Deck 16: Basic Properties of Stars

Question 1

By what factor would the brightness of a star increase if an observer moved from 5 parsecs to 1 parsec from the star?

A)5 times
B)25 times
C)125 times
D)625 times

Answer 1

25 times

Question 2

The absolute magnitude of a star is a measure of its

A)Distance
B)Temperature
C)Mass
D)Luminosity

Answer 2

Luminosity

Question 3

On a certain date,Mars has an apparent magnitude of +1 and Venus has an apparent magnitude of +2.Which is brighter and by how much?

A)Venus is twice as bright as Mars
B)Venus is 2.5 times as bright as Mars
C)Mars is twice as bright as Venus
D)Mars is 2.5 times as bright as Venus
E)Mars is 100 times as bright as Venus

Answer 3

Mars is 2.5 times as bright as Venus

Question 4

A solar-type star is observed with an apparent magnitude of 12.7.How far away is it? Recall that the absolute magnitude of the Sun is 4.7.

A)10 parsec
B)40 parsecs
C)400 parsecs
D)1000 parsecs

Question 5

The distance to a star is known if we know its

A)Parallax
B)Apparent magnitude
C)Surface temperature
D)Mass

Question 6

A star with a trigonometric parallax of .02 arcseconds has a distance of

A)20 pc
B)50 pc
C)2.0 light years
D)4 kpc
E)Need more information (magnitudes)

Question 7

A globular cluster is 1 kiloparsec away.What is its parallax?

A).001 seconds of arc
B)1 second of arc
C)1000 seconds of arc
D)0.1 seconds of arc

Question 8

Suppose you are an astronomer on Jupiter (distance to the Sun = 5 AU).You observe a star with a parallax of 0.1 arcseconds.What is the star's distance?

A)0.1 pc
B)2 pc
C)5 pc
D)50 pc

Question 9

A measurement of the parallax of a star allows us to determine the star's

A)Rotation rate
B)Temperature
C)Distance
D)Age

Question 10

How distant is a star with a parallax of 0.05 arcseconds?

A)0.05 parsecs
B)0.2 parsecs
C)2 parsecs
D)20 parsecs

Question 11

Star A has 4 times the radius of star B and is twice as hot.How does the luminosity of star A compare to that of star B?

A)8 times as great
B)1024 times as great
C)16 times as great
D)256 times as great

Question 12

Two stars,which differ in magnitude by 5,have a brightness ratio of

A)5:1
B)10:1
C)50:1
D)100:1

Question 13

How does the brightness of a fourth magnitude star compare with that of a ninth magnitude star?

A)It is 5 times brighter
B)It is 5 times fainter
C)It is 100 times brighter
D)It is 100 times fainter

Question 14

How much fainter is a twelfth magnitude star than an eighth magnitude star?

A)4 times
B)10 times
C)40 times
D)2.5 times

Question 15

If two stars differ in magnitude by 15 magnitudes,what is the ratio of their brightnesses?

A)15:1
B)300:1
C)1000:1
D)1,000,000:1

Question 16

Which of the following correctly describes the relative distances of the stars and planets? The stars are

A)About 10 times farther away than the nearest planets
B)About 100 times farther away than the nearest planets
C)About 100,000 times farther away than the nearest planets
D)Several billion times farther away than the nearest planets

Question 17

The star Capella has an apparent magnitude of 0 and is the same color as the Sun.Its distance is 14 parsecs.Which of the following describes its similarities with the Sun?

A)It must be identical to the Sun
B)It is less luminous than the Sun,but has the same temperature.
C)It is more luminous than the Sun,but has the same temperature
D)It is the same luminosity as the Sun,but has a different temperature

Question 18

The nearest known star is at a distance of about

A)1 light month
B)1 parsec
C)100 parsecs
D)1 arcsecond
E)1 kiloparsec

Question 19

The apparent magnitudes of stars A and B are 5.5 and 10.5 respectively.Which of the following is true ?

A)Star A appears 5 times brighter than star B
B)Star A appears 5 times dimmer than star B
C)Star A appears 100 times brighter than star B
D)Star A appears 100 times dimmer than star B
E)Star A is intrinsically 5.5 times dimmer than star B

Question 20

Two stars have the same color,but differ by 5 magnitudes in absolute magnitude.
What stellar property must be different in the two objects?

A)Distance
B)Radius
C)Mass
D)Location in the galaxy

Question 21

Which of the following spectral classes is coolest?

A)A
B)B
C)F
D)G

Question 22

The spectral class of a star is a measure of the star's

A)Chemical composition
B)Temperature
C)Radial velocity
D)Rate of rotation

Question 23

The hottest stars have spectral class

A)O
B)A
C)G
D)M

Question 24

How do the Sun,a white dwarf,and a red giant rank in descending order of luminosity?

A)Sun,white dwarf,red giant
B)Red giant,white dwarf,Sun
C)Red giant,Sun,white dwarf
D)White dwarf,Sun,red giant

Question 25

Which of the following processes will result in the emission of a photon?

A)The electron in an atom jumping to a higher energy level
B)The electron in an atom jumping to a lower energy level
C)An atom becoming ionized
D)The electron in an atom remaining in the ground state

Question 26

Which of the following can produce a continuous spectrum?

A)A cold gas at low density
B)A hot gas at low density
C)A gas consisting entirely of molecules
D)A hot solid

Question 27

Which of the following produces an emission line spectrum?

A)A glowing liquid
B)A glowing solid
C)A cool gas in front of a source of continuous radiation
D)A hot,thin gas

Question 28

What spectral class is just hotter than spectral class F?

A)O
B)B
C)A
D)K

Question 29

Suppose we observe a hot,tenuous gas with a cooler "black body" behind it.The combined spectrum will be

A)Absorption lines only
B)Continuous radiation only
C)Continuous radiation with emission lines superimposed
D)Continuous radiation with absorption lines superimposed

Question 30

When an atom loses one or more electrons it is said to be

A)Ionized
B)Excited
C)Collided
D)In the ground state

Question 31

The spectrum of light from a hot,rarefied gas

A)Has a continuous spectrum
B)Shows bright emission lines,at wavelengths that differ for each element
C)Shows bright emission lines,at the same wavelengths for all elements
D)Shows dark absorption lines

Question 32

Visual wavelength absorption lines of hydrogen are very weak in cool stars like red dwarfs.The Lyman lines of hydrogen involve transitions from the ground state to the first excited state.What would you say about the strength of the Lyman lines in red dwarfs?

A)They should be quite strong
B)They should be no stronger than the visual wavelength lines
C)There will be no such transitions in this type of star
D)Lines will be weak;these stars have little hydrogen

Question 33

Why are the Balmer lines of hydrogen weak in stars that are hotter than about 10,000 K?

A)Hydrogen is mostly ionized in hot stars
B)Hot stars are made mostly of helium
C)Most hydrogen atoms are in the ground state in hot stars
D)Most hydrogen is in molecular form in hot stars

Question 34

Suppose the electron in an atom is in an excited orbit.What will happen to the electron if nothing disturbs the atom?

A)It will remain in the same excited orbit
B)It will fly away from the atom,ionizing the atom
C)It will move to the lowest energy orbit
D)It will move to another excited orbit that has higher energy

Question 35

Consider two stars X and Y with surface temperatures of 3000 K and 10,000 K respectively.Which of the following is true?

A)Star X has less hydrogen
B)Star Y has less hydrogen
C)Hydrogen absorption lines will be stronger in star X
D)Hydrogen absorption lines will be stronger in star Y

Question 36

Suppose we observe a hot,tenuous gas against a dark background.What kind of spectrum will we see?

A)Absorption lines
B)Continuous radiation
C)Continuous radiation with emission lines superimposed
D)Emission line

Question 37

The spectral classification scheme,OBAFGKM,is correctly interpreted as a sequence in stellar

A)Distance
B)Size
C)Age
D)Temperature

Question 38

Star A is twice as hot as star B.The two stars have the same radius.How does the luminosity of star A compare to that of star B?

A)A and B have the same luminosity
B)A is twice as luminous
C)A is 4 times as luminous
D)A is 16 times as luminous

Question 39

What spectral class is found between O and A?

A)B
B)F
C)K
D)G

Question 40

When an electron of an atom moves to a higher energy state,the atom is said to be

A)Ionized
B)Excited
C)Electronized
D)Suspended

Question 41

Stars of different spectral classes,O,B,A,F,G,K,M,show differences in the strengths of absorption lines of various elements.These differences are due to differences in

A)The chemical compositions of stars
B)The surface temperatures of stars
C)Stellar distances
D)Stellar ages

Question 42

What kind of stars are found scattered across the top of the H-R diagram?

A)White dwarfs
B)Supergiants
C)Giants
D)Main sequence stars

Question 43

Why are there more main sequence stars than giant stars?

A)The main sequence stage for a typical star is longer than the giant stage
B)Giants are dim and hard to see
C)Most giant stars are drawn to the core of the galaxy
D)Few stars first form as giants rather than main sequence stars

Question 44

A star is observed to have extremely strong lines of hydrogen,very weak neutral helium,and weak neutral metals.The spectral type of such a star is closest to

A)O5
B)B2
C)A0
D)K5
E)M8

Question 45

Most of the stars in a typical H-R diagram fall on the

A)Main sequence
B)Giant region
C)Supergiant region
D)White dwarf region

Question 46

An H-R diagram can be made by plotting

A)Luminosity versus color
B)Spectral class versus distance
C)Luminosity versus magnitude
D)Temperature versus distance

Question 47

Two stars differ by 10 in absolute magnitude.What is the ratio of their luminosities?

A)10
B)100
C)1000
D)10,000

Question 48

If we choose a typical star in the vicinity of the Sun,it will be a

A)Spectral class O star
B)Cepheid variable
C)Neutron star
D)Red dwarf

Question 49

An H-R diagram for a group of stars cannot be produced by plotting their

A)Luminosities versus masses
B)Magnitudes versus spectral types
C)Temperatures versus luminosities
D)Colors versus magnitudes

Question 50

The stars located in the lower left corner of the H-R diagram are

A)White dwarfs
B)Main sequence stars
C)Giants
D)Supergiants