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银河系英文介绍The Milky Way is a spiral galaxy located in the Local Group, a cluster of galaxies in the universe. It is estimated to be around 13.6 billion years old and has a diameter of about 100,000 light-years. The Milky Way is home to billions of stars, along with planets, asteroids, and other celestial bodies.The galaxy gets its name from its appearance as a hazy band of light in the night sky, caused by the concentration of stars and interstellar dust. The Milky Way contains several prominent arms, including the Sagittarius Arm, Perseus Arm, and Orion Arm.The Milky Way is also home to our solar system, which is situated on one of the spiral arms. Our solar system consists of the Sun, eight planets, and numerous moons, comets, and asteroids. Earth, our home planet, is part of the Milky Way's Orion Arm.The study of the Milky Way and its structure is a complex field known as galactic astronomy. Scientists use various techniques, including radio astronomy and infrared imaging, to explore the galaxy and understand its characteristics.The Milky Way has been observed to have a supermassive black hole at its center, known as Sagittarius A*, which has a mass equivalent to millions of suns. It also exhibits other phenomena such as star formation regions, nebulae, and globular clusters. Due to the vastness of the Milky Way, it is believed to host billions of potentially habitable planets, making it a fascinating subject for researchers interested in the search for extraterrestrial life.Overall, the Milky Way is a captivating galaxy that continues to intrigue scientists and astronomers with its sheer size, diverse range of celestial objects, and potential for discovering new knowledge about the universe.。
中国天文学会天文学名词审定委员会第1-6批天文学名词的推荐译名The 1st - 6th Drafts for the Chinese-Translation of Astronomical Termsrecommanded byThe Astronomical Terminology Committee of the CASabsolute stability 绝对稳定性absorbing dust mass 致吸尘物质absorption trough 吸收槽abundance standard 丰度标准星accreting binary 吸积双星accretion column 吸积柱accretion flow 吸积流accretion mound 吸积堆accretion ring 吸积环accretion stream 吸积流acoustic mode 声模active binary 活动双星active chromosphere binary 活动色球双星active chromosphere star 活动色球星active optics 主动光学actuator 促动器Adams ring 亚当斯环adaptive optics 自适应光学additional perturbation 附加摄动AGB, asymptotic giant branch 渐近巨星支Alexis, Array of Low-Energy X-ray 〈阿列克希斯〉低能X 射线Imaging Sensors 成象飞行器AM Herculis star 武仙AM 型星amplitude spectrum 变幅谱angular elongation 距角anonymous galaxy 未名星系anonymous object 未名天体anti-jovian point 对木点annular-total eclipse 全环食aperture photometry 孔径测光APM, Automated Photographic Measuring 〈APM〉底片自动测量仪systemapoapse 远质心点apoapse distance 远质心距apogalacticon 远银心点apomartian 远火点apparent association 表观成协apparent luminosity function 视光度函数apparent superluminal motion 视超光速运动apsidal advance 拱线进动apsidal precession 拱线进动Arcturus group 大角星群area image sensor 面成象敏感器area photometry 面源测光area spectroscopy 面源分光argument of pericentre 近心点幅角ASCA, Advanced Satellite for Cosmology 〈ASCA〉宇宙学和天体物理学and Astrophysics 高新卫星asteroidal dynamics 小行星动力学asteroidal resonance 小行星共振asteroid family 小行星族asteroid-like object 类小行星天体asteroseismology 星震学astration 物质改造astroparticle physics 天文粒子物理学astrostatistics 天文统计学asymptotic branch 渐近支asymptotic branch giant 渐近支巨星atmospheric parameter 大气参数ATNT, Australia Telescope National 澳大利亚国立望远镜FacilityATT, Advanced Technology Telescope 〈ATT〉高新技术望远镜automated measuring machine 天文底片自动测量仪automatic photooelectric telescope 自动光电测光望远镜( APT )AXAF, Advanced X-ray Astrophysical 高新X射线天体物理台FacilityBaade's window 巴德窗Baade—Wesselink analysis 巴德—韦塞林克分析Baade—Wesselink mass 巴德—韦塞林克质量Baade—Wesselink method 巴德—韦塞林克方法Baade—Wesselink radius 巴德—韦塞林克半径background galaxy 背景星系Barnard's galaxy ( NGC 6822 ) 巴纳德星系barycentric dynamical time ( TDB ) 质心力学时Belinda 天卫十四Bianca 天卫八bidimensional spectrography 二维摄谱bidimensional spectroscopy 二维分光Big-Bang nucleosynthesis 大爆炸核合成binarity 成双性binary asteroid 双小行星binary flare star 耀变双星binary millisecond pulsar 毫秒脉冲双星binary protostar 原双星bioastronomy 生物天文学bipolar jet 双极喷流bipolar outflow 偶极外向流bipolar planetary nebula 双极行星状星云blazar 耀变体blazarlike activity 类耀活动blazarlike object 耀变体Black-eye galaxy ( M 64 ) 黑眼星系BL Lacertae object 蝎虎天体BL Lacertid 蝎虎天体blue compact galaxy ( BCG ) 蓝致密星系blue straggler 蓝离散星bolometric albedo 热反照率bolometric light curve 全波光变曲线bolometric temperature 热温度Bootes void 牧夫巨洞bow-shock nebula 弓形激波星云box photometry 方格测光broad-band imaging 宽波段成象broad-line radio galaxy ( BLRG ) 宽线射电星系buried channel CCD 埋沟型CCDButterfly nebula 蝴蝶星云BY Draconis star 天龙BY 型星BY Draconis variable 天龙BY 型变星CAMC, Carlsberg Automatic Meridian 卡尔斯伯格自动子午环Circlecannibalism 吞食cannibalized galaxy 被吞星系cannibalizing galaxy 吞食星系cannibalizing of galaxies 星系吞食carbon dwarf 碳矮星Cassegrain spectrograph 卡焦摄谱仪Cassini 〈卡西尼〉土星探测器Cat's Eye nebula ( NGC 6543 ) 猫眼星云CCD astronomy CCD 天文学CCD camera CCD 照相机CCD photometry CCD 测光CCD spectrograph CCD 摄谱仪CCD spectrum CCD 光谱celestial clock 天体钟celestial mechanician 天体力学家celestial thermal background 天空热背景辐射celestial thermal background radiation 天空热背景辐射central overlap technique 中心重迭法Centaurus arm 半人马臂Cepheid distance 造父距离CFHT, Canada-Franch-Hawaii Telecope 〈CFHT〉望远镜CGRO, Compton Gamma-Ray Observatory 〈康普顿〉γ射线天文台chaos 混沌chaotic dynamics 混沌动力学chaotic layer 混沌层chaotic region 混沌区chemically peculiar star 化学特殊星Christmas Tree cluster ( NGC 2264 ) 圣诞树星团chromosphere-corona transition zone 色球-日冕过渡层chromospheric activity 色球活动chromospherically active banary 色球活动双星chromospherically active star 色球活动星chromospheric line 色球谱线chromospheric matirial 色球物质chromospheric spectrum 色球光谱CID, charge injected device CID、电荷注入器件circular solution 圆轨解circumnuclear star-formation 核周产星circumscribed halo 外接日晕circumstellar dust disk 星周尘盘circumstellar material 星周物质circumsystem material 双星周物质classical Algol system 经典大陵双星classical quasar 经典类星体classical R Coronae Borealis star 经典北冕R 型星classical T Tauri star 经典金牛T 型星Clementine 〈克莱芒蒂娜〉环月测绘飞行器closure phase imaging 锁相成象cluster centre 团中心cluster galaxy 团星系COBE, Cosmic Background Explorer 宇宙背景探测器coded mask imaging 编码掩模成象coded mask telescope 编码掩模望远镜collapsing cloud 坍缩云cometary burst 彗暴cometary dynamics 彗星动力学cometary flare 彗耀cometary H Ⅱregion 彗状电离氢区cometary outburst 彗爆发cometary proplyd 彗状原行星盘comet shower 彗星雨common proper-motion binary 共自行双星common proper-motion pair 共自行星对compact binary galaxy 致密双重星系compact cluster 致密星团; 致密星系团compact flare 致密耀斑composite diagram method 复合图法composite spectrum binary 复谱双星computational astrophysics 计算天体物理computational celestial mechanics 计算天体力学contact copying 接触复制contraction age 收缩年龄convective envelope 对流包层cooling flow 冷却流co-orbital satellite 共轨卫星coplanar orbits 共面轨道Copernicus 〈哥白尼〉卫星coprocessor 协处理器Cordelia 天卫六core-dominated quasar ( CDQ ) 核占优类星体coronal abundance 冕区丰度coronal activity 星冕活动、日冕活动coronal dividing line 冕区分界线coronal gas 星冕气体、日冕气体coronal green line 星冕绿线、日冕绿线coronal helmet 冕盔coronal magnetic energy 冕区磁能coronal red line 星冕红线、日冕红线cosmic abundance 宇宙丰度cosmic string 宇宙弦cosmic void 宇宙巨洞COSMOS 〈COSMOS〉底片自动测量仪C-O white dwarf 碳氧白矮星Cowling approximation 柯林近似Cowling mechnism 柯林机制Crescent nebula ( NGC 6888 ) 蛾眉月星云Cressida 天卫九critical equipotential lobe 临界等位瓣cross-correlation method 交叉相关法cross-correlation technique 交叉相关法cross disperser prism 横向色散棱镜crustal dynamics 星壳动力学cryogenic camera 致冷照相机cushion distortion 枕形畸变cut-off error 截断误差Cyclops project 〈独眼神〉计划D abundance 氘丰度Dactyl 艾卫dark halo 暗晕data acquisition 数据采集decline phase 下降阶段deep-field observation 深天区观测density arm 密度臂density profile 密度轮廓dereddening 红化改正Desdemona 天卫十destabiliizing effect 去稳效应dew shield 露罩diagonal mirror 对角镜diagnostic diagram 诊断图differential reddening 较差红化diffuse density 漫射密度diffuse dwarf 弥漫矮星系diffuse X-ray 弥漫X 射线diffusion approximation 扩散近似digital optical sky survey 数字光学巡天digital sky survey 数字巡天disappearance 掩始cisconnection event 断尾事件dish 碟形天线disk globular cluster 盘族球状星团dispersion measure 频散量度dissector 析象管distance estimator 估距关系distribution parameter 分布参数disturbed galaxy 受扰星系disturbing galaxy 扰动星系Dobsonian mounting 多布森装置Dobsonian reflector 多布森反射望远镜Dobsonian telescope 多布森望远镜dominant galaxy 主星系double-mode cepheid 双模造父变星double-mode pulsator 双模脉动星double-mode RR Lyrae star 双模天琴RR 型星double-ring galaxy 双环星系DQ Herculis star 武仙DQ 型星dredge-up 上翻drift scanning 漂移扫描driving system 驱动系统dumbbell radio galaxy 哑铃状射电星系Du Pont Telescope 杜邦望远镜dust ring 尘环dwarf carbon star 碳矮星dwarf spheroidal 矮球状星系dwarf spheroidal galaxy 矮球状星系dwarf spiral 矮旋涡星系dwarf spiral galaxy 矮旋涡星系dynamical age 动力学年龄dynamical astronomy 动力天文dynamical evolution 动力学演化Eagle nebula ( M 16 ) 鹰状星云earty cluster 早型星系团early earth 早期地球early planet 早期行星early-stage star 演化早期星early stellar evolution 恒星早期演化early sun 早期太阳earth-approaching asteroid 近地小行星earth-approaching comet 近地彗星earth-approaching object 近地天体earth-crossing asteroid 越地小行星earth-crossing comet 越地彗星earth-crossing object 越地天体earth orientation parameter 地球定向参数earth rotation parameter 地球自转参数eccentric-disk model 偏心盘模型effect of relaxation 弛豫效应Egg nebula ( AFGL 2688 ) 蛋状星云electronographic photometry 电子照相测光elemental abundance 元素丰度elliptical 椭圆星系elliptical dwarf 椭圆矮星系emulated data 仿真数据emulation 仿真encounter-type orbit 交会型轨道enhanced network 增强网络equatorial rotational velocity 赤道自转速度equatorium 行星定位仪equipartition of kinetic energy 动能均分eruptive period 爆发周期Eskimo nebula ( NGC 2392 ) 爱斯基摩星云estimated accuracy 估计精度estimation theory 估计理论EUVE, Extreme Ultraviolet Explorer 〈EUVE〉极紫外探测器Exclamation Mark galaxy 惊叹号星系Exosat 〈Exosat〉欧洲X 射线天文卫星extended Kalman filter 扩充卡尔曼滤波器extragalactic jet 河外喷流extragalactic radio astronomy 河外射电天文extrasolar planet 太阳系外行星extrasolar planetary system 太阳系外行星系extraterrestrial intelligence 地外智慧生物extreme helium star 极端氦星Fabry-Perot imaging spectrograph 法布里-珀罗成象摄谱仪Fabry-Perot interferometry 法布里-珀罗干涉测量Fabry-Perot spectrograph 法布里-珀罗摄谱仪face-on galaxy 正向星系face-on spiral 正向旋涡星系facility seeing 人为视宁度fall 见落陨星fast pulsar 快转脉冲星fat zero 胖零Fermi normal coordinate system 费米标准坐标系Fermi-Walker transportation 费米-沃克移动fibre spectroscopy 光纤分光field centre 场中心field galaxy 场星系field pulsar 场脉冲星filter photography 滤光片照相观测filter wheel 滤光片转盘find 发见陨星finder chart 证认图finderscope 寻星镜first-ascent giant branch 初升巨星支first giant branch 初升巨星支flare puff 耀斑喷焰flat field 平场flat field correction 平场改正flat fielding 平场处理flat-spectrum radio quasar 平谱射电类星体flux standard 流量标准星flux-tube dynamics 磁流管动力学f-mode f 模、基本模following limb 东边缘、后随边缘foreground galaxy 前景星系foreground galaxy cluster 前景星系团formal accuracy 形式精度Foucaultgram 傅科检验图样Foucault knife-edge test 傅科刀口检验fourth cosmic velocity 第四宇宙速度frame transfer 帧转移Fresnel lens 菲涅尔透镜fuzz 展云Galactic aggregate 银河星集Galactic astronomy 银河系天文Galactic bar 银河系棒galactic bar 星系棒galactic cannibalism 星系吞食galactic content 星系成分galactic merge 星系并合galactic pericentre 近银心点Galactocentric distance 银心距galaxy cluster 星系团Galle ring 伽勒环Galilean transformation 伽利略变换Galileo 〈伽利略〉木星探测器gas-dust complex 气尘复合体Genesis rock 创世岩Gemini Telescope 大型双子望远镜Geoalert, Geophysical Alert Broadcast 地球物理警报广播giant granulation 巨米粒组织giant granule 巨米粒giant radio pulse 巨射电脉冲Ginga 〈星系〉X 射线天文卫星Giotto 〈乔托〉空间探测器glassceramic 微晶玻璃glitch activity 自转突变活动global change 全球变化global sensitivity 全局灵敏度GMC, giant molecular cloud 巨分子云g-mode g 模、重力模gold spot 金斑病GONG, Global Oscillation Network 太阳全球振荡监测网GroupGPS, global positioning system 全球定位系统Granat 〈石榴〉号天文卫星grand design spiral 宏象旋涡星系gravitational astronomy 引力天文gravitational lensing 引力透镜效应gravitational micro-lensing 微引力透镜效应great attractor 巨引源Great Dark Spot 大暗斑Great White Spot 大白斑grism 棱栅GRO, Gamma-Ray Observatory γ射线天文台guidscope 导星镜GW Virginis star 室女GW 型星habitable planet 可居住行星Hakucho 〈天鹅〉X 射线天文卫星Hale Telescope 海尔望远镜halo dwarf 晕族矮星halo globular cluster 晕族球状星团Hanle effect 汉勒效应hard X-ray source 硬X 射线源Hay spot 哈伊斑HEAO, High-Energy Astronomical 〈HEAO〉高能天文台Observatoryheavy-element star 重元素星heiligenschein 灵光Helene 土卫十二helicity 螺度heliocentric radial velocity 日心视向速度heliomagnetosphere 日球磁层helioseismology 日震学helium abundance 氦丰度helium main-sequence 氦主序helium-strong star 强氦线星helium white dwarf 氦白矮星Helix galaxy ( NGC 2685 ) 螺旋星系Herbig Ae star 赫比格Ae 型星Herbig Be star 赫比格Be 型星Herbig-Haro flow 赫比格-阿罗流Herbig-Haro shock wave 赫比格-阿罗激波hidden magnetic flux 隐磁流high-field pulsar 强磁场脉冲星highly polarized quasar ( HPQ ) 高偏振类星体high-mass X-ray binary 大质量X 射线双星high-metallicity cluster 高金属度星团;高金属度星系团high-resolution spectrograph 高分辨摄谱仪high-resolution spectroscopy 高分辨分光high - z 大红移Hinotori 〈火鸟〉太阳探测器Hipparcos, High Precision Parallax 〈依巴谷〉卫星Collecting SatelliteHipparcos and Tycho Catalogues 〈依巴谷〉和〈第谷〉星表holographic grating 全息光栅Hooker Telescope 胡克望远镜host galaxy 寄主星系hot R Coronae Borealis star 高温北冕R 型星HST, Hubble Space Telescope 哈勃空间望远镜Hubble age 哈勃年龄Hubble distance 哈勃距离Hubble parameter 哈勃参数Hubble velocity 哈勃速度hump cepheid 驼峰造父变星Hyad 毕团星hybrid-chromosphere star 混合色球星hybrid star 混合大气星hydrogen-deficient star 缺氢星hydrogenous atmosphere 氢型大气hypergiant 特超巨星Ida 艾达( 小行星243号)IEH, International Extreme Ultraviolet 〈IEH〉国际极紫外飞行器HitchhikerIERS, International Earth Rotation 国际地球自转服务Serviceimage deconvolution 图象消旋image degradation 星象劣化image dissector 析象管image distoration 星象复原image photon counting system 成象光子计数系统image sharpening 星象增锐image spread 星象扩散度imaging polarimetry 成象偏振测量imaging spectrophotometry 成象分光光度测量immersed echelle 浸渍阶梯光栅impulsive solar flare 脉冲太阳耀斑infralateral arc 外侧晕弧infrared CCD 红外CCDinfrared corona 红外冕infrared helioseismology 红外日震学infrared index 红外infrared observatory 红外天文台infrared spectroscopy 红外分光initial earth 初始地球initial mass distribution 初始质量分布initial planet 初始行星initial star 初始恒星initial sun 初始太阳inner coma 内彗发inner halo cluster 内晕族星团integrability 可积性Integral Sign galaxy ( UGC 3697 ) 积分号星系integrated diode array ( IDA ) 集成二极管阵intensified CCD 增强CCDIntercosmos 〈国际宇宙〉天文卫星interline transfer 行间转移intermediate parent body 中间母体intermediate polar 中介偏振星international atomic time 国际原子时International Celestial Reference 国际天球参考系Frame ( ICRF )intraday variation 快速变化intranetwork element 网内元intrinsic dispersion 内廪弥散度ion spot 离子斑IPCS, Image Photon Counting System 图象光子计数器IRIS, Infrared Imager / Spectrograph 红外成象器/摄谱仪IRPS, Infrared Photometer / Spectro- 红外光度计/分光计meterirregular cluster 不规则星团; 不规则星系团IRTF, NASA Infrared Telescope 〈IRTF〉美国宇航局红外Facility 望远镜IRTS, Infrared Telescope in Space 〈IRTS〉空间红外望远镜ISO, Infrared Space Observatory 〈ISO〉红外空间天文台isochrone method 等龄线法IUE, International Ultraviolet 〈IUE〉国际紫外探测器ExplorerJewel Box ( NGC 4755 ) 宝盒星团Jovian magnetosphere 木星磁层Jovian ring 木星环Jovian ringlet 木星细环Jovian seismology 木震学jovicentric orbit 木心轨道J-type star J 型星Juliet 天卫十一Jupiter-crossing asteroid 越木小行星Kalman filter 卡尔曼滤波器KAO, Kuiper Air-borne Observatory 〈柯伊伯〉机载望远镜Keck ⅠTelescope 凯克Ⅰ望远镜Keck ⅡTelescope 凯克Ⅱ望远镜Kuiper belt 柯伊伯带Kuiper-belt object 柯伊伯带天体Kuiper disk 柯伊伯盘LAMOST, Large Multi-Object Fibre 大型多天体分光望远镜Spectroscopic TelescopeLaplacian plane 拉普拉斯平面late cluster 晚型星系团LBT, Large Binocular Telescope 〈LBT〉大型双筒望远镜lead oxide vidicon 氧化铅光导摄象管Leo Triplet 狮子三重星系LEST, Large Earth-based Solar 〈LEST〉大型地基太阳望远镜Telescopelevel-Ⅰcivilization Ⅰ级文明level-Ⅱcivilization Ⅱ级文明level-Ⅲcivilization Ⅲ级文明Leverrier ring 勒威耶环Liapunov characteristic number 李雅普诺夫特征数( LCN )light crown 轻冕玻璃light echo 回光light-gathering aperture 聚光孔径light pollution 光污染light sensation 光感line image sensor 线成象敏感器line locking 线锁line-ratio method 谱线比法Liner, low ionization nuclear 低电离核区emission-line regionline spread function 线扩散函数LMT, Large Millimeter Telescope 〈LMT〉大型毫米波望远镜local galaxy 局域星系local inertial frame 局域惯性架local inertial system 局域惯性系local object 局域天体local star 局域恒星look-up table ( LUT ) 对照表low-mass X-ray binary 小质量X 射线双星low-metallicity cluster 低金属度星团;低金属度星系团low-resolution spectrograph 低分辨摄谱仪low-resolution spectroscopy 低分辨分光low - z 小红移luminosity mass 光度质量luminosity segregation 光度层化luminous blue variable 高光度蓝变星lunar atmosphere 月球大气lunar chiaroscuro 月相图Lunar Prospector 〈月球勘探者〉Ly-αforest 莱曼-α森林MACHO ( massive compact halo 晕族大质量致密天体object )Magellan 〈麦哲伦〉金星探测器Magellan Telescope 〈麦哲伦〉望远镜magnetic canopy 磁蓬magnetic cataclysmic variable 磁激变变星magnetic curve 磁变曲线magnetic obliquity 磁夹角magnetic period 磁变周期magnetic phase 磁变相位magnitude range 星等范围main asteroid belt 主小行星带main-belt asteroid 主带小行星main resonance 主共振main-sequence band 主序带Mars-crossing asteroid 越火小行星Mars Pathfinder 火星探路者mass loss rate 质量损失率mass segregation 质量层化Mayall Telescope 梅奥尔望远镜Mclntosh classification 麦金托什分类McMullan camera 麦克马伦电子照相机mean motion resonance 平均运动共振membership of cluster of galaxies 星系团成员membership of star cluster 星团成员merge 并合merger 并合星系; 并合恒星merging galaxy 并合星系merging star 并合恒星mesogranulation 中米粒组织mesogranule 中米粒metallicity 金属度metallicity gradient 金属度梯度metal-poor cluster 贫金属星团metal-rich cluster 富金属星团MGS, Mars Global Surveyor 火星环球勘测者micro-arcsec astrometry 微角秒天体测量microchannel electron multiplier 微通道电子倍增管microflare 微耀斑microgravitational lens 微引力透镜microgravitational lensing 微引力透镜效应microturbulent velocity 微湍速度millimeter-wave astronomy 毫米波天文millisecond pulsar 毫秒脉冲星minimum mass 质量下限minimum variance 最小方差mixed-polarity magnetic field 极性混合磁场MMT, Multiple-Mirror Telescope 多镜面望远镜moderate-resolution spectrograph 中分辨摄谱仪moderate-resolution spectroscopy 中分辨分光modified isochrone method 改进等龄线法molecular outflow 外向分子流molecular shock 分子激波monolithic-mirror telescope 单镜面望远镜moom 行星环卫星moon-crossing asteroid 越月小行星morphological astronomy 形态天文morphology segregation 形态层化MSSSO, Mount Stromlo and Siding 斯特朗洛山和赛丁泉天文台Spring Observatorymultichannel astrometric photometer 多通道天测光度计( MAP )multi-object spectroscopy 多天体分光multiple-arc method 复弧法multiple redshift 多重红移multiple system 多重星系multi-wavelength astronomy 多波段天文multi-wavelength astrophysics 多波段天体物理naked-eye variable star 肉眼变星naked T Tauri star 显露金牛T 型星narrow-line radio galaxy ( NLRG ) 窄线射电星系Nasmyth spectrograph 内氏焦点摄谱仪natural reference frame 自然参考架natural refenence system 自然参考系natural seeing 自然视宁度near-contact binary 接近相接双星near-earth asteroid 近地小行星near-earth asteroid belt 近地小行星带near-earth comet 近地彗星NEO, near-earth object 近地天体neon nova 氖新星Nepturian ring 海王星环neutrino astrophysics 中微子天文NNTT, National New Technology Telescope国立新技术望远镜NOAO, National Optical Astronomical 国立光学天文台Observatoriesnocturnal 夜间定时仪nodal precession 交点进动nodal regression 交点退行non-destroy readout ( NDRO ) 无破坏读出nonlinear infall mode 非线性下落模型nonlinear stability 非线性稳定性nonnucleated dwarf elliptical 无核矮椭圆星系nonnucleated dwarf galaxy 无核矮星系nonpotentiality 非势场性nonredundant masking 非过剩遮幅成象nonthermal radio halo 非热射电晕normal tail 正常彗尾North Galactic Cap 北银冠NOT, Nordic Optical Telescope 北欧光学望远镜nova rate 新星频数、新星出现率NTT, New Technology Telescope 新技术望远镜nucleated dwarf elliptical 有核矮椭圆星系nucleated dwarf galaxy 有核矮星系number density profile 数密度轮廓numbered asteroid 编号小行星oblique pulsator 斜脉动星observational cosmology 观测宇宙学observational dispersion 观测弥散度observational material 观测资料observing season 观测季occultation band 掩带O-Ne-Mg white dwarf 氧氖镁白矮星one-parameter method 单参数法on-line data handling 联机数据处理on-line filtering 联机滤波open cluster of galaxies 疏散星系团Ophelia 天卫七optical aperture-synthesis imaging 光波综合孔径成象optical arm 光学臂optical disk 光学盘optical light 可见光optical luminosity function 光学光度函数optically visible object 光学可见天体optical picture 光学图optical spectroscopy 光波分光orbital circularization 轨道圆化orbital eccentricity 轨道偏心率orbital evolution 轨道演化orbital frequency 轨道频率orbital inclination 轨道倾角orbit plane 轨道面order region 有序区organon parallacticon 星位尺Orion association 猎户星协orrery 太阳系仪orthogonal transformation 正交变换oscillation phase 振动相位outer asteroid belt 外小行星带outer-belt asteroid 外带小行星outer halo cluster 外晕族星团outside-eclipse variation 食外变光overshoot 超射OVV quasar, optically violently OVV 类星体variable quasar、optically violent variablequasaroxygen sequence 氧序pan 摇镜头parry arc 彩晕弧partial-eclipse solution 偏食解particle astrophysics 粒子天体物理path of annularity 环食带path of totality 全食带PDS, photo-digitizing system、PDS、数字图象仪、photometric data system 测光数据仪penetrative convection 贯穿对流pentaprism test 五棱镜检验percolation 渗流periapse 近质心点periapse distance 近质心距periapsis distance 近拱距perigalactic distance 近银心距perigalacticon 近银心点perimartian 近火点period gap 周期空隙period-luminosity-colour relation 周光色关系PG 1159 star PG 1159 恒星photoflo 去渍剂photographic spectroscopy 照相分光photometric accuracy 测光精度photometric error 测光误差photometric night 测光夜photometric standard star 测光标准星photospheric abundance 光球丰度photospheric activity 光球活动photospheric line 光球谱线planetary biology 行星生物学planetary geology 行星地质学Pleiad 昴团星plerion 类蟹遗迹plerionic remnant 类蟹遗迹plerionic supernova remnant 类蟹超新星遗迹plumbicon 氧化铅光导摄象管pluton 类冥行星p-mode p 模、压力模pointimg accuracy 指向精度point spread function 点扩散函数polarimetric standard star 偏振标准星polarization standard star 偏振标准星polar-ring galaxy 极环星系Portia 天卫十二post AGB star AGB 后恒星post-core-collapse cluster 核心坍缩后星团post-coronal region 冕外区post-main-sequence star 主序后星post red-supergiant 红超巨后星post starburst galaxy 星暴后星系post T Tauri star 金牛T 后星potassium-argon dating 钾氩计年precataclysmic binary 激变前双星precataclysmic variable 激变前变星preceding limb 西边缘、前导边缘precessing-disk model 进动盘模型precession globe 岁差仪precession period 进动周期preflash 预照光pre-main-sequence spectroscopic 主序前分光双星binarypre-planetary disk 前行星盘pre-white dwarf 白矮前身星primary crater 初级陨击坑primordial binary 原始双星principle of mediocrity 折衷原则progenitor 前身星; 前身天体progenitor star 前身星projected density profile 投影密度轮廓proper-motion membership 自行成员星proper reference frame 固有参考架proper reference system 固有参考系proplyd 原行星盘proto-binary 原双星proto-cluster 原星团proto-cluster of galaxies 原星系团proto-earth 原地球proto-galactic cloud 原星系云proto-galactic object 原星系天体proto-Galaxy 原银河系proto-globular cluster 原球状星团proto-Jupiter 原木星proto-planet 原行星proto-planetary disk 原行星盘proto-planetary system 原行星系proto-shell star 原气壳星proto-sun 原太阳pseudo body-fixed system 准地固坐标系Puck 天卫十五pulsar time scale 脉冲星时标pulsation axis 脉动对称轴pulsation equation 脉动方程pulsation frequency 脉动频率pulsation phase 脉动阶段pulsation pole 脉动极pulse light curve 脉冲光变曲线pyrometry 高温测量QPO, quasi-periodic oscillation 似周期振荡quantum cosmology 量子宇宙学quantum universe 量子宇宙quasar astronomy 类星体天文quiescence 宁静态radial pulsator 径向脉动星radial-velocity orbit 分光解radial-velocity reference star 视向速度参考星radial-velocity standard star 视向速度标准星radial-velocity survey 视向速度巡天radio arm 射电臂radio counterpart 射电对应体radio loud quasar 强射电类星体radio observation 射电观测radio picture 射电图radio pollution 射电污染radio supernova 射电超新星rapid burster 快暴源rapidly oscillating Ap star 快速振荡Ap 星readout 读出readout noise 读出噪声recycled pulsar 再生脉冲星reddened galaxy 红化星系reddened object 红化天体reddened quasar 红化类星体red horizontal branch ( RHB ) 红水平分支red nebulous object ( RNO ) 红色云状体Red Rectangle nebula 红矩形星云redshift survey 红移巡天red straggler 红离散星reflex motion 反映运动regression period 退行周期regular cluster 规则星团; 规则星系团relaxation effect 弛豫效应reset 清零resonance overlap theory 共振重叠理论return-beam tube 回束摄象管richness parameter 富度参数Ring nebula ( M 57、NGC 6720 ) 环状星云ring-plane crossing 环面穿越Rosalind 天卫十三ROSA T, Roentgensatellit 〈ROSAT〉天文卫星Rosette Molecular Cloud ( RMC ) 玫瑰分子云Rossby number 罗斯贝数rotating variable 自转变星rotational evolution 自转演化rotational inclination 自转轴倾角rotational modulation 自转调制rotational period 自转周期rotational phase 自转相位rotational pole 自转极rotational velocity 自转速度rotation frequency 自转频率rotation phase 自转相位rotation rate 自转速率rubber second 负闰秒rubidium-strontium dating 铷锶计年Sagittarius dwarf 人马矮星系Sagittarius dwarf galaxy 人马矮星系Sagittarius galaxy 人马星系Saha equation 沙哈方程Sakigake 〈先驱〉空间探测器Saturn-crossing asteroid 越土小行星Saturnian ringlet 土星细环Saturnshine 土星反照scroll 卷滚Sculptor group 玉夫星系群Sculptor Supercluster 玉夫超星系团Sculptor void 玉夫巨洞secondary crater 次级陨击坑secondary resonance 次共振secular evolution 长期演化secular resonance 长期共振seeing management 视宁度控管segregation 层化selenogony 月球起源学separatrice 分界sequential estimation 序贯估计sequential processing 序贯处理serendipitous X-ray source 偶遇X 射线源serendipitous γ-ray source 偶遇γ射线源Serrurier truss 赛路里桁架shell galaxy 壳星系shepherd satellite 牧羊犬卫星shock temperature 激波温度silicon target vidicon 硅靶光导摄象管single-arc method 单弧法SIRTF, Space Infrared Telescope 空间红外望远镜Facilityslitless spectroscopy 无缝分光slit spectroscopy 有缝分光slow pulsar 慢转脉冲星SMM, Solar Maximum MIssion 太阳极大使者SMT, Submillimeter Telescope 亚毫米波望远镜SOFIA, Stratospheric Observatory for 〈索菲雅〉机载红外望远镜Infrared Astronomysoft γ-ray burst repeater 软γ暴复现源soft γrepeater ( SGR ) 软γ射线复现源SOHO, Solar and Heliospheric 〈索贺〉太阳和太阳风层探测器Observatorysolar circle 太阳圈solar oscillation 太阳振荡solar pulsation 太阳脉动solar-radiation pressure 太阳辐射压solar-terrestrial environment 日地环境solitary 孤子性soliton star 孤子星South Galactic Cap 南银冠South Galactic Pole 南银极space density profile 空间密度轮廓space geodesy 空间大地测量space geodynamics 空间地球动力学Spacelab 空间实验室spatial mass segregation 空间质量分层speckle masking 斑点掩模speckle photometry 斑点测光speckle spectroscopy 斑点分光spectral comparator 比长仪spectrophotometric distance 分光光度距离spectrophotometric standard 分光光度标准星spectroscopic period 分光周期specular density 定向密度spherical dwarf 椭球矮星系spin evolution 自旋演化spin period 自旋周期spin phase 自旋相位spiral 旋涡星系spiral arm tracer 示臂天体Spoerer minimum 斯珀勒极小spotted star 富黑子恒星SST, Spectroscopic Survey Telescope 分光巡天望远镜standard radial-velocity star 视向速度标准星standard rotational-velocity star 自转速度标准星standard velocity star 视向速度标准星starburst 星暴starburst galaxy 星暴星系starburst nucleus 星暴star complex 恒星复合体star-formation activity 产星活动star-formation burst 产星暴star-formation efficiency ( SFE ) 产星效率star-formation rate 产星率star-formation region 产星区star-forming region 产星区starpatch 星斑static property 静态特性statistical orbit-determination 统计定轨理论theorysteep-spectrum radio quasar 陡谱射电类星体stellar environment 恒星环境stellar halo 恒星晕stellar jet 恒星喷流stellar speedometer 恒星视向速度仪stellar seismology 星震学Stokes polarimetry 斯托克斯偏振测量strange attractor 奇异吸引体strange star 奇异星sub-arcsec radio astronomy 亚角秒射电天文学Subaru Telescope 昴星望远镜subcluster 次团subclustering 次成团subdwarf B star B 型亚矮星subdwarf O star O 型亚矮星subgiant branch 亚巨星支submilliarcsecond optical astrometry 亚毫角秒光波天体测量submillimeter astronomy 亚毫米波天文submillimeter observatory 亚毫米波天文台submillimeter photometry 亚毫米波测光submillimeter space astronomy 亚毫米波空间天文submillimeter telescope 亚毫米波望远镜submillisecond optical pulsar 亚毫秒光学脉冲星submillisecond pulsar 亚毫秒脉冲星submillisecond radio pulsar 亚毫秒射电脉冲星substellar object 亚恒星天体subsynchronism 亚同步subsynchronous rotation 亚同步自转Sunflower galaxy ( M 63 ) 葵花星系sungrazer comet 掠日彗星supercluster 超星团; 超星系团supergalactic streamer 超星系流状结构supergiant molecular cloud ( SGMC ) 超巨分子云superhump 长驼峰superhumper 长驼峰星supermaximum 长极大supernova rate 超新星频数、超新星出现率supernova shock 超新星激波superoutburst 长爆发superwind galaxy 超级风星系supporting system 支承系统surface activity 表面活动surface-brightness profile 面亮度轮廓surface-channel CCD 表面型CCDSU Ursae Majoris star 大熊SU 型星SWAS, Submillimeter Wave Astronomy 亚毫米波天文卫星Satallitesymbiotic binary 共生双星symbiotic Mira 共生刍藁symbiotic nova 共生新星synthetic-aperture radar 综合孔径雷达systemic velocity 质心速度TAMS, terminal-age main sequence 终龄主序Taurus molecular cloud ( TMC ) 金牛分子云TDT, terrestrial dynamical time 地球力学时television guider 电视导星器television-type detector 电视型探测器Tenma 〈天马〉X 射线天文卫星terrestrial reference system 地球参考系tetrad 四元基thermal background 热背景辐射thermal background radiation 热背景辐射thermal pulse 热脉冲thermonuclear runaway 热核暴涨thick-disk population 厚盘族thinned CCD 薄型CCDthird light 第三光源time-signal station 时号台timing age 计时年龄tomograph 三维结构图toner 调色剂torquetum 赤基黄道仪TRACE, Transition Region and Coronal 〈TRACE〉太阳过渡区和日冕Explorer 探测器tracker 跟踪器transfer efficiency 转移效率transition region line 过渡区谱线trans-Nepturnian object 海外天体Trapezium cluster 猎户四边形星团triad 三元基tri-dimensional spectroscopy 三维分光triquetum 三角仪tuning-fork diagram 音叉图。
天文词汇Ggalactic cannibalism 星系相食宇宙中，大型星系并吞小型星系的现象。
galactic corona 银冕银晕外面物质密度更低的区域，延伸的距离可能是星系可见直径的数倍。
galaxy seeds 星系种子初期宇宙中，小型的重力引力中心。
这些星系种子进一步吸引更多物质，形成星系群、丝状结构和长城结构。
Galilean satellites 伽利略卫星木星的四颗卫星，因为是伽利略在十七世纪发现，因而得名。
gas tail (type I ) 气尾、气体尾受太阳风的吹袭，而落在彗星后方的游离化气体喷陷，颜色偏蓝。
参见尘尾 (dust tail) 。
Gauss (G) 高斯量测磁场强度的单位，一高斯是一特斯拉的一万分之一。
geocentric universe 地心宇宙模型认为地球是宇宙中心的宇宙模型，例如：托勒密宇宙模型。
geosynchronous orbit 地球同步轨道一种绕行地球的卫星轨道，周期为24小时而且是由西向东运行，卫星永远驻留在地球表面同一点的上方。
giant molecular clouds 巨大分子云星际空间，低温、巨大且致密的分子云，新恒星的诞生处。
giant stars 巨星恒星演化离开主序带后，体积膨胀、表面温度降低、变得非常明亮，因为这类恒星大约是太阳的10至100倍，所以被称为巨星。
巨星位在赫罗图的右上角。
glacial period 冰河期冰棚覆盖大范围地球表面的时期。
glitch 频率突变波霎 (旋转中子星) 的自转周期，突然发生改变的现象。
globular cluster 球状星团外观上，恒星的分布是球形的星团。
球状星团通常含有五万到一百万颗恒星，星团大小约有75光年，通常出现在星系的球状部份。
球状星团内的恒星，金属的含量低，年龄大。
graben rille 条状纹脉行星表面，因为断层运动或表壳陷落，所形成的直线形纹脉。
grand unified theories (GUTs) 大统一理论把电磁力、弱作用力和强作用力，纳入同一种理论架构的理论。
天文学专业词汇CAMC, Carlsberg Automatic Meridian 卡尔斯伯格自动子午环Circlecannibalism 吞食cannibalized galaxy 被吞星系cannibalizing galaxy 吞食星系cannibalizing of galaxies 星系吞食carbon dwarf 碳矮星Cassegrain spectrograph 卡焦摄谱仪Cassini 〈卡西尼〉土星探测器Cat's Eye nebula （ NGC 6543 ）猫眼星云CCD astronomy CCD 天文学CCD camera CCD 照相机CCD photometry CCD 测光CCD spectrograph CCD 摄谱仪CCD spectrum CCD 光谱celestial clock 天体钟celestial mechanician 天体力学家celestial thermal background 天空热背景辐射celestial thermal background radiation 天空热背景辐射central overlap technique 中心重迭法Centaurus arm 半人马臂Cepheid distance 造父距离CFHT, Canada-Franch-Hawaii Telecope 〈CFHT〉望远镜CGRO, Compton Gamma-Ray Observatory 〈康普顿〉γ射线天文台chaos 混沌chaotic dynamics 混沌动力学chaotic layer 混沌层chaotic region 混沌区chemically peculiar star 化学特殊星Christmas Tree cluster （ NGC 2264 ）圣诞树星团chromosphere-corona transition zone 色球-日冕过渡层chromospheric activity 色球活动chromospherically active banary 色球活动双星chromospherically active star 色球活动星chromospheric line 色球谱线chromospheric matirial 色球物质chromospheric spectrum 色球光谱CID, charge injected device CID、电荷注入器件circular solution 圆轨解circumnuclear star-formation 核周产星circumscribed halo 外接日晕circumstellar dust disk 星周尘盘circumstellar material 星周物质circumsystem material 双星周物质classical Algol system 经典大陵双星classical quasar 经典类星体classical R Coronae Borealis star 经典北冕 R 型星classical T Tauri star 经典金牛 T 型星Clementine 〈克莱芒蒂娜〉环月测绘飞行器closure phase imaging 锁相成象cluster centre 团中心cluster galaxy 团星系COBE, Cosmic Background Explorer 宇宙背景探测器coded mask imaging 编码掩模成象coded mask telescope 编码掩模望远镜collapsing cloud 坍缩云cometary burst 彗暴cometary dynamics 彗星动力学cometary flare 彗耀cometary H Ⅱ region 彗状电离氢区cometary outburst 彗爆发cometary proplyd 彗状原行星盘comet shower 彗星雨common proper-motion binary 共自行双星common proper-motion pair 共自行星对compact binary galaxy 致密双重星系天文学专业词汇compact cluster 致密星团; 致密星系团compact flare 致密耀斑composite diagram method 复合图法composite spectrum binary 复谱双星computational astrophysics 计算天体物理computational celestial mechanics 计算天体力学contact copying 接触复制contraction age 收缩年龄convective envelope 对流包层cooling flow 冷却流co-orbital satellite 共轨卫星coplanar orbits 共面轨道Copernicus 〈哥白尼〉卫星coprocessor 协处理器Cordelia 天卫六core-dominated quasar （ CDQ ）核占优类星体coronal abundance 冕区丰度coronal activity 星冕活动、日冕活动coronal dividing line 冕区分界线coronal gas 星冕气体、日冕气体coronal green line 星冕绿线、日冕绿线coronal helmet 冕盔coronal magnetic energy 冕区磁能coronal red line 星冕红线、日冕红线cosmic abundance 宇宙丰度cosmic string 宇宙弦cosmic void 宇宙巨洞COSMOS 〈COSMOS〉底片自动测量仪C-O white dwarf 碳氧白矮星Cowling approximation 柯林近似Cowling mechnism 柯林机制Crescent nebula （ NGC 6888 ）蛾眉月星云Cressida 天卫九critical equipotential lobe 临界等位瓣cross-correlation method 交叉相关法cross-correlation technique 交叉相关法cross disperser prism 横向色散棱镜crustal dynamics 星壳动力学cryogenic camera 致冷照相机cushion distortion 枕形畸变cut-off error 截断误差Cyclops project 〈独眼神〉计划D abundance 氘丰度Dactyl 艾卫dark halo 暗晕data acquisition 数据采集decline phase 下降阶段deep-field observation 深天区观测density arm 密度臂density profile 密度轮廓dereddening 红化改正Desdemona 天卫十destabiliizing effect 去稳效应dew shield 露罩diagonal mirror 对角镜diagnostic diagram 诊断图differential reddening 较差红化diffuse density 漫射密度diffuse dwarf 弥漫矮星系diffuse X-ray 弥漫 X 射线diffusion approximation 扩散近似digital optical sky survey 数字光学巡天digital sky survey 数字巡天disappearance 掩始cisconnection event 断尾事件dish 碟形天线disk globular cluster 盘族球状星团dispersion measure 频散量度dissector 析象管distance estimator 估距关系distribution parameter 分布参数disturbed galaxy 受扰星系disturbing galaxy 扰动星系Dobsonian mounting 多布森装置Dobsonian reflector 多布森反射望远镜Dobsonian telescope 多布森望远镜dominant galaxy 主星系double-mode cepheid 双模造父变星double-mode pulsator 双模脉动星double-mode RR Lyrae star 双模天琴 RR 型星double-ring galaxy 双环星系DQ Herculis star 武仙 DQ 型星dredge-up 上翻drift scanning 漂移扫描driving system 驱动系统dumbbell radio galaxy 哑铃状射电星系Du Pont Telescope 杜邦望远镜dust ring 尘环dwarf carbon star 碳矮星dwarf spheroidal 矮球状星系dwarf spheroidal galaxy 矮球状星系dwarf spiral 矮旋涡星系dwarf spiral galaxy 矮旋涡星系dynamical age 动力学年龄dynamical astronomy 动力天文dynamical evolution 动力学演化。
天文学常用术语英汉对译及解释LaRive nbsp天文学常用术语英汉对译及解释0000术语解释aberration光行差由于地球的运动所导致的天体的视位置与真实位置之间的差异。
absolute magnitude绝对星等恒星的真正亮度。
定义为恒星在距离我们 10 秒差距 (32.6光年) 时的视星等。
absolute zero绝对零度理论上的最低温度，等于0开尔文(-459.67° F or -273.15° C)。
absorption lines吸收线光谱里的暗线。
来自天体的光，被原子或分子选择性的吸收，导致那部分的光从星光中被消去，留下一条条的暗线。
accretion disk吸积盘指白矮星、中子星或黑洞等致密天体周围，由于物质受到引力作用向中心天体落下所形成的盘状结构。
achromatic lens消色差透镜由两种不同材质的透镜组合而成，消色差透镜的用途是把两种不同颜色的光聚焦到同一点，或称为修正色像差。
active galactic nuclei活动星系核某些星系中的特别明亮的核，被认为是由于物质落向质量极大的黑洞而引起的。
adaptive optics自适应光学计算机控制的望远镜镜面，能做区域性变形，以补偿大气扰动所产生的散焦效应。
albedo反照率行星或卫星反射光能力的标示值，定义为所反射的光和入射光的比值。
反照率的值介于 0 (完美的黑体) 到 1 (完全反射)之间。
月球的反照率为 0.07，而金星为 0.6。
altazimuth mount地平装置一种望远镜支撑方式，使镜筒能在平行和垂直水平的方向自由移动。
altitude地平纬度、高度 1.在海平面以上的高度2..天体在天球上距离地平线的角度 anaglyph立体照片用两台相机拍摄出的一种照片。
将右边拍摄的影像（通常是红色）和左边拍摄的影像（通常是蓝色）叠加起来，通过特殊的色彩滤镜，就能看到三维的效果。
剑桥商务英语听说星系The Milky Way GalaxyThe Milky Way is the galaxy that contains our Solar System, with the Earth and Sun. This galaxy is a vast, spinning collection of stars, planets, dust and gas, held together by gravity. It is just one of hundreds of billions of galaxies in the observable universe.The Milky Way galaxy is estimated to contain 100-400 billion stars and have a diameter between 100,000 and 180,000 light-years. It is the second-largest galaxy in the Local Group, with the Andromeda Galaxy being larger. As with other spiral galaxies, the Milky Way has a central bulge surrounded by a rotating disk of gas, dust and stars. This disk is approximately 13 billion years old and contains population I and population II stars.The solar system is located about 25,000 to 28,000 light-years from the galactic center, on the inner edge of one of the spiral-shaped concentrations of gas and dust called the Orion Arm. The stars in the Milky Way appear to form several distinct components including the bulge, the disk, and the halo. These components are made of different types of stars, and differ in their ages and their chemicalabundances.The Milky Way galaxy is part of the Local Group, a group of more than 50 galaxies, including the Andromeda Galaxy and several dwarf galaxies. The Local Group in turn is part of the Virgo Supercluster, a giant structure of thousands of galaxies. The Milky Way and Andromeda Galaxy are moving towards each other and are expected to collide in about 4.5 billion years, although the likelihood of any actual collisions between the stars themselves is negligible.The Milky Way has several major arms that spiral from the galactic bulge, as well as minor spurs. The best known are the Perseus Arm and the Sagittarius Arm. The Sun and its solar system are located between two of these spiral arms, known as the Local Bubble. There are believed to be four major spiral arms, as well as several smaller segments of spiral arms.The nature of the Milky Way's bar and spiral structure is still a matter of active research, with the latest research contradicting the previous theories. The Milky Way may have a prominent central bar structure, and its shape may be best described as a barred spiral galaxy. The disk of the Milky Way has a diameter of about 100,000 light-years. The galactic halo is a spherical component of the galaxy that extends outward from the galactic disk, as far as 200,000 light-years from the galactic center.The disk of the Milky Way Galaxy is marked by the presence of a supermassive black hole known as Sagittarius A*, which is located at the very center of the Galaxy. This black hole has a mass four million times greater than the mass of the Sun. The Milky Way's bar is thought to be about 27,000 light-years long and may be made up of older red stars.The Milky Way is moving with respect to the cosmic microwave background radiation in the direction of the constellation Hydra with a speed of 552 ± 6 km/s. The Milky Way is a spiral galaxy that has undergone major mergers with several smaller galaxies in its distant past. This is evidenced by studies of the stellar halo, which contains globular clusters and streams of stars that were torn from those smaller galaxies.The Milky Way is estimated to contain 100–400 billion stars. Most stars are within the disk and bulge, while the galactic halo is sparsely populated with stars and globular clusters. A 2016 study by the Sloan Digital Sky Survey suggested that the number is likely to be close to the lower end of that estimate, at 100–140 billion stars.The Milky Way has several components: a disk, in which the Sun and its planetary system are located; a central bulge; and a halo of stars, globular clusters, and diffuse gas. The disk is the brightest part of theMilky Way, as seen from Earth. It has a spiral structure with dusty arms. The disk is about 100,000 light-years in diameter and about 13 billion years old. It contains the young and relatively bright population I stars, as well as intermediate-age and old stars of population II.The galactic bulge is a tightly packed group of mostly old stars in the center of the Milky Way. It is estimated to contain tens of billions of stars and has a diameter of about 10,000 light-years. The Milky Way's central bulge is shaped like a box or peanut. The galactic center, which lies within this bulge, is an extremely active region, with intense radio source known as Sagittarius A*, which is likely to be a supermassive black hole.The Milky Way's halo is a spherical component of the galaxy that extends outward from the galactic disk, as far as 200,000 light-years from the galactic center. It is relatively sparse, with only about one star per cubic parsec on average. The halo contains old population II stars, as well as extremely old globular clusters.The Milky Way's spiral structure is uncertain, and there is currently no consensus on the nature of the Milky Way's spiral arms. Different studies have led to different results, and it is unclear whether the Milky Way has two, four, or more spiral arms. The Milky Way's spiral structure is thought to be a major feature of its disk, and it may berelated to the generation of interstellar matter and star formation.The Milky Way's spiral arms are regions of the disk in which the density of stars, interstellar gas, and dust is slightly higher than average. The arms are thought to be density waves that spiral around the galactic center. As material enters an arm, the increased density causes the material to accumulate, thus causing star formation. As the material leaves the arm, star formation decreases.The Milky Way's spiral arms were first identified in the 1950s, when radio astronomers mapped the distribution of gas in the Milky Way and found that it was concentrated in spiral patterns. Since then, astronomers have used a variety of techniques to study the Milky Way's spiral structure, including observations of the distribution of young stars, star-forming regions, and interstellar gas and dust.One of the key challenges in studying the Milky Way's spiral structure is that we are located within the disk of the galaxy, which makes it difficult to get a clear view of the overall structure. Astronomers have had to rely on indirect methods, such as measuring the distances and motions of stars and gas clouds, to infer the shape and structure of the galaxy.Despite these challenges, our understanding of the Milky Way's spiral structure has advanced significantly in recent years, thanks tonew observations and more sophisticated modeling techniques. Ongoing research is continuing to shed light on the nature and evolution of the Milky Way's spiral arms, and the role they play in the overall structure and dynamics of the galaxy.。
高一年级英语天文知识单选题40题1. Which planet is known as the "Red Planet" because of its reddish appearance?A. EarthB. MarsC. JupiterD. Venus答案：B。
解析：在太阳系中，火星（Mars）因为其表面呈现出红色的外观而被称为“Red Planet（ 红色星球）”。
地球（Earth）是我们居住的蓝色星球；木星（Jupiter）是一个巨大的气态行星，外观不是红色；金星 Venus）表面被浓厚的大气层覆盖，不是以红色外观著称。
2. Which planet has the most moons in the solar system?A. EarthB. MarsC. JupiterD. Mercury答案：C。
解析：木星（Jupiter）是太阳系中拥有最多卫星（moons）的行星。
地球（Earth）只有一颗卫星；火星（Mars）有两颗卫星；水星 Mercury）没有卫星。
3. The planet with the shortest orbit around the Sun is _.A. MercuryB. VenusC. EarthD. Mars答案：A。
解析：水星（Mercury）是距离太阳最近的行星，它的公转轨道是最短的。
金星 Venus）、地球 Earth）、火星 Mars）距离太阳比水星远，它们的公转轨道都比水星长。
4. Which planet has a thick atmosphere mainly composed of carbon dioxide?A. EarthB. MarsC. VenusD. Jupiter答案：C。
解析：金星（Venus）有一层非常厚的大气层，其主要成分是二氧化碳 carbon dioxide）。
地球 Earth）的大气层主要由氮气和氧气等组成；火星（Mars）大气层很稀薄，主要成分虽然有二氧化碳但比例和金星不同；木星（Jupiter）的大气层主要由氢和氦等组成。
Galactic aggregate 银河星集Galactic astronomy 银河系天文Galactic bar 银河系棒galactic bar 星系棒galactic cannibalism 星系吞食galactic content 星系成分galactic merge 星系并合galactic pericentre 近银心点Galactocentric distance 银心距galaxy cluster 星系团Galle ring 伽勒环Galilean transformation 伽利略变换Galileo 〈伽利略〉木星探测器gas-dust complex 气尘复合体Genesis rock 创世岩Gemini Telescope 大型双子望远镜Geoalert, Geophysical Alert Broadcast 地球物理警报广播giant granulation 巨米粒组织giant granule 巨米粒giant radio pulse 巨射电脉冲Ginga 〈星系〉X 射线天文卫星Giotto 〈乔托〉空间探测器glassceramic 微晶玻璃glitch activity 自转突变活动global change 全球变化global sensitivity 全局灵敏度GMC, giant molecular cloud 巨分子云g-mode g 模、重力模gold spot 金斑病GONG, Global Oscillation Network 太阳全球振荡监测网GroupGPS, global positioning system 全球定位系统Granat 〈石榴〉号天文卫星grand design spiral 宏象旋涡星系gravitational astronomy 引力天文gravitational lensing 引力透镜效应gravitational micro-lensing 微引力透镜效应great attractor 巨引源Great Dark Spot 大暗斑Great White Spot 大白斑grism 棱栅GRO, Gamma-Ray Observatory γ射线天文台guidscope 导星镜GW Virginis star 室女GW 型星habitable planet 可居住行星Hakucho 〈天鹅〉X 射线天文卫星Hale Telescope 海尔望远镜halo dwarf 晕族矮星halo globular cluster 晕族球状星团Hanle effect 汉勒效应hard X-ray source 硬X 射线源Hay spot 哈伊斑HEAO, High-Energy Astronomical 〈HEAO〉高能天文台Observatoryheavy-element star 重元素星heiligenschein 灵光Helene 土卫十二helicity 螺度heliocentric radial velocity 日心视向速度heliomagnetosphere 日球磁层helioseismology 日震学helium abundance 氦丰度helium main-sequence 氦主序helium-strong star 强氦线星helium white dwarf 氦白矮星Helix galaxy （NGC 2685 ）螺旋星系Herbig Ae star 赫比格Ae 型星Herbig Be star 赫比格Be 型星Herbig-Haro flow 赫比格-阿罗流Herbig-Haro shock wave 赫比格-阿罗激波hidden magnetic flux 隐磁流high-field pulsar 强磁场脉冲星highly polarized quasar （HPQ ）高偏振类星体high-mass X-ray binary 大质量X 射线双星high-metallicity cluster 高金属度星团;高金属度星系团high-resolution spectrograph 高分辨摄谱仪high-resolution spectroscopy 高分辨分光high - z 大红移Hinotori 〈火鸟〉太阳探测器Hipparcos, High Precision Parallax 〈依巴谷〉卫星Collecting SatelliteHipparcos and Tycho Catalogues 〈依巴谷〉和〈第谷〉星表holographic grating 全息光栅Hooker Telescope 胡克望远镜host galaxy 寄主星系hot R Coronae Borealis star 高温北冕R 型星HST, Hubble Space Telescope 哈勃空间望远镜Hubble age 哈勃年龄Hubble distance 哈勃距离Hubble parameter 哈勃参数Hubble velocity 哈勃速度hump cepheid 驼峰造父变星Hyad 毕团星hybrid-chromosphere star 混合色球星hybrid star 混合大气星hydrogen-deficient star 缺氢星hydrogenous atmosphere 氢型大气hypergiant 特超巨星Ida 艾达（小行星243号）IEH, International Extreme Ultraviolet 〈IEH〉国际极紫外飞行器HitchhikerIERS, International Earth Rotation 国际地球自转服务Serviceimage deconvolution 图象消旋image degradation 星象劣化image dissector 析象管image distoration 星象复原image photon counting system 成象光子计数系统image sharpening 星象增锐image spread 星象扩散度imaging polarimetry 成象偏振测量imaging spectrophotometry 成象分光光度测量immersed echelle 浸渍阶梯光栅impulsive solar flare 脉冲太阳耀斑infralateral arc 外侧晕弧infrared CCD 红外CCDinfrared corona 红外冕infrared helioseismology 红外日震学infrared index 红外infrared observatory 红外天文台infrared spectroscopy 红外分光initial earth 初始地球initial mass distribution 初始质量分布initial planet 初始行星initial star 初始恒星initial sun 初始太阳inner coma 内彗发inner halo cluster 内晕族星团integrability 可积性Integral Sign galaxy （UGC 3697 ）积分号星系integrated diode array （IDA ）集成二极管阵intensified CCD 增强CCDIntercosmos 〈国际宇宙〉天文卫星interline transfer 行间转移intermediate parent body 中间母体intermediate polar 中介偏振星international atomic time 国际原子时International Celestial Reference 国际天球参考系Frame （ICRF ）intraday variation 快速变化intranetwork element 网内元intrinsic dispersion 内廪弥散度ion spot 离子斑IPCS, Image Photon Counting System 图象光子计数器IRIS, Infrared Imager / Spectrograph 红外成象器/摄谱仪IRPS, Infrared Photometer / Spectro- 红外光度计/分光计meterirregular cluster 不规则星团; 不规则星系团IRTF, NASA Infrared Telescope 〈IRTF〉美国宇航局红外Facility 望远镜IRTS, Infrared Telescope in Space 〈IRTS〉空间红外望远镜ISO, Infrared Space Observatory 〈ISO〉红外空间天文台isochrone method 等龄线法IUE, International Ultraviolet 〈IUE〉国际紫外探测器ExplorerJewel Box （NGC 4755 ）宝盒星团Jovian magnetosphere 木星磁层Jovian ring 木星环Jovian ringlet 木星细环Jovian seismology 木震学jovicentric orbit 木心轨道J-type star J 型星Juliet 天卫十一Jupiter-crossing asteroid 越木小行星Kalman filter 卡尔曼滤波器KAO, Kuiper Air-borne Observatory 〈柯伊伯〉机载望远镜Keck ⅠTelescope 凯克Ⅰ望远镜Keck ⅡTelescope 凯克Ⅱ望远镜Kuiper belt 柯伊伯带Kuiper-belt object 柯伊伯带天体Kuiper disk 柯伊伯盘LAMOST, Large Multi-Object Fibre 大型多天体分光望远镜Spectroscopic TelescopeLaplacian plane 拉普拉斯平面late cluster 晚型星系团LBT, Large Binocular Telescope 〈LBT〉大型双筒望远镜lead oxide vidicon 氧化铅光导摄象管Leo Triplet 狮子三重星系LEST, Large Earth-based Solar 〈LEST〉大型地基太阳望远镜Telescopelevel-Ⅰcivilization Ⅰ级文明level-Ⅱcivilization Ⅱ级文明level-Ⅲcivilization Ⅲ级文明Leverrier ring 勒威耶环Liapunov characteristic number 李雅普诺夫特征数（LCN ）light crown 轻冕玻璃light echo 回光light-gathering aperture 聚光孔径light pollution 光污染light sensation 光感line image sensor 线成象敏感器line locking 线锁line-ratio method 谱线比法Liner, low ionization nuclear 低电离核区emission-line regionline spread function 线扩散函数LMT, Large Millimeter Telescope 〈LMT〉大型毫米波望远镜local galaxy 局域星系local inertial frame 局域惯性架local inertial system 局域惯性系local object 局域天体local star 局域恒星look-up table （LUT ）对照表low-mass X-ray binary 小质量X 射线双星low-metallicity cluster 低金属度星团;低金属度星系团low-resolution spectrograph 低分辨摄谱仪low-resolution spectroscopy 低分辨分光low - z 小红移luminosity mass 光度质量luminosity segregation 光度层化luminous blue variable 高光度蓝变星lunar atmosphere 月球大气lunar chiaroscuro 月相图Lunar Prospector 〈月球勘探者〉Ly-α forest 莱曼-α 森林MACHO （massive compact halo 晕族大质量致密天体object ）Magellan 〈麦哲伦〉金星探测器Magellan Telescope 〈麦哲伦〉望远镜magnetic canopy 磁蓬magnetic cataclysmic variable 磁激变变星magnetic curve 磁变曲线magnetic obliquity 磁夹角magnetic period 磁变周期magnetic phase 磁变相位magnitude range 星等范围main asteroid belt 主小行星带main-belt asteroid 主带小行星main resonance 主共振main-sequence band 主序带Mars-crossing asteroid 越火小行星Mars Pathfinder 火星探路者mass loss rate 质量损失率mass segregation 质量层化Mayall Telescope 梅奥尔望远镜Mclntosh classification 麦金托什分类McMullan camera 麦克马伦电子照相机mean motion resonance 平均运动共振membership of cluster of galaxies 星系团成员membership of star cluster 星团成员merge 并合merger 并合星系; 并合恒星merging galaxy 并合星系merging star 并合恒星mesogranulation 中米粒组织mesogranule 中米粒metallicity 金属度metallicity gradient 金属度梯度metal-poor cluster 贫金属星团metal-rich cluster 富金属星团MGS, Mars Global Surveyor 火星环球勘测者micro-arcsec astrometry 微角秒天体测量microchannel electron multiplier 微通道电子倍增管microflare 微耀斑microgravitational lens 微引力透镜microgravitational lensing 微引力透镜效应microturbulent velocity 微湍速度millimeter-wave astronomy 毫米波天文millisecond pulsar 毫秒脉冲星minimum mass 质量下限minimum variance 最小方差mixed-polarity magnetic field 极性混合磁场MMT, Multiple-Mirror Telescope 多镜面望远镜moderate-resolution spectrograph 中分辨摄谱仪moderate-resolution spectroscopy 中分辨分光modified isochrone method 改进等龄线法molecular outflow 外向分子流molecular shock 分子激波monolithic-mirror telescope 单镜面望远镜moom 行星环卫星moon-crossing asteroid 越月小行星morphological astronomy 形态天文morphology segregation 形态层化MSSSO, Mount Stromlo and Siding 斯特朗洛山和赛丁泉天文台Spring Observatorymultichannel astrometric photometer 多通道天测光度计（MAP ）multi-object spectroscopy 多天体分光multiple-arc method 复弧法multiple redshift 多重红移multiple system 多重星系multi-wavelength astronomy 多波段天文multi-wavelength astrophysics 多波段天体物。
a rXiv:as tr o-ph/46564v124J un24Globular Cluster and Galaxy Formation:M31,the Milky Way and Implications for Globular Cluster Systems of Spiral Galaxies David Burstein 1,Yong Li 1,Kenneth C.Freeman 2,John E.Norris 2,Michael S.Bessell 2,Joss Bland-Hawthorn 3,Brad K.Gibson 4,Michael A.Beasley 4,Hyun-chul Lee 4,Beatriz Barbuy 5,John P.Huchra 6,Jean P.Brodie 7,Duncan A.Forbes 4ABSTRACT We find that the globular cluster systems of the Milky Way and of our neigh-boring spiral galaxy,M31,comprise two distinct entities,differing in three re-spects.First,M31has a set of young globular clusters (GCs),ranging in age from a few 100Myr to 5Gyr old,as well as old globular clusters.No such very young GCs are known in the Milky Way.Second,we confirm that the oldest M31GCs have much higher nitrogen abundances than do Galactic GCs at equivalent metallicities.Third,Morrison et al.have shown that M31has a subcomponent of GCs that follow closely the disk rotation curve of that galaxy.Such a GC sys-tem in our own Galaxy has yet to be found.The only plausible scenario for the existence of the young M31GC comes from the hierarchical-clustering-merging (HCM)paradigm for galaxy formation.We infer that M31has absorbed more of its contingent of dwarf systems in the recent past than has the Milky Way.This inference has three implications:First,that all spiral galaxies could differ in their globular cluster properties,depending on how many companions each galaxy has,and when the parent galaxy absorbs them.In this spectrum of pos-sibilities,apparently the Milky Way ties down one end,in which almost all of its GCs were absorbed 10-12Gyr ago.Second,it suggests that young globularclusters are preferentially formed in the dwarf companions of parent galaxies,andthen absorbed by the parent galaxy during mergers.Third,the young GCs seenin tidally interacting galaxies might come from the dwarf companions of thesegalaxies,rather than be made a-new in the tidal interaction.Yet,there is noready explanation for the marked difference in nitrogen abundance for the starsin the old M31GCs relative to those in the oldest Galactic GCs,especially themost metal-poor GCs in both galaxies.The predictions made by Li&Bursteinregarding the origin of nitrogen abundance in globular clusters are consistentwith what is found for the old M31GCs compared to that for the two5Gyr-oldM31GCs.1Subject headings:globular clusters,formation;galaxies,formation1.IntroductionThe most studied globular system in ourfield of study are the globular clusters(GCs) in our own Galaxy.These clusters have been studied in numerous ways,including:detailed modeling of their color-magnitude diagrams(e.g.,Bergbusch&Vandenberg2001,and ref-erences therein)and spectra obtained of their giant stars,horizontal branch stars and their main sequence stars(e.g.,Kraft&Ivans2003;Castilho et al.2000;Carretta et al.2004;Behr 2003).Yet,it was not until Li&Burstein(2003)that it was discovered that in integrated light,the most metal-poor Galactic GCs show relatively strong molecular absorption systems for NH at3360˚A.Given all that we know about Galactic GCs,it was reasonable to assume that the GC systems around other spiral galaxies similar to ours would also be similar to ours:gener-ally old GCs having similar ages and metallicities among their constituent stars.However, recently several groups who have studied the M31globular cluster system have uncovered significant differences between that system and that of our own Galaxy.Morrison et al.(2004)have shown that one can use accurate radial velocities for M31 GCs to divide them into disk and bulge categories,with the disk GCs having radial velocities that closely follow the disk rotation curve of M31.Beasley,et al.(2004)and Barmby et al. (2000)show that M31has globular clusters that show A-type spectra,from which one infers that these GCs are very young.Two of us(YL and DB)have recently shown that four ofthe most luminous M31GCs have far stronger NH features in them than do Galactic GCs measured at otherwise similar,other metal-line indices,such as CH or Mg2(Li&Burstein 2003).In a follow-up to the Li&Burstein paper,our group has obtained spectra down to3250˚A of22new M31globular clusters spanning a wider range in absolute magnitude than the HST sample used by Ponder et al.(1998).These are combined with6young M31globular clusters observed by Barmby et al.(2000)to present a more coherent picture of the M31GC system. Section2of the present paper details the new MMT observations.Section3presents the spectra,together with spectra for the Galactic GCs we presented in Li&Burstein(2003). These spectra convincingly show that M31contains GCs with a range of age from as young as∼100Myr to5Gyr-old,to as old as the oldest Galactic GCs.They also clearly show the differences in nitrogen abundance between the old M31GCs and the old Galactic GCs. Section4discusses the various implications of the differences found between the M31and Milky Way GC systems for galaxy formation and the existence of young globular clusters in spiral galaxies and tidally-interacting galaxies.Section5contains our summary.2.The MMT ObservationsLi&Burstein were assigned two nights with the6.5m MMT on26/27Sep03and27/28Sep03 to use the Blue Channel spectrograph to obtain spectra that reach to the blue atmospheric limit of a selection of M31GCs.The GCs chosen for this study were taken from two sources: First,it was desirous to re-observe many of the M31GCs observed by Burstein,et al.(1984) in order to insure we were on the same absorption-line system as defined by the Lick Obser-vatory data.Many of these are also among the brightest M31GCs.For all but one of these Lick Observatory-observed M31GCs,Morrison et al.have defined whether or not these systems follow closely the rotation curve of M31or not.Second,our remaining GC sample are taken randomly from among the GCs that have the“residual”parameter defined by Morrison et al.It is this“residual”parameter that Morrison et e to measure how close or how far the radial velocity of a GC in M31is to the rotation curve of that galaxy.However,one can only be sure if a GC is a bulge GC, as there are no disk GCs with a residual parameter greater than2.2(e.g.,as can be seen in Fig.6of Morrison et al.2004).Hence,while one can choose GCs that are clearly bulge GCs,choosing disk GCs is more problematical.Given the distribution of residuals for disk GCs in Fig.6of Morrison et al.,we chose those M31GCs with residual parameters close to zero to maximize our chances of picking up true disk GCs in M31.We employed the300l blue grating with the Blue Channel of the MMT spectrograph blazed at4800˚A with a2′′×180′′long slit.(The2′′width to cover most of the area of these spatially-resolved GCs,the length to provide the background for many of these GCs, most of which was due to M31itself.).This combination yielded a spectral resolution close to13˚A.A grating angle of1.12◦was sufficient to get us to3200˚A in the blue,but still gives us out to6000˚A in the red,redward of which we run into2nd-order confusion with the spectra.Standard star observations of BD+332642,G138-31,BD+284211,G191-B2B and Feige110are interspersed with the program objects,to provide calibrations for spectral energy distributions for these GCs.Table1gives a log of our observations,including:the globular clusters observed,giving their Battistini et al.(B)and Sargent et al.(S)numbers, as well as their Vetesnik numbers(when available)Battistini,et al.(1980);Sargent,et al. (1977);Vetesnik1962(a,b));if there are HST(H)or Burstein et al.(L)observations of these clusters;the exposure times used for their spectra;their apparent magnitudes(not corrected for Galactic extinction);and their Morrison et al.residual parameters.We adopt a value for V mag Galactic extinction for these M31GCs from Burstein,et al.(1984)of A V=0.25 mag.3.The SpectraAs seen in Table1and stated above,11of the M31GCs in our sample were nominally observed by Burstein,et al.(1984).However,as we will see when we compare line strengths to the Lick Observatory M31GC sample,there is a question about the identity of one of the Lick Observatory M31GCs.Figures1-4contain the spectra we obtained for these22 M31GCs.Both their apparent V mag and their Morrison et al.residual parameter is given for each GC in Figs.1-4(when available).Figure5gives the spectra that we published in Li&Burstein(2003)for eight Galactic globular clusters for comparison.Figure6gives the Keck spectra from Barmby et al.(2000)for six of the globular clusters that they indicated in their table as being“young?”.Only two of the Barmby et al.GCs shown in Figure6 have Morrison et al.residual parameters,and both of these are consistent with these being disk GCs.The Keck spectra have been“Hanning-smoothed”(i.e,a running average offlux of(0.5×f1+f2+0.5×f3)/2).(Note that the Barmby et al.Keck spectra do not go much below3700˚A.)All spectra in Figures1-6are displayed in terms of log(flux)versus wavelength.The log stretch used for all of the spectra in this paper is1.1dex(versus0.7 dex used in Li&Burstein(2003)).Three things are notable about these new M31GC spectra:1.For the oldest12of the new M31GC(two are the same as previously observed byHST;cf.Table1),it is obvious that the strong NH absorption we saw for the spectra of4 M31GCs in Ponder et al.(1998)is also present in these new M31GC spectra.However, there is only one M31GC with a V mag fainter than17in this group(B001-S039),and its spectrum is far noisier than the other spectra in this group.Otherwise,all of the GCs with strong NH in their spectra have V mags between13.7and16.5(or,given a distance modulus to M31of24.38Freedman,et al.(2001),absolute V mags from near-11to-8,once Galactic extinction is taken into account).Most of the14GCs in Figures1and2are bulge/halo clusters,according to either their position on the sky(Mayall II)or their Morrison et al. residual parameter.Several have disk-like Morrison et al.residuals,but have spectra like those of the other bulge GCs(and,hence,are put in Figures1-2).2.In contrast,six of the M31GCs we observed have Morrison et al.residual parameters that place them squarely within the M31disk system.All six have quite remarkable spectra (Figure3).All show a very strong Balmer decrement,and a strong Balmer line series with the broad absorption hydrogen lines typical of dwarf A stars,and Ca II H+Hǫmuch stronger than the Ca II K line.Of these six M31GCs,two are in common with the Barmby et al. published sample of M31GCs(B216-S267and B315-S038).The spectra of six GCs taken from the sample observed by Barmby et al.(Figure6)show similar A-type stellar behavior, with a wider range Ca II H+K issues than those observed with the MMT.If we include all of the M31GCs indicate as“young?’by Barmby et al.,this makes as many as19young GCs in M31known so far.(However,not all of the Barmby et al.“young?”GCs have Morrison et al.parameters,so it is not clear if only disk GCs are preferentially young GCs.) We can an estimate of how young these M31GCs are by using the published integrated spectra of the young GCs in the Large Magellanic Cloud(LMC)given by Leonardi&Rose (2003).As the LMC spectra are alsofluxed,we see that the youngest LMC clusters(ages 200Myr or younger)have spectra that have deeper Balmer lines than the young M31GC in Fig.3.Hence,an estimate of500Myr is not an unreasonable estimate for the ages of these six MMT M31GC.It is possible that some of the Barmby et al.clusters are somewhat younger than this age(e.g.,B380-S313and B321-S046)and one perhaps as old as1Gyr (B347-S154).While Barmby et al.point out that others in the past have indicated that M31contains such young GCs,it really takes these kind of spectra to bring this issue home to all of us.3.The two M31GCs in Fig.4(B232-S286and B311-S033)also seem younger than the oldest M31GCs.Their spectra appear similar(modulo S/N issues)with the spectra of the LMC clusters NGC1795and NGC1754as seen in Leonardi&Rose(2003),which have estimated ages of order5Gyr.We can compare the absolute magnitudes of these young M31GCs with their com-patriots in the ing a distance modulus of18.50to the LMC(e.g.,Freedman,et al.2001),the LMC GCs that have ages200Myr and younger have absolute B magnitudes from M B=−6.5to-9.0,reddening-corrected.The two older,∼5Gyr-old LMC GCs have absolute magnitudes of-6.5and-7.3.There is no evidence from thefluxed spectra shown in Figures1-4that any of the M31 GCs we observed have significant reddening from inside M31itself,so we use the Galactic estimate of A V=0.25mag for all of the clusters.With this value of extinction,the younger M31GCs in Figs.3and6have apparent V magnitudes15.3-18.6,or absolute mags from -9to-5.5.This is quite similar to the range of absolute magnitudes of the200Myr LMC GCs.The absolute B magnitudes of the two∼5Gyr GCs are both close to-9.From this, we think we can conclude that the younger M31GCs are quite analogous to the younger LMC GCs,in that their high luminosities are not necessarily indicative of their overall mass. In contrast,the absolute magnitudes of the2,5-Gyr-old M31GCs indicate that they are considerably more massive than their LMC counterparts.3.1.The Line Strength MeasuresAmong the absorption line systems we have measured in our MMT spectra,for the present paper we include those of NH,CH(the G-band)and Mg2.2Measurement of the latter two indices are defined on the Lick Observatory system(e.g.,Burstein,et al.1984), but with the caveat that ourfluxed spectra define a different long-wavelength continuum than do the quartz-calibrated spectra that define the Lick system.We define the NH parameters according to the precepts of Davidge&Clark(1994),who did usefluxed data to obtain their measurements.Further,given that we separately observed the Galactic globular clusters by scanning the telescope in a large swath over them,we also need to see if the transformation to the Lick system is different for the Galactic GC as opposed to our MMT spectra for the M31GC.We give both our line strength data and those from the Lick observations(taken from Trager,et al.1998,for consistency)in Table2.We note that one of the M31GC in Table2shows a marked difference in the Mg2and CH measures we obtained for it compared to what was published in1984:B232-S288/Vetesnik 99.Our spectra clearly show this cluster to be very metal-poor,while the Lick spectra clearly show it to be more metal-rich.A check of our observing log position for this cluster confirms that we observed the cluster we have so-identified.Such confirmation is not available forthe older Lick data,so we assume that the M31cluster listed as V99in the Lick paper is not V99.Hence,we exclude this cluster from the line-strength comparisons with the Lick Observatory data(but not from other analyses).For the eight Galactic GC,wefind that the difference in magnitude for Mg2,in the sense of Trager et al.minus us,is−0.008±0.003average difference,with0.008mag error per object.Essentially all of the error is observational.For the10remaining M31GCs that are in common with the Trager et al.data,we have+0.029±0.003mag average difference,or 0.010mag error per observation.Most of the error is a combination of observational errors from both data sets.In the case of CH wefind an average difference for the8Galactic GCs of0.006˚A(Trager et al.minus Us),with a mean error of0.171˚A,and a single observational error of0.484˚A. We note that the mean error of the Lick observations is0.36˚A,more than sufficient to account for the errors observed between these two sets of data.For the10M31GCs,we get an average difference of0.146˚A with a mean error of0.235˚A with a single observational error of0.742˚A.Given that the mean difference is much smaller than the mean errors for the CH measurements of both the Galactic GCs and the M31GCs,we assume that we are on the Lick Observatory line-strength system for CH for both sets of data.We note that to place the2.4m Bok telescope observations of the125Lick Observatory stars observed by YL for his Ph.D.thesis,offsets in the sense of Trager et al.minus YL are +0.006±0.001for Mg2and+0.211±0.04for CH.These differences have been applied to the stellar data used in ourfigures.The differences in getting to the standard Lick system for stars versus GCs is understandable in terms of both Mg2and CH,given the wide wavelength regions that define both indices,and the differences in spectral energy distributions between individual stars and integrated stellar populations.In Table2we list the absorption line values for NH,CH and Mg2for both the M31GCs we observed here and the Galactic globular clusters we presented in Li&Burstein(2003), together with their errors and the absolute magnitudes of these clusters.In Figure7we present the relationships among NH,CH and Mg2for the17older M31GCs(including the two5-Gyr-old GCs,but not the500-Myr-old GCs),including the two HST-observed M31 GCs not observed by us with the MMT,as well as for the Galactic GCs.The M31GCs observed with the MMT and the Galactic GCs have their Mg2corrected by adding0.029 and-0.008mag,respectively,to their measured values to bring them into accord with the Lick standard system.(We note that,given the scale at which Figure7is plotted for CH, that mean offset calculated for CH for the M31GCs is smaller than the sizes of the symbols used to represent these GCs.)As one can see,the new M31GCs that are the oldest have the same kind of enhanced NH absorption feature as do the original4M31GCs that we investigated with HST/FOS. It is only the two5-Gyr-old M31GCs that have NH indices similar to that of Galactic GCs. Thus,wefind three differences among the globular clusters of M31and those of our own Milky Way:1.M31contains globular clusters with a range of age from∼100Myr old to500Myr old to5Gyr old to as old as the oldest Galactic GCs.In other words,M31contains GCs that are much younger than the known GC in our own Galaxy.2.While both the oldest and most metal-poor M31and Galactic GCs show enhanced nitrogen abundances in their integrated spectra,the main sequence stars in the M31GCs have markedly more nitrogen in their atmospheres than do the main sequence stars in either the Milky Way GCs or mostfield stars in the Milky Way that are of similar CH or Mg2line strengths.3.As Morrison et al.(2004)have shown,M31has a set of globular clusters that closely follow the rotation curve of M31.None of the known GCs in the Milky Way do this.3.2.Keeping Score with the PredictionsOne of the predictions of Li&Burstein(2003)from their GC and halo formation scenario is that younger GCs in other galaxies should have NH in proportion to their normal metallicity,as compared to the enhanced NH we see in the oldest clusters.In this regard, we note that the two5Gyr-old GCs in M31do have NH much weaker than their10-Gyr-old GC cousins,consistent with this prediction.Note,however,that even though the5Gyr-old M31GCs are weaker in NH than their older cousins,they are of comparable NH strength relative to the NH measures for the old Galactic GCs.This is perhaps an indication that nitrogen is greatly enhanced in M31GCs in general,not just in their oldest GCs.This makes one wonder whether olderfield stars in M31have enhanced nitrogen abundances relative to Galacticfield stars.Separately,as pointed out by Tomkin&Lambert(1984),CH(the G-band)and NH have very similar dissociation energies.The fact that CH lies1000˚A to the red of NH implies that the weakness of CH in the integrated spectra of the M31GCs relative means that carbon is very under abundant relative to nitrogen in these GCs(and also,in the Galactic GCs). Such was also found for main sequence stars in several Galactic GCs(e.g.Briley,Cohen,& Stetson2003).If these abundance differences are truly primordial in origin,are not these abundance anomalies telling us something about the elements thefirst stars produced?4.The Hierarchical-Clustering-Merging Paradigm and its Implication forGlobular Clusters of Other GalaxiesThe hierarchical-clustering-merging(HCM)paradigm is the current view of galaxy for-mation(e.g.,Burstein,et al.1997;Kauffmann,et al.1997).HCM pictures galaxy formation as small galaxies combining to form larger galaxies.In an HCM-dominated universe,each galaxy will undergo a series of major and minor mergers in its lifetime.If the merger pro-cess does not produce an E or S0galaxy,then it will produce a spiral galaxy.Since there are more spirals than E/S0galaxies in the Universe(e.g.,the galaxies in both the Uppsala General Catalog,Nilson(1973),and in the Third Reference Catalog of Bright Galaxies,de Vaucouleurs,et al.(1991),are dominated by spirals),it is clear that if HCM is the dominant mode of galaxy formation,spirals are its preferred output.In sum,the current evidence is consistent with the hypothesis that the HCM paradigm applies to all giant galaxies,Es,S0s and spirals(e.g.,Burstein,et al.1997).This,then begs a series of questions that follow in logical steps:1.How does the HCM paradigm relate to young M31GCs that wefind in M31but do notfind in our own Galaxy?2.Where else do wefind young globular clusters in the Local Group?3.Where do wefind most of the dwarf systems in the Local Group?4.Why do young GCs preferentially form in irregular or small spiral galaxies?5.Where do the young GCs seen in tidally interacting galaxies come from?The second question is the most obvious to answer.We see young GCs in the irregular companion galaxies to the Milky Way,the Large and Small Magellanic Clouds,as well as likely in the low luminosity Sc galaxy in the Local Group,M33(e.g.Ma,et al.2001).Indeed, we have used the integrated SEDs of LMC young GCs obtained by Leonardi&Rose(2003) to estimate the ages of our younger M31GCs.The answer to the third question comes from the fact that98%of the mass and lumi-nosity of galaxies in the Local Group is contained in just M31and the Milky Way.If you plot the known positions of the dwarf galaxies in the Local Group(data kindly given DB by Eva Grebel),one sees that both M31and the Milky Way have close contingents of these dwarf galaxies(e.g.,the LMC,SMC,and various dEs and dSphs close to the Milky Way).Put the answers together to the previous two questions and we have our answer to the first question.The young GCs seen in M31likely came from the small spiral and/or irregular galaxies that once were companions of M31and have since merged with M31.Since the LMC is less than1%the mass of M31,mergers with LMC-like irregulars would do little to the disk of this galaxy.That such a merger history has taken place in M31is consistent with what Brown et al..(2003)have found in their deep HST investigation of the halo of M31.Namely,theyfind an intermediate-aged stellar population,which could be the remnants of the dwarf system that produced the5Gyr-old GCs in M31.Furthermore,the fact that one sees what has been interpreted as a severe warp in front on the bulge of M31(Bajaja& Shane1982;Brinks&Burton1984)now can also be interpreted as the wrap-around debris from merger remnants.If a galaxy similar to the LMC were accreted by M31during the past100-200Myr,then all of the GCs in that irregular galaxy would now become GCs of M31,would they not? And,if that accretion took place such that the irregular galaxy would be tidally disrupted along the disk of M31,most of the GCs in this irregular galaxy would assume the rotation velocity of M31,forming its thin disk of GCs.And,it is in this thin disk of GCs that we find the young GCs of M31.(However,as noted above,these may not be the only types of disk GCs in M31.)If this is true for M31,why is it not true for the Milky Way?Because,in the HCM paradigm,what the merger history is of one galaxy does not predict what the merger history of another galaxy will be,even if they are close neighbors!Evidently,the Milky Way has not had a merger of an irregular galaxy like the LMC or the SMC in the past10billion years or so,else we would see younger GCs in our own Galaxy.Is it not likely that many,if not most,of the GCs in spiral galaxies were once in the smaller systems that combined to make the spirals we see today?If this is true,it is also true that the HCM paradigm does not dictate how and when such accretion will take place. As such,we feel it is a prediction of the HCM paradigm that the GC systems of all spiral galaxies(and for that matter,also gE and S0galaxies)are assembled in a rather haphazard “big-fish-eats-small-fish”manner.We see this happening today in our own Galaxy with the Sagittarius dwarf galaxy(e.g.,Ibata,Gilmore&Irwin1994)and the Canis Major dwarf (Forbes,Strader,&Brodie2004),both of which we are accreting,each adding4-6GCs to our GC contingent.(We note that two of GCs the Milky Way is accreting from each dwarf galaxy have ages∼7Gyr;e.g.,Forbes,Strader,&Brodie(2004).)Why do small spirals and irregulars preferentially form young GCs?We think this is because in such galaxies one does not have substantial rotational shear.This permits large molecular clouds(e.g.,with masses up to109M⊙Harris&Pudritz1994),to form that will not be sheared into smaller systems.In the Milky Way such sheared-stellar systems tend to form the open clusters wefind in our disk.If this interpretation is correct,then the fact that M31has both relatively young GCs(∼500Myr)as well as moderately old GCs(∼5 Gyr)strongly suggests that M31went at least a series of separate merging events with its contingent of small companion galaxies that contained many more GCs than the two dwarf galaxies that the Milky Way is currently absorbing(e.g,the Sagittarius dwarf galaxy and theCanis Major dwarf;Ibata,Gilmore&Irwin(1994)and Forbes,Strader,&Brodie(2004)).If our interpretation of the origin of the young GCs in M31is correct,then it shows that we might be able to study the relatively recent(say,the last10Gyr or so)merger history of other spiral galaxies by measuring the ages of their globular clusters.This possibility needs to be tested.If young GCs are preferentially formed in small galaxies with little or no net rotation velocities,then where do the young GCs that have been found around the Antennae galaxies (e.g.,Whitmore&Schweizer1995)come from?As an alternative hypothesis to these young clusters having been formed during the tidal interaction,what is the chance that either of the Antennae galaxies(NGC4038/9)had a one or two irregular galaxies containing young GCs that were“brought along for the ride”?Until we know more about where and how young globular clusters are formed outside of the Local Group,this idea is consistent with what we see for tidally interacting galaxies.The difference between M31and Milky Way GCs that we cannot explain is why the GCs in M31have markedly stronger NH absorption than do Galactic GCs of similar metalliticies. To-date,the M31GCs for which we have found very strong NH absorptions have luminosities ranging from-11(MII)to-8.5to-9(with apparent V mags of15.5-16.0).Ironically,all of the less luminous M31GCs we took with the MMT are of the young kind.However,even if this an issue of the luminosities of the oldest GCs in spiral galaxies, this still begs the question of how one gets a wide range of metallicity among these luminous GCs that spans a similar range as among the Galactic GCs.Of the three known differences among the GC systems of M31and the Galaxy,it is the difference in nitrogen abundance in them that is still the most puzzling and opens up a number of questions that need answers.5.SummaryIn this paper we present evidence that the globular cluster systems of the Milky Way and of M31,the two large spirals in the Local Group,have very different evolutionary histories. Whereas the Milky Way globular clusters are uniformly very old(10-12Gyr),those of M31 evidence at least three separate age epochs:100-500Myr,5Gyr and10-12Gyr old.We strongly suspect that the younger GCs in M31came from mergers of M31with its associated irregular galaxies in the past.We note that it might be happenstance that the Milky Way has not yet absorbed the Magellanic Clouds,for if it did,our Galaxy would also have a large number of young globular clusters in it.。
