Unit 3 Astronomy
Unit 3 AstronomyWhat Caused the Late Heavy Bombardment?Enjoy the beauty and magnificence of the UniverseDiscussion Are you interested in the Universe and what do you know about it? Do you know anything about the Late Heavy Bombardment?Late Heavy Bombardment, also known as Lunar Cataclysm. About 4 to 3.8 billion years ago a period of intense comet and asteroid bombardment is thought to have peppered all the planets including the Earth. Many of the numerous craters found on the Moon and other bodies in the Solar System record this event. One theory holds that a gravitational surge caused by the orbital interaction( 轨道相互作用) of Jupiter and Saturn sent Neptune careening(倾斜) into the ring of comets(彗星环) in the outer Solar System. The disrupted comets were sent in all directions and collided with the planets. These water-rich objects may have provided much of the water in the Earth's oceans.Introduction Impact crater 撞击坑、陨石坑 Impact basin 撞击盆地asteroid 小行星 comet 彗星Difference? 小行星主要沿椭圆形轨道运行;彗星 除了椭圆形轨道,还可以沿抛物线和 双曲线运行。 小行星较稳定,不太容易挥发物质; 彗星在距离太阳较近时,会挥发气体 。(彗星成分多为尘埃和冰块)meteor/meteorite 流星/流星体 比小行星和彗星更小的天体流星 体。 Note:流星是一种天文现象,流星体 是太阳系内,小至沙尘,大至巨砾, 成为颗粒状的碎片。 Inner solar system 内太阳系,多指太 阳、水星(Mercury)、金星(Venus)、 地球和火星(Mars)。 Hot water system (task: find out the correct translation of the term)Asteroid belt (主)小行星带 The asteroid belt is the region of the Solar System located roughly between the orbits of the planets Mars and Jupiter. It is occupied by numerous irregularly shaped bodies called asteroids or minor planets. The asteroid belt is also termed the main asteroid belt or main belt. Near-Earth asteroids (NEAs) 近地小 行星 近地天体(near-Earth Objects, NEO) 的一种。NEO是是轨道距离地球轨道 太近(最近距离<1.3个天文单位)并因 此有可能产生撞击危险的小行星、彗 星以及大型流星体的总称。 天文单位(astronomical unit),长度接 近于日地平均距离。 He has long suspected that two different projectile populations have been responsible for cratering inner solar system surfaces. (stellar) population 星族,指星系中在 年龄、化学组成、空间分布、运动特性 等方面相近的大量天体的集合。Spacewatch 太空监测计划 SPACEWATCH® is the name of a group at the University of Arizonas Lunar and Planetary Laboratory founded in 1980. The primary goal of Spacewatch is to explore the various populations of small objects in the solar system, and study the statistics of asteroids and comets in order to investigate the dynamical evolution (动 力学演化)of the solar system. Sloan Digital Sky Survey 斯隆数字巡天 The Sloan Digital Sky Survey (SDSS) is one of the most ambitious and influential surveys in the history of astronomy. Over eight years of operations, it obtained deep, multi-color images covering more than a quarter of the sky and created 3- dimensional maps containing more than 930,000 galaxies and more than 120,000 quasars(类星体). Gas Giant Planet 气体巨行星 又名类木行星,是不以岩石和固态物 质组成的巨行星。太阳系有4个气体 巨行星木星(Jupiter)、土星 (Saturn)、天王星(Uranus)与海王星 (Neptune)。一般大于十倍地球质量 的行星即为Cosmochemistry 宇宙化学 宇宙化学是研究宇宙物质的化学组成及其 演化规律的学科,研究对象包括陨石、月 球、行星系天体、行星际物质、太阳、恒 星、星际物质、星系等。 主要研究内容有:确定组成宇宙物质的 元素、同位素和分子,测定其含量。探 讨宇宙物质的化学演化。这对研究天体起 源和生命起源都有重要的意义。Marine Hydrothemal System深海热泉生 态系统 生命起源可能与热泉生态系统有关 。20世 纪70年代末,科学家在加拉帕戈斯群岛附近 发现了几处深海热泉,在这些热泉里生活着 众多的生物,这些生物群落生活在高温、高 压、缺氧、偏酸和无光的环境中。部分学者 认为,热泉喷口附近的环境不仅可以为生命 的出现以及其后的生命延续提供所需的能量 和物质,而且还可以避免地球外物体撞击地 球时所造成的有害影响,因此热泉生态系统 是孕育生命的理想场所。 Yarkovsky Effect 雅克夫斯基效应 这一效应是指小天体由于不均的热辐射而 获得动能的现象。当小行星暴露于太阳光 照之下时,其一面受热升温,热量辐射相 应增强,这将产生微弱的推进力。这种力 虽小,但作用于小天体,足以对其轨道产 生重大影响。 科学家认为,对火星和木星之间小行星带 里的某些小行星,雅科夫斯基效应会拉近 它们与地球的距离,增加它们对地球的威 胁。 Extensionsomething for fun 阿西莫夫 基地系列 刘慈欣 三体系列 Stargate Stargate: Atlantis Battlestar Galactica