Question 1

A particular star has an angle of parallax of 0.1 arcsec. What is the distance to this star?

Accepted Answer

A)  about 10 ly 
B)  about 33 ly 
C)  about 0.1 ly 
D)  about 3.3 ly

Question 2

What is the difference between an optical double star and a visual binary star?

Accepted Answer

A)  An optical double is an illusion-the stars are at vast distances from each other and are not actually orbiting each other-whereas in a visual binary, the stars are actually orbiting each other. 
B)  There is no difference; they are two names for the same thing. 
C)  The stars in an optical double star are actually orbiting each other, whereas a visual binary is an illusion. The stars are at vast distances from each other and are not actually orbiting each other. 
D)  Optical double stars can be seen as separate stars only through a telescope, whereas visual binaries can be seen with the unaided eye (e.g., the star Mizar in the Big Dipper's handle).

Question 3

A star has an absolute magnitude M = 1.69 and an apparent magnitude m = 1.04. How far away is this star?

Accepted Answer

A)  24.2 ly 
B)  43.2 ly 
C)  59.7 ly 
D)  160.2 ly

Question 4

Which of these statements BEST characterizes the human study of stellar evolution?

Accepted Answer

A)  The changes in the observable cosmos over a human lifetime are profound. 
B)  A human lifetime is long enough to witness the evolution of a star through much of its evolutionary history. 
C)  Astronomers have never witnessed a significant change in any single star. 
D)  At any moment. Stars can be observed in every phase of evolution.

Question 5

Two stars of equal mass form a visual binary system. The separation between the two stars is 4 au and the period of the orbital motion is 8 years. What is the mass of each star relative to the mass of the Sun?

Accepted Answer

A)  1 
B)  1/2 
C)  1/4 
D)  2

Question 6

Which two physical parameters of stars are plotted on the Hertzsprung-Russell diagram to show the systematics of a group of stars (e.g., a cluster)?

Accepted Answer

A)  mass and apparent magnitude 
B)  luminosity and radius 
C)  luminosity and surface temperature 
D)  surface temperature and mass

Question 7

The Sun has an absolute magnitude of +4.8. How far away would Earth have to be for the Sun to be just barely visible to the unaided eye (sixth-magnitude)?

Accepted Answer

A)  1.2 pc 
B)  6 pc 
C)  17.4 pc 
D)  22.4 pc

Question 8

What characterizes an A-type star?

Accepted Answer

A)  They have the strongest hydrogen lines. 
B)  They have the strongest calcium lines. 
C)  They are the hottest stars. 
D)  They are the largest stars.

Question 9

Which two fundamental parameters are MOST often used to place a particular star on a path of stellar evolution for comparison with theoretical models?

Accepted Answer

A)  apparent magnitude and distance 
B)  apparent magnitude and temperature 
C)  luminosity, or total energy output, and distance 
D)  luminosity, or total energy output, and temperature

Question 10

Sirius, visually the brightest star in Earth's night sky, has an apparent magnitude of about -1.5, while the Andromeda Galaxy has an apparent magnitude of about +3.5. What is the ratio of their brightnesses, as seen by Earthbound observers?

Accepted Answer

A)  The Andromeda Galaxy is 100 times brighter than Sirius. 
B)  The Andromeda Galaxy is 2 times fainter than Sirius. 
C)  The Andromeda Galaxy is 5 times brighter than Sirius. 
D)  The Andromeda Galaxy is 100 times fainter than Sirius.

Question 11

Two stars whose apparent magnitudes differ from each other by 5 magnitudes have a ratio of brightnesses of

Accepted Answer

A)  25. 
B)  10. 
C)  100. 
D)  2.5.

Question 12

The star Fomalhaut has an apparent magnitude of 1.15 and an absolute magnitude of 2.0. From this information (assuming that the starlight has not been dimmed by interstellar clouds), one can say for sure that Fomalhaut is _____.

Accepted Answer

A)  brightest in blue light 
B)  less than 10 pc away 
C)  brightest in red light 
D)  more than 10 pc away

Question 13

What is the ratio of the brightnesses of two stars if their apparent magnitudes differ by +1?

Accepted Answer

A)  about 2.5 
B)  100 
C)  2, by definition 
D)  10

Question 14

When observed through a set of photometric filters, a distant star is seen to be brightest through the ultraviolet filter, less bright through the blue filter, and faintest through the yellow filter. What conclusion can be drawn from this information, assuming no absorption of light between the star and Earth?

Accepted Answer

A)  The question gives insufficient information to draw a conclusion about a star's surface temperature. 
B)  The star has an intermediate temperature close to that of the Sun. 
C)  The star has a very high surface temperature. 
D)  The star has a very low surface temperature.

Question 15

What is spectroscopic parallax?

Accepted Answer

A)  apparent change in position of the absorption lines in a star's spectrum due to the Doppler shift caused by Earth's motion around the Sun 
B)  apparent change in position of a nearby star compared with distant background stars due to the motion of Earth around the Sun 
C)  change in position of the absorption lines in a star's spectrum due to the Doppler shift caused by the star's motion around the center of mass in a binary star system 
D)  distance to a star measured using the spectral luminosity class of the star and the inverse-square law

Question 16

The star Arcturus is classified as K2 III, which means that it is a

Accepted Answer

A)  hot giant. 
B)  cool supergiant. 
C)  cool giant. 
D)  cool main-sequence star.

Question 17

The Hipparcos satellite could measure stars up to approximately 150 pc away. What was the smallest parallax angle it could measure?

Accepted Answer

A)  150 arcsec 
B)  1/150 arcsec 
C)  1/150 degrees 
D)  1/75 arcsec

Question 18

The luminosity of a star is a unique measure of its

Accepted Answer

A)  total energy output. 
B)  velocity of recession away from Earth. 
C)  temperature. 
D)  physical size.

Question 19

Using the Hertzsprung-Russell diagram (Figure 12-7 in the text), determine which type of star has these characteristics: surface temperature 10,000 K and luminosity 1/100 times that of the Sun.

Accepted Answer

A)  red supergiant 
B)  main-sequence star 
C)  white dwarf 
D)  red giant

Question 20

How many second-magnitude stars would be needed in a close cluster to match the light intensity of a first-magnitude star?

Accepted Answer

A)  about 2.5 
B)  2 
C)  about 10 
D)  about 0.4, or 1/2.5

Exam 12: Characterizing Stars