Question 1

What assignment is given to a galaxy with a moderately sized nuclear bulge and moderately wound arms starting from a bar through the central part of the galaxy?

Accepted Answer

SBb galaxies are characterized by having a bar structure through the central part of the galaxy, a moderately sized nuclear bulge, and moderately wound arms, fitting the description given.

Question 2

At the conclusion of the Shapley-Curtis debate in April 1920,the general understanding of the astronomical community toward the "spiral nebulae" was

Accepted Answer

The Shapley-Curtis debate did not resolve the question of the nature of "spiral nebulae"; opinions remained divided, and the astronomical community did not reach a consensus, leaving the issue inconclusive at that time.

Question 3

Variable stars,such as Cepheid variables and RR Lyrae stars,are used in what important measurement in astronomy?

Accepted Answer

Variable stars, such as Cepheid variables and RR Lyrae stars, are used to measure distances to galaxies through a method known as the period-luminosity relationship. By observing the period and brightness of these stars, astronomers can determine the distance to the galaxy they are located in.

Question 4

The method used by Hubble to determine the distance to the Andromeda Galaxy (M31),thereby establishing the concept of separate and individual galaxies throughout the universe,was the

Accepted Answer

Hubble used the observation of Cepheid variable stars in M31 to determine its distance. Cepheid variables are very luminous stars whose brightness varies in a regular pattern that can be used to determine their distance. This method allowed Hubble to establish the concept of separate and individual galaxies throughout the universe.

Question 5

In the Hubble classification scheme for spiral galaxies,the tightness of the winding of the spiral arms appears to be directly related to the

Accepted Answer

The tightness of the winding of the spiral arms in the Hubble classification scheme is directly related to the size of the central bulge of the galaxy. Galaxies with small central bulges have loosely wound spiral arms, while galaxies with large central bulges have tightly wound spiral arms.

Question 6

The results of the 1920 Shapley-Curtis debate on the nature of "spiral nebulae" were inconclusive.What was really needed to provide an answer to the question was

Accepted Answer

The debate centered around whether spiral nebulae were part of the Milky Way or separate galaxies. To determine this, distances to the spiral nebulae were needed.

Question 7

In determining the distance to a galaxy by using observations of a Cepheid variable star,which of the following is NOT needed?

Accepted Answer

The answer of In determining the distance to a galaxy...

Question 8

According to the Hubble classification scheme,an Sa galaxy has a(n)

Accepted Answer

An Sa galaxy has a prominent central bulge and tightly wound, smooth spiral arms.

Question 9

Why does the central bulge of a spiral galaxy appear red when compared to the color of the spiral arms?

Accepted Answer

The central bulge of a spiral galaxy appears red because there is no star formation there, and the star population is dominated by old, long-lived, low-mass red stars.

Question 10

The observation by Hubble that demonstrated for the first time that the Andromeda "nebula" was at a very large distance from the Sun,and outside our Galaxy,was that

Accepted Answer

Hubble observed Cepheid variable stars in the Andromeda "nebula" and used their known luminosity-period relationship to calculate their distance. The faintness of these stars indicated that Andromeda was much farther away than previously thought, placing it well outside our own Galaxy.

Question 11

Distances to a nearby galaxy can be determined most accurately by

Accepted Answer

Using pulsating stars, such as Cepheid variables, allows astronomers to determine distances using the period-luminosity relationship. This method has been shown to be more accurate than other distance measurement techniques, such as measuring spectral lines or total energy received from a galaxy.

Question 12

The Hubble classification for a spiral galaxy with a prominent central bulge and smooth,broad spiral arms is

Accepted Answer

The description of a prominent central bulge and smooth, broad spiral arms fits the characteristics of a Sa galaxy according to the Hubble classification. The other options (Sc, E0, SBa) don't fully match the given description.

Question 13

The observational fact about a Cepheid variable star that leads to a measurement of its distance from Earth is that its period of variation is directly related to its

Accepted Answer

The period of variation of a Cepheid variable star is directly related to its absolute magnitude or luminosity. Therefore, by measuring its period of variation, astronomers can determine its absolute magnitude, which can then be compared to its apparent magnitude (as observed from Earth) to calculate its distance using the inverse square law of brightness.

Question 14

The Andromeda Galaxy (M31)is best described as a(n)

Accepted Answer

The Andromeda Galaxy (M31) is a spiral collection of stars, dust, and gas, which is approximately 200,000 light-years across. It is one of the closest galaxies to the Milky Way and is often referred to as its sister galaxy. The other options, such as an extension of the Milky Way or a gaseous nebula, do not accurately describe the Andromeda Galaxy. There is no evidence that the galaxy has a vortex surrounding a black hole.

Question 15

A particular galaxy has a nuclear region of more-or-less uniform brightness from which long lanes of stars curve outward.What type of galaxy is this?

Accepted Answer

This is a description of a spiral galaxy, with a central bulge or nucleus and curved arms or lanes of stars extending outward. Lenticular galaxies have a disk-like shape but lack prominent spiral arms, elliptical galaxies lack any distinct structure or arms, and irregular galaxies have a chaotic and uneven appearance.

Question 16

Which of the following fundamental astronomical questions did Curtis and Shapley debate in 1920 in their famous confrontation?

Accepted Answer

Curtis and Shapley debated whether the "spiral nebulae" were part of the Milky Way Galaxy or more distant, separate entities. This debate was critical in understanding the size and structure of the universe.

Question 17

Who developed the classification system that divides galaxies into spiral,elliptical,and irregular,and classified spirals by the size of their nuclear region and the tightness of winding of their arms?

Accepted Answer

Edwin Hubble developed the classification system that divides galaxies into spiral, elliptical, and irregular, and classified spirals by the size of their nuclear region and the tightness of winding of their arms.

Question 18

An astronomer studying a distant cluster of galaxies finds that several of the galaxies are spiral shaped,with a nuclear region of moderate size and moderately wound arms.How should the astronomer classify these galaxies?

Accepted Answer

Spiral galaxies are classified based on the size of their nuclear region and the winding of their arms. "Moderate size and moderately wound arms" correspond to Sb galaxies according to the Hubble classification system.

Question 19

What does a spiral galaxy look like when seen edge-on?

Accepted Answer

When seen edge-on, a spiral galaxy appears as a thick, flat line with a bulge in the center. This is because the dust and gas in the galaxy disc block the light from the stars in the spiral arms, making them difficult to see. The bulge in the center is often composed of older stars that are tightly packed together.

Question 20

In the Hubble classification scheme,the four main categories of galaxies include all of the following EXCEPT

Accepted Answer

The four main categories of galaxies in the Hubble classification scheme are normal spirals (S), barred spirals (SB), ellipticals (E), and irregulars (Ir). Starbursts are not a main category, but rather a type of galaxy that experiences a burst of star formation activity.

Quiz 14: Investigating Other Galaxies