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Astronomy 209 / ASTR 209 Final Exam – Latest
2026/2027 Update | Practice Review with
Verified Questions & Answers | Grade A
What two forces are balanced in what we call gravitational equilibrium?
- the electromagnetic force and gravity
- outward pressure and the strong force
- outward pressure and inward gravity.
- the strong force and gravity
the strong force and kinetic energy
outward pressure and inward gravity
Where in the Sun do fusion reactions happen?
core and radiation zone
only the core
everywhere inside the Sun
everywhere inside the Sun
1. What two things do we need to measure in order to determine a star's luminosity?
Apparent brightness and distance
1. Suppose the distance to a star was doubled but everything else about the star stayed the same.
What would happen to the star's luminosity and apparent brightness?
Luminosity remains the same, but the apparent brightness is decreased by a factor of 4
1. Stars X and Y have the same luminosity, but star Y is 10 times as far from Earth as star X.
How much brighter will star X appear in our sky than star Y?
100 times
1. Suppose that you measure the parallax angle for a particular star to be 0.5 arcseconds. What is
the distance to this star?
2 parsecs, which is about 6.52 light-years
1. Suppose that you measure the parallax angle for a particular star to be 0.1 arcseconds. What is
the distance to this star? (Hint: A star at a distance of 3.26 light-years has a parallax angle of 1.0
arcseconds.)
0.326 light years
, 1. A star's spectral type can be used to determine its
Surface temperature
1. Which of the following correctly lists spectral types in order of decreasing temperature (from
hottest to coolest)?
OBAFGKM
1. Which stellar spectral type has the strongest molecular absorption lines in its visible light
spectrum?
M
1. Which spectral type represents stars with spectra that peak at the shortest ultraviolet
wavelengths?
O
1. Besides mass, what else can be determined about the stars in an eclipsing binary system by
observing only their light curve?
Their radii
1. Which of the following best describes the axes of a Hertzsprung-Russell (H-R) diagram?
Surface temp on the horizontal axis and luminosity on the vertical axis
1. Based on the H-R diagram shown above, what is the spectral type of a main-sequence star
with a luminosity 100 times greater than that of the Sun?
O
1. Based on the H-R diagram shown above, what is the approximate luminosity of a main-
sequence M star?
0.01 times that of the Sun
1. On a Hertzsprung-Russell diagram, where on the main sequence would we find stars that have
the greatest mass?
Upper left
1. How do stars on the main sequence obtain their energy?
By converting hydrogen to helium in their cores
1. Which of the following is the most common type of main-sequence star?
M star
1. Which main sequence stars have the shortest lifetimes?
spectral type O
Astronomy 209 / ASTR 209 Final Exam – Latest
2026/2027 Update | Practice Review with
Verified Questions & Answers | Grade A
What two forces are balanced in what we call gravitational equilibrium?
- the electromagnetic force and gravity
- outward pressure and the strong force
- outward pressure and inward gravity.
- the strong force and gravity
the strong force and kinetic energy
outward pressure and inward gravity
Where in the Sun do fusion reactions happen?
core and radiation zone
only the core
everywhere inside the Sun
everywhere inside the Sun
1. What two things do we need to measure in order to determine a star's luminosity?
Apparent brightness and distance
1. Suppose the distance to a star was doubled but everything else about the star stayed the same.
What would happen to the star's luminosity and apparent brightness?
Luminosity remains the same, but the apparent brightness is decreased by a factor of 4
1. Stars X and Y have the same luminosity, but star Y is 10 times as far from Earth as star X.
How much brighter will star X appear in our sky than star Y?
100 times
1. Suppose that you measure the parallax angle for a particular star to be 0.5 arcseconds. What is
the distance to this star?
2 parsecs, which is about 6.52 light-years
1. Suppose that you measure the parallax angle for a particular star to be 0.1 arcseconds. What is
the distance to this star? (Hint: A star at a distance of 3.26 light-years has a parallax angle of 1.0
arcseconds.)
0.326 light years
, 1. A star's spectral type can be used to determine its
Surface temperature
1. Which of the following correctly lists spectral types in order of decreasing temperature (from
hottest to coolest)?
OBAFGKM
1. Which stellar spectral type has the strongest molecular absorption lines in its visible light
spectrum?
M
1. Which spectral type represents stars with spectra that peak at the shortest ultraviolet
wavelengths?
O
1. Besides mass, what else can be determined about the stars in an eclipsing binary system by
observing only their light curve?
Their radii
1. Which of the following best describes the axes of a Hertzsprung-Russell (H-R) diagram?
Surface temp on the horizontal axis and luminosity on the vertical axis
1. Based on the H-R diagram shown above, what is the spectral type of a main-sequence star
with a luminosity 100 times greater than that of the Sun?
O
1. Based on the H-R diagram shown above, what is the approximate luminosity of a main-
sequence M star?
0.01 times that of the Sun
1. On a Hertzsprung-Russell diagram, where on the main sequence would we find stars that have
the greatest mass?
Upper left
1. How do stars on the main sequence obtain their energy?
By converting hydrogen to helium in their cores
1. Which of the following is the most common type of main-sequence star?
M star
1. Which main sequence stars have the shortest lifetimes?
spectral type O
