Deck 13: Measuring the Properties of Stars

Question 1

What is parallax?

A) the distance to an object, measured in parsecs
B) the difference between the apparent and absolute magnitude
C) the apparent shift in position of an object caused by a change in the observer's position
D) the shift in angular position of an object as the object actually moves in space

Answer 1

the apparent shift in position of an object caused by a change in the observer's position

Question 2

Parallax measurements of the distances to the nearest stars use _____ as a baseline.

A) Earth's orbit
B) Earth's diameter
C) Earth-Moon distance
D) about the length of a football field

Answer 2

Earth's orbit

Question 3

A star has a parallax angle of 0.2 arc seconds, which means it is at a distance of

A) 2 parsecs.
B) 2 light-years.
C) 5 parsecs.
D) 5 light-years.

Answer 3

5 parsecs.

Question 4

The parallax of a star is ____ usually measured in ____.

A) a distance; arc seconds
B) an angle; arc seconds
C) an angle; parsecs
D) a distance; AUs

Question 5

If the distance between Earth and a star is measured using parallax measurements, how far apart in time should the two measurements be made to make the parallax measurement as accurate as possible?

A) instantaneously
B) a day
C) six months
D) a year

Question 6

If Star A has a parallax angle of 3 arc seconds while Star B has a parallax angle of 9 arc seconds then we know that

A) Star A is three times farther away.
B) Star A is nine times farther away.
C) Star B is three times farther away.
D) Star B is nine times farther away.

Question 7

A star's parallax can reveal its distance. Stars with larger parallaxes are _______.

A) farther away
B) closer
C) the same distance as other stars
D) This is a trick question. Parallax cannot be measured for stars!

Question 8

A star has a parallax of 0.04 arc seconds. What is its distance?

A) 4 light-years
B) 4 parsecs
C) 25 light-years
D) 25 parsecs

Question 9

The method of standard candles can be used to measure a star's ____.

A) distance
B) luminosity
C) mass
D) brightness
E) absolute magnitude

Question 10

If it were possible to move a star closer to Earth then its apparent magnitude number would ______ while its absolute magnitude number would _______.

A) decrease; increase
B) decrease; stay the same
C) increase; decrease
D) increase; stay the same

Question 11

If a star has an apparent magnitude of 8 and an absolute magnitude of 6 it is

A) much closer than 10 parsecs away.
B) slightly closer than 10 parsecs away.
C) exactly 10 parsecs away.
D) slightly farther than 10 parsecs away.
E) much farther than 10 parsecs away.

Question 12

The amount of energy emitted by a star each second is the ______________ and is measured in ______________.

A) apparent brightness; degrees K
B) temperature; degrees K
C) Apparent brightness; watts
D) luminosity; watts

Question 13

A light source at a distance of 1 meter that emits 50 watts of visible radiation has the same _____________ as a source emitting 200 watts and is located ____________.

A) luminosity; 2 meters away
B) luminosity; 4 meters away
C) apparent brightness; 2 meters away
D) apparent brightness; 4 meters away

Question 14

A star of apparent magnitude 6 appears ___ times brighter than a star of apparent magnitude 7.

A) 1.00
B) 13.0
C) 2.51
D) 0.5
E) 10.0

Question 15

A star of apparent magnitude ____ appears 2.51 times brighter than a star of apparent magnitude 4.

A) 1
B) 1.49
C) 3
D) 6.51
E) 10

Question 16

If Star A is twice as far as Star B, and they are identical in all other ways, then the brightness of Star A would be

A) one-fourth the brightness of Star B.
B) one-half the brightness of Star B.
C) the same brightness as Star B.
D) twice the brightness of Star B.
E) four times the brightness of Star B.

Question 17

A 10^th magnitude star is ____________ than a 5^th magnitude star.

A) 2 times brighter
B) 2 times fainter
C) 100 times brighter
D) 100 times fainter

Question 18

Differences in apparent magnitude correspond to ratios of ____.

A) luminosity
B) brightness
C) mass
D) temperature
E) distance

Question 19

Differences in absolute magnitude correspond to ratios of ____.

A) luminosity
B) brightness
C) mass
D) temperature
E) distance

Question 20

Star A and Star B have same temperatures, but Star A is more luminous than Star B. Based on this information, which of the following must be the case?

A) Star A is smaller than Star B.
B) Star A is larger than Star B.
C) Star A and Star B have same size.
D) Star A is more massive than Star B.

Question 21

Luminosity (absolute brightness) of a star depends on its ___________.

A) temperature and radius
B) radius and distance
C) distance and mass
D) mass and age
E) age and temperature

Question 22

Star A and Star B have the same size, but Star A is more luminous than Star B. Based on this information, which of the following must be the case?

A) Star A is cooler than Star B.
B) Star A is hotter than Star B.
C) Star A and Star B have same temperature.
D) Star A is more massive than Star B.

Question 23

_____ can be used to measure the _____ of nearby stars.

A) Parallax measurements; radius
B) The method of standard candles; brightness
C) Interferometry; radius
D) Spectroscopy; brightness

Question 24

The luminosity of a star is determined by the star's _____________ and _____________.

A) brightness; temperature
B) apparent brightness; surface temperature
C) diameter; surface temperature
D) distance; surface temperature
E) diameter; distance

Question 25

A star with a spectrum that peaks at a wavelength of 1 micron (1 × 10^-6) would have a surface temperature of _________ and be an __ star.

A) 2,900 K; O
B) 2,900 K; M
C) 29,000 K; O
D) 29,000 K; M

Question 26

How does Rigel, a bluish star, surface temperature compare to Betelgeuse, a reddish star.

A) Rigel's surface temperature is less than Betelgeuse's.
B) Rigel's surface temperature is greater than Betelgeuse's.
C) They have the same surface temperature because they are both members of the constellation Orion.
D) It is impossible to say without knowledge of the sizes of the stars.

Question 27

A star radiates most strongly at 600 nanometers. What is its surface temperature?

A) 483 K
B) 4,830 K
C) 6,000 K
D) 72,500 K
E) 7,250 K

Question 28

A star radiates most strongly at 400 nm. What is its surface temperature?

A) 483 K
B) 4,830 K
C) 7,250 K
D) 72,500 K

Question 29

Which of the following stars has the hottest stellar surface temperature?

A) M6
B) A0
C) G5
D) B2
E) K9

Question 30

Which of the following stars is reddish in color?

A) F6
B) A0
C) G5
D) B2
E) K9

Question 31

Which of the following is a main sequence star hotter than the Sun? (Note: the Sun is a G2V star.)

A) K2V
B) G1II
C) G2III
D) G1V
E) O2II

Question 32

Which of the following statements would explain the fact that larger molecules, such as amino acids, do not produce spectral lines in the OBAFGKM classification?

A) Larger molecules require higher temperatures to show absorption lines.
B) The spectra of hydrogen and helium are sufficient to classify stars.
C) The spectra of larger molecules are too complicated.
D) Larger molecules break apart at the high temperatures of stellar atmospheres.
E) All of these choices are correct.

Question 33

How can we explain the fact that hydrogen Balmer lines are essentially absent in the hot O type and the cool M stars?

A) O type stars do not contain hydrogen.
B) In cool stars hydrogen combines to form large molecules.
C) In O stars hydrogen is ionized and in M stars the electrons of hydrogen are in level 1, not level 2.
D) All of these choices are correct.

Question 34

The spectrum of a star shows the 656 nm absorption line shifted to 654 nm. Which of the following can we conclude about this star?

A) The star is approaching us with an approximate speed of 1,800 km/sec.
B) The star is receding with an approximate speed of 1,800 km/sec.
C) The star is approaching us with an approximate speed of 900 km/sec.
D) The star is receding with an approximate speed of 900 km/sec.
E) The star is spinning rapidly.

Question 35

If a main sequence, giant, and a supergiant all have the same spectral class, what characteristic is known to make these stars different?

A) luminosity
B) distance
C) surface temperature
D) color
E) It shows that the more massive stars are cooler.

Question 36

Analysis of stellar spectra shows that most stars consist of 71% ___, 27% ___, and a 2% mix of the other elements.

A) hydrogen; oxygen
B) hydrogen; helium
C) helium; hydrogen
D) oxygen; nitrogen

Question 37

The Balmer lines correspond to wavelengths in the ____ part of the spectrum of a(n) ____ atom.

A) ultraviolet; helium
B) visible; hydrogen
C) infrared; hydrogen
D) X-ray; helium

Question 38

The hydrogen absorption lines are the strongest in ___ type stars.

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

Question 39

Lines from molecules are strongest in ___ type stars.

A) A
B) F
C) M
D) K
E) O

Question 40

In ___ stars most of the electrons in the hydrogen atom are above level 2 and in ___ stars most of the electrons are below level 2, therefore the _____ are essentially absent in both types.

A) type M; type O; Balmer lines
B) type O; type M; Balmer lines
C) type A; type M; emission lines
D) type M; type A; absorption lines
E) type O; type A; emission lines

Question 41

Yellow dwarfs have ____ spectral lines than red giants.

A) narrower
B) stronger
C) weaker
D) wider

Question 42

Why do stars have dark lines in their spectra?

A) The cooler atoms in their surface layers absorb the radiation at some wavelengths.
B) They simply don't emit light at certain wavelengths.
C) Magnetic fields in Earth's atmosphere absorb the radiation at some wavelengths.
D) The statement is false. Stars have bright emission lines in their spectra, but no absorption lines.

Question 43

Which of the following stellar spectral types is cooler than our Sun?

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

Question 44

What distinguishes the spectral type of a star?

A) its brightness
B) the lines in its spectrum
C) its distance
D) its velocity

Question 45

If a star exhibits no Doppler shift in its emitted light, it must be true that _______________.

A) the star is not moving relative to Earth
B) the star is neither moving toward nor away from Earth
C) the star only displays proper motion
D) the star does not emit much visible light

Question 46

Which of the following stars is hottest?

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

Question 47

Eighty percent of ________ type stars have orbiting companions.

A) O and B
B) A and F
C) F and G
D) K and M

Question 48

In which binary system can we observe both the stars separately and follow their orbits around each other?

A) visual binary system
B) spectroscopic binary system
C) eclipsing binary system
D) transiting binary system

Question 49

Binary star systems are very important because they allow

A) measurement of star masses.
B) measurement of the speed of stars.
C) more precise measurement of the distance of stars.
D) more precise measurement of the temperature of stars.
E) more precise measurement of the spectral type of stars.

Question 50

What is the difference between spectroscopic and visual binaries?

A) Spectroscopic binaries have double spectral lines but do not move.
B) Visual binaries are pairs of stars in the same region in the sky but are not gravitationally interacting.
C) A visual binary does not show changes in the spectral lines.
D) In a visual binary we can see two distinct stars; in spectroscopic binaries, the images of the two stars cannot be resolved.

Question 51

A visual binary star system has rotation period, P = 10 years. The semi-major axis of the orbit of one of the stars is 5 AU. What is the combined mass of the binary star system?

A) 0.4 solar masses
B) 8 solar masses
C) 4 solar masses
D) 40 solar masses
E) 200 solar masses

Question 52

The study of eclipsing binary stars is very important because it allows astronomers to determine

A) the distance between two stars.
B) the speed of stars from the Doppler shift of their spectral lines.
C) the diameters of stars.
D) the luminosity of each star.
E) the brightness of each star.

Question 53

____ binary star systems are important because they allow astronomers to determine the mass and the ____ of the stars in the system.

A) Eclipsing; temperature
B) Spectroscopic; diameter
C) Spectroscopic; temperature
D) Eclipsing; diameter
E) Visual; temperature

Question 54

Analysis of ___ stars has shown that star masses are in the range of ___ to ____ solar masses.

A) binary; 1; 10
B) spinning; 1,000; 0.1
C) binary; 100; 1
D) spinning; 1; 100
E) binary; 30; 0.1

Question 55

A binary star is a pair of stars that orbit around each other. By detecting this orbital motion, and using Kepler's laws and the law of gravitation, one can directly measure the stars' ____.

A) temperatures
B) luminosities
C) masses
D) distances

Question 56

What is a spectroscopic binary?

A) a spectroscopic binary looks, to us on Earth, like a single star, but its spectrum shows double lines that shift
B) a visual binary for which we have spectra of both stars
C) a visual binary in which one or both stars have peculiar spectra
D) a visual binary that is shown by its spectrum to be a single star

Question 57

In the above H-R diagram sketch, which star is a white dwarf?

A) A
B) B
C) C
D) D
E) E

Question 58

In the above H-R diagram sketch, which star is a red dwarf?

A) A
B) B
C) C
D) D
E) E

Question 59

In the above H-R diagram sketch, which star is a red giant?

A) A
B) B
C) C
D) D
E) E

Question 60

In the above H-R diagram sketch, which star is a blue giant?

A) A
B) B
C) C
D) D
E) E

Question 61

In the above H-R diagram, which main sequence star is bluish in color?

A) A
B) B
C) C
D) D
E) E

Question 62

In the above H-R diagram, which main sequence star is reddish in color?

A) A
B) B
C) C
D) D
E) E

Question 63

In the above H-R diagram, which main sequence star is biggest in size?

A) A
B) B
C) C
D) D
E) E

Question 64

The H-R diagram is a diagram plotting the stars according to their

A) apparent brightness and temperature.
B) spectral type and temperature.
C) brightness and luminosity class.
D) luminosity and temperature.
E) mass and diameter.

Question 65

The star Aldebaran is a red giant, and is much more luminous than the Sun. What conclusions can be drawn from this fact?

A) Aldebaran is hotter and much more massive than the Sun.
B) Aldebaran is cooler than the Sun, but has larger diameter than the Sun.
C) In the H-R diagram, Aldebaran is above and to the left of the Sun.
D) Aldebaran is a binary star.
E) None of these choices is correct.

Question 66

The star Aldebaran is cooler and much more luminous than the Sun. Where do you expect to find Aldebaran in the H-R diagram?

A) top left
B) top right
C) center
D) bottom right
E) bottom left

Question 67

Stars on the main sequence have different luminosities because

A) they have different chemical compositions.
B) they have different ages.
C) they are at different distances from the Sun.
D) they have different masses.
E) they have different apparent magnitudes.

Question 68

Star A is located at the top left of the H-R diagram and has the same luminosity as Star B which is located at the top right of the H-R diagram. How must these stars differ?

A) Star A is hotter and bigger than Star B.
B) Star A is cooler and bigger than Star B.
C) Star A is hotter and smaller than Star B.
D) Star A is cooler and smaller than Star B.

Question 69

An M type star 1,000 times more luminous than the Sun will be located near the ___ part of the H-R diagram.

A) top left
B) top right
C) center
D) bottom right
E) bottom left

Question 70

A main sequence star has 3 times the mass of the Sun. Using ____ we find that the star is ___ times more luminous than the Sun.

A) the mass-luminosity relation; 9
B) the Stefan-Boltzmann law; 3
C) Wien's law; 3
D) the mass-luminosity relation; 3
E) the inverse-square law; 9

Question 71

If two stars are stacked vertically on a H-R diagram then they necessarily differ in their

A) distance.
B) luminosity class.
C) spectral class.
D) temperature.

Question 72

A star that is hot and has low luminosity must have ___________________.

A) a very large radius
B) a very small radius
C) a very small mass
D) a very great distance
E) a very low velocity

Question 73

In what part of the H-R diagram are white dwarfs?

A) upper left
B) lower center
C) upper right
D) lower right
E) just above the Sun on the main sequence

Question 74

The H-R diagram is a plot of stars' ______________.

A) temperature vs. mass
B) mass vs. luminosity
C) luminosity vs. temperature
D) mass vs. diameter

Question 75

What is the main sequence?

A) a region of cool, luminous stars in the upper right corner of the H-R diagram
B) a region of hot dim stars in the lower left corner of the H-R diagram
C) an approximately straight line on the H-R diagram along which 90% of stars lay
D) the order in which spectral types are listed

Question 76

A cool but very luminous star must have _______________.

A) a very large radius
B) a very small radius
C) a very small mass
D) a very low velocity

Question 77

Cooler, less luminous main sequence stars have _______________.

A) higher masses
B) lower masses
C) the same masses as hotter stars
D) masses that vary widely

Question 78

Where are red giants on the H-R diagram?

A) upper left
B) upper right
C) lower left
D) lower right

Question 79

How does the spectrum of a star depend on its surface temperature?

A) The hotter the star, the more colors will be present in its continuous spectrum.
B) The cooler the star, the more molecular absorption bands will be present in its spectrum.
C) Hot stars and cool stars can both have weak hydrogen lines.
D) All of these choices are correct.
E) None of these choices are correct.

Question 80

What was Cecilia Payne's discovery?

A) She proved that stars are composed mainly of hydrogen.
B) She classified stellar spectra by temperature.
C) She showed how to calculate the level in which an atom's electrons were most likely to be found.
D) All of these choices are correct.