Question 1

If the density of normal matter, such as protons and electrons, were higher in the early universe, would there have been more or less 4He made in the Big Bang?

Accepted Answer

If there were more protons and

Question 2

The cosmic microwave background (CMB) has a temperature of approximately 2.7 K and a Planck blackbody spectrum. Calculate the wavelength where the CMB spectrum peaks.

Accepted Answer

@#LAT-DLM&_peak = 2,

Question 3

What were the positions taken by Heber Curtis and Harlow Shapley in their "Great Debate," and how were both of them partially correct?

Accepted Answer

Curtis believed in a smaller galaxy (rou

Question 4

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 5

Astronomers have known that galaxies are separate entities outside of our own for roughly the last:

Accepted Answer

A)  35 years 
B)  60 years 
C)  90 years 
D)  150 years 
E)  210 years 
A)  35 years 
B)  60 years 
C)  90 years 
D)  150 years 
E)  210 years

Question 6

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 7

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 8

Does the expansion of the Universe make the Sun bigger? What about the Milky Way? Why or why not?

Accepted Answer

The expansion of the universe is only de

Question 9

If the distance of a galaxy is 10 Mpc, what is its recessional velocity if the Hubble constant is 70 km/s/Mpc?

Accepted Answer

A)  700 km/s 
B)  1,000 km/s 
C)  3,500 km/s 
D)  5,000 km/s 
E)  7,000 km/s 
A)  700 km/s 
B)  1,000 km/s 
C)  3,500 km/s 
D)  5,000 km/s 
E)  7,000 km/s

Question 10

Galaxy peculiar velocities are typically about 300 km/s. How far away do you have to look in order to see galaxies recessional velocities that are 10 times this peculiar velocity?

Accepted Answer

A)  12 Mpc 
B)  25 Mly 
C)  37 Mpc 
D)  43 Mpc 
E)  52 Mpc 
A)  12 Mpc 
B)  25 Mly 
C)  37 Mpc 
D)  43 Mpc 
E)  52 Mpc

Question 11

The apparent recessional velocities of galaxies at large distances are due mainly to the actual motions of the galaxies through space.

Accepted Answer

A) True 
 B)False

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

Name two predictions of the standard Big Bang theory that have been verified by observations.

Accepted Answer

The existence of cosmic microw

Question 14

Which of the following is NOT a prediction of the standard Big Bang theory that has been successfully verified by observations?

Accepted Answer

A)  The universe is expanding. 
B)  The most distant galaxies are redder because they are older. 
C)  Helium and lithium were made as the universe cooled after the initial Big Bang. 
D)  The early universe was very hot and dense. 
E)  The most distant galaxies are redder because their light has been stretched during the time it took for the light to reach Earth. 
A)  The universe is expanding. 
B)  The most distant galaxies are redder because they are older. 
C)  Helium and lithium were made as the universe cooled after the initial Big Bang. 
D)  The early universe was very hot and dense. 
E)  The most distant galaxies are redder because their light has been stretched during the time it took for the light to reach Earth.

Question 15

Distant galaxies we can see today with a redshift of z $\approx$ 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 16

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 17

What do astronomers mean when they say that the universe is isotropic?

Accepted Answer

A)  Far away parts of the universe look just like nearby parts. 
B)  All galaxies are spiral galaxies like our own. 
C)  Intergalactic gas has the same density everywhere in the universe. 
D)  The laws of physics apply everywhere in the universe. 
E)  The universe looks the same no matter what direction you look. 
A)  Far away parts of the universe look just like nearby parts. 
B)  All galaxies are spiral galaxies like our own. 
C)  Intergalactic gas has the same density everywhere in the universe. 
D)  The laws of physics apply everywhere in the universe. 
E)  The universe looks the same no matter what direction you look.

Question 18

If you found a galaxy with an H$\alpha$ emission line that had a wavelength of 756.3 nm, what would be the galaxy's redshift? Note that the rest wavelength of the H$\alpha$ 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 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

The only chemical elements that formed as the universe cooled down after the Big Bang were hydrogen, deuterium, and helium.

Accepted Answer

A) True 
 B)False

Exam 19: The Expanding Universe

If the density of normal matter, such as protons and electrons, were higher in the early universe, would there have been more or less 4He made in the Big Bang?

The cosmic microwave background (CMB) has a temperature of approximately 2.7 K and a Planck blackbody spectrum. Calculate the wavelength where the CMB spectrum peaks.

What were the positions taken by Heber Curtis and Harlow Shapley in their "Great Debate," and how were both of them partially correct?

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?

Astronomers have known that galaxies are separate entities outside of our own for roughly the last:

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.

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:

Does the expansion of the Universe make the Sun bigger? What about the Milky Way? Why or why not?

If the distance of a galaxy is 10 Mpc, what is its recessional velocity if the Hubble constant is 70 km/s/Mpc?

Galaxy peculiar velocities are typically about 300 km/s. How far away do you have to look in order to see galaxies recessional velocities that are 10 times this peculiar velocity?

The apparent recessional velocities of galaxies at large distances are due mainly to the actual motions of the galaxies through space.

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

Name two predictions of the standard Big Bang theory that have been verified by observations.

Which of the following is NOT a prediction of the standard Big Bang theory that has been successfully verified by observations?

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

The spectra of most galaxies tell us that:

What do astronomers mean when they say that the universe is isotropic?

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

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?

The only chemical elements that formed as the universe cooled down after the Big Bang were hydrogen, deuterium, and helium.

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 Adornmentsmoons 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

If the density of normal matter, such as protons and electrons, were higher in the early universe, would there have been more or less ⁴He made in the Big Bang?

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

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