Question 1

Galaxies are distributed through the universe in

Accepted Answer

Galaxies are not randomly scattered throughout the universe but are actually distributed in clusters, which are then linked together to form superclusters. These superclusters are often found around large voids, creating a bubble-like appearance. Isolated clusters may also exist, but they are not as common as clusters in superclusters.

Question 2

The largest range of sizes of galaxies is found in which class of galaxies?

Accepted Answer

Elliptical galaxies have the largest range of sizes, from dwarf ellipticals smaller than some globular clusters to giant ellipticals that dominate galaxy clusters and can contain more than a trillion stars.

Question 3

The following distance-measuring techniques,arranged in order of the distance for which they are most effective,from smallest to greatest,are

Accepted Answer

Spectroscopic parallax is effective for measuring distances up to a few hundred light years. Cepheid variables are effective for measuring distances up to tens of millions of light years. Tully-Fisher relation becomes useful for measuring distances beyond the range of Cepheid variables, up to hundreds of millions of light years. Type Ia supernovae are the most distant objects observed in the universe, and are used to measure cosmic distances up to billions of light years away. Therefore, the correct order is spectroscopic parallax, Cepheid variables, Tully-Fisher relation, and Type Ia supernovae, which is best represented by choice C.

Question 4

Which of the following statements is NOT characteristic of elliptical galaxies?

Accepted Answer

Elliptical galaxies do not have a disk structure with a central bulge like spiral galaxies do; instead, they have an ellipsoidal shape without spiral arms, making choice D incorrect.

Question 5

The largest galaxies in the universe come from which classification group?

Accepted Answer

Giant elliptical galaxies are the largest galaxies in the universe, with sizes ranging from hundreds of thousands to over a million parsecs. These galaxies are classified as elliptical because of their smooth, featureless appearance and lack of significant ongoing star formation.

Question 6

Which of the following techniques are NOT used for distance measurement to distant galaxies?

Accepted Answer

Hot white dwarf stars are not used for distance measurement to distant galaxies. They can be used for studying our own Milky Way galaxy's history, but not for studying other galaxies. Supernova explosions, Tully-Fisher relationship, and Cepheid variable stars are all commonly used techniques for distance measurement to distant galaxies.

Question 7

How are galaxies spread throughout the universe?

Accepted Answer

Galaxies are not spread evenly throughout the universe. Instead, they are grouped into clusters, which are then grouped into even larger structures called superclusters. The distribution of galaxies is not uniform but rather clumped into these hierarchical structures.

Question 8

The Tully-Fisher relationship relies on broadening of the 21-cm radio line in distant spiral galaxies.What causes this broadening?

Accepted Answer

The broadening of the 21-cm radio line in distant spiral galaxies is caused by the rotation of the galaxy. The faster a galaxy rotates, the broader the 21-cm line appears. This relationship between the velocity of a galaxy's rotation and the width of the 21-cm line is the basis for the Tully-Fisher relationship.

Question 9

What is the Local Group?

Accepted Answer

The Local Group is a cluster of about 40 galaxies, including the Milky Way, that are relatively close to each other and gravitationally bound together. Option A describes a star cluster, option B describes a group of planets, and option C describes a satellite group orbiting around a single dominant galaxy.

Question 10

Which of the following types of galaxies contains primarily population II,low-mass,long-lived stars?

Accepted Answer

Elliptical galaxies are composed mainly of older, population II stars that formed early in the universe's history. These stars are low-mass, long-lived stars that are deficient in heavy metals.

Question 11

The Tully-Fisher relation provides a method of determining distances to galaxies by estimating the galaxy luminosity from the measurement of what parameter relating to the 21-centimeter atomic hydrogen radio emission line?

Accepted Answer

The Tully-Fisher relation is based on the assumption that there is a correlation between the width of the 21-centimeter atomic hydrogen radio emission line and the luminosity of a galaxy. Therefore, the parameter that is measured to estimate the galaxy luminosity is the width of the emission line.

Question 12

To an astronomer,what is a "standard candle"?

Accepted Answer

A "standard candle" is any astronomical object of known luminosity (absolute magnitude), which can be used to determine distances to other similar objects using their apparent brightness (apparent magnitude). This is based on the inverse square law of radiation, which states that the apparent brightness of an object decreases with the square of the distance from the observer. By comparing the apparent and absolute magnitudes of standard candles, astronomers can calculate how far away other objects are. Examples of standard candles include Cepheid variables, supernovae, and certain types of stars and galaxies. Choice A is incorrect because a standard candle is not a specific light source that can be placed in a telescope, but rather a concept used for distance determination. Choice C is incorrect because redshift is a measure of an object's velocity relative to the observer, not its luminosity. Choice D is incorrect because the magnitude scale is a relative measure of brightness, not an accurately defined scale for standard candles.

Question 13

Are there types of galaxies in which we can see completely through their centers?

Accepted Answer

Dwarf galaxies are less densely populated with stars, including in their centers, making it possible to see through them.

Question 14

Of the following distance measurement techniques,which one can be used to find the farthest distances?

Accepted Answer

Type Ia supernova apparent brightness measurement can be used to find the farthest distances as they are extremely luminous and can be observed at extremely great distances.

Question 15

What is an elliptical galaxy?

Accepted Answer

An elliptical galaxy is characterized by its smooth distribution of brightness, without any spiral arms, and an overall elliptical shape.

Question 16

The Hubble classification for a very flat elliptical galaxy is

Accepted Answer

The Hubble classification for a very flat elliptical galaxy is E7. The Hubble sequence classifies elliptical galaxies on a scale from E0, being nearly spherical, to E7, being the most elongated or flat.

Question 17

What is a rich cluster of galaxies?

Accepted Answer

A rich cluster of galaxies is a cluster that contains thousands of galaxies. These clusters are the largest and most massive structures in the universe, held together by the gravitational attraction between their constituent galaxies. Rich clusters are typically dominated by elliptical galaxies and are important for studying the evolution of galaxies and the large-scale structure of the universe.

Question 18

What is the Tully-Fisher relation?

Accepted Answer

The Tully-Fisher relation is an empirical relationship between the luminosity (brightness) of a galaxy and the width of its 21-cm radio emission line. In other words, the brighter the galaxy, the wider the 21-cm radio emission line. This relationship is useful for measuring distances to galaxies and for studying their properties.

Question 19

Which of the following types of galaxies contain little or no interstellar dust or gas?

Accepted Answer

Elliptical galaxies are typically composed of older stars and contain very little interstellar dust and gas, which is why they are often referred to as "red and dead" galaxies.

Question 20

What is a lenticular (S0)galaxy?

Accepted Answer

A lenticular (S0) galaxy has a disk and central bulge like a spiral galaxy but lacks prominent spiral arms, making option D the best choice. Lenticular galaxies are classified as intermediate between elliptical and spiral galaxies.

Quiz 14: Investigating Other Galaxies