第02章天体化学

1、89Hubble law tell that galaxies move away from us at a speed proportional to their distances V= Ho d (Ho=70 km/s/mpc)Are we at the center of the expansion ?No! - Every galaxy is moving away from every other galaxyThe entire universe is expanding10Galaxies are like dots on an expanding baloonWhile a

2、photon emitted from a distant galaxy travel toward us, the universe expand and the photon get stretched.When we observe the photon it appear redder that it was originallyCosmological redshift P（质子）（质子）+（中子）（中子）D（2H）T=1012K密度无穷大密度无穷大T1032K基本粒子基本粒子反粒子反粒子1H + 1H 2D + + + 2D + 1H 3He + h3He + 3He 4He +

3、1H + 1H Summary equation:Summary equation:1H4He 1H2h + A t h i g h e r temperature theres another possible way of this chain with carbon as the catalyst and nitrogen and o x y g e n a s interproducts. 太阳的质量73为H，25%He，其它元素仅占2%。用光谱方法测定太阳光谱成分everythingelse90% H10% He 1% 其它 (正是这些构成星体）SunMercuryVenusEart

4、hMarsJupiterSaturnUranusNeptunePluto由岩石和金属组成不太大靠近太阳由气体组成非常大远离太阳 由岩石和金属组成 非常小 主要分布在火星和木星之间 主要由冰组成 非常小 大部分在海王星之外 古怪的轨道 非类地行星非类木行星 H compounds - methane, ammonia, water, etc. (1.4 %) rocky stuff (0.4 %) metallic stuff (0.2 %)It is thought that planetary systems form in large dust and gas clouds such as

5、 this one (Orion nebula, as seen by the Hubble Space Telescope).clickGRV020003-典型的具有熔壳的陨石陨石陨石石陨石石陨石石铁陨石石铁陨石铁陨石铁陨石球粒陨石球粒陨石 无球粒陨石无球粒陨石多种类型多种类型未分异陨石未分异陨石分异陨石分异陨石多种类型多种类型分异陨石分异陨石分异陨石分异陨石石石-铁陨石铁陨石铁陨石铁陨石which solidified from melt dropletswhich solidified from melt dropletsSome chondrules are glassy, imply

6、ing extremely rapid cooling from meltSome chondrules are glassy, implying extremely rapid cooling from meltComposition nearly solarComposition nearly solar - most easily accessible sample of the average - most easily accessible sample of the average solar system composition of most elementssolar sys

7、tem composition of most elementsOrdinary H3 chondriteCarbonaceous CM2 chondriteType 1 through 6 according to decreasing volatility/acqueous alterationType 1 through 6 according to decreasing volatility/acqueous alterationType 3 apparently the least altered and most representative of protoplanetary T

8、ype 3 apparently the least altered and most representative of protoplanetary conditions, with type 4, 5 and 6 indicating increasing metamorphic processingconditions, with type 4, 5 and 6 indicating increasing metamorphic processingType 1 is devoid of chondrules, which were either never present or de

9、stroyed by Type 1 is devoid of chondrules, which were either never present or destroyed by acqueous processesacqueous processeselementselementsEucriteShergottiteLunarPallasiteMesosiderite H群：FeO含量，高 L群： FeO含量，低 LL群： FeO含量，最低 1型3型：原始 4-6型：重结晶 7型：无球粒出现The Peekskill meteoriteOctober, 199214 km/s veloci

10、ty46 km heightClick here1 1101010010010001000LaLa CeCe PrPr NdNd SmSm EuEu GdGd TbTb DyDy HoHo ErEr TmTm YbYb LuLu样品/ 球粒 陨石样品/ 球粒 陨石N-MORBE-MORB辉绿岩安山岩海洋沉积物铁陨石铁陨石（球粒陨石化学群）（球粒陨石化学群）碳质球粒陨石（碳质球粒陨石（C群）群）中的包体中的包体星云凝聚的连续系列星云凝聚的连续系列C型包体的初始物质型包体的初始物质B型包体的初始物质型包体的初始物质陨石中的太阳系外物质陨石中的太阳系外物质太阳星云的不均一性太阳星云的不均一性超新星成

11、因超新星成因SiC E H L LL C无球粒陨石无球粒陨石石石-铁陨石铁陨石顽辉石球粒陨石（顽辉石球粒陨石（E群）群）发现新的过渡群发现新的过渡群还原条件下星云的凝聚还原条件下星云的凝聚还原条件下陨石的热变质还原条件下陨石的热变质氧化氧化(形成条件形成条件)熔融分异型陨石熔融分异型陨石阵风悬崖南段蓝冰型陨石阵风悬崖南段蓝冰型陨石无熔壳陨石的确定（本次陨石回收突破之一）无熔壳陨石的确定（本次陨石回收突破之一）l金刚石金刚石: Lewis et al. (1987)lSiC: Bernatowicz et al. (1987)l石墨石墨: Amari et al. (1990)lAl2O3: H

12、uss et al. (1994) lSi3N4: Nittler et al. (1995)lMgAl2O4: Choi et al. (1998)l硅酸盐硅酸盐: Messenger et al. (2003)Highly porous 10 m size IPD collected in the stratosphere, of chondritic composition1,200 feet in diameter.Is this a meteorite crater?Meteor crater, ArizonaDo we know absolutely that it is a me

13、teor crater and not, say a volcanic crater?No, but the evidence is pretty strong for a meteor.meteorite fragmentsexplosionshattered rock (shattercones)high-pressure mineralsA 30 m diameter mass of nickel-iron at 20 km/s.Roughly equivalent to 20-30 megaton nuclear explosion.Mostly vaporizedAbout 50,0

14、00 years ago.Circular crater no matter what direction of GAIL CHRISTESONPalaeo.gly.bris.ac.uk/Communication/Hanks/Fig6.htmlhttp:/wwwdsa.uqac.ca/mhiggins/MIAC/chicxulub.htm/SIC/impact_cratering/Chicxulubprpage/Chicxulub_drilling_hires.jpghttp:/wwwdsa.

15、uqac.ca/mhiggins/MIAC/chicxulub.htmThe moment of impact 65 million years ago near what is now the Yucatan Peninsula . and the Chicxulub crater, a few days later. Note the inner ring.http:/ effectsFrom http:/ very rough approximation centered on SDSUfireballsevere shockwaveTunguska event In 1908, som

16、ething exploded above Siberia. People knocked down 60 km away; one man killed 30 km away.Trees knocked down over a large area. Explosion registered on seismographs and barographs in Europe.Thought to be a large meteorite about 40-50 m in diameter that exploded in mid-air. Not investigated until 1921. But no crater.why?Cretaceous-Tertiary (K/T) boundary (65 Ma)Second largest mass extinction in Earths historyHalf of life on Earth died out (3/4 spec