astro chp 15 – Flashcards
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Which of the following types of galaxies has experienced no significant star formation during the last 10 billion years
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Elliptical
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As we progress in the Hubble classification sequence of spiral galaxies from type Sa to Sb to Sc, how do the physical characteristics change
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The central bulges become smaller, while the spiral arms become less tightly wound
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Which of the following statements describes the orbits of stars within most elliptical galaxies
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They have random orbits in three dimensions
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Which type of galaxy exhibits the largest range of sizes and masses
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elliptical
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The Tully-Fisher relation uses the close correlation between the rotational speed of a spiral galaxy and its luminosity as a distance indicator. Why does this correlation exist
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The greater the mass of a galaxy, the faster it spins, and the more mass there is to give off light
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Why do errors and uncertainties in distance measurements get bigger the farther out we measure
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The techniques used to measure far distances are calibrated by using more local measurements; therefore, any errors accumulate
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Which of these standard candles has been used to determine distances to the most distant galaxies
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Type I supernovae
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What is the criterion for a group of galaxies to be considered a cluster
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Galaxies in a cluster are bound together by their mutual gravitational pull
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According to Hubble's law, as the distance to galaxies ________, the ________ increases
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increases; apparent recessional velocity
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Which of the following is NOT an implication of Hubble's law
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The Milky Way Galaxy is at the center of the Universe
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Active galaxies give off more energy than "normal" galaxies in what part of the electromagnetic spectrum
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All of the above
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What characteristic of some radio lobe galaxies suggests that their energy emission changes over time
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They display "blobs" of material along their lengths that indicate this material was ejected in bursts
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What is observed that connects radio emissions in the galactic nucleus with the emissions in the halo or radio lobes
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There is a jet of matter coming out of the nucleus, which often points toward the lobes
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How does the energy output from active galactic nuclei differ from the energy output from normal galaxies
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The emission of active galactic nuclei is nonstellar, whereas the emission of a normal galaxy is stellar
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What is the best explanation of the differences between a lobe radio galaxy and a core-dominated radio galaxy
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There is no real difference. When we look at core-dominated radio galaxies, we are looking at the galaxy through one of its lobes and along one of the jets
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Except for the nucleus, what does a Seyfert galaxy look like
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a spiral galaxy
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Early attempts to explain the spectra of quasars were unsuccessful because the spectra were which of the following
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redshifted by a larger amount than expected
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The fact that the energy output of active galactic nuclei can vary significantly over a short time indicates that the central object emitting the energy is which of the following
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much less than a parsec across
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Which of the following is NOT a characteristic of an active galaxy
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a regular, rapid pattern of radio frequency and optical emission peaks ranging from milliseconds to seconds in repetition rate
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The large amount of synchrotron radiation coming from an active galaxy indicates the presence of what in the active galaxy
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A powerful magnetic field
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Using the method of standard candles, we can, in principle, find the distance to a campfire if we know
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the number of logs used
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If the light from a galaxy fluctuates in brightness very rapidly, the region producing the radiation must be
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very small
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Active galaxies are very luminous because they
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contain black holes in their cores
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Quasar spectra
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are strongly redshifted
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According to Figure 15.18 (Galaxy Energy Spectra) in the textbook, active galaxies
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emit large amounts of energy at all wavelengths
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Most galaxies are spirals like the Milky Way
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F
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Most elliptical galaxies contain only young stars
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F
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Type I supernovae can be used to determine distances to galaxies
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T
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Most galaxies are receding from the Milky Way Galaxy
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T
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Within 30 Mpc of the Sun, there are about
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few thousand galaxies
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Hubble's law states that
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the greater the distance to a galaxy, the greater is the galaxy's redshift
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Irregular galaxies, although small, have lots of star formation taking place in them
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T
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Hubble's law can be used to determine distances to the farthest objects in the universe
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T
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Active galaxies can emit thousands of times more energy than our own Galaxy
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T
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If the galaxy in Figure 15.10 (Galaxy Rotation) in the textbook were smaller and spinning more slowly, then the igure should be redrawn to show
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a narrower combined line
