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Galaxies

Galaxies. Chapter 16. Galaxies. Star systems like our _______ _____. Contain a few __________to tens of _______of stars. Large variety of shapes and sizes. Galaxy Diversity. Even seemingly __________regions of the sky contain __________of very _____, very distant __________.

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Galaxies

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  1. Galaxies Chapter 16

  2. Galaxies • Star systems like our _______ _____ • Contain a few __________to tens of _______of stars. • Large variety of shapes and sizes

  3. Galaxy Diversity Even seemingly __________regions of the sky contain __________of very _____, very distant __________ : The Hubble Deep Field: 10-day exposure on an apparently empty field in the sky

  4. Galaxy Classification E0, …, E7 Sa Large _________; tightly wound ________ E0 = _________ E1 Sb Sc Small ________; loosely wound __________ E7 = Highly ____________ E6

  5. Gas and Dust in Galaxies Spirals are rich in ______and _______ Ellipticals are almost devoid of ____and ___ Galaxies with disk and bulge, but no dust are termed ______

  6. Barred Spirals • Some spirals show a pronounced ______structure in the center • They are termed _________spiral galaxies • Sequence: • ____, …, ______, • analogous to regular spirals

  7. Irregular Galaxies Often: result of galaxy _________/ ___________ Often: Very active star ___________(“Starburst galaxies”) The Cocoon Galaxy NGC 4038/4039 Some: Small (“dwarf galaxies”) satellites of larger galaxies (e.g., Magellanic Clouds) Large Magellanic Cloud

  8. Distance Measurements to Other Galaxies (2): The Hubble Law E. Hubble (1913): Distant galaxies are moving _________from our Milky Way, with a recession velocity, vr, proportional to their distance d: vr = H0*d H0≈ 70 km/s/Mpc is the Hubble constant • Measure vr through the __________effect infer the _____________

  9. The Extragalactic Distance Scale • Many galaxies are typically millions or billions of _______________from our galaxy. • Typical distance units: • Mpc = ______________= 1 million __________ • Gpc = ______________= 1 billion __________ • Distances of Mpc or even Gpc The light we see left the galaxy _______or __________of years ago!! • “Look-back times” of _______or _______of years

  10. Supermassive Black Holes From the measurement of stellar _________near the center of a galaxy: Infer mass in the very center ______black holes! Several million, up to more than a billion ______ __________! Supermassive black holes

  11. Our Galaxy Cluster: The Local Group Milky Way Andromeda galaxy Small Magellanic Cloud Large Magellanic Cloud

  12. Galactic Cannibalism • Collisions of large with small galaxies often result in complete _______of the _______galaxy. • ______galaxy is “swallowed” by the ______one. NGC 5194 • This process is called “galactic cannibalism”

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