邮票上的物理学史(66)--天体物理学:恒星及其演化(续)

1967年,剑桥大学卡文迪什实验室的射电天文学家休伊什领导一个小组,研制了一台射电望远镜,以观测小角直径射电源的行星际闪烁现象.和其他射电望远镜相比,它的特点是时间分辨率达到0.1 s,能够记录快速变化的信号(当时不知道有发射快变信号的射电源,为了平滑掉噪声,普遍将接收机设计成只能接收经过几 s积分的平均信号).休伊什让他的研究生贝尔(女)负责观测和分析数据.贝尔做事是极其认真细致的.     

邮票上的物理学史(67)--天体物理学:星云和星系

比恒星更高的天体层次是星系.我们怎么知道有星系这个层次存在呢?我们自己属于哪个星系?     

邮票上的物理学史(63) --天体物理学:新的观测手段

天体物理学是天文学三大分支中最现代和最活跃的一个分支(另外两个分支是天体测量学和天体力学),也是物理学的一个重要分支,它研究的对象是自然界中尺度最大的客体天体和宇宙,而且它们是处在人类在地球上无法复现的极端物理条件(超高温、超高压、超高密度、超强磁场、超强辐射等)之下.     

邮票上的物理学史(74)--电子学

电子学是一门应用科学,用来研究和利用电子在真空、气体和固体中的运动及其和电磁波的相互作用,特别是制成各种电子器件,为信息、能源和材料科学服务．前面说过,电子学和无线电波的研究和应用是分不开的,二者合起来构成无线电电子学．我们分成了两节来介绍,前面已介绍过无线电,本节专门讨论电子器件的发展,一是因为内容大多,二是因为晶体管是在固体能带论和半导体物理学的指导下发明的,在凝聚态物理学之后来讲更合适．     

邮票上的物理学史(26)--热学的宏观理论

与热学有关的邮票不多.许多对热学的建立作出了巨大贡献的科学家,如迈耶、焦耳、卡诺、克劳修斯、吉布斯等,迄今都没有发行过与他们有关的邮票,因此我们沿着邮票轨迹对热学历史的追踪将是极其粗线条的.     

天体物理学讲座：第一讲 恒星的演化

恒星结构和演化理论是研究恒星内部的物理过程、结构和恒星如何演化的科学、文章介绍了恒星结构和演化模型的计算方法,恒星在赫罗图中的分布规律,恒星的形成和早期演化特性,质量不同的各类恒星从主序开始的演化进程,恒星演化的晚期阶段的产物;白矮星、超新星和中子星。     

邮票上的物理学史(59)--加速器·物理实验的大型化(续)

用回旋加速器加速粒子的能量 ,实际上要受到D形盒大小 (即磁极大小 )和磁场强度的限制 .为了提高粒子能量 ,加速器越做越大 ,带来了许多技术问题 .例如D形盒内高真空度的保持 ,磁铁的建造和供电等 .此后 ,劳伦斯一心专注于组织管理工作 ,他筹措经费 ,招揽了电工、无线电、探测器等各方面的人才 ,发挥了其高超的组织才能 ,分工协作 ,在自己周围形成了一个坚强的研究集体 .他只对加速器的开发和性能的提高感兴趣 ,将各种技术工作以及加速器在科学上的应用研究都交给合作者去完成 .他的合作者之一塞格雷评论劳伦斯说 :“从本质上看 ,他更像一…     

邮票上的物理学史(78)--诺贝尔物理学奖

每年10月上旬,人们的目光都移向斯德哥尔摩,都在猜测：本年度的诺贝尔奖将花落谁家?诺贝尔奖是科学界的最高荣誉,每年一度的诺贝尔奖,对于把公众的注意力引向当前的科学前沿起了不可替代的作用．     

邮票上的物理学史(73)--现代光学

现代光学的进展主要集中在四个方面：信息光学,激光,非线性光学,光电子学．     

Single star evolution I. Massive stars and early evolution of low and intermediate mass stars

We survey the results of those model calculations of the early evolution of single stars that have been obtained over approximately the last decade, and compare some of these results with the observations, concentrating particularly on the comparison between theoretical predictions regarding surface abundances of red giants and Cepheids and abundance estimates obtained by an analysis of spectral data.For massive stars, we discuss the ramifications of the fact that the time scale for mass loss (via stellar winds) during main sequence and red supergiant evolution can be comparable to the nuclear burning timescale, noting in particular the unusual distribution of stars in the Hertzsprung-Russell diagram, and the probability that significant mass loss is responsible for the chemically highly evolved spectra of Wolf-Rayet stars. finally, we sketch (1) recent progresses in following the evolution of massive stars to the presupernova stage, which is described by a configuration consisting of a core of near-Chandrasekhar mass made up of iron peak elements and a series of “onion”-skin layers of less highly thermonuclearly processed matter and (2) recent progress in understanding the nature of the type II supernova phenomenon.For low and intermediate mass stars, we discuss postulated “extramixing” (beyond convective) processes, which may occur on the main sequence and on the first red giant branch, and continue on to a discussion of asymptotic giant branch evolution, placing considerable emphasis on the character of the thermal pulses that occur in such stars and, in particular, on the nucleosynthesis that occurs in the helium burning convective shells during these pulses and on the dredge-up phenomenon that brings fresh carbon and neutron-rich isotopes to the surface following pulse peak.     

Massive neutron stars and their implications

Recent observations of high mass pulsar PSRJ1614-2230 has raised serious debate over the possible role of exotics in the dense core of neutron stars. The precise measurement of mass of the pulsar may play a very important role in limiting equation of state (EoS) of dense matter and its composition. Indirectly, it may also shape our understanding of the nucleon–hyperon or hyperon–hyperon interactions which is not well known. Within the framework of an effective chiral model, we compute models of neutron stars and analyse the hyperon composition in them. Further related implications are also discussed.     

Astrophysics and Cosmology

The Review summarizes much of particle physics and cosmology.Using data from previous editions,plus 3,062 new measurements from 721 papers,we list,evaluate,and average measured properties of gauge bosons and the recently discovered Higgs boson,leptons,quarks,mesons,and baryons.We summarize searches for hypothetical particles such as supersymmetric particles,heavy bosons,axions,dark photons,etc.All the particle properties and search limits are listed in Summary Tables.We also give numerous tables,figures,formulae,and reviews of topics such as Higgs Boson Physics,Supersymmetry,Grand Unified Theories,Neutrino Mixing,Dark Energy,Dark Matter,Cosmology,Particle Detectors,Colliders,Probability and Statistics.Among the 117 reviews are many that are new or heavily revised,including new reviews on Pentaquarks and Inflation.     

转动双星模型及演化

提出了转动双星的结构和演化模型,给出了主星的重力势,并模拟其加速度在等势面上的分布.结果表明在忽略自引力势高阶项的情况下,极地处重力加速度最大,赤道上长轴顶点处重力加速度最小.自转、公转和伴星潮汐作用力的联合效应降低了子星的有效温度,延长了子星在氢主序上的演化时间.     

Rotational energy conversion and thermal evolution of neutron stars

Pulsars are rapidly spinning, strongly magnetized neutron stars. Their electromagnetic dipole radiation is usually assumed to be at the expense of the rotational energy. In this work, we consider a new channel through which rotational energy could be radiated away directly via neutrinos. With this new energy conversion channel, we can improve the chemical heating mechanism that originates in the deviation from β equilibrium due to spin-down compression. The improved chemical and thermal evolution equations with different magnetic field strengths are solved numerically. The results show that the new energy conversion channel could raise the surface temperature of neutron stars, especially for weak field stars at later stages of their evolution. Moreover, our results indicate that the new energy conversion channel induced by the non-equilibrium reaction processes should be taken into account in the study of thermal evolution.