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The Science of Astronomy

by: Thomas Konopelski

The Science of Astronomy AST 207

Marketplace > Michigan State University > Astronomy > AST 207 > The Science of Astronomy
Thomas Konopelski
GPA 3.83


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Class Notes
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This 4 page Class Notes was uploaded by Thomas Konopelski on Saturday September 19, 2015. The Class Notes belongs to AST 207 at Michigan State University taught by Staff in Fall. Since its upload, it has received 52 views. For similar materials see /class/207490/ast-207-michigan-state-university in Astronomy at Michigan State University.


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Date Created: 09/19/15
Ast 207 F2005 Weighing Univ Timing Expansion of Universe 28 Nov galaxy Though a good deal is too strange to be believed nothing is too strange to have happened Thomas Hardy How to weigh universe 7 Mass in a large sphere surrounding us pulls on a galaxy on the surface 7 Measure how much the galaxy slows 7 Use supernovae What we will nd Galaxies speed up 7 Dark energy is repulsive whereas matter and radiation are attractive Distant supernovae R1255 et al 2mm ApJ BEI7 BB5 A51 2m FZEIEIE Timing the motion Method for astronomical weighing 7 De ne amotion Universe expands by a factor of 2 from a12 to 7 Time the motion 3 1 NEW 7 If the motion takes longer the 0 0 D W mass IS ess For a greater mass density the a 1 time for U to expand by a factor V oftwo is smaller because gravity is a bigger effect proxy galaxy mus 39 faster in the past for it to have slowed to its present speed 0 z DlstanCeDlstanceNow o o Timef Might tEI re Eh us 0 71 708706704702 0 H x tlme A51 2m FZEIEIE r a Ifthe motion takes longer the mass is less Method for astronomical weighing 7 De ne a motion galaxy Universe expands by a factor on from a12 to 1 7 Time the motion 2 Ifthe motion takes longer the mass is less ltgt Use a proxy Supemova in a galaxy on surface of a big v sphere centered on us Sphere contains many galaxies 7 Is a fair sample ofthe Universe Mass inside sphere pulls on galaxy amp slows expansion Present speed vmW amp present distance Rm are xed by Hubble s R Law v Assume mass inside sphere is large galax When R12 Rnuw was v larger same or smaller than vmw b Is time for U to expand by a factor oftwo larger same or smaller A51 2m FZEIEIE N 7 39r vneT Timing the motion with supernovae Method for astronomical weighing De ne a motion Universe aipands by a factor on om alZ to l 7 Time the motion gt 7 Ifthe motion takes longer the massis less galaxy For th hm fr to aipand by a factor oftwo is smaller because gravity is a brgger effect proxy DZEIEIEIl the past for it to have slowed to its presents eed Proxy is Type I supernova in a distant galaxy o o If we want the motion to be expansion by a factor of 2 we need a supernova 39 reds i z i If supernova is brighter then distance is less and time is shorter and mass density ofU is greater A51 2m FZEIEIE DlstanCeDlstanceNow o o D 0 71 708706704702 0 H x tlme Nov05 Annie Jump Cannon 18631941 1425i 23939 Henry N Russell 18771957 Einar Hertzsprung 1873196739 el Orion Constellation Globular Cluster M15 You are a young astronomer in 1890 and you want to study stars The distances to a few dozen stars are known How do you attack this problem Spectra of Stars Spread light by color Each element has characteristic colors called lines Classify stars by their spectra Originally by strength of hydrogen lines ABCDEFGHIJKLM Now in order by temperature OBAFGKM October Brings A Football Game Kill Michigan 7 Emy Ibrahim Our Blessings Are From God s Kingdom Majestic 7 Latoya Baker Model of Starsi HUI repealralclss M n l Lumlnaus l 29 Sep v t a HertzsprungRussell dlagram 39 Speetral lass 7 ghlgeggnegrllgssme Huttest stars unle Absolute magnltude measures bnghtness wlth all stars plaeed at same drstanee 7 Bnghtest stars untnp Model 7 Temperature ze Lherefure narnes dwarfs i gants Absolute M agmt sl amp ll Aslmph x and lwemle eemuvy aslmnnmylu lean nf mn n N r why119 A The Hotplate Model of a Star The surface ofa star is made oftiles ofhot plates How does the energy from the hotplate get to my hand Key obseryahon lean hold my hand much closer to the hot plate when lt faces to the slde rather the WW acemavtcamvvavmcsnmtmmvmdu1sWELLVV7ELm luv The Hotplate Model of a Star The surface uf a star ls made uf tales efhet plates Huw duesthe ener yfmm the hetplate gette my mm 7 yabswmumlcanhnldmy whznltf es tn r mmw Energy muves hem the hut plate tn my hand by mavzmzntafhm nr 7 byn auan nasdym ued hgnt Huw dues energy muve frum the sun tn the eznh7 A Eynduumanly E Eyrnnyernentnfhntnrnnly c EmhA amp E the WW eemntemhnmshmemmlpnenewzlmugm luv The Hotplate Model ofa Star The surface of a star ls made oftlles of hot plates A By radlanun unly B B rneyernent efhet alrunly C Bath A amp B Energy leayes stars pnrnanly by radlatlon 7 Futhe sun theraalataenls musdy ultraylelethgnt ylslhle hght and m 39zred hght We eoneentrate on the ranhatlon produced by the hot plate the WW eemntemhnmshmemmlpnenewzlmugm luv


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