Question 1

There is no special center to the expansion of the universe.

Accepted Answer

A) True 
 B)False

Question 2

How did Edwin Hubble definitively prove that "spiral nebulae" were individual galaxies that were separate from the Milky Way?

Accepted Answer

Hubble identified Cepheid variable stars

Question 3

Charles Messier published the first galaxy catalog containing over 2,000 nearby galaxies.

Accepted Answer

A) True 
 B)False

Question 4

Why is it not possible to look all the way back to the Big Bang itself?

Accepted Answer

A) Photons are not produced until the stars begin to shine at a redshift of z ≈ 20. 
B) From redshifts of z = 0 to 100,photons are gravitationally lensed by the dark matter in the universe. 
C) At redshifts of z > 1,000,most of the photons are blocked by large amounts of cold gas and dust. 
D) For redshifts of z > 1,000,photons are heavily altered because they easily react with individual protons and electrons in the universe. 
E) Photons from the Big Bang would be so strongly redshifted that we could never detect them. 
A) Photons are not produced until the stars begin to shine at a redshift of z ≈ 20. 
B) From redshifts of z = 0 to 100,photons are gravitationally lensed by the dark matter in the universe. 
C) At redshifts of z > 1,000,most of the photons are blocked by large amounts of cold gas and dust. 
D) For redshifts of z > 1,000,photons are heavily altered because they easily react with individual protons and electrons in the universe. 
E) Photons from the Big Bang would be so strongly redshifted that we could never detect them.

Question 5

The temperature of the CMB is hotter on one side of the sky than on the other by approximately 3 mK.What does this tell us?

Accepted Answer

A) The Earth has a peculiar velocity of about 8,000 km/s with respect to the CMB. 
B) The Earth has a peculiar velocity of about 400 km/s with respect to the CMB. 
C) The Earth is near the center of the universe's expansion,but not exactly at the middle. 
D) The universe is expanding faster on one side of us than the other. 
E) The universe is homogeneous but not isotropic. 
A) The Earth has a peculiar velocity of about 8,000 km/s with respect to the CMB. 
B) The Earth has a peculiar velocity of about 400 km/s with respect to the CMB. 
C) The Earth is near the center of the universe's expansion,but not exactly at the middle. 
D) The universe is expanding faster on one side of us than the other. 
E) The universe is homogeneous but not isotropic.

Question 6

The current temperature of the cosmic microwave background radiation is 17 K.

Accepted Answer

A) True 
 B)False

Question 7

According to Hubble's law,as the distance of a galaxy __________ its __________ increases.

Accepted Answer

A) increases;luminosity 
B) increases;recessional velocity 
C) decreases;luminosity 
D) decreases;recessional velocity 
E) decreases;peculiar velocity 
A) increases;luminosity 
B) increases;recessional velocity 
C) decreases;luminosity 
D) decreases;recessional velocity 
E) decreases;peculiar velocity

Question 8

Order the following objects by the maximum distance they can be detected: Cepheid variables,RR Lyrae stars,Type I supernovae,and low-mass main-sequence stars.Explain your reasoning.

Accepted Answer

Objects can be seen to farther distances

Question 9

If the Hubble constant were equal to 50 km/s/Mpc,what would the approximate age of the universe (the Hubble time)be,assuming that the expansion rate has stayed approximately constant over time? Note that 1 Mpc = 3.1 × 1019 km and 1 year = 3.17 × 107 s.

Accepted Answer

The age of the universe would

Question 10

If the distance of a galaxy at a redshift z 0.5 is 1,800 Mpc,how many years back into the past are we looking when we observe this galaxy?

Accepted Answer

A) 500 million years 
B) 2 billion years 
C) 6 billion years 
D) 9 billion years 
E) 10 billion years 
A) 500 million years 
B) 2 billion years 
C) 6 billion years 
D) 9 billion years 
E) 10 billion years

Question 11

If you found a galaxy with an Hα emission line that had a wavelength of 756.3 nm,what would be the galaxy's redshift? Note that the rest wavelength of the Hα emission line is 656.3 nm.

Accepted Answer

A) 0.05 
B) 0.07 
C) 0.10 
D) 0.13 
E) 0.15 
A) 0.05 
B) 0.07 
C) 0.10 
D) 0.13 
E) 0.15

Question 12

What is a standard candle,and why is it useful for measuring distances?

Accepted Answer

A standard candle is any object that has

Question 13

Where in the universe did the Big Bang take place?

Accepted Answer

A) near the Milky Way Galaxy 
B) near the Virgo cluster 
C) near some unknown location on the other side of the universe 
D) everywhere in the universe 
E) at the center of the universe,not too far from the center of the cosmic background radiation 
A) near the Milky Way Galaxy 
B) near the Virgo cluster 
C) near some unknown location on the other side of the universe 
D) everywhere in the universe 
E) at the center of the universe,not too far from the center of the cosmic background radiation

Question 14

The spectra of most galaxies tell us that:

Accepted Answer

A) most galaxies appear to be moving away from us 
B) their light comes predominantly from objects other than stars 
C) most galaxies contain clouds of gas that are absorbing their favorite wavelengths 
D) galaxies in the past rotated at a faster rate than they do today 
E) galaxies are rushing through space at high speeds 
A) most galaxies appear to be moving away from us 
B) their light comes predominantly from objects other than stars 
C) most galaxies contain clouds of gas that are absorbing their favorite wavelengths 
D) galaxies in the past rotated at a faster rate than they do today 
E) galaxies are rushing through space at high speeds

Question 15

In the early 1960s,physicists named Penzias and Wilson detected a persistent noise at a wavelength of 1 mm in their radio telescope that came from all directions in the sky due to:

Accepted Answer

A) synchrotron emission from the Crab Nebula 
B) emission from newly formed stars in the Orion Nebula 
C) cellphone usage 
D) photons left over from the Big Bang 
E) television and radio broadcasting 
A) synchrotron emission from the Crab Nebula 
B) emission from newly formed stars in the Orion Nebula 
C) cellphone usage 
D) photons left over from the Big Bang 
E) television and radio broadcasting

Question 16

In the Great Debate of 1920,Curtis and Shapley argued over whether or not:

Accepted Answer

A) the Big Bang occurred 
B) the age of the universe was 14 billion years 
C) the universe was contracting 
D) life existed outside of Earth 
E) the spiral nebulae were located outside the Milky Way 
A) the Big Bang occurred 
B) the age of the universe was 14 billion years 
C) the universe was contracting 
D) life existed outside of Earth 
E) the spiral nebulae were located outside the Milky Way

Question 17

Distant galaxies we can see today with a redshift of z ≈ 6 emitted their light when the universe was:

Accepted Answer

A) five times smaller than it is today 
B) six times smaller than it is today 
C) seven times smaller than it is today 
D) eight times smaller than it is today 
E) the same size as it is today 
A) five times smaller than it is today 
B) six times smaller than it is today 
C) seven times smaller than it is today 
D) eight times smaller than it is today 
E) the same size as it is today

Question 18

We see the universe around us expanding,which gives distant galaxies an apparent velocity of 70 km/s/Mpc.If you were an astronomer living today in a galaxy that was located 1 billion light years away from us,at what rate would you see the galaxies moving away from you?

Accepted Answer

Because the universe appears to be homog

Question 19

You observe a distant quasar in which the Lyman alpha line of hydrogen (rest wavelength = 121.6 nm)is found at a wavelength of 547.2 nm.When the light from this quasar was emitted,how large was the universe compared to its current size?

Accepted Answer

Using the formula for the redshift,this

Question 20

When we look at galaxies in the universe and measure their star formation rates,we find that galaxies at redshifts z ≈1 have higher star formation rates than they do now.At that time,the universe was __________ times the size it is today.

Accepted Answer

A) 0.1 
B) 0.2 
C) 0.5 
D) 0.7 
E) 0.90 
A) 0.1 
B) 0.2 
C) 0.5 
D) 0.7 
E) 0.90

Exam 19: The Expanding Universe

There is no special center to the expansion of the universe.

How did Edwin Hubble definitively prove that "spiral nebulae" were individual galaxies that were separate from the Milky Way?

Charles Messier published the first galaxy catalog containing over 2,000 nearby galaxies.

Why is it not possible to look all the way back to the Big Bang itself?

The temperature of the CMB is hotter on one side of the sky than on the other by approximately 3 mK.What does this tell us?

The current temperature of the cosmic microwave background radiation is 17 K.

According to Hubble's law,as the distance of a galaxy __________ its __________ increases.

Order the following objects by the maximum distance they can be detected: Cepheid variables,RR Lyrae stars,Type I supernovae,and low-mass main-sequence stars.Explain your reasoning.

If the Hubble constant were equal to 50 km/s/Mpc,what would the approximate age of the universe (the Hubble time)be,assuming that the expansion rate has stayed approximately constant over time? Note that 1 Mpc = 3.1 × 1019 km and 1 year = 3.17 × 107 s.

If the distance of a galaxy at a redshift z 0.5 is 1,800 Mpc,how many years back into the past are we looking when we observe this galaxy?

If you found a galaxy with an Hα emission line that had a wavelength of 756.3 nm,what would be the galaxy's redshift? Note that the rest wavelength of the Hα emission line is 656.3 nm.

What is a standard candle,and why is it useful for measuring distances?

Where in the universe did the Big Bang take place?

The spectra of most galaxies tell us that:

In the early 1960s,physicists named Penzias and Wilson detected a persistent noise at a wavelength of 1 mm in their radio telescope that came from all directions in the sky due to:

In the Great Debate of 1920,Curtis and Shapley argued over whether or not:

Distant galaxies we can see today with a redshift of z ≈ 6 emitted their light when the universe was:

We see the universe around us expanding,which gives distant galaxies an apparent velocity of 70 km/s/Mpc.If you were an astronomer living today in a galaxy that was located 1 billion light years away from us,at what rate would you see the galaxies moving away from you?

You observe a distant quasar in which the Lyman alpha line of hydrogen (rest wavelength = 121.6 nm)is found at a wavelength of 547.2 nm.When the light from this quasar was emitted,how large was the universe compared to its current size?

When we look at galaxies in the universe and measure their star formation rates,we find that galaxies at redshifts z ≈1 have higher star formation rates than they do now.At that time,the universe was __________ times the size it is today.

Why Learn Astronomy

Patterns in the Skymotions of Earth

Motion of Astronomical Bodies

Gravity and Orbits

Light

The Tools of the Astronomer

The Birth and Evolution of Planetary Systems

The Terrestrial Planets and Earths Moon

Atmospheres of the Terrestrial Planets

Worlds of Gas and Liquid the Giant Planets

Planetary Adornments Moons and Rings

Dwarf Planets and Small Solar System Bodies

Taking the Measure of Stars

Our Starthe Sun

Star Formation and the Interstellar Medium

Evolution of Low-Mass Stars

Evolution of High-Mass Stars

Relativity and Black Holes

Galaxies

The Milky Waya Normal Spiral Galaxy

Modern Cosmology

Large-Scale Structure in the Universe

Life

Filters

According to Hubble's law,as the distance of a galaxy its increases.

If the Hubble constant were equal to 50 km/s/Mpc,what would the approximate age of the universe (the Hubble time)be,assuming that the expansion rate has stayed approximately constant over time? Note that 1 Mpc = 3.1 × 10¹⁹ km and 1 year = 3.17 × 10⁷ s.