Chapter 24

25 July 2022
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Most galaxies are spirals.
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False
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Most galaxies are members of some sort of cluster of galaxies.
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True
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The Tully-Fisher relation is much like the mass-luminosity relationship, except that the galaxy's rotation is used to find its mass; the greater the mass, the faster the rotation rate.
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True
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Our own Local Group is dwarfed by the much larger Virgo Cluster, about 50 million light years distant.
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True
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Type I supernovae can be used to determine distances to galaxies much better than type II supernovae.
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True
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The expansion of the universe means that stars in our Milky Way Galaxy are getting increasingly farther apart.
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False
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If the redshift is an accurate indication of the distance to that galaxy, then this is considered a cosmological redshift.
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True
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The first hint that the universe might be expanding came from Vesto Slipher's work with the spectra of spiral nebulae in 1912.
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True
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Active galactic nuclei are usually powered by supermassive black holes.
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True
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Quasars can emit as much as thousands of times as much energy as normal galaxies.
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True
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The first clue to the significance of quasars came from the discovery that some of these "stars" were much stronger radio sources than any normal star.
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True
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There is very little interstellar gas or dust in most elliptical galaxies.
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True
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Orientation counts; if looking down the jets of an active core, we see a blazar.
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True
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Some lobes of radio galaxies are in fact moving faster than the speed of light.
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False
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Astronomers observe unobscured X-rays generated in active galactic nuclei.
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False
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Galaxies are classified into types solely on the basis of their color.
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False
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Type Sc are the dustiest of the galaxies.
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True
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M-31 in Andromeda is a slightly bigger version of our own Milky Way.
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True
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While our two companions, the Magellanic Clouds, are irregulars, Andromeda's two companions, M-32 and M-110, are dwarf ellipticals.
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True
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The latest evidence from 2MASS suggests our own Milky Way is type SBb.
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True
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The smallest dwarf irregular galaxies are no richer in stars than the largest known globular clusters.
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True
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Irregular galaxies, although small, have large H II regions and much on-going star formation for their size.
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True
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A spherical galaxy, like M87, which looks like a monster globular cluster, is type:
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E0.
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When mass is accreted into a black hole, how much total mass-energy can be radiated away?
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20%
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The Milky Way is often considered to be an intermediately wound, barred spiral, which would be type ________ according to Hubble.
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SBb
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The greatest variation in size, mass, and luminosity occurs in:
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elliptical galaxies.
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Which of the following is NOT one of Hubble's types of galaxies?
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Seyfert spirals
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Which of the following is true about the ages and masses of spiral and elliptical galaxies?
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Both types are about the same age, but spirals vary less in mass.
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Which of these would be made up of only Population II stars?
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elliptical galaxies
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Within the boundaries of the constellations Coma and Virgo are found:
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the largest nearby superclusters of galaxies.
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Most of the galaxies in the Local Group are:
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small ellipticals like the companions to M31 in Andromeda.
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What is the nearest huge cluster of galaxies to our Local Group?
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Virgo Cluster
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The Tully-Fisher relation exists between the galaxy's luminosity and its:
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rotation.
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The flattest of the ellipticals are class:
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E7.
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Which statement about the Local Group is FALSE?
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It contains the large radio galaxy Centaurus A.
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What is the nearest huge cluster of thousands of galaxies, to which the Local Group may belong?
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Virgo Cluster
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Most galaxies in the Local Group are:
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dwarf ellipticals, similar to the companions of M-31.
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Why does the Cepheid "standard candle" have limited usefulness beyond 20 Mpc?
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Cepheids are too faint to be seen beyond that distance, even with HST.
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Which of the following paraphrases Hubble Law?
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The greater the distance to a galaxy, the greater its redshift.
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What is true of spiral galaxies?
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They are relatively rare in regions of high galaxy density.
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According to the Hubble Law, a galaxy with a velocity of 25,000 km/s will be:
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400 million pcs away.
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For finding the distance to M31, Hubble relied upon:
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Cepheid variables in its spiral arms.
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According to Hubble's Law, the greater a galaxy's redshift, the:
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farther it is from us.
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While examining the spectrum of a galaxy you find all the hydrogen lines are shifted to longer wavelengths. This galaxy is:
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moving away from us.
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In this diagram, the galaxy at the left side is a(n):
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Elliptical.
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How does the modern value of Hubble's constant compare to Hubble's original published value?
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The modern value is about 7 times lower than the original value.
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Quasars usually have their distances measured by what technique?
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Hubble's Law
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Why do some quasars have redshifts greater than 1?
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They are very distant, with relativistic redshifts that take into account dilation of space-time, as Einstein predicted.
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The look-back time of an object is directly related to its:
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distance.
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A supernova that occurred 30,000 years ago in a galaxy 100,000 light years away will be observed on Earth:
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70,000 years from now.
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That quasars were at cosmological distances yet appeared like ordinary faint stars meant:
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they must be producing such large quantities of energy than even fusion could not explain their output.
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Quasar's spectral lines are:
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emission lines with large redshifts.
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In active galaxies, their central engines may be temporarily fed by:
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a close encounter with a neighbor galaxy.
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Why is the energy source for active nuclei like Seyferts thought to be compact?
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The light can vary over short time intervals.
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What is true of the lobes of a radio galaxy?
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They are perpendicular to the galactic plane.
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Which type of galaxy has a stellar disk, but without gas and dust?
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S0
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The lobes of a radio galaxy can be as much as:
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millions of light years from the galaxy's nucleus.
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In what sense are the quasars "quasi-stellar"?
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In short time exposures, their images looked stellar.
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Most active galactic nuclei are powered by:
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supermassive black holes.
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If we are directly in the line of a jet coming out of the lobe galaxy's core, we see a:
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blazar.
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The huge lobe radio galaxy at the center of the Virgo Supercluster is:
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M-87, a giant elliptical galaxy.
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The quasars with the largest presently known redshifts are close to:
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8.
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A billion solar mass black hole would still have a radius of only:
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20 AU.
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Which of the following does the intensity of synchrotron radiation NOT depend on?
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temperature
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The type of radiation coming from active nuclei due to electrons spiraling in very strong magnetic fields at relativistic speeds is:
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synchrotron radiation.
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Synchrotron radiation produces a(n) ________ spectrum.
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continuous nonthermal
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You observe a spiral galaxy with a large central bulge and tightly wrapped arms. It would be classified an:
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Sa.
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The energy radiated by a typical quasar requires that its black hole accrete about:
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ten solar masses a year.
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Not only does the central engine of active galaxies and quasars require a black hole, but also ________ to provide the radiate energy.
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an accretion disk of infalling matter
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The magnetic fields carried by jets coming from active galactic nuclei are generated by:
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charged matter in the accretion disk of the central black hole.
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Although theory says a massive black hole with an accretion disk should be emitting X-rays, many black holes emit:
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mostly in the infrared.
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A galaxy that was once a quasar is likely to:
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have a black hole at its nucleus.
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An intermediately wound barred spiral galaxy would, in Hubble's system, be:
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SBb.
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In Hubble's classification, which type of galaxy has a small bulge and loose, widely spread, poorly defined spiral pattern?
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SO
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In Hubble's classification, which type of galaxy has no stellar disk and no gas or dust?
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E0
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The Large and Small Magellanic Clouds fall into Hubble's class
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Irr I.