synonymProtostar(an object in a slow shrinking stage) usually refers to a primitive star
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Primitive starIt is reported by the American Science Daily that astronomers have discovered the "wreckage" of the early universe - a second generation star formed after the Big Bang.It is located in the Yufu constellation, a dwarf galaxy 290000 light-years away from the Earth. This star has an unusual chemical composition of the oldest star in the Milky Way.This research will confirm that the Milky Way has experienced a "feeding stage", and the Milky Way gradually increases its current size by annexing dwarf galaxies and other galaxy components.
Chinese name
Primitive star
Alias
Second generation stars
Classification
fixed star
Primitive star
The second generation stars in the dwarf galaxy Yufu constellation
Anna Frebel, an astronomer at the Harvard Smithsonian Center for Astrophysics, said: "This star is likely to be close to the age of the universe." This research report was published in the journal Nature.Dwarf galaxies are small galaxies with only a few billion stars, while the Milky Way has hundreds of billions of stars.In the theory of galaxy formation, larger galaxies have expanded their size by absorbing smaller neighboring galaxies in the past few billion years.
depth analysis
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Frebel explained that if you watch the "delayed movie" of the formation of the Milky Way, you will see a group of dwarf galaxies around the hive like bees. As time goes on, these small galaxies collide together, and their stars gradually mix, forming a larger galaxy like the Milky Way.
If dwarf galaxies are indeed "building blocks" of larger galaxies, then the same type offixed starIt will exist in dwarf galaxies and larger galaxies, especially those cold, "metal deficient" stars.According to astronomers, "metals" are heavier chemical elements than hydrogen or helium. Since they were formed in the process of star evolution, metal materials rarely exist in the early universe, so ancient stars tend to lack metal materials.
The ancient stars in the halo of the Milky Way have less metal material, and their metal material composition ratio is 100000 times lower than that of the sun. The sun is a typical young star, rich in metal stars.In the past decades of star surveys, it is very difficult to find such stars lacking metal in dwarf galaxies.
Josh Simon, one of the co authors of the Carnegie Institution Observatory, said: "The number of stars in the Milky Way at the beginning is more than that of any previous dwarf galaxy. If the dwarf galaxy has the original origin of the Milky Way, it will be difficult to understand why there are no similar stars."
The research team speculated that the method used to measure the metal deficient stars in dwarf galaxies may be biased due to the inability to measure more metal deficient stars.Evan Kirby, an astronomer at the California Institute of Technology in the United States, is one of the members of the research team. He has recently developed a method that can evaluate the metal composition of a large number of stars in turn, so as to find more stars lacking metal composition in dwarf galaxies as effectively as possible.
S1020549
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Kirby said, "It's more difficult than picking a needle in the haystack. We finally selected our detection target from hundreds of candidate galaxies." Among the many survey targets, the research team found that there was a dim, 18th star in the dwarf galaxy Yufu constellation, S1020549,The measurement results of the stellar light spectrometer of the Magellan Astronomical Telescope of the Carnegie Institution in Chile show that,S1020549 StarThe ratio of metal composition of the star is 6000 times higher than that of the sun, which is five times lower than that of any dwarf galaxy found so far.
The researchers measuredS1020549 StarAll metal substances contained, such as magnesium, calcium, titanium and iron.These elements are similar to the ancient stars in the Milky Way, which supports that the stars in large galaxies such as the Milky Way originally originated from dwarf galaxies.
The researchers hope that future exploration will find other metal deficient stars in dwarf galaxies, although the distance and brightness of these stars are related to the currentOptical telescopeSurveying is a major challenge.Like a giant with a diameter of 24.5 metersMagellan telescopeThe next generation of super large optical telescopes will be equipped with high-definition acoustic spectrometers, which will reveal a new way to study galaxy expansion by analyzing the chemical composition of stars.
Simon said that in this study, the ultra-low metal content of S1020549 star will mark how to understand the composition principle of the Milky Way. The theory that the Milky Way halo formed during the destruction of a large number of dwarf galaxies is correct.
Simulate primitive stars
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Using a large number of computer simulations, astronomers have for the first time obtained the distribution pattern of the first generation stars in the Milky Way, which have never been observed before.This is very important to solve the problem of stellar ancestors that has puzzled scientists for a long time.Their results will be published in the Astrophysical Journal this week.
??Despite many years of searching, no one has found these stars.Evan Scannapieco of the Kavli Institute of Theoretical Physics, Santa Barbara, California University, said: "Many astronomers think this is because these stars do not contain heavy elements. Since our galaxies form from the inside out, ancient stars should be in the center of the galaxy. But the center of the Silver River system is very crowded, and it is difficult to detect these ancient stars."
??These early stars should look very different from those formed later.Oxygen, carbon, and most other elements on Earth are generated in stars, not in the Big Bang.Brad K. Gibson, of theoretical astrophysics at Central Lancashire University in the UK, said: "These heavy elements are generated in the center of the star and can only be released when the star dies and explodes, which means that the first generation of stars that still exist should show the characteristics of no heavy elements."
??Using the detailed simulation of the formation of the Milky Way, scientists not only get the process of star formation, but also get the chemical composition of its gas.Daisuke Kawata of Carnegie Observatory thinks: "The ancient stars die in the center of the Milky Way, and its heavy elements take a long time to disperse. Therefore, the stars formed in the later period only contain primitive elements. These stars should exist widely." Because these stars around the Milky Way are easier to detect,So there should be other reasons why these primitive stars were not detected.
