex Arm, and the inside is called the Centaur Vortex Arm.The sun is inside the Orion vortex arm.This confirms the vortex structure of the Milky Way. UnfortunatelyOptical telescopeIn the end, it is not the enemy of interstellar light absorption. If the angle difference exceeds 5000, it can not be seen. Therefore, only local structures can be obtained, and large structures can not be seen without radio telescopes.
In the same year (1952), Ott and Vandher published their radio observation results. Because of the poor rotation of the Milky Way, it is fast inside and slow outside. Using geometric principles, the rotation rate of the Milky Way through the sun's great circle can be calculated. The rotation outside the big picture cannot be calculated correctly, but it is commonly usedExtrapolationThere are quite a fewaccuracy。In this way, we can establish a relationship between the rotation rate and the central distance, and use this relationship to roughly determine the hydrogen atom in the Milky WayGas distribution。Ott and Vandahl determined the structure of the northern half of the Milky Way Galaxy. A few years later, Kerr of Austria observed the southern half, clearly showing the vortex structure;The structure near the sun is roughly the same asOptical observationThe results are the same.Although the vortex system in the distance is disordered, there are veins to be found.Of course, this vortex structure is not very complete, and there are many irregular parts. This is a common phenomenon in vortex galaxies, and the Milky Way is no exception.
Density waves of the Milky Way
It takes about 250 million years for galaxies to rotate once, so it is impossible to directly observe how the vortex arms rotate, but we know that these galaxies have strong poor rotation, which creates a fact called the spin contradiction, which has become the core problem for theorists studying the structure of the galaxy,SwedenAfter paying attention to this problem, astronomer Lindbergh got experience by calculating a large number of orbital problems. He thought that vortex b might not be matter, butDensity waveHowever, he did not solve the problem, which was solved by Lin Jiaqiao, a Chinese scientist in the United States,Lin JiaqiaoThe existence of vortex density waves is theoretically verified, and evidence is found from astronomical observations.
Density waves can be applied to any spiral galaxy. Because people have the most comprehensive knowledge of the Milky Way, they focus on the Milky Way.According to the theory of density wave, a wave pattern with two vortex arms can be calculated. This wave pattern starts at a distance of 4000 seconds. The angular velocity of the density wave around the center of the Milky Way is called the formula velocity. The formula velocity of the Milky Way is only half of the rotation of the Milky Way (subject to the sun)Density ratioThe average density is only one tenth higher, and this one tenth is mainly caused by interstellar gas and low-speed stars. Because low-speed stars are mostly newborn stars, the vortex arms are very bright although they are not too massive.
Impact on the biosphere
Announce
edit
Earth（solar system）The time of circling the center of the Milky Way is continuously extended, which shows thatGalaxyIs expanding.At the same time, the orbit of the solar system is continuously elongated along the extension line of the line connecting the two centers of its ellipse.It means that there are neighbors outside the Milky WayGalaxy pairThe attraction of the solar system is growing.Is that the earth goes around the center of the Milky Wayenvironmental change , causing many times of life on the earthMass extinction。The essence is not extinction, butAnimal kingdomOne ofcomprehensive developmentProcess.Analysis in animal kingdomDevelopment stageThe species and number of animals are increasing.To the analysis and comprehensive development of the animal kingdomqualitative changecritical pointOn the other hand, the species and number of animals reached the maximum, and then entered the stage of comprehensive development.In the comprehensive development stage of the animal kingdom, the species of animals are increasing, the number of individuals is decreasing, but the quality is improving.Because of this, although there have been many animal mass extinctions, the animal kingdom itself has not been extinct, but has become more and more prosperous, andAdvanced animal——Human.Human beings belong to the animal kingdom,Mammalia、Primates、Human family、Homo、Homo sapiens。[7]
Related culture
Announce
edit
In ancient China, the Milky Way was also called Tianhe, Xinghe, Hehan, etc.As early asPre QinIn the era of "Chuang Tzu - Leisure Journey", there was a saying that "I am frightened and my words are just like a river man without limit", which originally meantYellow RiverAndHanshui, later referred to the Milky Way in the sky.[8]
Guo Moruo, a modern Chinese poet, once wrote in his poem: "Look at the shallow Tianhe River, it must not be very broad. I think the Niunu across the river must be able to ride the cows. I think they must be wandering in the Tianjie at this moment. Don't believe it, look at the meteor, they are walking with lanterns".
Galaxy has many interesting nicknames in Chinese classical poetry, such as:
Han Dynasty《Yuefu》"Hehan" in the poem "Faraway Altair", "Faraway Altair, bringing a beautiful Hehan woman. Hehan is clear and shallow, how many times do you want to go back?".
Land-based aircraftThe "Heavenly Han" in the "Pretending the Bright Moon Brings Night Light", which means to flaunt the northwest, and the Tianhan leans southeast ".
Li BaiIn "Drinking Alone under the Moon", "You will never forget to travel, and you will meet Miao Yunhan".
Du FuIn Late Pavilion, the "Milky Way" in "the sound of drums and horns at the fifth watch is solemn and stirring, and the Three Gorges Milky Way is shaken".
The "Tianhe" in Wang Jian's Autumn Night Song, "The Tianhe River is long and leaky, and the South Tower and the Big Dipper are equal".
Li He《The stream is cool in the evening》The "Silver Bay" in "Jade smoke is green, wet and white like a building, and the silver bay flows from dawn to east of the sky".
lunar calendarJuly 7thThis day is the most romantic "Double Seventh Festival" in Chinese traditional festivalsa cowboyAndwoman weaverThe annual meeting at the Milky Way Magpie Bridge.[9]
Literary works have been included in the Han Dynasty at the latest. The "Hehan" in the poem "Faraway Altair" in the Yuefu poem of the Han Dynasty, "Faraway Altair, bringing a beautiful river woman. The river is clear and shallow, and how many times do you want to go?" refers to the Milky Way.[10]
Qixi Festival has also gradually evolved into China's Valentine's Day.Therefore, every Tanabata, lovers always look up at the stars and pray for love.
Meet the Magpies and Bridges
In midsummer, the brightness is zero around 9:00 p.mwoman weaverThe star first appeared near the zenith, and then there was another star in its south directionFirst-class starOfNiulang StarIn the suburbs far away from the city lights, when citizens look up at the night sky, they will be surprised to find that there is a vast white Milky Way (the Milky Way) across the north and south between the two stars. The cowherd is in the east of the river and the weaver girl is in the west of the river. They look at each other wordlessly, which is quite poetic.
On a sunny night, you can find a safe place that is not affected by the city lights, preferably about two hours after dark. At this time, there is not much moonlight, so you can make an appointment with relatives, friends or lovers in advancedeck chair。When you look up at the Milky Way across the sky in the quiet night, you will have a comfortable spiritual enjoyment.Near the top of the head, there are three bright stars in the middle and on both sides of the Milky Way, and the brightest one is bluish white. She is in the northwest of the Milky Way, which is Vega.There are four darker stars below Vega, forming a smallparallelogramThey are the beautiful clouds and rainbows woven by the Weaver Maid in myths and legendsshuttle。Another bright star is in the south by east of Vega, the southeast of the Milky Way. It is Altair (also known as AltairHegu II)。Altair is a bright yellowish star. The two small stars on both sides of Altair are calledShoulder pole starIt is said that Niulang is carrying a pair of children.
According to modern astronomical observation and calculation results, Niulang Star is 16 light years away from the Earth (1 light yearApproximately equal to10 trillion kilometers), Vega is 26 light years away from the earth, and the two stars are 16 light years apart, so their annual "July 7 meeting" is fundamentalImpossibleOf.
Legend has it that the day of "July 7th" is counted asthe cowherd and the weaving maid lovers separated by the milky way -- husband and wife living apartBecause the ancients believed that "seven" was a lucky number with the meaning of completeness.Moreover, on the night of "July 7th", when the moon approaches the Milky Way, the brightness of the moon can also shine on the Milky Way, which is more convenient for people to watch the stars.TonightAstronomical telescopeIf you watch, you will see the dense stars in the Milky Way.The afterglow of half a moon on the Milky Way has become people's imagination“Magpie bridge" 。
Foreign legends
There are many myths surrounding the creation of heaven and earth around the worldGalaxyDeveloped.
1. The Milky Way in Ancient Greek Mythology
Zeus, king of gods
In particularancient GreekThere are two similar Greek fairy tales explaining how the Milky Way came into being.Some myths combine the Milky Way with the constellations, believing that the milk of herds of cattle has whitened the dark blue sky.stayEast AsiaIt is believed that the fog belt between stars in the sky is a silver river, which is Tianhe.Akashaganga is the name given by Indians to the Milky Way, which means the Ganges River in the sky.
Milky wayGreekγ α λ α ξ is literally "the way of milk", based onancient GreekMyth, the Milky Way isHeraFound onZeusHe tricked him into feeding young Hercules, which splashed in the skyMilk juice。Another way of saying it isHermesTake Hercules secretlyOlympus, while Hera was sleeping, he stole his milk, and some milk was shot into the sky, thus forming the Milky Way.[1]
In Finnish mythology, the Milky Way is called the path of birds, because they have noticed that migratory birds are guided by the Milky Way when migrating to the south. They also believe that the Milky Way is the real residence of birds.Scientists have confirmed that this observation is correct. Migratory birds really rely on the Milky Way to guide them and can live in the warm southern land in winter.Even now,FinnishThe word Linnunrata is still used in Galaxy.
3. The Milky Way in Swedish Mythology
In Sweden, the Milky Way is considered the winter road becauseScandinaviaIn winter, the Milky Way is the easiest to see in a year.The ancient Armenian myth called the Milky Way the Road of Straw Thieves. It is described that a god tried to escape from heaven with a wooden van after stealing straw, but some straw fell on the way.
