By the late 20th century, it was clear that there were many different kinds of very luminous, active galaxies, including (but not limited to) (1) blazars, which are radio-loud (meaning bright in radio waves) extremely compact quasars; (2) Type I Seyfert galaxies, which show the broadest emission lines, indicating fast-moving gas; (3) Type II Seyfert galaxies show only narrower emission lines, indicating that the material is moving less rapidly.
One of the achievements of 20th-century astronomy is the development of the unified active galactic nuclei (AGN) model. This model explains that the various types of active galaxies can be explained by the same kind of supermassive black hole structure at the center of a galaxy but viewed from different angles. Match the active galaxy type with the viewing point.
Seyfert I - Seyfert II - blazars
A - Seyfert I
B - Seyfert II
C - blazars
Which of the following is not evidence that it is a supermassive black hole that powers active galactic nuclei?
Choose one:
A. Whatever is creating the AGN must have lots of energy at its disposal.
B. The source at the base of the jet is seen to be only a few astronomical units across at most.
C. The speeds of the jets are relativistic, approaching the speed of light, requiring a huge power source.
D. We see a small dark spot at the base of the jets seen coming from some active galaxies.
E. The rapid variability of quasars and blazars suggests a very small size scale, no more than a few astronomical units in size.