Category: 2. Active Galaxies, Quasars, & Supermassive Black Holes

Learning Objectives By the end of this section, you will be able to: The quasars’ brilliance and large distance make them ideal probes of the far reaches of the universe and its remote past. Recall that when first introducing quasars, we mentioned that they generally tend to be far away. When we see extremely distant…

Learning Objectives By the end of this section, you will be able to: In order to find a common model for quasars (and their cousins, the AGNs), let’s first list the common characteristics we have been describing—and add some new ones: The readers of this text are in a much better position than the astronomers who…

Learning Objectives By the end of this section, you will be able to: The name “quasars” started out as short for “quasi-stellar radio sources” (here “quasi-stellar” means “sort of like stars”). The discovery of radio sources that appeared point-like, just like stars, came with the use of surplus World War II radar equipment in the…

During the first half of the twentieth century, astronomers viewed the universe of galaxies as a mostly peaceful place. They assumed that galaxies formed billions of years ago and then evolved slowly as the populations of stars within them formed, aged, and died. That placid picture completely changed in the last few decades of the…