Exam 3 Review

Question 1

Light leaving a point source spreads out so that the apparent brightness, b varies with distance d according to which of the following laws? (∝ means "proportional to.")   
A)  b ∝ 1/d   
B)  b ∝ 1/d2   
C)  b = constant   
D)   b ∝ d2

Answer 1

B) b ∝ 1/d2

Question 2

Parallax is the:
A) distance to an object, measured in parsecs.
B) angle subtended by an object, as see by us.
C) apparent shift in position of a nearby object as we move.
D) shift in position of an object as it moves.

Answer 2

C) apparent shift in position of a nearby object as we move.

Question 3

The luminosity of a star is:
A) another name for its temperature.
B) its brightness as seen by people on Earth.
C) its total energy output over all wavelengths.
D) another name for its size.

Answer 3

C) its total energy output over all wavelengths.

Question 4

What does apparent brightness tell us about a star?
A) Its size compared to the Sun.
B) The intrinsic brightness of a star.
C) The brightness of a star as it appears in our sky.
D) The brightness the star would appear to have if it were exactly 10 parsec from the Earth.

Answer 4

C) The brightness of a star as it appears in our sky.

Question 5

The spectral type of a star is most directly related to (and determines uniquely) its: 
A)  size or radius   
B)  absolute magnitude 
C)  luminosity    
D)  surface temperature

Answer 5

D) surface temperature

Question 6

Two stars in our sky have the same apparent brightness. If neither of them is hidden behind gas or dust clouds, then we know that they:
A) may be at different distances, in which case the nearest one must have the greater luminosity.
B) must have formed from the same star cluster.
C) may be at different distances, in which case the farther one must have the greater luminosity.
D) may be cousins to one another.

Answer 6

C) may be at different distances, in which case the farther one must have the greater luminosity.

Question 7

The spectral type of the Sun is G2 and the star Enif is K2. From the information, we know that Enif is:
A) intrinsically fainter than the Sun.
B) cooler than the Sun
C) intrinsically brighter than the Sun.
D) hotter than the Sun.
E) A & B

Answer 7

E) A & B

Question 8

Where on the Hertzsprung-Russell diagram do most local stars in our universe congregate?
A) In the supergiant area, where most massive stars spend significant time.
B) In the giant area, where most stars spend the longest time of their lives.
C) In the white dwarf area, the “graveyard” of stars.
D) On the main sequence where stars generate energy by hydrogen burning.

Answer 8

D) On the main sequence where stars generate energy by hydrogen burning.

Question 9

Compared to a star in the middle of the diagram, a star in the lower left part of the Hertzsprung-Russell diagram is: 
A)  brighter.   
B) larger.   
C)  cooler.   
D) smaller.

Answer 9

D) smaller.

Question 10

Which important stellar parameter can be determined by the study of binary stars?  
A)  The age of the stars.  
B)  Stellar masses.  
C)   Surface temperature of the stars. 
D)  The distance of the stars from Earth

Answer 10

B) Stellar masses.

Question 11

Where do we find the most massive stars on the main sequence in a Hertzsprung-Russell diagram?
A) Upper left.
B) They all have approximately the same mass, because this is what defines the main sequence.
C) Lower right.
D) Center, with lower mass stars on either side.

Answer 11

A) Upper left.

Question 12

Spectroscopic parallax is the:
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 to distant background stars, due to the motion of Earth around the Sun.
C) apparent 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 type and luminosity class.

Answer 12

D) distance to a star measured using the spectral type and luminosity class.

Question 13

What is the difference between an optical double star and a visual binary star?
A) There is no difference — they are two names for the same thing.
B) Optical double stars can be seen as separate stars only through a telescope, whereas visual binaries can be seen with the unaided eye.
C) 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.
D) 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.

Answer 13

C) 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.

Question 14

A simple relationship exists between mass and luminosity for: 
A)   all stars.  
B)   main sequence stars.  
C)   giant stars. 
D)   supergiant stars and white dwarfs.

Answer 14

B) main sequence stars.

Question 15

The mechanism at work when energy is transmitted by convection is:
A) the successive exchange of energy between atoms.
B) the passage of radiation through a gas.
C) the mass motion of hot gases.
D) the countless interactions of photons.

Answer 15

C) the mass motion of hot gases.

Question 16

The neutrino is:
A) an uncharged nuclear particle with mass intermediate between those of the electron and the proton.
B) another name for an electron that carries a positive charge instead of negative charge.
C) an elusive, subatomic particle having little or no mass and no charge, and very difficult to detect.
D) a heavy, uncharged nuclear particle, easily detected.

Answer 16

C) an elusive, subatomic particle having little or no mass and no charge, and very difficult to detect.

Question 17

What name is given to the visible "surface" of the Sun?  
A) Corona  
B)  Chromosphere  
C)  Photosphere  
D)  Prominence

Answer 17

C) Photosphere

Question 18

The granulation pattern seen on the visible “surface” of the Sun is indicative of:
A) convection of gas in the region under the surface.
B) heating of the Sun’s atmosphere by solar flares.
C) the differential rotation of the Sun.
D) strong magnetic fields cooling the gas in certain regions.

Answer 18

A) convection of gas in the region under the surface.

Question 19

The center of the granular cells on the surface of the Sun are brighter than the edges of the cells because:
A) the centers are composed of different gases than the edges.
B) the centers are hotter than the edges.
C) the centers are devoid of any matter.
D) the centers are cooler than the edges.

Answer 19

B) the centers are hotter than the edges.

Question 20

The technique used to obtain the direct information about the internal structure of the Sun is: 
A) helioseismology. 
B) spectroscopy. 
C) neutrinos. 
D) Newton’s law of gravitation.

Answer 20

A) helioseismology.

Question 21

Sunspots appear dark because they:
A) are shadows on the surface of the Sun caused by planets.
B) are cooler than surrounding regions.
C) are regions from which the light is prevented from escaping by strong magnetic field.
D) have a different chemical composition than the surrounding surface.

Answer 21

B) are cooler than surrounding regions.

Question 22

Which of the following methods is not used to transport energy from the core to the surface of the Sun?
A) Radiation
B) Convection
C) Conduction
D) All of the above are important in the solar interior.

Answer 22

C) Conduction

Question 23

The chromosphere appears red because:
A) it is hotter than the photosphere.
B) as the Sun rotates, the chromosphere appears to move away from us radially.
C) it has a higher concentration of heavy metals.
D) its spectrum is dominated by hydrogen emission.

Answer 23

D) its spectrum is dominated by hydrogen emission.

Question 24

The space between stars is now known to contain:
A) large quantities of dust that absorb light but no gas, either atomic or molecular.
B) gas, made up of atoms, molecules, and dust particles.
C) a perfect vacuum.
D) variable amounts of gas but no dust, because dust forms only in planetary systems near stars.

Answer 24

B) gas, made up of atoms, molecules, and dust particles.

Question 25

An H II region is a region of:
A) ionized hydrogen (one electron is knocked off).
B) molecular hydrogen inside a giant molecular cloud.
C) neutral, atomic hydrogen in interstellar space.
D) gas and dust formed by the explosion of a massive star.

Answer 25

A) ionized hydrogen (one electron is knocked off).

Question 26

The effect of interstellar dust on starlight is:
A) to scatter the red light from stars preferentially, making them appear more blue than expected.
B) almost nonexistent, because light does not interact with dust.
C) to dim and redden distant stars by preferentially scattering their blue light.
D) to make stars appear less bright than expected by absorbing light about equally at all wavelengths.

Answer 26

C) to dim and redden distant stars by preferentially scattering their blue light.

Question 27

The distinctive color of a reflection nebula is:
A) blue, caused by the preferential scattering of starlight by very small dust grains.
B) predominantly in the part of the spectrum due to reflection by ice crystal of water, ammonia, and methane.
C) a mixture of several specific colors coming from atoms excited by ultraviolet radiation emitted by hot stars.
D) red, coming from hydrogen gas.

Answer 27

A) blue, caused by the preferential scattering of starlight by very small dust grains.

Question 28

The most likely places in which stars and planetary systems are forming in the universe are:
A) the rarified outer space between galaxies.
B) regions of hot gas in the spiral arms of galaxies.
C) cold nebulae.
D) the centers of galaxies.

Answer 28

C) cold nebulae.

Question 29

What condition is considered sufficient for an interstellar cloud to collapse and form a star or stars?
A) The cloud must be alone in space, far from the gravitational influence of stars or other interstellar clouds.
B) The cloud must be at room temperature.
C) Gravity must dominate gas pressure inside the cloud.
D) Temperature must dominate gravity inside the cloud.

Answer 29

C) Gravity must dominate gas pressure inside the cloud.

Question 30

Protostars are:
A) stars made almost entirely out of protons.
B) objects with masses less than about 0.08 solar masses, which do not have enough mass to become true stars.
C) old stars, contracting after using up all of their available hydrogen fuel.
D) very young objects, still contracting before becoming true stars.

Answer 30

D) very young objects, still contracting before becoming true stars.

Question 31

A stars evolutionary track is:
A) its movement (not a physical movement) when plotted on a H-R diagram, as it evolves in luminosity and temperature.
B) its motion through the dark, dense cloud from which it was formed.
C) the line across the H-R diagram denoting stars identified as main-sequence stars .
D) its movement when plotted on a map of the galaxy as it takes part in the overall galactic rotation.

Answer 31

A) its movement (not a physical movement) when plotted on a H-R diagram, as it evolves in luminosity and temperature.

Question 32

The luminosity of white dwarf is produced:
A) by Kelvin-Helmholtz contraction.
B) by hydrogen fusion in their centers.
C) from the residual heat left over from the thermonuclear fusion reactions when it was a star.
D) by the camp fire set by the alien on the white dwarf.

Answer 32

C) from the residual heat left over from the thermonuclear fusion reactions when it was a star.

Question 33

The evolution of a star is controlled by its: 
A) initial mass. 
B) location in the galaxy. 
C) surface temperature. 
D) chemical composition.

Answer 33

A) initial mass.