DISCOVER THE UNIVERSE
DISCOVER THE UNIVERSE AST 1002
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This 4 page Class Notes was uploaded by Ms. Adrian Buckridge on Friday September 18, 2015. The Class Notes belongs to AST 1002 at University of Florida taught by George Lebo in Fall. Since its upload, it has received 12 views. For similar materials see /class/206976/ast-1002-university-of-florida in Astronomy at University of Florida.
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Date Created: 09/18/15
Admin 1 Class website 2 Discussion sections Tuesday period4 10 4011 30am Bryant 3 Wednesday period 8 3pm3 50pm Bryant 7 Thursday period 5 1145arn12 35pm Bryant 3 of ce hr Thursday period 7 140pm 2 40pm Bryant 302 3 Homework 7 due 6pm Saturday 29th Nov will appear on class website soon 4 Telescope observing project see class website due Tuesday 25th Nov 5 Use name tags in class 6 Reading Intro Chapters 113 not 134 14 15 Final Exam Tuesday 9th December in class About 12 of the questions will be on material since midterm 2 l Weighing the Milky Way All the stars amp gas in the Milky Way are on orbits 7 This keeps gravity from collapsing the galaxy 7 This allows us to measure the mass of the galaxy using Newton s adaptation of Kepler s Third Law M W 7 a 26000 LY 16 x 109 AU 7 P 225 x 108 years Mganxy t Mun 2X10 This estimate tells us how much mass is inside the Sun s orbit Key Concepts Lecture 31 The Milky Way and Other Galaxies Our first encounter with Dark Matter too much mass in our Galaxy The Center of Our Galaxy A Supermassive Black Hole Historical debate on the existence of galaxies beyond the Milky Way Can we write this in terms of the speed Newton s version of Kepler s 3rd law Malax Mm a31gt2 P distance speed P 21 a v 0C a V Malax Msun 0c a v2 We see that v is approximately constant in galaxies does not depend on a Therefore the Mass inside radius a increases linearly with a Mass oflhe Milky Wa Dark Matter mmmnaummnmcmmps MM u ammmwznmnw WM r m I a New W WNW r d mm smgm m my 9 9 3quot My 39Exvncsubammxcpamdes m5 mmmmmmm 4 m u Mmmwmmymymmm wwwmw mdmymm pm mmrommmm 5 m1 ymmmmm W rhggmumme Makwa Theexadcenteruf Seagagging 155 Bur Galaxym Em Mm bngm suurce ny v x 7 Anxymms 31 Law 7 y mamMm me m hm mum 45mm whim AbbckhduVexy 39 3 NW 7 mmw mmmmmm mm nun w m mm Other Galaxies The Nebulae Astronomers Hershel amp Messler etc cataloged thousands ofnebula e Nebula were fuzzy amp nonstellar 7 Almost no detall could be seen Wlth mall telescopes e To the eye many appeared to be somewhat attened What Were they e Immanuel Kant 17244804 Island Unwersequot r e they were other galaxles e preneSrmon de Laplace Nebular Hypotheslsquot r e they were new stars formlng ln our own Galaxy The Nebular Band Wagon Early in the 1900 s the nebular hypothesis was widely believed James Jeans showed that a collapsing gas cloud should be attened Supported by poor observations 7 Eg claimed Parallax ofAndromeda The Nature of the Nebulae In the 18th century the race Was on to build bigger telescopes e Hershel bullt largertelescopes In the early 1800s Tnedto bulld hls own Money from George 111 e burlt a 500 long telescope e 1850 Earl ofRoss bullt a o a dla telescope He was the rstto see splral structurequot Photography revealed the nebula Isa c R0 e s found most were splrals 1880 e James Keeler estlmates 100000 nebulae could be seen wlth the chk telescopes Spectra e Jullus Schelner of German 1896 Andromeda had absorptron llnes srmrlarto stars Some nebula mustbe made of stars e Vesto Sllpher ofLowell Observatory 1912 r ar shuts forgalaxles up to 1800lcmsec Muchlargerthan for Galacac stars e dlfferent group of objects Variabili e supemoya 1885 ln Andromeda s Andromeda enear center sputter of protostarv n t The CurtisShapley Debate See also link section of class web page April 1920 after a dinner at the US National Academy of Selences Summarized the arguments over the nature of galaxies model hypothesis The Controversy Ends 0 Walter Baade used the 100 Mt Wilson telescope to resolve the disk of Andromeda into stars Hubble identi ed Cepheid variables in Andromeda 7 Sent a note to Shapley You will be interested to hear that I have found a Cepheid variable in the Andromeda Nebula Feb 19 1924 7 Andromeda was 1000000 LY away Herbert Curtis represented the island universe Harlow Shapley represented the nebular Cepheid Variables Henrietta Leavitt at Harvard College 1908 7 Studied plates from Peru for variable stars 7vmi 7 Her plates included the large Magellanic cloud l 39 Nearest galaxy to the Milky Way J I All stars at the same distance A mm mm 7 She noted brighter pulsating stars had longer periods ES Period luminosity relationship mummnm n1 4 a s w Fenml ways We live in one of a multitude of galaxies 7 Each degree of the sky holds gt700000 galaxies 7 There are gt2x1010 galaxies in the sky The universe is truly vast 7 HDF about angular size of a grain of sand at your feet
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