Free Practice Quiz Question List

04 Measuring and Classifying Stars Online Quiz Questions

Use this free practice quiz with 20 questions to review 04 Measuring and Classifying Stars, test your knowledge, and prepare for your next test or exam.

20 questions

True or false

1 point

True or false: A star's spectral type is primarily a classification of its surface temperature, rather than a direct measure of its size or luminosity.

A
True
B
False

True or false

1 point

True or false: A star's absolute magnitude describes how bright it appears from Earth at its actual distance.

A
True
B
False

Choose one

1 point

An astronomer places a star on an H–R diagram and finds that it is hot but faint. Which classification best fits this position?

A
It is cool and unusually luminous for its temperature, so it belongs among the giants.
B
It is hot but faint, so it belongs among the white dwarfs.
C
It is hot and unusually luminous for its temperature, so it belongs among the main-sequence stars.
D
Its spectral type alone establishes that it is a supergiant.

Choose one

1 point

A distant star's annual geometric shift is too small to measure reliably. Which approach describes the historically named method of spectroscopic parallax?

A
Measure the star's apparent annual shift against distant background stars.
B
Estimate its type and luminosity class from its spectrum, then compare inferred luminosity with apparent brightness.
C
Measure how far its spectral lines shift toward longer wavelengths.
D
Count the star's spectral lines and use that count as its geometric parallax.

Choose one

1 point

Two stars have the same luminosity, but one has a lower effective temperature than the other. According to the Stefan–Boltzmann relation, which star has the larger radius?

A
The cooler star has the smaller radius because lower temperature always means a smaller star.
B
The cooler star has the larger radius.
C
Both stars must have the same radius because their luminosities are equal.
D
Their relative radii cannot be inferred even if their luminosities and temperatures are known.

Choose all

1 point

Select all accurate statements about how astronomers measure a star's motion relative to an observer.

A
Proper motion is apparent movement across the sky after the annual parallax shift is separated out.
B
With a distance measurement, proper motion can be used to determine transverse speed.
C
Radial velocity is determined from the star's apparent movement across the sky over time.
D
Radial velocity is measured from Doppler shifts of spectral lines and indicates motion toward or away from the observer.

Choose all

1 point

Select all accurate statements about inferring a star's chemical composition from its spectrum.

A
Characteristic wavelengths of spectral lines can help identify elements in a star's outer layers.
B
The number of observed lines alone gives a direct measurement of each element's abundance.
C
Astronomers compare observed lines with laboratory measurements and models.
D
Line strengths can depend on temperature, pressure, and ionization as well as composition.

Written response

1 point

A star is 2 parsecs away. Using the conversion 1 parsec is about 3.26 light-years, what is its distance in light-years?

Fill in the blank

1 point

For a nearby star with parallax angle $p$ measured in arcseconds, its distance in parsecs is $d =$ .

Fill in the blank

1 point

On a standard H–R diagram, temperature usually decreases from left to .

Open ended

1 point

Explain how observations of a binary star system can be used to measure stellar mass, and identify the key feature of the system that makes this possible.

Choose one

1 point

An unobscured star's distance from an observer doubles while its luminosity stays the same. According to $F = \frac{L}{4\pi d^2}$ , how does the received flux change?

A
It becomes one quarter as large.
B
It becomes one half as large.
C
It remains unchanged.
D
It becomes twice as large.

Choose one

1 point

Two stars have equal luminosity. One has twice the effective temperature of the other. Which statement about their radii follows from $L = 4\pi R^2\sigma T^4$ ?

A
The hotter star has the larger radius.
B
The cooler star has the larger radius.
C
The stars have the same radius.
D
The cooler star has twice the radius of the hotter star.

Choose one

1 point

Which star is hotter, a B2 star or a B8 star?

A
B2
B
B8
C
Both have the same temperature because they are class B stars.
D
The subclass number indicates luminosity, not temperature.

True or false

1 point

True or false: Measuring a nearby star’s parallax requires knowing its intrinsic brightness.

A
True
B
False

Written response

1 point

A star has a parallax of $0.2$ arcseconds. What is its distance in parsecs?

Choose one

1 point

An unobscured star's luminosity stays the same, but its distance from an observer doubles. What happens to the received flux?

A
It becomes twice as large.
B
It becomes one-quarter as large.
C
It becomes half as large.
D
It stays the same.

Written response

1 point

After an astronomer separates a star's annual parallax shift from its apparent movement across the sky over time, what is that remaining motion called?

Choose one

1 point

A distant star's distance is estimated by identifying its type and luminosity class from its spectrum, then comparing its inferred luminosity with its apparent brightness. Why is this method not a geometric parallax measurement?

A
It measures the star's annual apparent shift against background stars.
B
It directly measures the time a light signal takes to reach Earth.
C
It estimates intrinsic luminosity from the spectrum and compares it with apparent brightness.
D
It determines distance from the star's radial velocity alone.

Written response

1 point

An observing plan needs to measure each target star’s apparent brightness and color, not its position or a wavelength-resolved spectrum. Which observing method should the team use?