Question 1

Why can Type I supernovae be used to determine a galaxy's distance?
A)Type I supernovae occur only in very luminous galaxies.
B)Type I supernovae have approximately the same luminosity.
C)Type I supernovae have approximately the same size.
D)A Type I supernova occurs in a typical galaxy about once every 100 years.
E)Type I supernovae occur even in very small galaxies.

Accepted Answer

Type I supernovae have approximately the same luminosity, making them useful as a standard candle to determine distances. By measuring the apparent brightness of a Type I supernova, astronomers can determine its distance from Earth based on its known luminosity.

Question 2

To be a standard candle,an object must have a constant:
A)lifetime
B)brightness
C)luminosity
D)distance
E)mass

Accepted Answer

A standard candle is an object with a known luminosity, meaning that it emits a constant amount of light. This allows astronomers to use them as a reference point for measuring distances in space. Objects with varying brightness (A) or lifetime (B) cannot be relied upon to provide accurate distance measurements. Distance (D) is the quantity being measured, not a characteristic of the standard candle itself. Mass (E) is also not a factor in determining if an object can be a standard candle.

Question 3

If a galaxy has a recessional velocity of 50,000 km/s,at what wavelength will you observe the Hαemission line? Note that the rest wavelength of the Hα emission line is 656.3 nm.
A)695.7 nm
B)719.4 nm
C)742.3 nm
D)766.0 nm
E)1750 nm

Accepted Answer

The answer of If a galaxy has a recessional velocity...

Question 4

You see a galaxy in which the Hα line (rest wavelength = 656.3 nm)is observed at a wavelength of 756.3 nm.What would be the observed wavelength of a particular helium line,which has a rest wavelength of 1,083 nm?
A)1,083 nm
B)1,183 nm
C)1,248 nm
D)1,440 nm
E)3,142 nm

Accepted Answer

Using the formula λ_observed = (1+z)*λ_rest, where z is the redshift, we can solve for the redshift of the galaxy:
756.3 nm = (1+z)*656.3 nm
z = 0.151
Next, we can use this redshift to find the observed wavelength of the helium line:
λ_observed = (1+z)*λ_rest
λ_observed = (1+0.151)*1083 nm
λ_observed = 1248 nm
Therefore, the observed wavelength of the helium line would be 1,248 nm, which is choice C.

Question 5

If a galaxy has an apparent velocity of 700 km/s,what is its distance if the Hubble constant is 70 km/s/Mpc?
A)10 Mpc
B)70 Mpc
C)100 Mpc
D)700 Mpc
E)1,000 Mpc

Accepted Answer

The answer of If a galaxy has an apparent velocity...

Question 6

Which of the following lists distance indicators that are used to measure distances ranging from the very nearest to the very farthest?
A)Cepheids,parallax,main-sequence fitting,Type I supernovae
B)parallax,main-sequence fitting,Cepheids,Type I supernovae
C)parallax,main-sequence fitting,Type I supernovae,Cepheids
D)main-sequence fitting,parallax,Cepheids,Type I supernovae
E)Cepheids,Type I supernovae,main-sequence fitting,parallax

Accepted Answer

The answer of Which of the following lists distance indicators...

Question 7

Galaxies move away from us in all directions because:
A)the force of gravity increases with distance
B)the force of gravity weakens with distance
C)space is expanding
D)our galaxy has expelled all other galaxies
E)we are at the center of the expansion of the universe

Accepted Answer

Galaxies are observed to be moving away from us in all directions, at speeds proportional to their distance from us. This observation is consistent with the theory of the Big Bang, which posits that the universe began as an extremely hot, dense, and small point, and has been expanding ever since. While gravity does play a role in the evolution of galaxies and the overall structure of the universe, it is the expansion of space itself that is responsible for the observed motion of galaxies away from us. Thus, the correct answer is C, that space is expanding.

Question 8

Which distance indicator can be used to measure the most distant objects?
A)Cepheids
B)parallax
C)Type I supernovae
D)main-sequence fitting
E)RR Lyrae stars

Accepted Answer

Type I supernovae can be used as distance indicators for the most distant objects because they are extremely bright and can be seen across vast distances in the universe. They also have a well-documented and understood relationship between their luminosity and period of brightness.

Question 9

If you found a galaxy with an Hα emission line that had a wavelength of 756.3 nm,what would be the galaxy's distance if the Hubble constant is 70 km/s/Mpc? Note that the rest wavelength of the Hα emission line is 656.3 nm.
A)650 Mpc
B)760 Mpc
C)3,200 Mpc
D)6,400 Mpc
E)7,600 Mpc

Accepted Answer

The redshift z can be calculated using z = (observed wavelength - rest wavelength) / rest wavelength = (756.3 nm - 656.3 nm) / 656.3 nm = 0.152. The velocity v = z * c = 0.152 * 3 x 10^5 km/s = 45,600 km/s. Using Hubble's law, distance = velocity / Hubble constant = 45,600 km/s / 70 km/s/Mpc = 650 Mpc.

Question 10

Astronomers use galactic redshift as a measure of:
A)gravity
B)luminosity
C)velocity
D)mass
E)distance

Accepted Answer

The answer of Astronomers use galactic redshift as a measure...

Question 11

Hubble's constant,H₀,represents: A)the rate of expansion of the universe B)the speed at which galaxies are moving away from us C)the time it takes a galaxy to move twice as far away from us D)the size of the universe E)the amount of time since the Solar System formed

Accepted Answer

Hubble's constant represents the rate of expansion of the universe. It is expressed in units of kilometers per second per megaparsec.

Question 12

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

Accepted Answer

The answer of If you found a galaxy with an...

Question 13

The spectra of most galaxies tell us that:
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

Accepted Answer

The spectra of most galaxies show a redshift, indicating that most galaxies are moving away from us. This is consistent with the expansion of the universe.

Question 14

If the distance of a galaxy is 10 Mpc,what is its recessional velocity if the Hubble constant is 70 km/s/Mpc?
A)700 km/s
B)1,000 km/s
C)3,500 km/s
D)5,000 km/s
E)7,000 km/s

Accepted Answer

The answer of If the distance of a galaxy is...

Question 15

If the spectrum of a distant galaxy is observed to have a calcium K absorption line that occurs at a wavelength of 500.4 nm,what is this galaxy's distance if the rest wavelength of this absorption line is 393.4 nm? Assume the Hubble constant is 70 km/s/Mpc.
A)720 Mpc
B)950 Mpc
C)1,200 Mpc
D)2,500 Mpc
E)3,700 Mpc

Accepted Answer

We can use the formula for redshift:

z = (observed wavelength - rest wavelength) / rest wavelength

Plugging in the given values:

z = (500.4 nm - 393.4 nm) / 393.4 nm
z = 0.272

Next, we can use the Hubble law to find the galaxy's distance:

v = H0 * d

where v is the recession velocity (which we assume is solely due to the expansion of the universe), H0 is the Hubble constant, and d is the distance to the galaxy.

We can convert the redshift to velocity using:

z = v / c

where c is the speed of light.

Plugging in the known values:

0.272 = v / 3e5 km/s
v = 81,600 km/s

Now we can use the Hubble law to find the distance:

81,600 km/s = 70 km/s/Mpc * d
d = 1,165 Mpc

Thus, the answer is C) 1,200 Mpc.

Question 16

According to Hubble's law,as the distance of a galaxy __________ its __________ increases.
A)increases;luminosity
B)increases;recessional velocity
C)decreases;luminosity
D)decreases;recessional velocity
E)decreases;peculiar velocity

Accepted Answer

Hubble's law states that the recessional velocity of a galaxy is proportional to its distance from us. As the distance increases, the recessional velocity also increases.

Question 17

If we lived in a galaxy one billion light-years from our own,what would we see?
A)a universe 1 billion years younger than ours
B)a universe 1 billion years older than ours
C)much the same universe we see here
D)the universe is expanding at a slower rate than we see from Earth
E)the universe is expanding at a faster rate than we see from Earth

Accepted Answer

From a billion light-years away, we would still be within the Milky Way galaxy and would see much the same universe we see here. The structures and positions of galaxies far beyond our own would also appear mostly the same from this distance. However, we may see a slightly younger universe since we would be observing it from a time when light had taken a billion years longer to reach us, but this effect would be minor. The rate of expansion of the universe would also not be noticeably different from what we see here.

Question 18

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

Accepted Answer

When astronomers say that the universe is isotropic, they mean that it looks the same no matter which direction you look. This means that the properties of the universe are the same in every direction, such as the temperature, density, and distribution of galaxies.

Question 19

If suddenly we find that the distances between the Sun and nearby stars are now 10 percent larger than we thought it was before,what measured properties will we not have to adjust? A)the distances of stars B)the size of our galaxy C)the value of H₀ D)the fact that the universe is expanding E)the luminosity of Type II supernovae

Accepted Answer

The fact that the universe is expanding is not affected by the change in the distances between the Sun and nearby stars. All other options will have to be adjusted to account for the new measurements.

Question 20

In an imaginary universe,astronomers find that there are thousands of galaxies within a few million light years,but beyond those galaxies there is nothing but empty space.Such a universe would be:
A)isotropic and homogeneous
B)isotropic but not homogenous
C)homogeneous but not isotropic
D)neither homogeneous nor isotropic
E)lacking any evidence for the Big Bang

Accepted Answer

The answer of In an imaginary universe,astronomers find that there...

Quiz 19: The Expanding Universe

Why can Type I supernovae be used to determine a galaxy's distance?

To be a standard candle,an object must have a constant:

If a galaxy has a recessional velocity of 50,000 km/s,at what wavelength will you observe the Hαemission line? Note that the rest wavelength of the Hα emission line is 656.3 nm.

You see a galaxy in which the Hα line (rest wavelength = 656.3 nm) is observed at a wavelength of 756.3 nm.What would be the observed wavelength of a particular helium line,which has a rest wavelength of 1,083 nm?

If a galaxy has an apparent velocity of 700 km/s,what is its distance if the Hubble constant is 70 km/s/Mpc?

Which of the following lists distance indicators that are used to measure distances ranging from the very nearest to the very farthest?

Galaxies move away from us in all directions because:

Which distance indicator can be used to measure the most distant objects?

If you found a galaxy with an Hα emission line that had a wavelength of 756.3 nm,what would be the galaxy's distance if the Hubble constant is 70 km/s/Mpc? Note that the rest wavelength of the Hα emission line is 656.3 nm.

Astronomers use galactic redshift as a measure of:

Hubble's constant,H₀,represents:

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.

The spectra of most galaxies tell us that:

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

If the spectrum of a distant galaxy is observed to have a calcium K absorption line that occurs at a wavelength of 500.4 nm,what is this galaxy's distance if the rest wavelength of this absorption line is 393.4 nm? Assume the Hubble constant is 70 km/s/Mpc.

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

If we lived in a galaxy one billion light-years from our own,what would we see?

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

If suddenly we find that the distances between the Sun and nearby stars are now 10 percent larger than we thought it was before,what measured properties will we not have to adjust?

In an imaginary universe,astronomers find that there are thousands of galaxies within a few million light years,but beyond those galaxies there is nothing but empty space.Such a universe would be: