PHYS 1600 : Week 11

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silvergoat980

13 Dec 2011

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Document Summary

Our home galaxy (milky way): inside distribution of stars = flat and disk-like, younger stars outside distribution of stars = spherical, older stars. Can be determined by a galaxy"s rotation around its center. Most of a galaxy"s mass is in form of dark matter. There"s a black hole in the center of our galaxy & probably all galaxies. The various shapes have different sizes and populations of stars. Because the rotation curves of all galaxies resembles ours. The relationship between recession velocities of galaxies and their distances. The shape of our galaxy: (chapter 15, sect. 1 + intro, 2, 3, 4, 5) Billions of galaxies in the universe, forming clusters and superclusters of galaxies. Most of the stars making up our galaxy located on a disk. Inner part of disk filled with stars. Spiral arms swirl out from the ends of the bar, new stars form here. Outside part is a two-shell spherical halo.

Related Questions

The great astronomer Edwin Hubble discovered that all distant galaxies are receding from our Milky Way Galaxy with velocities proportional to their distances. It appears to an observer on the Earth that we are at the center of an expanding universe. Figure 3.64 illustrates this for five galaxies lying along a straight line, with the Milky Way Galaxy at the center. Using the data from the figure, calculate the velocities: (a) relative to galaxy 2 and (b) relative to galaxy 5. The results mean that observers on all galaxies will see themselves at the center of the expanding universe, and they would likely be aware of relative velocities, concluding that it is not possible to locate the center of expansion with the given information.

Figure 3.64 Five galaxies on a straight line, showing their distances and velocities relative to the Milky Way (MW) Galaxy. The distances are in millions of light-years (Mly), where a light-year is the distance light travels in one year. The velocities are nearly proportional to the distances. The sizes of the galaxies are greatly exaggerated; an average galaxy is about 0.1 MlY across.

ceruleangiraffe295

(a) relative to galaxy 2 and

(b) relative to galaxy 5.

The results mean that observers on all galaxies will see themselves at the center of the expanding universe, and they would likely be aware of relative velocities, concluding that it is not possible to locate the center of expansion with the given information.