Thought Questions

Suppose you observe a star-like object in the sky. How can you determine whether it is actually a star or a quasar?

Why don’t any of the methods for establishing distances to galaxies, described in Galaxies (other than Hubble’s law itself), work for quasars?

One of the early hypotheses to explain the high redshifts of quasars was that these objects had been ejected at very high speeds from other galaxies. This idea was rejected, because no quasars with large blueshifts have been found. Explain why we would expect to see quasars with both blueshifted and redshifted lines if they were ejected from nearby galaxies.

A friend of yours who has watched many Star Trek episodes and movies says, “I thought that black holes pulled everything into them. Why then do astronomers think that black holes can explain the great outpouring of energy from quasars?” How would you respond?

Could the Milky Way ever become an active galaxy? Is it likely to ever be as luminous as a quasar?

Why are quasars generally so much more luminous (why do they put out so much more energy) than active galaxies?

Suppose we detect a powerful radio source with a radio telescope. How could we determine whether or not this was a newly discovered quasar and not some nearby radio transmission?

A friend tries to convince you that she can easily see a quasar in her backyard telescope. Would you believe her claim?