Stellar Remnants White Dwarfs, Neutron Stars & Black Holes
star的结构 -回复
star的结构-回复Title: The Structure and Evolution of StarsIntroduction:Stars, the celestial bodies that have fascinated and inspired humanity for centuries, are marvels of nature. They are born, evolve, and eventually die in a complex and intricately structured manner. In this article, we will explore the fascinating structure of stars, from their birth in stellar nurseries to their ultimate demise as white dwarfs, neutron stars, or black holes.1. Stellar Nurseries:Stellar nurseries, also known as molecular clouds, are vast regions of interstellar gas and dust that serve as the birthplace of stars. Gravitational forces act upon these clouds, causing them to collapse under their own weight. As the cloud contracts, it rotates and flattens into a disk-like structure known as a protoplanetary disk. Within this disk, a dense core forms, attracting surrounding material through gravitational attraction.2. Protostars:As matter continues to accrete onto the dense core, it becomes aprotostar. This initial phase of stellar evolution can take thousands to millions of years. The protostar steadily grows through the accumulation of mass. Simultaneously, it emits vast amounts of energy in the form of infrared radiation due to gravitational contraction. Eventually, when nuclear fusion reactions begin, the protostar achieves a stable state and becomes a main-sequence star.3. Main-Sequence Stars:Main-sequence stars, like our sun, are at the prime of their lives. These stars maintain stability by balancing the inward pull of gravity with the outward pressure generated by nuclear fusion reactions in their cores. The fusion of hydrogen atoms into helium releases immense amounts of energy, which is radiated as visible light, giving stars their brilliance. The balance between gravity and fusion reactions allows main-sequence stars to maintain a relatively constant size and temperature for billions of years.4. Stellar Evolution:The lifespan of a star depends primarily on its initial mass. Less massive stars, called red dwarfs, have longer lifespans and can burn through their fuel reserves for tens to hundreds of billions of years.On the other hand, more massive stars, with masses several times that of the sun, have shorter lifetimes of a few million years.5. Red Giants and Supernovae:As a main-sequence star exhausts its hydrogen fuel, it starts to expand and becomes a red giant. During this phase, the star's outer layers become cooler and redder while its core contracts and heats up. Eventually, the core reaches temperatures high enough to ignite the fusion of helium, forming heavier elements. The fusion of heavier elements consumes the remaining fuel, generating a massive explosion known as a supernova. This cataclysmic event scatters elements synthesized within the star into space, enriching the interstellar medium with heavy elements.6. Compact Stellar Remnants:After a supernova, the core of a massive star may collapse to form a neutron star or, in the case of extreme mass, a black hole. Neutron stars are incredibly dense, with the mass of our sun compressed into a sphere only 12 miles in diameter. They emit beams of radiation, called pulsars, as they rotate. Black holes, on the other hand, have gravitational forces so strong that nothing, not even light, can escape their pull.7. White Dwarfs:Stars with masses similar to or slightly higher than that of the sun typically evolve into white dwarfs. These remnants of dead stars are composed of extremely dense matter, with electrons and atomic nuclei forced together. Without fusion reactions, white dwarfs gradually cool over billions of years, fading away as dim,Earth-sized objects.Conclusion:The structure of stars, from their birth within stellar nurseries to their final stages as remnants such as white dwarfs, neutron stars, or black holes, follows a fascinating and diverse path. Understanding the intricate processes that govern the life cycle of stars not only contributes to our knowledge of the universe but also sheds light on our own origins. As we continue to explore the cosmos, the study of stars remains a captivating and continuously evolving field of research.。
TheAppearanceof
What the core is doing is not obvious from the surface of the starWhat will be the structure of the Sun 5billion years from now?Outer layers of starswell up and cool -->red giant (not obvious)Old core (nowhelium) continues tocontract (it’s not inhydrostaticequilibrium)demoEventually, temperatures in compact core reach high enough temperatures for helium fusion reactions, the “triple alpha process”Triple alpha process can proceed when thetemperature reaches 100 million K.Later in the future life of the SunRussell diagramnebulas, revealing the weird coressaw it during the field trip)As cores contract, the density goes to “astronomical” levels, matter acts in funnyways•Gas in this room, the “perfect gas law”PV=nRT. Pressure depends on both density and temperature•Extremely dense, “degenerate” gasPV=Kn. Pressure depends only on density•DemoThe contracted core reaches a new balance between gravity and degenerategas pressureWhat are the physical properties of theseobjects?Gas pressure Self gravityView from a spaceship in the Sirius system We know the white dwarfs must have the properties as described (we’re not makingthis up)There are many known examples of white dwarfs;they are a common phenomenon in the galaxy / WDCatalog/index.html。
黑洞的由来的英语作文
黑洞的由来的英语作文The Origin of Black Holes: A Journey into Cosmic Mysteries。
Introduction。
Black holes, enigmatic entities lurking in the depthsof space, have captivated the imagination of scientists and laypersons alike. Their origins, shrouded in cosmic mystery, have been the subject of intense study and speculation. In this essay, we embark on a journey to unravel the secretsof black holes, exploring their formation, properties, and significance in the universe.Formation of Black Holes。
The genesis of black holes begins with the demise of massive stars. When a massive star exhausts its nuclear fuel, it undergoes a cataclysmic event known as a supernova explosion. During this explosive phase, the outer layers ofthe star are ejected into space, while its core undergoes gravitational collapse. If the core's mass exceeds acritical threshold, it collapses into a singularity—a point of infinite density—giving birth to a black hole.The process of black hole formation can also occur through the gravitational collapse of dense stellar remnants, such as neutron stars, or through the merger of two compact objects, such as neutron stars or black holes. These pathways lead to the creation of different types of black holes, ranging from stellar-mass black holes to supermassive black holes found at the centers of galaxies.Properties of Black Holes。
关于太空现象的英语术语
关于太空现象的英语术语Space Exploration and Its TerminologySpace exploration has been a captivating field of study for centuries, capturing the imaginations of people around the world. As we delve deeper into the mysteries of the cosmos, the need for precise and comprehensive terminology becomes increasingly important. This essay will explore some of the key terms and concepts associated with space phenomena, providing a comprehensive overview of the language used in this fascinating domain.One of the most fundamental terms in space exploration is "galaxy."A galaxy is a vast, gravitationally bound system consisting of stars, stellar remnants, interstellar gas, dust, and dark matter. Our own Milky Way galaxy is just one of the countless galaxies that populate the observable universe, each with its own unique characteristics and composition. The study of galaxies, their formation, evolution, and interactions, is a crucial aspect of astrophysics.Another essential term in the realm of space is "star." Stars are massive, luminous celestial bodies held together by their own gravity. They are the building blocks of galaxies and play a crucial role in thelife cycle of the universe. The study of stars, their properties, and their life cycles is known as stellar astronomy or stellar astrophysics.Closely related to stars are the concept of "exoplanets." Exoplanets are planets that orbit stars other than our Sun. The discovery and study of exoplanets have revolutionized our understanding of planetary systems and the potential for life beyond Earth. Astronomers use various techniques, such as the transit method and the radial velocity method, to detect and characterize these distant worlds.Another important term in space exploration is "nebula." A nebula is a vast, diffuse cloud of gas and dust in space, often illuminated by the light of nearby stars or energized by the radiation from young, hot stars. Nebulae play a crucial role in the formation of stars and can take on a variety of shapes and colors, depending on their composition and the processes occurring within them.The concept of "black holes" is also central to our understanding of space phenomena. Black holes are regions in space where the gravitational pull is so strong that nothing, not even light, can escape. These enigmatic objects are formed when a massive star collapses in on itself, and their study has led to groundbreaking discoveries in the field of general relativity and the nature of spacetime.In addition to these fundamental terms, space exploration also encompasses a wide range of specialized vocabulary. For example, "supernova" refers to the explosive death of a massive star, while "neutron star" describes the extremely dense, rapidly rotating remnant of a supernova. "Quasar" is a term used to describe the extremely luminous and energetic cores of active galactic nuclei, powered by supermassive black holes.The language of space exploration also includes terms related to the various instruments and technologies used to study the cosmos. "Telescope" is a device that uses lenses or mirrors to gather and focus light, allowing astronomers to observe distant celestial objects in detail. "Spectrometer" is an instrument that analyzes the spectrum of light emitted or absorbed by an object, providing valuable information about its composition and physical properties.Finally, the field of space exploration is also closely tied to the concept of "cosmology," the study of the origin, evolution, and ultimate fate of the universe. Fundamental terms in cosmology include "Big Bang," the proposed initial state of the universe, and "dark matter" and "dark energy," the mysterious components that make up the majority of the universe's mass and energy.In conclusion, the language of space exploration is rich and diverse, reflecting the depth and complexity of our understanding of thecosmos. From the basic terms like "galaxy" and "star" to the more specialized concepts like "exoplanet" and "quasar," the vocabulary of this field is essential for scientists, researchers, and enthusiasts alike to communicate and share their discoveries. As we continue to explore the wonders of the universe, the importance of this specialized terminology will only grow, serving as a crucial tool for expanding our knowledge and understanding of the cosmos.。
天文词汇大全
celestial /adj.天上的,天体的,神圣的astronomical, heavenly . The book showed a map of the selestial realms.universe /n.宇宙cosmosuniversal /adj.宇宙的orbit /n.轨道.Our planet is in orbit around the sun.comet /n.慧星galaxy /n.星系constellation /n.星座asteroid /n.小行星planet /n.行星chondrite /n.球粒状陨石cluster /n.星团meteor /n.流星;大气现象. meteor shower流星雨dwarf /n.白矮星star /n.恒星stellar /adj.恒星的cosmos /n.宇宙cosmic /adj.宇宙的cosmology /n.宇宙哲学,宇宙论nebula /n.星云quasar /n.恒星状球体,类星体space /n.空间planeroid /n.位面intergalactic /adj.银河间的interplanetary /adj.行星间的,太阳系内的interstellar /adj.星际的corona /n.日冕chromosphere /n.色球solar /adj.太阳的.solar system 太阳系;solar corona日冕;solar eclipse日食;solar radiation 太阳辐射photosphere /n.光球pseudoscience /n.假科学,伪科学astronomy /n.天文学astronomical /adj.天文学的;庞大无法估计的/n.天文.astronomical observatory天文台astrology /n.占星术,占星学astrophysics /n.天体物理学Jupiter /n.木星Lunar /adj.月的,月亮的Mars /n.火星mercury /n.水星,水银,汞Earth /n.地球Uranus /n.天王星Venus /n.金星Pluto /n.冥王星;阴间之神Neptune /n.海王星Saturn /n.土星emission /n.光,热等的散发,发射,喷射infinite /adj.无穷的,无限的,无数的,极大的interferometer /n.干涉仪radiation /n.发散,辐射;放射物revolve /v.使旋转.Their troubles revolve around money management.land /vt.着陆,降落. The plane finally landed ifself safely on the ground.spaceship /n.太空船telescope /n.望远镜Cosmos宇宙world世界milky way银河solar system太阳系interplanetary形星际的sky天zenith天顶fixed star恒星planet行星asteroid小行星satellite卫星shooting star流星Mercury水星Venus金星earth地球Mars火星Jupiter木星Saturn土星Uranus天王星Neptune海王星Pluto冥王星morning star 晨星evening star 昏星aureole光环eclipse食astronaut宇航员shuttle航天飞机east东west西south南north北northeast 东北northwest 西北southeast 东南southwest 西南center中心continent 大陆equator赤道meridian经线parallel纬线torrid zonesunrise 日出sunset日落dawn黎明daybreak 黎明dusk黄昏nightfall 黄昏rainbow 彩虹Aries白羊座Taurus金牛座Gemini双子座Cancer巨蟹座Leo狮子座Virgo处女座LibraScorpio天蝎星座Sagittarius射手座polestar北极星Altair牵牛星Vega织女星nova 新星super nova 超新星quasar类星体meteor流星satellite卫星planet行星star恒星comet彗星constellation星座galaxy星系nebula星云white dwarf白矮星red giant红巨星neutron star中子星cluster星团asteroid小行星atmosphere大气nadir天底zenith天顶ecliptic黄道eclipse食light-year光年orbit轨道solar system太阳系sunmoon九大行星:MercuryVenusEarthMarsJupiterSaturnUranusNeptunePlutoPolaris北极星Sirius天狼星Vega织女arcturus大角antares心宿二zodiac十二宫GeminiCancerLeoVirgo Pisces Aquarius Libra Taurus Aries Capricorn Sagittarius Scorpio。
关于星星的英语
关于星星的英语Title: The Enchanting Spendor of StarsThe universe has always held a certain mystique, captivating the human imagination with its vast expanse and uncharted territories. Among the celestial bodies that adorn the night sky, stars hold a special place in the hearts of many. These luminous orbs, scattered across the cosmos, have been the subject of poetic musings, scientific inquiries, and philosophical contemplations for millennia. Their enduring allure lies not only in their sheer beauty but also in the deeper questions they evoke about our place in the universe and the fundamental nature of existence.Stars, often described as distant suns, are essentially massive, self-luminous balls of plasma held together by their own gravity. They range in size, color, and brightness, each presenting a unique spectacle to those who take the time to observe them. The life cycle of a star is a fascinating journey that begins with the gravitational collapse of a cloud of gas and dust, leading to the formation of a protostar. This phase is followed by nuclear fusion in the core, where hydrogen atoms combine to form helium, releasing an enormous amount of energy in the process. It is this fusion that powers the star,allowing it to shine brilliantly for millions, even billions, of years.The life span of a star varies depending on its mass; more massive stars burn through their fuel much faster than smaller ones. Eventually, stars exhaust their nuclear fuel and enter their death throes, shedding their outer layers and possibly collapsing into dense remnants such as white dwarfs, neutron stars, or black holes. This cosmic dance of creation, life, and death continues unabated, shaping the very fabric of the universe.Beyond their physical characteristics, stars have played a crucial role in guiding human navigation through the ages. Before the advent of modern technology, sailors and explorers relied on celestial bodies to chart their course across the seas and lands. The North Star, for instance, has been a constant beacon for travelers lost under the night sky. Stars served not only as guideposts but also as inspirations for countless myths, legends, and cultural traditions around the world.In contemporary society, the study of stars has given rise to sophisticated fields such as astrophysics and astrochemistry, which seek to understand the complex processes governing stellar behavior. T elescopic advancements and space missionshave allowed us to peer deeper into space than ever before, uncovering secrets about distant galaxies and the potential for extraterrestrial life. The iconic Hubble Space Telescope, launched in 1990, has provided some of the most breathtaking images of the cosmos, revealing nebulae, supernovae, and other phenomena that were once thought to be beyond our reach.Yet, despite our technological prowess and scientific achievements, there remains an element of mystery surrounding these celestial beacons. Stars remind us of our smallness in the grand scheme of things, prompting introspection about our purpose and place in the universe. They evoke a sense of wonderment and curiosity that transcends cultural and linguistic boundaries, uniting humanity in its quest to understand the cosmos.In conclusion, stars are more than just tiny points of light in the night sky; they are profound symbols of the universe's grandeur and complexity. From ancient civilizations to modern societies, they have fascinated and inspired countless generations. As we continue to explore the depths of space, the study of stars promises to unlock further secrets about the universe's origins, its evolution, and perhaps even its ultimatefate. In the end, stars teach us that there is still much to learn, inviting us to look up at the night sky with a sense of humility and boundless curiosity.。
美丽的星空 英语作文
The Majestic Beauty of the Night SkyAs the sun dips below the horizon, painting the sky with hues of orange and pink, it ushers in the tranquility of the night. The transition from day to twilight and then to the full embrace of darkness is a magical process, one that reveals the hidden treasures of the universe. The night sky, adorned with its celestial jewels, offers a spectacle that has captivated humanity since the dawn of time.When darkness falls, the stars begin their nightly dance across the vast canvas of the heavens. They twinkle like distant lanterns, each with its own story to tell. Some stars are so bright that they seem to burn with an intensity that belies their immense distance from our earthly vantage point. Others are faint whispers, barely visible to the naked eye, yet their collective glow bathes the landscape in a soft, ethereal light. To gaze upon the star-studded sky is to witness the grandeur of creation. The Milky Way, our home galaxy, stretches across the firmament like a luminous river, its milky-white band a testament to the billions of stars that make up this cosmic structure. It is a humbling experience to consider that we are but specks within this vast expanse, sharing the cosmos with countless other worlds, some perhaps cradling life as we know it.The night sky is not just a backdrop for stars; it is also the stage for other celestial phenomena. The moon, Earth’s faithful companion, cycles through its phases, casting its own brand of enchantment on the world below. Comets streak across the heavens like shooting stars, leaving trails of light and wonder in their wake. And during meteor showers, the sky becomes a canvas splattered with the fleeting brilliance of fireballs, each a tiny piece of space debris burning up in the atmosphere.Observing the night sky is not only a visual treat; it is also a journey into the realms of science and imagination. Each star represents a potential story of stellar evolution, from the birth of stars in nebulae to their eventual demise as white dwarfs, neutron stars, or black holes. The night sky invites us to ponder the mysteries of dark matter and dark energy, forces that govern the expansion of the universe.In conclusion, the beauty of the night sky is a timeless source of inspiration. It connects us to the infinite, reminding us of the delicate balance between the vastness of space and the intimacy of our human existence. Whether through the lens of poetry or the language of astronomy, the night sky continues to be a subject of fascination, a window into the wonders that lie beyond our planet.Feel free to modify and personalize this essay to better reflect your own experiences and insights. Remember, the best essays often come from personal connections to the topic at hand.。
universe(宇宙简介)
4. Asymptotic-giant-branch phase（渐近巨星分支） 高时，太阳外层将会膨胀
5. Massive stars（大质量恒星） 6. Supernova（超新星）
。当其核心温度升高到 100000000K时，将发生 氦的聚变而产生碳，从而
③ Stellar remnants（恒星残骸）
费里德曼模型
费里德曼：俄罗斯 数学家和物理学 家，用数学方法提出宇宙模型的第一
支撑费里德曼模型的基本理论
人，动力气象学的奠基人
1. 任何两个星系相互离开的速度是及他们之间的距离成正比的
2. 广义相对论和量子力学的不确定原理（测不准原理）：时间和空间都是有限 而无界的
两个假设 1. 从任何方向观测宇宙都相同 2. 从任何地点观测宇宙都相同
质量变化不大，但它的亮度、温度和颜色是变化的。除密近双星外， 恒星在它的各个演化阶段，质量基本不变。
恒星的亮度一般称为光度(恒星的发光能力)。在天文学上，用星 等表示，星等越高，亮度越低。 ( 二等星比一等星光度暗10倍，比
一等星亮10倍的就是0等星，依此类推。)
1. 主序星阶段
恒星质量小，亮度低。恒星质量大，亮度高。
hole(黑洞)
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The evolution of the universe(宇宙的演化)
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Quantum Fluctuations【量子波动】：
Under the big bang theory, quantum fluctuations cause the universe to spring into existence out of "nothing"
在我们习以为常的现实世界下，是另一个 令人惊叹的世界
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Sirius & Sirius B a White Dwarf Star
White Dwarfs
• composed mainly of Carbon & Oxygen • formed from stars that are no more than 8 Solar masses • White Dwarfs can be no more than 1.4 Solar masses and have diameters about the size of the Earth (1/100 the diameter of the Sun). • If a White Dwarf is in a binary system and close enough to its companion A White Dwarf pulling material star it may draw material off off of another star in a binary system this star. This material can then build up on the surface of the White Dwarf. 2
– once matter or light crosses the event horizon it can never return – tidal forces are extreme at the event horizon
11
Two dimensional representation of the Event Horizon
Neutron Stars
• Except for a thin crust of iron atoms a neutron star is composed entirely of neutrons. • The gravitational forces inside a neutron star are too strong for atoms to exist. • Instead electrons get crushed into the protons in the atomic nucleus forming neutrons. • Neutron stars have very intense magnetic fields and very rapid rotatdius: The Radius of the Event Horizon
• The Event Horizon is the spherical region of space surrounding the Black Hole from which no light may escape
4
Stellar Remnants and the Chandrasekhar • Stellar remnants Limit greater than 1.4
Solar masses cannot form White Dwarfs. • Objects this massive cannot support their own weight but collapse to form either Neutron Stars or Black Holes. • This maximum mass is called the Chandrasekhar 5 Limit.
12
Escape Velocity and Event Horizon
6
Neutron Stars weigh more than the Sun and are as large a city.
Pulsars
• Neutron stars can sometimes be directly observed. • Astronomers have discovered rapidly spinning stars emitting strong, very regularly timed bursts of radio waves. • These types of neutron stars are called pulsars. • Pulsar bursts are as regular as some of the best clocks on Earth.
•Consider a 2-D universe (graph paper) instead of a 3-D universe. •The massive Black Hole bends space (the graph paper). •Light paths near the Black Hole are bent. •Light paths that intersect the Event Horizon terminate at the Black Hole
3
Another Kind of Supernova
• If too much material accumulates the White Dwarf may collapse. • Rapid fusion reactions of Carbon & Oxygen begin. Carbon & Oxygen fuse into Silicon and Silicon into Nickel. • The energy from this event may cause the entire White Dwarf to explode leaving nothing behind. • This is called a supernova but it is a different process from that which occurs for massive stars.
Stellar Remnants
White Dwarfs, Neutron Stars & Black Holes
• These objects normally emit light only due to their very high temperatures. • Normally nuclear fusion has completely stopped. • These are very small, dense objects. • They exist in states of matter not seen anywhere on Earth. They do not behave like normal solids, liquids or gases. • They often have very strong magnetic fields and very rapid spin rates. 1
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All objects exert a gravitational pull on all other objects in the Universe. One way to picture gravity’s effect is by imagining space as a rubber sheet. Heavy objects bend this sheet more than light objects. Black Holes are like tears in this sheet.
As the beam from a pulsar sweeps past Earth we see a brief pulse.
7
The Discovery of Pulsars
• In 1967 in Cambridge England, Jocelyn Bell, a graduate student in astronomy, discovered very regularly spaced bursts of radio noise in data from the radio telescope at Cambridge University. • After eliminating any possible manmade sources she realized this emission must be coming from space. • The regularity of these pulses at first made her and her co-workers think they had discovered alien life. Jocelyn Bell Burnell in front • Later they realized these must be of the radio telescope used to due to rapidly spinning neutron stars. 8 discover pulsars.
White Dwarfs in Binary Systems
• This material pulled off the companion star is mostly Hydrogen. • As it accumulates on the star it may become hot enough for nuclear fusion to occur. • The Hydrogen begins to fuse and the White Dwarf emits a bright burst of light briefly. • We see this on Earth as a nova. • This process can repeat as new material accumulates.
9
Escape Velocity & Curved Space