Astronomy Ch 25-28

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

Maarten Schmidt

Your weird cousin, who is really into astronomy, decides that the return address he uses on his letters is incomplete! To his city, state, and country, he begins to add: "North America, Earth, Solar System..." If he now wants to include the name of the Galaxy's spiral-structure feature in which the Earth is located, how should his address end?

Orion Spur

The rich galaxy cluster that is closest to our Local Group of galaxies is the

Virgo Cluster

Which of the following statements about dark matter in the Galaxy is FALSE?

While the dark matter cannot be observed with our present-day instruments, we still have a pretty good idea what it consist of

Astronomers today know a lot about the size and shape of the Milky Way Galaxy. Which of the following common objects most resembles the shape of our Galaxy?

a CD or DVD

The central region of our Galaxy is not as flat as its main disk of stars. Which of the following has roughly the same shape as our central region of stars?

a peanut

You suddenly get an uncontrollable urge to find out more about the other side of the Milky Way Galaxy (the regions beyond the center). Where should you rush off to?

a radio telescope that can observe at 21-cm wavelengths

When astronomers have examined rich clusters of galaxies with their instruments, they have found that these clusters

are more likely to contain giant elliptical galaxies than poor clusters

Which type of galaxy is very difficult to see, but (astronomers recently realized) may be very common?

dwarf elliptical

One of the main projects being carried out by the Hubble Space Telescope is to measure the distances of galaxies located in groups dozens of millions of lightyears away. What method do astronomers use with the Hubble to find such distances?

finding Cepheid variables and measuring their periods

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

What objects did Harlow Shapley use as "signposts" to figure out the extent of the Milky Way Galaxy and the location of its center?

globular clusters

In a distant galaxy, whose light is just arriving from 10 billion light years away, our spectroscope should reveal that the most common element is

hydrogen

Which of the following statements about the implications of Hubble's Law is FALSE?

if you were observing the universe from a distant galaxy, you would NOT see all the galaxies (except those in your own group) moving away from YOU

If we want to see what galaxies looked like at a time close to the beginning of the universe, where should we look?

in a direction away from the plane of the Milky Way, where we can see very faint galaxies that are more than 10 billion light years away

An astronomer who loved reading the Guinness Book of World Records when she was a child becomes obsessed with quasars and wants desperately to find the most distant quasar ever (the one with the largest redshift.) Where should she be looking to have the best chance of finding such a quasar?

in or near a distant cluster of galaxies that can act like a gravitational lens

If a galaxy contains a great deal of "dark matter," what will that do the galaxy's mass-to-light ratio?

increase it quite a bit

According to the Cosmological Principle, the universe

is isotropic and homogeneous

Which of the following is not true about the Local Group of galaxies (of which the Milky Way is a member)?

it has about a thousand member galaxies

According to our modern "bottom-up" model of the formation of large structures in the universe, the structures that formed first were about the mass of a

large globular cluster or a small galaxy

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

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

Radio astronomy has played a pivotal role in showing us the detailed structure of the Milky Way Galaxy. Which of the following techniques would a radio astronomer use as an essential part of an investigation of this structure?

measuring the Doppler shift of a line in a radio spectrum

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

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

Our Milky Way Galaxy is what type of galaxy?

spiral

The Tully-Fisher relation (looking at rotation speeds) only works for:

spiral galaxies

Why do galaxies collide, while stars almost never do?

stars are much further apart (compared to how big they are) than galaxies are

The new instrument that made it possible for Edwin Hubble to demonstrate the existence of other galaxies in the early 1920's was:

the 100-inch reflector on Mount Wilson

Which of the following is NOT part of the growing chain of evidence that makes many astronomers suspect there is a black hole at the very center of the Milky Way Galaxy?

the Hubble Space Telescope has shown us a visible-light image of an accretion disk at the center of the Galaxy

Which of the following statements about the nuclear bulge of our Galaxy is FALSE?

the best way to learn more about it is to observe higher energy radiation, such as ultraviolet and x-rays

Astronomers believe that the center of our Galaxy has a black hole with enough mass inside to make almost 4 million Suns! How do astronomers think a black hole could acquire so much mass?

the center of our Galaxy is a much more crowded region than where the Sun is found; we still see material falling toward the center and material has fallen in for billions of years

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

Edwin Hubble was able to show that (with the exception of our nearest neighbors) the farther a galaxy is from us, the

the faster it is moving away from us

If a very distant galaxy looks blue overall to astronomers, from this they can conclude that:

the galaxy must have a lot of young stars and thus active star formation must still be going in it

An astronomer discovers a massive galaxy which has four nuclei. What is a likely explanation for a galaxy having more than one nucleus?

the galaxy must have swallowed several smaller galaxies that were its neighbors

When astronomers make counts of how many quasars there are at different distances from us, what do they find?

the largest number of quasars can be seen at about the distance corresponding to a time when the universe was only 20% its current age (a time when the universe was still young)

For galaxies that have super-massive black holes at their centers, how do astronomers find that the mass of the host galaxy and the mass of the black hole are related?

the more massive the galaxy, the more massive the central black hole

The Andromeda Galaxy (our nearest spiral neighbor) has spectral lines that show a blue shift. From this, we may conclude that:

this particular nearby galaxy is moving toward us

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?

ultraviolet

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

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

Which of the following can we NOT learn from studying the Doppler shifts in the spectrum of galaxies beyond our Local Group?

whether they have Jupiter-mass planets around many of their stars