Q&A Hero

Q: In its most energetic phase, a quasar can probably only last A) a few days. B) a few years. C) a few thousand years. D) a few million years. E) a few billion years.

Q: The height of the quasar epoch was A) 5 billion years ago. B) when there was still sufficient mass to fuel the supermassive black holes at their center. C) before the formation of galaxies. D) less than 1 billion years ago. E) before mass had a chance to accumulate at the nucleus.

Q: What is true of galaxies at the larger redshifts compared to ones nearby? A) They appear smaller and more irregular. B) They appear larger and more regular. C) They are redder. D) They are almost all ellipticals. E) They are mostly giants.

Q: According to the HST data, very distant (and early) galaxies tend to be A) larger and bluer that modern galaxies. B) nothing but quasars. C) smaller, bluer, and more irregular than modern ones. D) redder, due to the recession of the universe. E) very well formed into clusters of nothing but spirals.

Q: The pregalactic blobs had masses similar to A) the Earth. B) the Sun. C) dwarf galaxies. D) open clusters of stars. E) the Milky Way.

Q: Which of these is the next evolutionary track for the Large Magellanic Cloud? A) contraction into a spiral B) expansion into a giant elliptical C) It will become a satellite galaxy of Andromeda. D) It will be free of our Local Group. E) collision with the Milky Way

Q: Astronomers believe that a spiral galaxy may form A) from a collision between a small and a large galaxy. B) due to a quasar shutting down. C) from the sudden contraction of an elliptical galaxy. D) from the collision of two giant elliptical galaxies. E) from the explosion of a dwarf irregular galaxy.

Q: What is true of spiral galaxies? A) They are much less common at larger redshifts. B) They are relatively rare in regions of high galaxy density. C) They are only found in the center of rich galaxy clusters. D) They have never been seen to have large redshifts. E) They evolve from giant ellipticals.

Q: Collisions between galaxies A) are much rarer than collisions between stars. B) can turn elliptical galaxies into spirals. C) cause large numbers of stars to collide and explode. D) cause the gas and dust clouds to collide, leading to rapid star formation. E) are the best explanation for gamma-ray burst events.

Q: Collisions between galaxies are thought to A) have stopped about 5 billion years ago. B) be commonplace. C) have never occurred. D) be extremely rare. E) have only occurred between 10 and 15 billion years ago.

Q: A radio galaxy whose lobes are swept back as if forming a tail probably indicates A) evidence for intergalactic matter. B) the galaxy is about to evolve into a spiral. C) the galaxy is isolated, not part of a cluster. D) the galaxy is moving towards Earth. E) there must be another galaxy nearby.

Q: Based on galactic rotation curves and cluster dynamics, we think dark matter A) is a minor component of the entire mass of the universe. B) is best detected from the X-rays it produces in the intergalactic medium. C) will have no effect on the fate of the universe. D) comprises over 90% of the entire mass of the universe. E) will doom the universe to collapse, overcoming the redshifts we now observe.

Q: The type of radio galaxy that reveals its motion through the intergalactic medium is called a A) quasar. B) dual lobe. C) bi-polar jet. D) head-tail. E) Seyfert.

Q: Mapping the intracluster gas is best done with A) the Arecibo radio dish. B) the HST with hydrogen alpha light. C) the Chandra X-ray Observatory in space. D) the Keck telescope in the infrared. E) the COBE satellite in microwaves.

Q: As we look at larger and larger scales in the universe, we find A) smaller and smaller masses. B) almost exclusively visible matter. C) a larger and larger percentage of the matter is visible. D) a larger and larger percentage of the matter is dark. E) an equal amount of visible and dark matter.

Q: How massive are the largest known galaxies? A) a few million solar masses B) a hundred million solar masses C) a few billion solar masses D) a trillion solar masses E) hundreds of trillions of solar masses

Q: Rotation curves for spiral galaxies show A) they are slowing down. B) rotation speed drops off further from the nucleus. C) most have dark halos. D) most of the mass lies in the nucleus. E) no relation to mass.

Q: The greater the mass of the foreground cluster of galaxies, the more warped the images of the distant galaxies are when they undergo gravitational lensing.

Q: When we see a doubling of the image of single quasar, the body creating the gravity lens is just a brown dwarf close to us.

Q: The absorption lines we find in quasar redshifts that arise from intervening gas clouds show even larger redshifts than the quasar spectra, due to dust absorption.

Q: The Great Wall is a huge sheet of galaxies that stretches for over 100 Mpc.

Q: Redshift surveys are designed to find which galaxies are oldest and youngest.

Q: Beyond the scale of superclusters, galaxies are randomly distributed throughout the universe.

Q: Quasars were used to determine the size of the Local Supercluster.

Q: It is currently believed that superclusters lie on the surfaces of "bubbles" in space.

Q: There is presently no evidence for large-scale structure bigger than about 200 Mpc.

Q: The Milky Way is at the center of our Local Supercluster.

Q: The "Great Wall" is the structure in the Large Magellanic Cloud near where Supernova 1987A occurred.

Q: Astronomers have discovered two black holes in the process of merging.

Q: The rapid decline in quasars 10 billion years ago signifies a rapid decline in galactic mergers.

Q: Virgo A (M87) is probably a dead quasar, but our Milky Way is not.

Q: Quasars may come from mergers of black holes in early galaxies.

Q: The more its central black hole was fed, the more likely the galaxy was to show up as a quasar.

Q: No binary black hole has ever been detected.

Q: In its early stages, the Milky Way was probably a quasar.

Q: The brightest active galaxies are giant ellipticals.

Q: Like supernovae, quasars must end with a violent explosion.

Q: Mergers between equally massive galaxies usually produce elliptical galaxies.

Q: Hubble reveals the most distant (first) galaxies were bluer than those of today.

Q: Galactic evolution is due to collisions between galaxies.

Q: Supermassive galaxies are found at the core of rich galaxy clusters.

Q: The pregalactic blobs started with masses comparable to big globular clusters.

Q: Most galaxies are isolated in space.

Q: Our theories of galaxy formation are just as well developed and tested as are our theories of star and planet formation.

Q: When galaxies collide, the large-scale galactic structure is affected, but most of the individual stars are not.

Q: In the larger clusters, colliding galaxies tend to pass through one another.

Q: Galactic collisions mostly involve interactions between gas and dust clouds rather than individual stars.

Q: Galactic collisions are believed to be commonplace.

Q: Collisions between galaxies have little effect on the individual stars.

Q: The Andromeda galaxy will eventually collide with the Milky Way.

Q: The stability of clusters of galaxies suggests that there is between 10 and 100 times as much dark matter as visible in the galaxies.

Q: Both spiral and elliptical galaxies seem to have dark haloes of similar proportions relative to their visible matter.

Q: The largest known galaxies contain about 10 billion solar masses.

Q: The masses of most spiral galaxies, like ours, are a few billion solar masses.

Q: Galaxies contain less mass as dark matter than as visible stars.

Q: Head-tail radio galaxies reveal their motion through the intergalactic gas with a tail-like structure.

Q: The percentage of dark matter in galactic clusters is less than the percentage in individual galaxies.

Q: The total mass of a galaxy tends to be only slightly larger than the visible mass.

Q: For nearby galaxies, determining the rotation curve allows us to calculate the mass.

Q: As with stars, binary galaxy pairs are useful in finding their total mass.

Q: Because of the great masses and speeds involved, Newton's laws are useless in measuring the mass of a galaxy.

Q: Mapping the intracluster gas is largely done with red light from the ionized emission lines of hot hydrogen.

Q: There are large amounts of superhot intergalactic matter.

Q: Most of the mass in the universe is dark matter.

Q: The Tully-Fisher relation exists between the galaxy's luminosity and its A) color. B) age. C) rotation. D) mass. E) size.

Q: For finding the distance to M31, Hubble relied upon A) RR Lyrae stars in its globular clusters. B) Type I supernova in its core. C) Type II supernova in its spiral arms. D) Cepheid variables in its spiral arms. E) planetary nebulae near its core.

Q: Most of the galaxies in the Local Group are A) big spirals like our Galaxy and M31. B) small spirals like M33 and the LMC. C) small irregulars like the Magellanic Clouds. D) active galaxies like Centaurus A. E) small ellipticals like the companions to M31 in Andromeda.

Q: Which statement about the Magellanic Clouds is false? A) They are both irregular galaxies. B) They are companions of the Milky Way. C) They contain regions of rapid star formation. D) They are the two closest galaxies to us. E) They are close to the south pole of the sky.

Q: What are Type I supernovae used for? A) Explaining the pulsars in supernova remnants. B) Calculating the density of the interstellar medium from their remnants. C) Age-dating the massive stars in clusters where they blow up. D) Standard candles for determining distances to other galaxies. E) Determining the half-lives of the heavy elements they create.

Q: What is the nearest huge cluster of thousands of galaxies, to which the Local Group may belong? A) The Great Wall B) Coma Cluster C) Virgo Cluster D) Corona Borealis Cluster E) Sagittarius Cluster

Q: Why does the Cepheid distance method fail us beyond about 20 Mpc? A) Distant galaxies are seen in the past, and Cepheids evolve with time. B) Distant galaxies are younger than our Milky Way; too young to have Cepheids yet. C) The intergalactic dust reddens the Cepheid's light and apparent brightness. D) Even with the HST, the most luminous Cepheids are too faint to be seen beyond 20 Mpc. E) The periods of Cepheids grows longer as the distances increase.

Q: About how many galaxies are presently known in our Local Group? A) 3 B) 27 C) 55 D) 107 E) 254

Q: Within the boundaries of the constellations Coma and Virgo are found A) all the galaxies in the Local Group. B) the most distant known quasars. C) the largest nearby superclusters of galaxies. D) the closest red dwarfs to the Sun. E) the Large and Small Magellanic Clouds.

Q: What is true of the Local Group? A) The Andromeda galaxy is a satellite of the Milky Way. B) The giant ellipticals are the largest members. C) It consists of mostly spirals. D) The Andromeda galaxy (M31), and the Milky Way are the two largest galaxies. E) It contains about 2500 galaxies.

Q: Which of these would be made up of only Population II stars? A) elliptical galaxies B) Irr type I C) Irr type II D) barred spirals E) Seyfert spirals

Q: You observe a spiral galaxy with a large central bulge and tightly wrapped arms. It would be classified a A) Sc. B) Sb. C) Sa. D) SO. E) E7.

Q: Which of the following is not one of Hubble's types of galaxies? A) normal spirals B) barrel spirals C) Seyfert spirals D) irregular type II E) dwarf ellipticals

Q: A galaxy with little cool gas or dust and no evidence of ongoing star formation is most likely a(n) A) elliptical. B) spiral. C) barred spiral. D) irregular. E) Seyfert.

Q: The greatest variation in size, mass, and luminosity occurs in A) globular clusters. B) elliptical galaxies. C) spiral and barred spiral galaxies. D) Irr I vs Irr II galaxies. E) Seyfert galaxies.

Q: Which type of galaxy has a stellar disk, but without gas and dust? A) E0 B) E7 C) Irr I D) S0 E) SE