Question 1

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 2

The MOST straightforward way to determine the distance to a nearby star involves the measurement of the:

Accepted Answer

A)  star's spectrum. 
B)  ratio of the star's apparent and absolute magnitudes. 
C)  Zeeman effect of spectral lines in the star's spectrum. 
D)  star's parallax.

Question 3

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),we can say for sure that Fomalhaut is _____ away.

Accepted Answer

A)  more than 10 ly 
B)  less than 10 pc 
C)  less than 10 ly 
D)  more than 10 pc

Question 4

Using the Hertzsprung-Russell diagram in Figure 10-7 of Comins,Discovering the Essential Universe,6th ed.,and the mass-luminosity relationship for main-sequence stars shown in Figure 10-14,which list is the CORRECT sequence of stars in increasing order of mass?

Accepted Answer

A)  Regulus, Barnard's Star, Sun, Altair 
B)  Barnard's Star, Altair, Sun, Regulus 
C)  Barnard's Star, Sun, Altair, Regulus 
D)  Regulus, Altair, Sun, Barnard's Star

Question 5

The chemical makeup of the Sun's surface can be determined by:

Accepted Answer

A)  taking a sample of the star's surface with a space probe. 
B)  examining the chemicals present in a meteorite because it is part of the solar system. 
C)  measuring the components of the solar wind with Earth-orbiting spacecraft. 
D)  solar spectroscopy.

Question 6

A particular star has an angle of parallax of 0.2 arcsecond.What is the distance to this star?

Accepted Answer

A)  50 pc 
B)  2 pc 
C)  5 pc 
D)  0.2 pc

Question 7

What is the physical reason astronomers can find the luminosity class (I,II,III,IV,or V)of a star using the star's spectrum?

Accepted Answer

A)  The wavelength of maximum emission (given by Wien's law) is affected by the size of the star. 
B)  The relative amounts of hydrogen, helium, and other elements are different for stars of different luminosity classes. 
C)  The absorption lines in the spectrum are affected by the density and pressure of the star's atmosphere. 
D)  The absorption lines in the spectrum are affected by the star's surface temperature.

Question 8

A white dwarf star whose temperature is the same as that of the Sun will have a radius that is (see Fig.10-8,Comins,Discovering the Essential Universe,6th ed.):

Accepted Answer

A)  10 times smaller than that of the Sun. 
B)  the same size as the Sun's. 
C)  2 times smaller than that of the Sun. 
D)  100 times smaller than that of the Sun.

Question 9

The star Arietis has an apparent magnitude of +2.7 and a distance of 52 ly.According to the equation in Discovery 10-2 in Comins,Discovering the Essential Universe,6th ed.,what is its absolute magnitude?

Accepted Answer

A)  +1.7 
B)  -0.9 
C)  +6.2 
D)  +3.7

Question 10

The luminosity class of a star (I,II,III,IV,or V)is MOST closely related to which physical characteristic of the star?

Accepted Answer

A)  the surface temperature 
B)  the radius 
C)  the radial velocity 
D)  the chemical composition (amount of hydrogen, helium, etc.)

Question 11

Which molecule produces the strong absorption bands in the spectrum of a cool M-type star,as can be seen in Figure 10-5 of Comins,Discovering the Essential Universe,6th ed.?

Accepted Answer

A)  HCl, hydrogen chloride 
B)  CaI, calcium iodide 
C)  H₂O, water vapor 
D)  TiO, titanium oxide

Question 12

The star Spica is classified as B1 V,which means that it is a:

Accepted Answer

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

Question 13

A star of apparent magnitude +3.5 appears _____ than a star of apparent magnitude +3.3.

Accepted Answer

A)  farther away 
B)  fainter 
C)  either brighter or fainter, depending on the distance to the stars, 
D)  brighter

Question 14

The Hipparcos satellite was able to measure parallax for stars out to about 150 pc.This distance includes roughly 2.5 million stars.What is the average number of stars in one cubic parsec?

Accepted Answer

A)  5.1 X 10-³ 
B)  0.18 
C)  5.65 
D)  8.84

Question 15

A list of four stars and their apparent magnitudes is given.Which star looks brightest when viewed from Earth?

Accepted Answer

A)  Tau Ceti m = +3.49 
B)  Alpha Centauri B m = 1.34 
C)  Barnard's star m = +9.53 
D)  61 Cygni A m = +5.21

Question 16

A star with a surface temperature of 4000 K and a luminosity of about 10-² times that of the Sun is a member of which luminosity class? (See Figure 10-10,Comins,Discovering the Essential Universe,6th ed.)

Accepted Answer

A)  III, giant 
B)  I, supergiant 
C)  II, bright giant 
D)  V, main-sequence

Question 17

Which star,according to its apparent magnitude,would NOT be visible to the unaided eye on a clear night?

Accepted Answer

A)  Tau Ceti m = +3.49 
B)  Alpha Centauri B m = 1.34 
C)  Barnard's star m = +9.53 
D)  61 Cygni A m = +5.21

Question 18

The symbol He II stands for a:

Accepted Answer

A)  helium atom that has lost two electrons. 
B)  neutral helium atom (atomic number = 2) that has lost no electrons. 
C)  helium molecule that contains two helium atoms. 
D)  helium atom that has lost one electron.

Question 19

Which important property of stars can be best determined by observations of binary stars systems?

Accepted Answer

A)  stellar mass 
B)  surface temperature 
C)  distance from Earth 
D)  pulsation period

Question 20

What is spectroscopic parallax?

Accepted Answer

A)  an 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)  an apparent change in position of a nearby star compared with distant background stars due to the motion of Earth around the Sun 
C)  a 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)  the distance to a star measured using the spectral luminosity class of the star and the inverse square law

Exam 10: Characterizing Stars

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) ?