Astronomy 101 The Solar System Tuesday Thursday Tom Burbine tomburbine astro umass edu Course Course Website http blogs umass edu astron101 tburbine Textbook Pathways to Astronomy 2nd Edition by Stephen Schneider and Thomas Arny You also will need a calculator There is an Astronomy Help Desk that is open MondayThursday evenings from 7 9 pm in Hasbrouck 205 There is an open house at the Observatory every Thursday when it s clear Students should check the observatory website before going since the times may change as the semester progresses and the telescope may be down for repairs at times The website is http www astro umass edu orchardhill index html HW 10 11 12 and 13 Due March 30th at 1 pm What are the assumptions to get an age What are the assumptions No loss of parent atoms Loss will increase the apparent age of the sample No loss of daughter atoms Loss will decrease the apparent age of the sample No addition of daughter atoms or if daughter atoms was present when the sample formed If there was the age of the sample will be inflated These can possibly be all corrected for Radiogenic Radioactive Daughter Parent P D 40K Stable Reference S Half life t 109 y Decay constant l y 1 40Ar 36Ar 1 25 0 58x10 10 87Rb 87Sr 86Sr 48 8 1 42x10 11 147Sm 143Nd 144Nd 106 6 54x10 12 232Th 208Pb 204Pb 14 01 4 95x10 11 235U 207Pb 204Pb 0 704 9 85x10 10 238U 206Pb 204Pb 4 468 1 55x10 10 Commonly Used Long Lived Isotopes in Geochronology How do you determine isotopic values How do you determine isotopic values Mass Spectrometer It is easier To determine ratios of isotopic values than actual abundances Example 87Rb 87Sr electron antineutrino energy Half life is 48 8 billion years 87Sr 87Srinitial 87Rb e t 1 Divide by stable isotope 87 Sr 87Srinitial 87Rb e t 1 Sr 86 86 Sr 86 Sr Example Formula for line 87Sr 87Srinitial e t 1 87Rb Sr 86 y Sr b 86 86 mx Sr http www asa3 org aSA resources wiens2002 images wiensFig4 gif e t 1 Carbon 14 99 of the carbon is Carbon 12 1 is Carbon 13 0 0000000001 is Carbon 14 The half life of carbon 14 is 5730 40 years It decays into nitrogen 14 through beta decay electron and an anti neutrino are emitted Due to Carbon 14 s short half life can only date objects up to 60 000 years old Plants take up atmospheric carbon through photosynthesis http hyperphysics phy astr gsu edu hbase nuclear cardat html When something dies it stops being equilibrium with the atmosphere http hyperphysics phy astr gsu edu hbase nuclear cardat html Why is Carbon 14 still present if it has such a short half life Why is Carbon 14 still present if it has such a short half life Cosmic rays impact Nitrogen 14 and create Carbon 14 Cosmic rays are energetic particles 90 are protons originating from space From the Sun solar cosmic rays or outside the solar system galactic cosmic rays n 14N 14C p http en wikipedia org wiki Image Radiocarbon bomb spike svg Composition of the Planets Different bodies have different densities Density Mass Volume M 4 2d3 GP2 V 4 3 R3 Life of a Star A star forming cloud is called a molecular cloud because low temperatures allow Hydrogen to form Hydrogen molecules H2 Temperatures like 10 50 K Region is approximately 50 light years across Condensing Interstellar clouds tends to be lumpy These lumps tend to condense into stars That is why stars tend to be found in clusters Protostar The dense cloud fragment gets hotter as it contracts The cloud becomes denser and radiation cannot escape The thermal pressure and gas temperature start to rise and rise The dense cloud fragment becomes a protostar When does a protostar become a star When the core temperatures reaches 10 million K hydrogen fusion can start occurring Formation of Solar System Solar Nebula Theory 18th century Solar System originated from a rotating disk shaped cloud of gas and dust Modern theory is that the Solar System was born from an interstellar cloud an enormous rotating cloud of gas and dust Composition 71 is Hydrogen 27 is Helium 2 are other elements Fe Si O in the form of interstellar grains Show animation Dust grains collide and stick to form larger and larger bodies When the bodies reach sizes of approximately one kilometer then they can attract each other directly through their mutual gravity becoming protoplanets Protoplanets collide to form planets Asteroids such as Ceres and Pallas are thought to be leftover protoplanets Condensation conversion of free gas atoms or molecules into a liquid or solid Volatile Elements or compounds that vaporize at low temperatures Form atmosphere and oceans If you want to find life outside our solar system You need to find planets Extrasolar Planets Today there are over 400 known extrasolar planets 430 extrasolar planets known as of today Star Names A few hundred have names from ancient times Betelgeuse Algol etc Another system A star gets name depending on what constellation it is in With a Greek letter at the beginning Alpha Andromeda Beta Andromeda etc Only works for 24 brightest star Star Names now Stars are usually named after the catalog they were first listed in HD209458 is listed in the Henry Draper HD Catalog and is number 209458 HD209458a is the star HD209458b is the first objects discovered orbiting the star Our Solar System has basically two types of planets Small terrestrial planets Made of Oxygen Silicon etc Large gaseous giants Made primarily of hydrogen and a little helium Jupiter 90 Hydrogen 10 Helium Saturn 96 Hydrogen 3 Helium Uranus 83 Hydrogen 15 Helium Neptune 80 Hydrogen 20 Helium Things to Remember The Milky Way has at least 200 billion other stars and maybe as many as 400 billion stars Jupiter s mass is 318 times than the mass of the Earth Question How many of these stars have planets What is the problem when looking for planets What is the problem when looking for planets The stars they orbit are much much brighter than the planets Infrared image of the star GQ Lupi A orbited by a planet b at a distance of approximately 20 times the distance between Jupiter and our Sun GQ Lupi is 400 light years from our Solar System and the star itself has approximately 70 of our Sun s mass Planet is estimated to be between 1 and 42 times the mass of Jupiter http en wikipedia org wiki Image GQ Lupi jpg So what characteristics of the planets may allow you to see the planet So what characteristics of the planets may allow you to see the planet Planets have mass Planets have a diameter Planets orbit the star http upload wikimedia org wikipedia commons d de Extrasolar
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