Chapter 24 - Physics1902 Galaxiesetc. Lecture W10.a Chapter...

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1 Physics 1902 Galaxies etc. Lecture W10.a Chapter 24/25
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2 Galaxies 
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3 Questions about Galaxies Where are they? What are they made of? How old are they? Do they evolve? Why the different types?
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4 Types of Galaxies Galaxies appear to come in several different types Spirals, Barred Spirals, Elipticals, Irregulars
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5 Spiral Type Sa Condensed Nucleus Tightly wound arms
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6 Type Sb Less prominent nucleus More open arms
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7 Type Sc Little condensation Open arms Much blue light
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8 Spirals seen edge on ‘Sombrero Galaxy’ IR Image showing dust
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9 Another edge on spiral
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10 Barred Spirals – Type SBa
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11 Barred Spiral Type SBb
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12 Barred Spiral Type SBc
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13 Elliptical Galaxies E2 E3 E5
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14 Irregulars – Magellanic clouds Irregular shapes influenced by tidal forces SMC LMC
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15 M82 – a collision between 2 galaxies
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Collisions with M81 occur every 100 million  years 16
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17 Hubble Classification This is pure stamp collecting
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18 Where are the Galaxies Galaxies are very distant Nearest large galaxy is Andromeda Distance is 2.5 M Ly or almost 1 MPc How do we know this? First step is from study of Cepheid variable stars
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19 Impact of Cepheids We can now measure the distance to nearby galaxies By about 25 Mpc we stop resolving individual stars in the galaxies and need a new measure We can see that there is a ‘Local Group’ of about 50 galaxies There are 3 spirals (Milky way, Andromeda and M33 plus satellite elliptical and irregulars
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M33 20
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Local group 21
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22 Expanding the Neighbourhood The Virgo Cluster is located 17 MPc away Contains 2500 galaxies including some giant ellipticals (M86 and M87). Group is 3 Mpc in diameter
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23 Virgo Cluster Clusters within Clusters
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24 New Distance Scale Required In looking at galaxies within the range where Cepheids can be used to determine distance, a relationship was noted between rotation speed and luminosity for spirals Rotation speed measured by broadening of the 21 cm line of hydrogen Known as Tulley-Fisher relation Gets us out to 200 Mpc
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25 Abell 1689 Cluster
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26 Hubble’s Law Hubble used Doppler shift to measure the relative velocities of galaxies wrt Milky way
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27 Galaxy red shift of lines in Ca
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28 Ursa Major
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29 Corona Borealis
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30 Bootes
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This note was uploaded on 10/05/2010 for the course PHYS 1902 taught by Professor Staff during the Winter '10 term at Carleton CA.

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Chapter 24 - Physics1902 Galaxiesetc. Lecture W10.a Chapter...

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