Deck 11: Measuring the Stars: Giants, Dwarfs, and the Main Sequence

Question 1

A unique characteristic of type O stars is ionized helium lines in its spectrum.

Answer 1

True

Question 2

A +6.0 magnitude star is brighter than a +3.0 magnitude star.

Answer 2

False

Question 3

The Hipparcos satellite has extended our accurate parallax distance measurements to over 200 parsecs.

Answer 3

True

Question 4

Hydrogen lines are strongest in class A stars.

Question 5

A 3rd magnitude star appears 2.5 times brighter than a 4th magnitude star.

Question 6

Two stars have the same absolute magnitude, but one lies twice as far from Earth as the other. It will appear half as bright.

Question 7

A parsec is slightly more than 200,000 AU.

Question 8

A type B9 star is hotter than a type A0 star.

Question 9

A parsec is about 3.3 light- years.

Question 10

Our nearest stellar neighbor is a little less than 1 parsec away.

Question 11

Combining a star's proper motion and its distance allows us to determine its transverse velocity.

Question 12

The parallactic angle is the total shift observed over a six- month interval.

Question 13

At its brightest, Venus, at magnitude - 4, is 100 times brighter than a 1st magnitude star.

Question 14

Of all the stars in the sky, Barnard's star, the next closest beyond Alpha Centauri, appears to move the fastest.

Question 15

If a star has a parallax of 0.25", then its distance is about 13 light- years.

Question 16

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

Question 17

A type B star is bluer than a type G star.

Question 18

The Sun, at absolute magnitude +4.8, would be one of the brightest stars in the sky if seen from 32 light- years distance.

Question 19

To get the space velocity of a star in three dimensions, you need its proper motion, distance, and radial velocity.

Question 20

Fewer than 100 stars lie within 5 parsecs of the Sun.

Question 21

Ionized helium lines are found in both type B and O stars.

Question 22

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

Question 23

Molecular lines, such as TiO, are only found in very hot stars.

Question 24

Hydrogen lines are weak in M class stars because they have much less of it than do A class stars.

Question 25

Almost all stars on the main sequence range from 1 to 10 solar luminosities.

Question 26

Spectroscopic parallax is more accurate than trigonometric parallax for nearby stars.

Question 27

The pressure in the photosphere affects the width of spectral lines.

Question 28

The main sequence is luminosity class V.

Question 29

Luminosity class V stars are larger than class Ia stars.

Question 30

Main sequence stars lie at the top right corner of the H- R diagram.

Question 31

Most naked- eye stars would fall to the top left on the H- R diagram.

Question 32

Almost all stars on the main sequence range from 0.1 to 15 solar radii.

Question 33

A star of the same diameter, but twice as hot as our Sun, must be 16 times more luminous.

Question 34

A G2V star would be the same temperature as a G2Ib star, but much smaller and less luminous.

Question 35

White dwarfs lie on the lower left portion of the H- R diagram.

Question 36

Main sequence stars are fusing hydrogen into helium in their cores.

Question 37

Our Sun lies about the middle of the main sequence and the H- R diagram.

Question 38

Only A type stars show hydrogen lines in their spectra.

Question 39

Most stars are single stars like our Sun.

Question 40

Deneb's estimated distance of 1400 light- years comes from spectroscopic parallax measurements.

Question 41

A star's absolute magnitude is its apparent brightness as seen from

A) Alpha Centauri.
B) 10 light- years distance.
C) Pluto.
D) 100 parsecs distance.
E) 10 parsecs distance.

Question 42

A star is 10 parsecs from Earth. Which statement is true?

A) The star's apparent magnitude is smaller than its absolute magnitude.
B) The star's parallax is 1.0 arc seconds.
C) The star is about 33 ly away.
D) The star is in a different galaxy.
E) The star's apparent magnitude is larger than its absolute magnitude.

Question 43

The stars a Cygni and fi Cygni are in the constellation Cygnus. Which statement is true?

A) a Cygni appears brighter.
B) fi is hotter.
C) fi Cygni appears brighter.
D) a must be the eastern most star in the constellation.
E) fi appears redder.

Question 44

How much brighter will a 4th magnitude star appear than a 6th magnitude star?

A) 2.0 times
B) 6.25 times
C) 16 times
D) 2.5 times
E) 8 times

Question 45

A star has a parallax of .05". Its distance is

A) 5 light- years.
B) 200 parsecs.
C) 66 parsecs.
D) 20 parsecs.
E) 660 light- years.

Question 46

What can be said with certainty about a red star and a blue star?

A) The red star is more massive than the blue star.
B) The blue star is hotter than the red star.
C) The red star has a greater radial velocity than the blue star.
D) The red star is closer to Earth than the blue star.
E) The blue star has a greater proper motion than the red star.

Question 47

Rigel has an apparent magnitude of + 0.18 and Betelgeuse an apparent magnitude of +0.45. What can you conclude from this?

A) Rigel is brighter than Betelgeuse.
B) Betelgeuse must be closer to Earth.
C) Betelgeuse is brighter than Rigel.
D) Rigel must be closer to Earth.
E) Both stars are brighter than the full moon.

Question 48

If Vega is apparent magnitude zero, and Deneb first magnitude, then

A) Vega must be 2.5× hotter than Deneb.
B) Deneb must be a main sequence star, and Vega a giant.
C) Vega is about 100× brighter than Deneb.
D) Deneb is one magnitude brighter than Vega.
E) Vega is 2.5× brighter than Deneb.

Question 49

Almost all properties of other stars are described relative to our Sun.

Question 50

Which of these stars would be the hottest?

A) M10
B) G2
C) B0
D) A0
E) K9

Question 51

The full Moon's apparent magnitude is

A) - 26.2.
B) - 12.5.
C) +12.7.
D) +4.83.
E) - 1.4.

Question 52

If spectroscopic luminosity classification gives us an estimated distance to the faint star SAO 47552 of about 3300 light- years, then its parallax would be only

A) 0.1".
B) 0.01".
C) 0.001".
D) 3.3".
E) 0.033".

Question 53

A star has a parallax of 0.01 arc seconds. Its distance is

A) 10 parsecs
B) 100 parsecs.
C) 1 parsec.
D) 0.1 parsecs.
E) 0.01 parsecs.

Question 54

On a night when a human eye can see a fourth magnitude star, a 60mm telescope, with 100× the surface area as our pupil, would be able to just barely detect

A) eleventh magnitude Tethys, Saturn's second largest moon.
B) seventh magnitude Titan, Saturn's largest moon.
C) ninth magnitude Barnard's Star.
D) eighth magnitude Uranus.
E) thirteenth magnitude Pluto.

Question 55

The Hipparcos data give us

A) parallaxes to the nearest galaxies.
B) parallaxes as small as 0.005".
C) information on only the 6,000 brightest stars.
D) distances to about 100 billion stars, practically everything in the Milky Way Galaxy.
E) an accurate distance to the Moon.

Question 56

Which statement about stellar motion is incorrect?

A) Proper motion is measured in intervals of six months.
B) The space velocity can be found from the radial and transverse velocities.
C) You must also know the parallax to get the transverse velocity.
D) Radial velocity is measured by the Doppler shifts of the spectral lines.
E) The closer stars usually show larger proper motions.

Question 57

The mass of a newly formed star will determine its position on the main sequence.

Question 58

Our best stellar parallax measurements to date come from

A) the Hipparcos satellite.
B) radio interferometry.
C) ground based measurements taken six months apart.
D) observations made by astronauts.
E) the Keck telescope.

Question 59

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

A) temperature
B) density
C) luminosity
D) composition
E) mass

Question 60

Two stars both have parallaxes of 0.023", but star A has apparent magnitude +2.3, while star B is magnitude +7.3. Which statement is true?

A) Star A is both 100× brighter and larger than star B.
B) Star B must be ten times more luminous.
C) Star A must be ten times closer.
D) Star A is both 100× brighter and more luminous than star B.
E) Nothing, since we do not know their absolute magnitudes.

Question 61

In general, what can be said about type O and B stars compared to type K and M stars?

A) They are hotter and younger.
B) They are cooler and older.
C) They are hotter and older.
D) They are cooler and younger.
E) They are neither hotter nor cooler, younger nor older.

Question 62

Compared to the size of the Sun, stars of all types range from

A) 0.5 to 50 solar radii.
B) 0.01 to 1,000 solar radii.
C) 0.001 to 50,000 solar radii.
D) 0.08 to 8,000 solar radii.
E) 0.1 to 10 solar radii.

Question 63

A star near the lower right of the H- R diagram is likely to be

A) red, with high luminosity.
B) yellow, with luminosity similar to our Sun's.
C) red, with low luminosity.
D) blue, with high luminosity.
E) hot, bright, and very large.

Question 64

On the H- R diagram, the bright blue stars that dominate the naked- eye sky lie

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

Question 65

Which of these binaries would appear most similar in color telescopically?

A) F0V and G9III
B) O2V and M4Ia
C) A2Ia and F7Ia
D) F3IV and G8III
E) M1V and K9V

Question 66

If we know the average separation and period of revolution for a binary system, we can then measure

A) their absolute magnitudes.
B) the actual sizes of the two stars.
C) the actual luminosity of each star.
D) the actual mass of both individual stars.
E) the total mass of the system.

Question 67

In the H- R diagram, what are the two most important types of data plotted?

A) absolute and apparent magnitudes
B) spectral classes and absolute magnitudes
C) apparent magnitudes and temperatures
D) luminosities and masses
E) sizes and temperatures

Question 68

The H- R diagram can plot

A) apparent magnitude versus spectral classes.
B) temperature versus mass.
C) temperature versus luminosity.
D) radius versus luminosity.
E) radius versus mass.

Question 69

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

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

Question 70

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

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

Question 71

The stars with masses comparable to our Sun's, but sizes like the Earth are

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

Question 72

Binary stars separated enough to be resolved in a telescope are called

A) line- of- sight binaries.
B) astrometric binaries.
C) spectroscopic binaries.
D) visual binaries.
E) orbital binaries.

Question 73

On the H- R diagram, the Sun lies

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

Question 74

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

A) virtual
B) astrometric
C) visual
D) eclipsing
E) spectroscopic

Question 75

Compared to a type A0 star, a type A9 star is

A) more massive.
B) more luminous.
C) cooler.
D) hotter.
E) bluer.

Question 76

The Doppler shift is used to find

A) eclipsing binaries.
B) spectroscopic binaries.
C) photometric binaries.
D) astrometric binaries.
E) visual binaries.

Question 77

In what range of masses are most stars found?

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

Question 78

Stellar masses are measured directly by observations of the motions of

A) eclipsing binary systems.
B) visual binary systems.
C) spectroscopic binary systems.
D) All of the above can give us their masses.
E) Stellar masses cannot be measured directly by any method.

Question 79

What information can be gained from the light curves of eclipsing binaries?

A) their masses
B) their luminosities
C) their sizes
D) their distances
E) their temperatures

Question 80

The star's color index is a quick way of determining its

A) mass.
B) temperature.
C) composition.
D) density.
E) luminosity.