Introduction to Astronomy
Prof. Sébastien R. A. Foucaud Department of Earth Sciences National Taiwan Normal University
Unless noted, the course materials are licensed under Creative Commons 1 Attribution-NonCommercial-ShareAlike 3.0 Taiwan (CC BY-NC-SA 3.0) Credits: Chris Hetlage
2 Syllabus Astronomical techniques • Lecture 1: Finding its way on the night… • Lecture 2: Moving blindly and seeing the light… • Lecture 3: Eyes better than my eyes: the telescopes The solar system • Lecture 4: Home: Earth • Lecture 5: Our close friend: The Moon • Lecture 6: Our neighborhood: Rocky Planets • Lecture 7: The good Monsters: Giant Planets • Lecture 8: Dwarf Planets, minor bodies and scenario of solar system formation Stars and planets • Lecture 9: Our king: The Sun • Lecture 10: Shades of colors: so many stars… • Lecture 11: The life of a star: from its birth to its death • Lecture 12: The quest for another Earth: extrasolar planets The Milky-Way, galaxies and our Universe • Lecture 13: The cosmic carrousel: galactic structure & Galaxy formation • Lecture 14: Hubble, the expansion of the Universe and the Big-Bang Theory • Lecture 15: Einstein and the relativity 3 Lecture 13
The cosmic carrousel:
galactic structure 4 Galaxies Spiral Galaxy NGC 253 Almost Sideways Credit & Copyright: Jean-Charles Cuillandre (CFHT) Hawaiian Starlight, CFHT APOD: 2003 May 25
• Star systems like our Milky Way •Few million to tens of billions of stars. • Large variety of shapes and sizes 5 Charles Messier (1730-1817)
6 M31
M51
M82 M82 New General Catalogue (NGC)/Johan Ludvig Emil Dreyer, William 7 Herschel, John Dunlop, Charles Messier M104 Messier Catalog, 1751 M31: The Andromeda Nebula
8 M51: The Whirlpool Galaxy
9 M82: An Exploding Galaxy
10 M1: The Crab Nebula
11 M57: The Ring Nebula
12 The Spiral Nebulae?
• Nature unknown • Avoided the Milky Way • Immanuel Kant (1724 – 1804) speculated about “Island Universes”. – Spiral Nebulae are other Milky Ways – Very distant and external to our Galaxy • 3rd Earl of Rosse (William Parsons) (1800 – 1867) built a giant reflector to observe them carefully.
13 The Leviathan of Parsonstown: 1840
183 cm (Primary mirror) 14 1920’s: The Great Debate Shapley vs. Curtis
Are these nearby Or distant stellar clouds of gas? systems (galaxies) 15 ESO Projects The “Discovery” of Galaxies
Edwin P. Hubble (1889-1953) Wikipedia Adabow • 1920’s: new 100in telescope built on Mt. Wilson • 1924: Hubble found cepheids in M31 beyond the Milky Way • Prove that M31 is another galaxy 16 Cepheids
17 National Taiwan Normal University Kuan Chen 70 years later: Hubble Deep Field
• 10 day exposure photo! • Over 1500 galaxies in a spot 1/30 the diameter of the Moon • 1011 galaxies in the observable universe • Farthest and oldest objects are 13 billion light years away! • Space observations as a time machine
18 Heaven on Earth (Milky Way from Northern Hemisphere) Credit & Copyright: Richard Payne (Arizona Astrophotography) APOD: 2004 February 23
19 The Milky Way at 5000 Meters (Milky Way from Southern Hemisphere) Credit & Copyright: Serge Brunier APOD: 2008 January 4
20 The Milky Way from Cerro Tololo Inter-American Observatory in the Chilean Andes. (NOAO/AURA Photo)
21 The Milky Way
•A faint band goes across the sky •Galileo showed that the band was made of individual stars •We are inside of the galaxy, so its hard to see what the overall structure of it is 22 Edge-on View of the Milky Way
halo globular star clusters & individual stars M104 bulge sun stars, gas & dust disk stars, gas & dust
28,000 light years 1,000 light years
100,000 light years
National Taiwan Normal University 23 Sébastien R.A Foucaud Milky Way Illustrated Illustration Credit & Copyright: Mark Garlick (Space-art) APOD: 2005 January 4
24 Other Galaxies
• Over 100 billion in the observable universe
• Many different shapes and sizes
25 Irregulars
http://cas.sdss.org/dr5/en/ Properties of Galaxies
Property Spirals Ellipticals Irregulars
9 11 5 13 8 10 Mass/M 10 - 4x10 10 - 10 10 - 3x10
8 10 5 11 7 9 Luminosity/L 10 - 2x10 3x10 - 10 10 - 3x10 Diameter 16x103 - 8x105 3x103 - 7x105 3x103 - 3x104 (light years)
Population 77% 20% 3% 27 Spiral galaxies
M51 M104
28 M31: The Andromeda Galaxy Credit & Copyright: Robert Gendler (robgendlerastropixs.com) APOD: 2004 July 18 Disk: Gas, dust, young and old stars
Bulge: Old stars Orbits of Stars
• Disk stars go around the center of the galaxy – Also oscillate above and below the disk • Halo and bulge stars move around randomly – Can be very far away from the disk • Study orbits of stars to determine mass of the galaxy 31 M51: The Whirlpool Galaxy in Dust and Stars Credit: N. Scoville (Caltech), et al., Hubble Heritage Team, NASA APOD: 2006 February 19
32 Edge-On Galaxy NGC 5866 Credit: NASA, ESA, and The Hubble Heritage Team (STScI/AURA); Acknowledgment: W. Keel (U. Alabama) APOD: 2006 June 12
33 M64: The Sleeping Beauty Galaxy Credit: NASA and the Hubble Heritage Team (AURA/STScI), S. Smartt (IoA) & D. Richstone (U. Michigan) et al. 34 APOD: 2004 February 11 Barred Spiral Galaxy NGC 1300 Credit: Hubble Heritage Team, ESA, NASA APOD: 2006 August 27
35 Spiral Arms
M74
36 So what causes spiral arms?
National Taiwan Normal University Kuan Chen It happens too fast: Universe ~10-15 billion years, Arms so tightly wrapped, therefore invisible! 37 Density waves
38 National Taiwan Normal University Kuan Chen Spiral arms are patterns
• According to the density-wave theory, spiral arms are created by density waves that sweep around the Galaxy • The gravitational field of this spiral pattern causes stars and gas to slow down near the arm • This compresses the interstellar clouds, triggering the formation of stars • The entire arm pattern rotates around the Milky Way once every 500 million years
39 Spiral arms and density waves
Wikipedia: Author Unknown, User: Dbenbenn / Mysid 40 Wikipedia Ingo Berg Elliptical galaxies
M32 M110
42 Elliptical galaxies
E0 (M1050 E3 (NGC4365) E6 (NGC3377)
• little interstellar gas and dust • very little star formation • mainly old stars (billions of years old) • few or no young stars (millions of years old) • Random velocities of stars
43 National Taiwan Normal University Kuan Chen Irregular Galaxies
I Zwicky 18 The Antennae
44 The Large Cloud of Magellan Credit & Copyright: Wei-Hao Wang (IfA, U. Hawaii) APOD: 2006 May 10 The Small Cloud of Magellan Credit & Copyright: Josch Hambsch, Robert Gendler APOD: 2005 June 17 Galaxies love to live in group The Local Group
47 Wikipedia Richard Powell Galaxy Group HCG 87 Credit: GMOS-S Commissioning Team, Gemini Observatory APOD: 2005 July 16 48 The Perseus Cluster of Galaxies Credit: Jim Misti (Misti Mountain Observatory) APOD: 2004 October 25
49 The Coma Cluster of Galaxies Credit & Copyright: Jim Misti (Misti Mountain Observatory) APOD: 2006 March 21
50 Large Scale Structure
51 Galaxy Facts
Grouping: • Spiral galaxies in small groups • Ellipticals in large clusters
Size (decreasing order): • Giant elliptical galaxies (clusters) • Spiral galaxies • Small ellipticals (near large spirals)
52 Galaxies quite close to each other!
Galaxy size ~ 100 kpc Separation between galaxies ~ 1 Mpc Size/Separation > 0.1 !
For stars, Size/Separation ~ 10-7
Galaxies interact and collide very often!
53 Galaxy interactions
• Galaxies rarely in isolation (In the past even closer) • Take hundreds of millions of years to be completed • Rip stars out of galaxies, producing tidal tails • Gas settles in the center and forms many new stars • Disturb gas in and between galaxies, producing starbursts • Randomize stellar orbits leading to the formation of elliptical galaxies
54 Spiral Galaxies in Collision Credit: Debra Meloy Elmegreen (Vassar College) et al., & the Hubble Heritage Team (AURA/ STScI/ NASA) APOD: 2004 November 21
55 Antennae galaxy 56 56 Hubble Space Telescope – WFPC2 + ACS 57 Milky Way eating neighbors
58 Galactic cannibalism
Giant elliptical in the cluster center gets bigger by eating neighbors
59 Galaxy Formation • No stars formed yet so no direct observations – Extensive use of computer simulations • Assume that Hydrogen and Helium gas spread (almost) uniformly throughout the universe • Rotation of the galactic disks established after the first generation of stars • Galaxy formed from a Protogalactic Cloud • Multiple clouds • Protogalactic Cloud Differences – Protogalactic spin might have varied – Protogalactic density might have varied 60 Galaxy Formation
National Taiwan Normal University Kuan Chen
61 National Taiwan Normal University Kuan Chen Galactic Recycling • Stars don’t form uniformly in the galaxy • Stars form in the spiral arms of galaxies - Arms “blue” while other parts “red” • Spiral density waves probably responsible • Stars dump material into the ISM as they die • Gravity drags gas and cools it • Large gas clouds formed, from which stars can form again 62 Galaxy Formation
• This picture of galaxy formation is incomplete
• Mergers, collisions, and interactions between galaxies very important in their formation, • Particularly in the early stages of the Universe
• Anything else? (Black holes)
63 Galaxy growth via interactions
• Galaxies initially form from mergers of several gas clouds • Galaxies then are changed by interactions • Galaxies grow gradually by galactic cannibalism • Interactions disturb gas leading to starbursts • Collisions randomize stellar orbits leading to the formation of elliptical galaxies
64 Galaxy growth via interactions
This work is licensed by Andrey Kravtsov/The Center for Cosmological Physics for the use of “Course Database 65 of General Education TW” ONLY. The copyright belongs to the above mentioned entity and GET does not have the right to sub-license. Copyright privileges have to be negotiated with the copyright owner(s) for separately. Galaxy Formation
• Bottom-to-top formation? 6 - Objects of globular cluster size ~ 10 M formed first; then clustered into bigger galaxies, groups, etc.
• Top-to-bottom formation? - Supercluster-size objects formed first, and smaller scales later
66 Galaxy Formation
Top-to-bottom
time Primordial gas
Bottom-to-top
National Taiwan Normal University Sébastien R.A Foucaud 67 Rotation Curve and Mass Rotation curves of : 1. a rigid body 2. a system with concentrated mass…
68 The Department of Physics and Astronomy, The University of North Carolina at Chapel Hill Rotation curve of Milky Way
Doppler measurements of the rotation curve
Wikipedia Brews Ohare Dl V = r l c 69 Rotation Curve of Spiral Galaxies
If we measure the Doppler shift of the galaxy along the red line, we would see a spectra like this…
70 National Taiwan Normal University Kuan Chen Dark Matter in Galaxy Halos • Galaxies rotate like solid spheres, not Keplerian.
GM(< r) V 2 = V r
Keplerian 1/r1/2
r National Taiwan Normal University Sébastien R.A Foucaud M 1 • For V=const, need M( • Yields dark matter = 5 x stellar mass 71 Dark Matter in spiral galaxies • A galaxy like the Milky Way or Andromeda has a 10 total visible mass of about 610 Msun. • The rotation velocity is ~220 km/sec • The radius about ~30 kpc • Newton: GM v2 R v = Þ M = rot rot R G 11 total mass: 3.310 Msun ~5 times more mass than visible 72 Dark Matter in spiral galaxies Observations of the mass in spiral galaxies suggest: – Majority of masses in spiral galaxies contained in a spherical halo that surrounds the disk of our galaxy – 90% of mass of spiral galaxies do not emit light: Dark Matter – Only about 10% of the mass in the spiral galaxies in luminous form concentrated in the disk of the galaxies… 90% 10% 73 What is Dark Matter? • WE DON’T KNOW! • Ordinary matter = baryons • MACHOs (MAssive Compact Halo Objects) – Brown Dwarfs, black holes, neutron stars – Ruled out due to lensing • Nonbaryonic matter – Neutrinos (too light) – WIMPs (Weakly Interacting Massive Particles) – Interact weakly – Very small 74 The Universe credit: NASA 75 Dark Matter and Galaxies • Dark Matter = primary gravity source in galaxy formation • Clustering = result of dark matter • Matter arranged in huge chains (or walls) and large voids 76 Dark Matter and Galaxies Simulation courtesy of Springel, White, and Hernquist This work is licensed by VIRGO Consortium/Springel et al. (2005) for the use of “Course Database of General Education TW” ONLY. The copyright belongs to the above mentioned entity and GET does not have the authorization right. Copyright 77 privileges have to be negotiated with the copyright owner(s) for separately. Thanks! 78 78 Copyright Declaration Work Licensing Author/Source NASA http://map.gsfc.nasa.gov/universe/bb_cosmo_struct.html 2012/03/06 visited NASA/Chris Hetlage http://apod.nasa.gov/apod/ap120607.html 2012/07/12 visited NASA/Jean-Charles Cuillandre (CFHT), Hawaiian Starlight, CFHT http://apod.nasa.gov/apod/ap030525.html 2012/07/12 visited Wikipedia: Author Unknown http://zh.wikipedia.org/wiki/File:Charles_messier.jpg 2012/07/12 visited New General Catalogue (NGC)/Johan Ludvig Emil Dreyer, William Herschel, John Dunlop, Charles Messier http://www.geocaching.com/seek/cache_details.aspx?guid=1781a7d1-b759-4ddb- b890-11794083078c 2012/07/12 visited NASA/Robert Gendler (robgendlerastropics.com) http://apod.nasa.gov/apod/ap090510.html 79 2012/07/12 visited Copyright Declaration Work Licensing Author/Source NASA/S. Beckwith (STScI), Hubble Heritage Team, (STScI/AURA), ESA, Robert Gendler http://apod.nasa.gov/apod/ap080614.html 2012/07/12 visited NASA/ESA, The Hubble Heritage Team, (STScI/AURA) http://apod.nasa.gov/apod/ap120326.html 2012/07/12 visited NASA/ESA, J. Hester, A. Loll (ASU); Acknowledgement: Davide De Martin (Skyfactory) http://apod.nasa.gov/apod/ap111225.html 2012/07/12 visited NASA/H. Bond et al., Hubble Heritage Team (STScI/AURA), NASA http://apod.nasa.gov/apod/ap091115.html 2012/07/12 visited Wikipedia: Author Unknown http://en.wikipedia.org/wiki/File:Immanuel_Kant_(painted_portrait).jpg 2012/07/12 visited Wikipedia: Author Unknown http://en.wikipedia.org/wiki/Image:William_Parsons,_3rd_Earl_of_Rosse.jpg?uselan g=ja 80 2012/07/12 visited Copyright Declaration Work Licensing Author/Source Wikipedia: Author Unknown http://en.wikipedia.org/wiki/File:WilliamParsonsBigTelescope.jpg 2012/07/12 visited Wikipedia NASA and European Space Agency http://en.wikipedia.org/wiki/File:Messier51_sRGB.jpg 2012/07/12 visited Wikipedia Lord Rosse http://en.wikipedia.org/wiki/File:M51Sketch.jpg 2012/07/12 visited NASA/Robert Nemiroff (MTU) & Jerry Bonnell (USRA) http://apod.nasa.gov/diamond_jubilee/debate20.html 2012/07/12 visited NASA/Robert Nemiroff (MTU) & Jerry Bonnell (USRA) http://apod.nasa.gov/diamond_jubilee/debate20.html 2012/07/12 visited ESO Projects http://www.eso.org/public/outreach/eduoff/cas/cas2002/cas- projects/italy_betel_1/orion.htm 2012/07/12 81 Copyright Declaration Work Licensing Author/Source Wikipedia NASA and European Space Agency http://en.wikipedia.org/wiki/File:Messier51_sRGB.jpg 2012/07/12 visited This work is from Wikipedia http://en.wikipedia.org/wiki/File:Edwin_Hubble_with_pipe.jpg, but the original source is from the Edwin Hubble Biography http://www.wwu.edu/depts/skywise/hubble.html It is used subject to the fair use doctrine of: •Articles 52 & 65 of Taiwan Copyright Act. •Copyright law of the United States NASA/The Huntington Library, San Marino, California http://imagine.gsfc.nasa.gov/YBA/M31-velocity/hubble-more.html 2012/07/12 visited NASA/Robert Gendler (robgendlerastropics.com) http://apod.nasa.gov/apod/ap090510.html 2012/07/12 visited National Taiwan Normal University Kuan Chen NASA/ ESA, and the Hubble Heritage Team (STScI/AURA) http://www.nasa.gov/mission_pages/hubble/science/star-v1.html 82 2012/07/12 visited Copyright Declaration Work Licensing Author/Source Wikipedia R. Williams (STScl), the Hubble Deep Field Team and NASA http://en.wikipedia.org/wiki/File:HubbleDeepField.800px.jpg 2012/07/12 visited NASA/Richard Payne (Arizona Astrophotography) http://apod.nasa.gov/apod/ap040223.html 2012/07/12 visited NASA /Serge Brunier http://apod.nasa.gov/apod/ap080104.html 2012/07/12 visited NASA /Roger Smith, AURA, NOAO, NSF http://apod.nasa.gov/apod/ap010514.html 2012/07/12 visited NASA /Tunç Tezel (TWAN) http://apod.nasa.gov/apod/ap110924.html 2012/07/12 visited NASA/ESO http://www.nasaimages.org/luna/servlet/view/all/where/M104/?pgs=100 2012/07/12 visited 83 Copyright Declaration Work Licensing Author/Source National Taiwan Normal University Sébastien R.A Foucaud NASA/Mark Garlick (Space-art) http://apod.nasa.gov/apod/ap050104.html 2012/07/12 visited Wikipedia R. Williams (STScI), the Hubble Deep Field Team and NASA http://en.wikipedia.org/wiki/File:HubbleDeepField.800px.jpg 2012/07/12 visited Wikipedia NASA http://en.wikipedia.org/wiki/File:HubbleTuningFork.jpg 2012/07/12 visited Wikipedia NASA, ESA, and The Hubble Heritage Team (STScI/AURA) http://en.wikipedia.org/wiki/File:Irregular_galaxy_NGC_1427A_(captured_by_the_ Hubble_Space_Telescope).jpg 2012/07/12 visited Wikipedia NASA http://en.wikipedia.org/wiki/File:M101_hires_STScI-PRC2006-10a.jpg 84 2012/07/12 visited Copyright Declaration Work Licensing Author/Source Wikipedia J. Blakeslee (Washington State University) http://en.wikipedia.org/wiki/File:Abell_S740,_cropped_to_ESO_325-G004.jpg 2012/07/12 visited Wikipedia NASA, ESA, and The Hubble Heritage Team (STScI/AURA) http://en.wikipedia.org/wiki/File:Irregular_galaxy_NGC_1427A_(captured_by_the_ Hubble_Space_Telescope).jpg 2012/07/12 visited NASA/S. Beckwith (STScI), Hubble Heritage Team, (STScI/AURA), ESA, Robert Gendler http://apod.nasa.gov/apod/ap091226.html 2012/07/12 visited NASA/Vicent Peris (OAUV / PTeam), MAST, STScI, AURA http://apod.nasa.gov/apod/ap080308.html 2012/07/12 visited NASA/Robert Gendler (robgendlerastropixs.com) http://apod.nasa.gov/apod/ap040718.html 2012/07/12 visited NASA/I. Rodrigues and I. F. Mirabel (IAFE, SAp/CEA) et al., NRAO, AUI, NSF (Orbit Illustration) http://apod.nasa.gov/apod/ap010921.html 2012/07/12 visited 85 Copyright Declaration Work Licensing Author/Source NASA/N. Scoville (Caltech), T. Rector (U. Alaska, NOAO) et al., Hubble Heritage Team http://apod.nasa.gov/apod/ap060219.html 2012/07/12 visited NASA/ESA, and The Hubble Heritage Team (STScI/AURA); Acknowledgment: W. Keel (U. Alabama) http://apod.nasa.gov/apod/ap060612.html 2012/07/12 visited NASA/ the Hubble Heritage Team (AURA/STScI), S. Smartt (IoA) & D. Richstone (U. Michigan) et al. http://apod.nasa.gov/apod/ap040211.html 2012/07/12 visited NASA/Hubble Heritage Team, ESA http://apod.nasa.gov/apod/ap060827.html 2012/07/12 visited NASA/Descubre Foundation, Calar Alto Observatory, OAUV, DSA, V. Peris (OAUV), J. L. Lamadrid (CEFCA), J. Harvey (SSRO), S. Mazlin (SSRO), I. Rodriguez (PTeam), O. L. (PTeam), J. Conejero (PixInsight). http://apod.nasa.gov/apod/ap110406.html 2012/07/12 visited National Taiwan Normal University Kuan Chen 86 Copyright Declaration Work Licensing Author/Source National Taiwan Normal University Kuan Chen Wikipedia: Author Unknown, User: Dbenbenn / Mysid http://en.wikipedia.org/wiki/File:Spiral_galaxy_arms_diagram.svg 2012/07/12 visited Wikipedia Ingo Berg http://en.wikipedia.org/wiki/File:Spiral_arms.ogv 2012/07/12 visited NASA/Jean-Charles Cuillandre (CFHT) & Giovanni Anselmi (Coelum Astronomia), Hawaiian Starlight http://apod.nasa.gov/apod/ap080909.html 2012/07/12 visited NASA/Thomas M. Brown (GSFC) et al. http://apod.nasa.gov/apod/ap991103.html 2012/07/12 visited Wikipedia NASA http://en.wikipedia.org/wiki/File:Messier_105.jpg 2012/07/12 visited 87 Copyright Declaration Work Licensing Author/Source NASA/T. H. Puzia (Sternwarte Munich), S E. Zepf (Yale / Michigan State) et al., ESO, ESA http://apod.nasa.gov/apod/ap020704.html 2012/07/12 visited Wikipedia Commons en:NASA, en:STScI, en:WikiSky http://commons.wikimedia.org/wiki/File:NGC_3377_Hubble_WikiSky.jpg 2012/07/12 visited National Taiwan Normal University Kuan Chen NASA/ESA, and A. Aloisi (ESA & STScI) http://apod.nasa.gov/apod/ap071017.html 2012/07/12 visited NASA/Daniel Verschatse (Antilhue Observatory) http://apod.nasa.gov/apod/ap060630.html 2012/07/12 visited NASA/Wei-Hao Wang (IfA, U. Hawaii) http://apod.nasa.gov/apod/ap060510.html 88 2012/07/12 visited Copyright Declaration Work Licensing Author/Source NASA/Josch Hambsch, Robert Gendler http://apod.nasa.gov/apod/ap050617.html 2012/07/12 visited Wikipedia Richard Powell http://en.wikipedia.org/wiki/File:Local_Group.svg 2012/07/12 visited NASA/GMOS-S Commissioning Team, Gemini Observatory http://apod.nasa.gov/apod/ap050716.html 2012/07/12 visited NASA/Jim Misti (Misti Mountain Observatory) http://apod.nasa.gov/apod/ap041025.html 2012/07/12 visited NASA/Jim Misti (Misti Mountain Observatory) http://apod.nasa.gov/apod/ap060321.html 2012/07/12 visited NASA/Matthew Colless (ANU) et al., 2dF Galaxy Redshift Survey http://apod.nasa.gov/apod/ap010904.html 89 2012/07/12 visited Copyright Declaration Work Licensing Author/Source NASA/GMOS-S Commissioning Team, Gemini Observatory http://apod.nasa.gov/apod/ap030731.html 2012/07/12 visited NASA/N. Benitez (JHU), T. Broadhurst (Hebrew Univ.), H. Ford (JHU), M. Clampin (STScI), G. Hartig (STScI), G. Illingworth (UCO/Lick), ACS Science Team, ESA http://apod.nasa.gov/apod/ap040627.html 2012/07/12 visited NASA/Debra Meloy Elmegreen (Vassar College) et al., & the Hubble Heritage Team (AURA/ STScI) http://apod.nasa.gov/apod/ap041121.html 2012/07/12 visited NASA/Brad Whitmore (STScI) http://hubblesite.org/gallery/album/pr1997034d/ 2012/07/12 visited NASA/Daniel Verschatse (Antilhue Observatory) http://apod.nasa.gov/apod/ap060630.html 2012/07/12 visited NASA/Kirk Borne (STScI) http://apod.nasa.gov/apod/ap981219.html 90 2012/07/12 visited Copyright Declaration Work Licensing Author/Source NASA/JPL-Caltech/R. Hurt (SSC/Caltech) http://www.spitzer.caltech.edu/images/2138-sig07-008-Rings-Around-the-Galaxy- Annotated- 2012/07/12 visited NASA/Michael J. West (St. Mary's U.), ESO 1-m Telescope http://apod.nasa.gov/apod/ap980831.html 2012/07/12 visited National Taiwan Normal University Kuan Chen National Taiwan Normal University Kuan Chen Wikipedia NASA Headquarters - Greatest Images of NASA (NASA-HQ-GRIN) http://zh.wikipedia.org/wiki/File:NGC_4414_(NASA-med).jpg 2012/06/21 visited NASA/U. Hwang (GSFC/UMD), J.M. Lamming (NRL), et al., CXC http://science.nasa.gov/science-news/science-at-nasa/2010/07jan_nustar/ 2012/07/12 visited 91 Copyright Declaration Work Licensing Author/Source This work is licensed by Andrey Kravtsov/The Center for Cosmological Physics for the use of “Course Database of General Education TW” ONLY. The copyright belongs to the above mentioned entity and GET does not have the right to sub- license. Copyright privileges have to be negotiated with the copyright owner(s) for separately. National Taiwan Normal University Sébastien R.A Foucaud This work is from The Department of Physics and Astronomy, The University of North Carolina at Chapel Hill http://www.physics.unc.edu/~evans/pub/A31/Lecture21-Milky-Way/rotation- comparison.jpg It is used subject to the fair use doctrine of: •Articles 52 & 65 of Taiwan Copyright Act. The "Code of Best Practices in Fair Use for OpenCourseWare 2009 (http://www.centerforsocialmedia.org/sites/default/files/10-305-OCW-Oct29.pdf)" by A Committee of Practitioners of OpenCourseWare in the U.S. The contents are based on Section 107 of the 1976 U.S. Copyright Act Wikipedia NASA/JPL-Caltech/R. Hurt http://en.wikipedia.org/wiki/File:236084main_MilkyWay-full-annotated.jpg 2012/07/12 visited Wikipedia Brews Ohare http://en.wikipedia.org/wiki/File:Rotation_curve_(Milky_Way).JPG 2012/07/12 visited NASA/Robert Gendler http://apod.nasa.gov/apod/ap051222.html 2012/07/12 visited 92 Copyright Declaration Work Licensing Author/Source National Taiwan Normal University Kuan Chen National Taiwan Normal University Sébastien R.A Foucaud NASA/CXC/M.Weiss http://chandra.harvard.edu/resources/illustrations/milkyWay.html#milkyWayHalo 2012/07/12 visited NASA http://zh.wikipedia.org/wiki/File:Cosmological_composition.jpg 2012/07/12 visited NASA/Gott and Juric http://heasarc.nasa.gov/docs/cosmic/sheets_voids_info.html 2012/07/12 visited This work is licensed by VIRGO Consortium/Springel et al. (2005) for the use of “Course Database of General Education TW” ONLY. The copyright belongs to the above mentioned entity and GET does not have the right to sub-license. Copyright93 privileges have to be negotiated with the copyright owner(s) for separately.