What Do Astronomers Expect to Be the Relationship Between the Number

question 49

Multiple Choice

What do astronomers expect to be the relationship between the number of active galaxies they detect and the number of active galaxies that actually exist?

• A) The energy output from active galaxies is so large that it is easy to detect them. Thus, astronomers believe that they have detected all that exist.
• B) The nuclei of many active galaxies are hidden by dust in the accretion disk. Thus, astronomers expect the actual number to be much greater than the observed number.
• C) Astronomers cannot detect active galaxies unless the jets are pointed more or less toward Earth. The jets point toward Earth in only a few cases, so they expect the actual number to be greater than the observed number.
• D) Active galaxies are created in galaxy collisions. But galaxy collisions occurred only in the early universe and are no longer occurring. The active galaxies all died off while their light was traveling to Earth.

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