Quasars and Supermassive Black Holes

After several decades of observation, astronomers have concluded that quasars are

a. very powerful and compact sources of energy at the centers of distant galaxies

The astronomer who first solved the problem of the strange red-shifts seen in quasar spectra and thus helped us understand that the quasars must be distant objects was

b. Maarten Schmidt

An astronomer claims that the large redshifts of all quasars are caused by some new mechanism and not the expansion of the universe. The redshift tells us nothing, he says, about where any quasar is located. Which of the following would be a way to disprove his view of quasars?

b. find a number of cases where a quasar seen in a cluster of galaxies has the same redshift as all the galaxies in the cluster

What observation in astronomy, made AFTER the discovery of quasars, was a big help to astronomers in figuring out what quasars really were?

b. the discovery that the Milky Way Galaxy has a black hole at the center with enough mass for 4 million Suns

What makes astronomers believe that the energy source in quasars is only a few light months across (the distance light travels in a few months)?

c. quasars show variations in their energy output that have a period of a few months

Today we know that what all quasars have in common is that they appear to be small sources of energy with

c. redshifts that indicate they are far away

A distant quasar shows a large redshift -- one so large, in fact, that the features we now see in the visible-light region of the spectrum would be invisible to us, were it not for the redshift. What band of the electro-magnetic spectrum were these features most likely in, before the spectrum was redshifted?

c. ultraviolet

A Congressman from Texas visits our National Observatory in Tucson, Arizona, and wants to be shown an object in the universe with the "biggest darn redshift you ever saw". What type of object should the astronomers show him?

d. a quasar

What method would astronomers use to find the distance to a remote quasar?

d. finding the redshift and using Hubble's Law

Which of the following observations is a convincing argument for the idea that quasars are located inside galaxies?

d. relatively nearby quasars show "fuzz" around them with the same spectra and redshift as the quasar

If quasars are at the distances most astronomers believe they are, then (for the most luminous ones) their luminosities must be

e. like the combined luminosity of a hundred trillion (1014) Suns

If quasars often resemble little blue stars, what was it about them that so surprised astronomers when they were discovered?

e. their spectral lines were at first hard to recognize and then turned out to have large redshifts

When quasars "shine" (in visible light and other kinds of radiation) with a lot of energy, where (what location) does this huge amount of energy come from?

from an accretion disk around a supermassive black hole

Today, astronomers find compelling evidence that the energy source of the quasars and active galaxies is

matter falling toward a supermassive black hole at the center of a galaxy

How do astronomers now explain the fact that the energy emitting regions for quasars are so small?

quasars are the result of matter falling into a black hole; the event horizons of even supermassive black holes are extremely small on the cosmic scale

The Hubble Space Telescope has enabled astronomers to explore an active galaxy such as M87 in remarkable detail. Which of the following observations of M87 is NOT an important part of the web of evidence that shows it must have a supermassive black hole at the center?

the discovery of a gravitational lens in M87

A friend of yours who is a science fiction fan hears you talk about the fact that astronomers now believe that the mechanism for the large energy output of quasars involves a supermassive black hole. He challenges you, saying something like "Oh come on, every science fiction fan knows that nothing, not even light, can escape from a black hole! How can a black hole be an energy source?" How would you respond to his objection?

the energy we see from quasars comes from regions where matter is falling in; these regions are still outside the event horizon

How do astronomers explain the energetic jets that come out of quasars and active galactic nuclei in opposite directions?

the jets are "spit out" from the chaotic accretion disks of supermassive black holes in directions that are perpendicular to the disk

Astronomers have established that quasars and active galaxies have a lot of mass at their centers in a very small volume of space. Why can't this mass be in the form of a cluster of stars that are quite close to each other?

to fit as much matter into the cluster as we observe, the stars in the cluster must be so close to each other they would merge into a superstar and soon collapse into a black hole