The unusually bright centers found in some galaxies are called 1.active galactic nuclei. 2.starbursts. 3.halos. 4.supermassive black holes.
According to current understanding, what is a quasar? 1.An active galactic nucleus that is particularly bright. 2.Any object with an extremely large redshift. 3.A galaxy with an unusually high rate of star formation. 4.A very large galaxy thought to be formed by the merger of several smaller galaxies, typically found in the center of a galaxy cluster.
The luminosity of a quasar is generated in a region the size of 1.the Milky Way. 2.a star cluster. 3.the solar system. 4.a planet.
The observed relationship between the masses of central black holes and the bulge masses of galaxies implies that 1.the black holes will eventually suck in the rest of the galaxy. 2.the biggest galaxies have the most luminous quasars. 3.quasars were more common 10 billion years ago than they are today. 4.galaxy formation and supermassive black holes formation must be related somehow.
The best evidence for the existence of supermassive black holes is 1.large quantities of high-energy emission, such as X-rays and gamma rays, and radio emission from relativistic electrons. 2.jet velocities that approach the speed of light. 3.huge dark regions in the centers of galaxies, where black holes have been sucking in the galaxy from the inside out. 4.very high orbital velocities in a very compact region.
A quasar’s spectrum is hugely redshifted. What do most astronomers think this large redshift tells us about the quasar? 1.The size of the quasar’s central supermassive black hole. 2.The type of host galaxy in which the quasar resides. 3.The composition of the quasar. 4.The distance to the quasar.
Most active galactic nuclei are found at large distances from us, with relatively few nearby. What does this imply? 1.Supermassive black holes existed only when the universe was young, and no longer exist today. 2.The jets seen in many active galactic nuclei must cause them to move far away from us. 3.Active galactic nuclei tend to become less active as they age. 4.Active galactic nuclei can form only at large distances from the Milky Way.