Question 1

These three barred spirals are the largest members of the Local Group:

Accepted Answer

The largest barred spiral galaxies in the Local Group are Andromeda, the Milky Way, and Triangulum.

Question 2

Outline the major differences between the thin and the thick disks of the Milky Way Galaxy.

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Question 3

Describe, for each component of the Milky Way Galaxy labeled in the figure below, the typical heavy-element abundances found in that region, and what causes that region to have those abundances.

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Question 4

What are spiral arms, and what is thought to cause them?

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The answer of What are spiral arms, and what is...

Question 5

Astronomers expect life to be rare (and maybe impossible) in the Milky Way's bulge because

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The central regions of the Milky Way's bulge have high levels of radiation, which can be detrimental to the development and sustainability of life.

Question 6

Suppose it was discovered that the galaxy has constantly been absorbing large amounts of pristine gas that never had any stars form in it.Would this complicate our interpretation of ages and chemical enrichment?

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The answer of Suppose it was discovered that the galaxy...

Question 7

What is ripping apart the Sagittarius dwarf spheroidal galaxy?

Accepted Answer

The Sagittarius dwarf spheroidal galaxy is being torn apart by the gravitational tidal forces exerted by the Milky Way galaxy as it orbits around it.

Question 8

Astronomers have identified examples of extraordinarily massive globular clusters (in both the Milky Way and Andromeda) that contain several million solar masses worth of stars.Moreover, these clusters also show evidence of multiple stellar populations.What would be a reasonable interpretation for such atypical clusters?

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The answer of Astronomers have identified examples of extraordinarily massive...

Question 9

Suppose that scientists in the future are able to observe a star orbiting the central region of the Andromeda Galaxy and find that it has an orbital period of 31 years and a semimajor axis of 4,500 AU.The mass of Andromeda's central black hole must then be around

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Question 10

By comparing globular clusters, you find that Cluster A's RR Lyrae stars are 225 times fainter than Cluster B's RR Lyrae stars.You know that both clusters have approximately the same chemical composition and age, and thus their RR Lyrae stars should have the same luminosities.Which cluster has the larger distance, and what is the ratio of the clusters' distances?

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Question 11

How would we explain why are there are no known disk stars with exceptionally low abundances of massive elements?

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Question 12

The most distant galaxy observable with the naked eye from Earth is the

Accepted Answer

The Andromeda Galaxy is the most distant galaxy visible to the naked eye from Earth, located about 2.537 million light-years away.

Question 13

The Milky Way and Andromeda are on a collision course.When will the initial collision happen?

Accepted Answer

The Milky Way and Andromeda galaxies are expected to begin colliding in about 4 billion years.

Question 14

What is expected to happen to our Solar System when the Andromeda and Milky Way galaxies collide?

Accepted Answer

When the Andromeda and Milky Way galaxies collide, it is expected that the Sun may be thrown into a different orbit within the merged galaxies, but the solar system itself will remain relatively unchanged due to the vast distances between stars.

Question 15

What would be the apparent angular size of a 100 light-year-diameter globular cluster in the Andromeda Galaxy (2.5 x10⁶ light-years away), as measured from Earth?

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Question 16

How do we know that globular cluster stars are not the first stars that have ever formed? Would this understanding change if some or all globular clusters came into the galaxy by accretion of small satellite galaxies?

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Question 17

The presence of dwarf galaxies in orbit around the Milky Way supports what picture of our galaxy's formation?

Accepted Answer

The presence of dwarf galaxies in orbit around the Milky Way supports the idea that the galaxy was formed by the merger of smaller protogalactic clumps, as these dwarf galaxies are remnants of those smaller systems.

Question 18

The Andromeda Galaxy is

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The Andromeda Galaxy is the largest member of the Local Group, which includes the Milky Way and other smaller galaxies.

Question 19

What are the main observational difficulties in observing the shape and spiral arm pattern of the Milky Way?

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Question 20

Because of the ages of globular clusters in the Milky Way, we think our galaxy's early formation history was characterized by

Accepted Answer

The ages of globular clusters suggest that the Milky Way formed through the merging of protogalactic fragments, which led to a high rate of star formation in the early history of the galaxy.

Quiz 20: The Milky Waya Normal Spiral Galaxy