Deck 9: Measuring the Stars

Question 1

Which of the following best describes the size and distance relationship of our Sun and the nearest star?

A) A tennis ball here, another on the Moon
B) Two beach balls separated by 100 city blocks
C) Two grains of sand separated by 100 light-years
D) Two golf balls separated by 300 kilometers
E) Two baseballs separated by 100 yards

Answer 1

Two golf balls separated by 300 kilometers

Question 2

The nearest naked- eye star to our Sun, Alpha Centauri, is still over a parsec distant.

Answer 2

True

Question 3

Hydrogen lines are weaker in both very hot and very cool stars.

Answer 3

True

Question 4

For luminosity classification, fat stars have skinny spectral lines.

Question 5

On the main sequence, almost all stars have radii between about 0.1 and 10 times the Sun.

Question 6

Eclipsing binaries are the most useful, giving us sizes as well as masses of the pair.

Question 7

The proper motion of a star, its distance, and Doppler shift can give us its space velocity.

Question 8

Star A and star B have the same apparent magnitude. Star A is twice as distant as star B. Therefore, star A has twice the luminosity as star B.

Question 9

The vast majority of stars near us would fall to the bottom right on the H-R diagram.

Question 10

What is proper motion?

A) It is the true, not apparent, motion of a star in space.
B) It is the apparent shift as we go to opposite sides of our orbit every six months.
C) It is the annual apparent motion of a star across the sky.
D) It is the motion of a star towards or away from us, revealed by Doppler shifts.
E) It is the orbital motion of a star around the Galaxy.

Question 11

Which statement about stellar motion is incorrect?

A) In general, the closer a star is, the more its proper motion.
B) The radial velocity is measured by the Doppler shift.
C) The transverse velocity is measured by the proper motion and the distance.
D) Like parallax, proper motion is measured over intervals of exactly six months.
E) The Pythagorean theorem relates space, transverse, and radial velocities.

Question 12

A type B9 star is hotter than a type A0.

Question 13

The proper motion of a star is its true velocity through space.

Question 14

A star of the Sun's diameter, but twice as hot, must be 16X more luminous than the Sun.

Question 15

First magnitude Spica appears 2.5 times brighter than second magnitude Polaris.

Question 16

If a star were moved 10 times farther away, its absolute magnitude would drop five magnitudes.

Question 17

A nearby star has a parallax of 0.2 arc seconds. What is its distance?

A) 0.1 parsec
B) 0.2 parsec
C) 0.5 parsec
D) 5 parsecs
E) 50 parsecs

Question 18

In a spectroscopic binary, the star whose lines shift the most weighs the most.

Question 19

If a star were moved 10 times farther away, its apparent magnitude would drop by five magnitudes.

Question 20

In a binary system, the more massive stars always stay closer to the center of mass and move slower.

Question 21

Star A has an absolute magnitude of 2.5 and star B has an apparent magnitude of 2.5, but star A is a main sequence star and star B is a red giant. Which statement below is correct?

A) Star A appears brighter than star B, but star B and star A have the same intrinsic brightness.
B) Star B appears brighter than star A, but star B and star A have the same intrinsic brightness.
C) Star A and star B appear to have the same brightness, but star B is intrinsically brighter than star A.
D) Star A and star B appear to have the same brightness, but star A is intrinsically brighter than star B.
E) It is impossible to determine how bright these stars are or appear to be relative to one another, given the information above.

Question 22

What is the absolute magnitude of our Sun?

A) -23.0
B) -4.6
C) -1.4
D) +4.8
E) +9.4

Question 23

Perhaps the greatest of the Greek astronomers, ________ compiled the first catalog of stars, accurately measured their positions, and defined the basic system of stellar brightnesses.

A) Erastothenes
B) Aristotle
C) Ptolemy
D) Hipparchus
E) Aristarchus

Question 24

What physical property of a star does the spectral type measure?

A) Density
B) Luminosity
C) Temperature
D) Mass
E) Composition

Question 25

Star A and star B both have an absolute magnitude of 2.0, but star A has an apparent magnitude of 5.0 and star B has an apparent magnitude of 7.0. Which statement below is correct?

A) Star A appears brighter than star B, but star B and star A have the same intrinsic brightness.
B) Star B appears brighter than star A, but star B and star A have the same intrinsic brightness.
C) Star A and star B appear to have the same brightness, but star B is intrinsically brighter than star A.
D) Star A and star B appear to have the same brightness, but star A is intrinsically brighter than star B.
E) It is impossible to determine how bright these stars are or appear to be relative to one another, given the information above.

Question 26

If a star has a parallax of 0.05", then its distance in light-years is about

A) 6.4 light-years.
B) 12.7 light-years.
C) 20 light-years.
D) 65 light-years.
E) 100 light-years.

Question 27

Star A and star B both have an apparent magnitude of 4.0, but star A has an absolute magnitude of 1.0 and star B has an absolute magnitude of 7.0. Which statement below is correct?

A) Star A appears brighter than star B, but star B and star A have the same intrinsic brightness.
B) Star B appears brighter than star A, but star B and star A have the same intrinsic brightness.
C) Star A and star B appear to have the same brightness, but star B is intrinsically brighter than star A.
D) Star A and star B appear to have the same brightness, but star A is intrinsically brighter than star B.
E) It is impossible to determine how bright these stars are or appear to be relative to one another, given the information above.

Question 28

If a star is found by spectroscopic observations to be about 500 parsecs distant, its parallax is

A) 0.2".
B) 0.5".
C) 0.02".
D) 0.002".
E) 0.005".

Question 29

At the distance of Jupiter (6 times further away from the Sun than Earth) the amount of sunlight received per square centimeter different by what factor?

A) 6 times less
B) 12 times less
C) 36 times less
D) 6 times more
E) 12 times more

Question 30

The absolute magnitude of a star is its brightness as seen from a distance of

A) one million kilometers.
B) one astronomical unit.
C) one light-year.
D) ten parsecs.
E) 10 light-years.

Question 31

In order to turn a star's proper motion into its space velocity, we must also know

A) its mass and spectral type.
B) its temperature and age.
C) its distance and radial velocity.
D) its distance and mass.
E) its spectral type and period of rotation.

Question 32

If a star appears to move back and forth relative to other stars over a six-month period, this motion is due to the star's

A) transverse motion.
B) radial motion.
C) parallax shift.
D) Doppler shift.
E) true space motion.

Question 33

Roughly how many stars are within 4 parsecs of the solar system?

A) 3
B) 30
C) 3000
D) 300,000
E) 200 billion

Question 34

If a star appears to move relative to other stars over a one-year period, this motion is due to the star's

A) transverse motion.
B) radial motion.
C) parallax shift.
D) Doppler shift.
E) true space motion.

Question 35

Star A is a main sequence star of spectral type G5 and star B is a red giant of spectral type K2. Which statement below is correct?

A) Star A appears brighter than star B.
B) Star B appears brighter than star A.
C) Star A is hotter than star B.
D) Star B is hotter than star A.
E) None of the above can be said about these two stars.

Question 36

Star A and star B both have an apparent magnitude of 7.0, but star A is at a distance of 15 pc and star B is at a distance of 30 pc. Which statement below is correct?

A) Star A appears brighter than star B, but star B and star A have the same intrinsic brightness.
B) Star B appears brighter than star A, but star B and star A have the same intrinsic brightness.
C) Star A and star B appear to have the same brightness, but star B is intrinsically brighter than star A.
D) Star A and star B appear to have the same brightness, but star A is intrinsically brighter than star B.
E) It is impossible to determine how bright these stars are or appear to be relative to one another, given the information above.

Question 37

Star A is a main sequence star of spectral type F2 and star B is a white dwarf of spectral type B4. Which statement below is correct?

A) Star A appears brighter than star B.
B) Star B appears brighter than star A.
C) Star A is hotter than star B.
D) Star B is hotter than star A.
E) None of the above can be said about these two stars.

Question 38

Star A and star B both have an absolute magnitude of 2.0, but star A is at a distance of 50 pc and star B is at a distance of 20 pc. Which statement below is correct?

A) Star A appears brighter than star B, but star B and star A have the same intrinsic brightness.
B) Star B appears brighter than star A, but star B and star A have the same intrinsic brightness.
C) Star A and star B appear to have the same brightness, but star B is intrinsically brighter than star A.
D) Star A and star B appear to have the same brightness, but star A is intrinsically brighter than star B.
E) It is impossible to determine how bright these stars are or appear to be relative to one another, given the information above.

Question 39

In comparing first magnitude Deneb with second magnitude Polaris, we find that

A) Polaris is in reality much more luminous.
B) Deneb must be much hotter than Polaris.
C) Deneb appears 2.5 times brighter to us than does Polaris.
D) Polaris is really 100 times brighter than nearby Deneb.
E) Deneb is really much closer than Polaris.

Question 40

Procyon lies about 13 light-years distant, thus its parallax is about

A) 0.01".
B) 0.25".
C) 0.40".
D) 0.65".
E) 1.3".

Question 41

Compared to the size of the Sun, in what range of sizes are nearly all stars found?

A) 0.5 to 2 solar radii
B) 0.1 to 1.0 solar radii
C) 0.5 to 50 solar radii
D) 1 to 100 solar radii
E) 0.01 to 100 solar radii

Question 42

How might the most common occurring stars be described, based on our stellar neighborhood?

A) White dwarfs
B) K giants
C) G main sequence
D) A main sequence
E) M main sequence

Question 43

In a spectroscopic binary system, the star showing the larger blue shift is

A) cooler and receding the fastest.
B) less massive of the pair and receding slower.
C) more massive and approaching us.
D) less massive and approaching us at this moment.
E) hotter and receding faster.

Question 44

On the H-R diagram, red supergiants like Betelgeuse lie

A) at the bottom left.
B) at the bottom right.
C) at the top left.
D) at the top right.
E) They can't be plotted, for they are not main sequence.

Question 45

In the H-R diagram, the bright blue-white stars that dominate the naked eye sky lie to the

A) top left.
B) top right.
C) middle of the main sequence.
D) top center.
E) bottom left.

Question 46

Two red stars have surface temperatures of 3000 K, but Star A's luminosity is about 5% of the Sun's and Star B's luminosity is about 32,000 times the luminosity of the Sun. How much bigger is star B than star A?

A) They are the same size.
B) Star B's radius is about 16 times larger than star A's radius.
C) Star B's radius is about 800 times larger than star A's radius.
D) Star B's radius is about 640,000 times larger than star A's radius.
E) This cannot be determined from the information given.

Question 47

Which of the following is the most common type of star?

A) High mass main sequence
B) Low mass main sequence
C) White dwarfs
D) Red giants
E) Blue supergiants

Question 48

A star with a parallax of 1 second of arc is at a distance of ________ by definition.

Question 49

On the H-R diagram, white dwarfs lie Sirius B and Procyon B lie

A) at the top left.
B) at the top right.
C) close to the Sun, near the center.
D) at the lower left.
E) at the lower right.

Question 50

Upon what data do measurements of sizes of eclipsing binaries depend?

A) Their orbital periods and separations
B) Their masses and luminosities
C) Their Doppler shifts and durations of stages of their eclipses
D) Their temperatures and speeds
E) Their temperatures and masses

Question 51

Which type of binary can have their sizes measured directly by photometry?

A) Virtual
B) Visual
C) Eclipsing
D) Spectroscopic
E) Astrometric

Question 52

The Hertzsprung-Russell Diagram plots ________ against the spectral type or temperature.

A) distance
B) luminosity or absolute magnitude
C) brightness or apparent magnitude
D) size or density
E) mass

Question 53

In a spectroscopic binary, if a pair shows a combined set of lines tonight, but a maximum split two nights later, its orbital period must be

A) one day.
B) two days.
C) four days.
D) eight days.
E) twelve days.

Question 54

In what range of masses are most stars found?

A) 0.1 to 2 solar masses
B) 1 to 3 solar masses
C) 0.1 to 100 solar masses
D) 0.01 to 100 solar masses
E) Stars can have any mass.

Question 55

Stars that have masses similar to the Sun's, and sizes similar to the Earth are

A) main sequence stars.
B) white dwarfs.
C) red giants.
D) red dwarfs.
E) brown dwarfs.

Question 56

On the H-R diagram, the Sun lies

A) at the top left.
B) at the bottom left.
C) at the bottom right.
D) about the middle of the main sequence.
E) at the top right.

Question 57

In general, the narrower the spectral line of a star

A) the hotter the star is.
B) the bigger the star is.
C) the denser the star is.
D) the smaller the star is.
E) the cooler the star is.

Question 58

In a visual binary system with circular orbits, if in 20 years the two stars' position angles have shifted by 30 degrees, the pair's period must be

A) 60 years.
B) 90 years.
C) 120 years.
D) 240 years.
E) 360 years.

Question 59

Having nothing to do with trigonometry, ________ parallaxes use the width of absorption lines to estimate the star's luminosity and size and distance.

A) bolometric
B) photometric
C) spectroscopic
D) holographic
E) videometric

Question 60

What are the two most important intrinsic properties used to classify stars?

A) Mass and age
B) Luminosity and surface temperature
C) Distance and luminosity
D) Distance and surface temperature
E) Distance and color

Question 61

Knowledge of a star's temperature and ________ enables us to calculate its radius, surface area, and volume from the appropriate radiation law.

Question 62

Why must both parallax and proper motion be known to give transverse velocity?

Question 63

How is distance determined to the nearest stars? How far out can this technique be applied? How many stars can be measured in this way?

Question 64

On the main sequence on an H-R diagram, our Sun lies at about ________.

Question 65

All classes of binary stars yield the basic information on stellar ________.

Question 66

The apparent magnitude of the Sun is -26, while Sirius has an apparent magnitude of -1; how much brighter does the Sun appear than Sirius?

Question 67

What types of observations are necessary to determine the motion of a star through space?

Question 68

In an eclipsing binary, the longer the stages of the eclipse take, the ________ the star.

Question 69

How is proper motion measured?

Question 70

On the H-R diagram, most bright naked eye stars would lie at the ________.

Question 71

From hottest to coolest, the seven letters for the star types are ________.

Question 72

The ________ magnitude of a star depends directly upon its luminosity and distance.

Question 73

How can a white dwarf be hotter than our Sun, yet much less luminous?

Question 74

Capella is the same temperature as our Sun, but about ten times the Sun's diameter; it must be about ________ times as luminous as our star.

Question 75

Contrast main sequence stars of type B and G.

Question 76

What is proper motion? How is it related to transverse velocity?

Question 77

Why is the main sequence main? Why are these stars so common?

Question 78

If two stars are the same size and one is twice the temperature of the other, how much more luminous is the hotter one?

Question 79

What role does hydrogen play in spectral classification?

Question 80

A star's motion across the sky is its ________ motion.