Question 1

What evidence supports the theory that there is a black hole at the center of our galaxy?

Accepted Answer

A)  We observe an extremely bright X-ray source at the center of our galaxy.
B)  We can see gas falling into an accretion disk and central mass at the center of our galaxy.
C)  The motions of the gas and stars at the center indicate that it contains a million solar masses within a region only about 1 parsec across.
D)  We observe a large,dark object that absorbs all light at the center of our galaxy.
E)  all of the above

Question 2

What evidence do we have that the halo population of stars are older than other stars in the galaxy?

Accepted Answer

A)  They are farther away.
B)  They have higher masses than other stars in the galaxy.
C)  They have fewer planets.
D)  They have a smaller proportion of heavy elements.
E)  They move slower than other stars in the galaxy.

Question 3

What produces the 21-cm line that we use to map out the Milky Way Galaxy?

Accepted Answer

A)  atomic hydrogen
B)  ionized hydrogen
C)  molecular hydrogen
D)  carbon monoxide
E)  helium

Question 4

Approximately how far is the Sun from the center of the galaxy?

Accepted Answer

A)  27 light-years
B)  270 light-years
C)  2,700 light-years
D)  27,000 light-years
E)  27 million light-years

Question 5

Which of the following comprise the oldest members of the Milky Way?

Accepted Answer

A)  the Sun and other solar mass stars
B)  O stars
C)  red giant stars in spiral arms
D)  Cepheid variables
E)  globular clusters

Question 6

Briefly explain why stars that formed early in the history of the galaxy contain a smaller proportion of heavy elements than stars that formed more recently.

Accepted Answer

The star-gas-star cycle gradually enrich...

Question 7

If you could watch a time-lapse movie of the interstellar medium over hundreds of millions of years,what would you see?

Accepted Answer

A)  Gas that changes only in very slow and steady ways,so that the movie would in fact be quite boring.
B)  The entire disk of the Milky Way would pulsate in and out as it contracts to form stars and then blows out in supernovae and then contracts to form stars again and so on.
C)  The movie would alternate back and forth between being very bright when there is a lot of gas and very dark when there is very little gas.
D)  Gas that is often moving at high speed,particularly after one or more supernovae,and constantly changing form between molecular clouds,atomic hydrogen,and hot,ionized bubbles and superbubbles.

Question 8

What observational evidence supports the galactic fountain model (which describes how gas cycles between the disk of the galaxy and regions high above the disk) ?

Accepted Answer

A)  We have discovered a jet of ionized gas shooting out of the bulge of our galaxy.
B)  We have discovered that the entire galactic disk is being uniformly "rained on" by cool gas coming from the halo.
C)  We see hot gas high above the region of the disk near our solar system,along with cool gas that appears to be raining down from the halo.
D)  We have observed a lot of water molecules in the interstellar medium.

Question 9

Most nearby stars move relative to the Sun at speeds below about 30 km/s.Suppose you observe a nearby star that is moving much faster than this (say,300 km/s) .Which of the following is a likely explanation for its high speed?

Accepted Answer

A)  It is probably a halo star that is currently passing through the disk.
B)  It is a very young star,recently formed.
C)  It has been pushed to high speed by the shock wave from a nearby supernova.
D)  It is a very high mass star.

Question 10

All the following types of objects are found almost exclusively in the disk (rather than the halo) of the Milky Way except

Accepted Answer

A)  young stars.
B)  globular clusters.
C)  X-ray binaries.
D)  high-mass,red supergiant stars.

Question 11

Over time,the star-gas-star cycle leads the gas in the Milky Way to

Accepted Answer

A)  have a greater abundance of heavy elements.
B)  have a lower abundance of heavy elements.
C)  become denser and have a greater abundance of heavy elements.
D)  become denser and hotter.

Question 12

If we could see our own galaxy from 2 million light-years away,it would appear

Accepted Answer

A)  as a flattened disk with a central bulge and barred-spiral arms.
B)  as a faintly glowing band of light stretching all the way around the sky.
C)  to fill the sky with widely spaced stars.
D)  like a single,dim star.

Question 13

Which of the following statements about the disk of the Milky Way is false?

Accepted Answer

A)  The average age of disk stars is less than that of halo stars.
B)  Disk stars are all younger than 5 billion years.
C)  Disk stars have a higher proportion of heavy elements,on average,than halo stars.
D)  Disk stars orbit in the same direction around the Galactic center.
E)  The length of the disk is about 100 times its thickness.

Question 14

What can cause a galactic fountain?

Accepted Answer

A)  winds and jets from newly-formed protostars
B)  a supernova occurring in the halo
C)  multiple supernovae occurring together
D)  the combined effect of spiral density waves
E)  molecular clouds falling towards the galactic center

Question 15

The Milky Way looks the same in X-rays as it does at infrared wavelengths.

Accepted Answer

A) True 
 B)False

Question 16

Suppose a scientist holds a press conference at which he claims that 10% of the matter in the Milky Way is in the form of dust grains.Does his claim seem reasonable? Why or why not?

Accepted Answer

A)  It is reasonable,because we already know that interstellar dust obscures our view through the disk of the galaxy.
B)  The 10% figure is too low,because most of the mass of the galaxy is in the form of interstellar dust.
C)  The 10% figure is too high because there are not enough heavy elements to make that much dust.
D)  It seems reasonable as long as we assume that red giant stars-which produce dust grains in their stellar winds-are more common than we thought.

Question 17

Compared with our Sun,most stars in the halo are

Accepted Answer

A)  young,red,and dim and have fewer heavy elements.
B)  young,blue,and bright and have much more heavy element material.
C)  old,red,and dim and have fewer heavy elements.
D)  old,red,and dim and have much more heavy element material.
E)  old,red,and bright and have fewer heavy elements.

Question 18

Which of the following statements comparing halo stars to our Sun is not true?

Accepted Answer

A)  Most stars in the halo have cooler surface temperatures than the Sun.
B)  Most stars in the halo are less luminous than the Sun.
C)  Most stars in the halo contain a much lower percentage of heavy elements than the Sun.
D)  Most stars in the halo have either died or are in their final stages of life,while the Sun is only in about the middle of its lifetime.

Question 19

What makes up the interstellar medium?

Accepted Answer

A)  open clusters
B)  O and B stars
C)  K and M stars
D)  gas and dust
E)  all of the above

Question 20

What do we mean by a protogalactic cloud?

Accepted Answer

A)  a cloud of hydrogen and helium that contracts to become a galaxy
B)  a term once used historically to refer to any galaxy
C)  the cloud-like halo that surrounds the disks of spiral galaxies
D)  a cloud of gas that was once a galaxy

Exam 19: Our Galaxy

All the following types of objects are found almost exclusively in the disk (rather than the halo) of the Milky Way except

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Which of the following comprise the oldest members of the Milky Way?

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If you could watch a time-lapse movie of the interstellar medium over hundreds of millions of years,what would you see?

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Which of the following statements about the disk of the Milky Way is false?

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Most nearby stars move relative to the Sun at speeds below about 30 km/s.Suppose you observe a nearby star that is moving much faster than this (say,300 km/s) .Which of the following is a likely explanation for its high speed?

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What do we mean by a protogalactic cloud?

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What evidence supports the theory that there is a black hole at the center of our galaxy?

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Over time,the star-gas-star cycle leads the gas in the Milky Way to

Correct AnswerverifiedShow Answer

Briefly explain why stars that formed early in the history of the galaxy contain a smaller proportion of heavy elements than stars that formed more recently.

Correct AnswerverifiedThe star-gas-star cycle gradually enrich...View AnswerShow Answer

If we could see our own galaxy from 2 million light-years away,it would appear

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Suppose a scientist holds a press conference at which he claims that 10% of the matter in the Milky Way is in the form of dust grains.Does his claim seem reasonable? Why or why not?

Correct AnswerverifiedShow Answer

The Milky Way looks the same in X-rays as it does at infrared wavelengths.

Correct AnswerverifiedShow Answer

Which of the following statements comparing halo stars to our Sun is not true?

Correct AnswerverifiedShow Answer

What evidence do we have that the halo population of stars are older than other stars in the galaxy?

Correct AnswerverifiedShow Answer

What observational evidence supports the galactic fountain model (which describes how gas cycles between the disk of the galaxy and regions high above the disk) ?

Correct AnswerverifiedShow Answer

Approximately how far is the Sun from the center of the galaxy?

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What produces the 21-cm line that we use to map out the Milky Way Galaxy?

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Compared with our Sun,most stars in the halo are

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What makes up the interstellar medium?

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What can cause a galactic fountain?

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The star-gas-star cycle gradually enrich...
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