Deck 10: Measuring the Stars

Question 1

In the quantum mechanical view of the atom,an electron is best thought of as:

A) a cloud that is centered on the nucleus.
B) a pointlike particle orbiting the nucleus.
C) free to orbit at any distance from the nucleus.
D) All of the above are true.

Answer 1

a cloud that is centered on the nucleus.

Question 2

Stars A and B appear equally bright,but star A is twice as far away from us as star B.Which of the following is true?

A) Star A is twice as luminous as star B.
B) Star A is four times as luminous as star B.
C) Star B is twice as luminous as star A.
D) Star B is four times as luminous as star B.

Answer 2

Star A is four times as luminous as star B.

Question 3

The spectrum in the figure below is:

A) an absorption spectrum.
B) an emission spectrum.
C) a thermal spectrum.
D) not any of these types.

Answer 3

an absorption spectrum.

Question 4

Stars are made mostly of:

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

Question 5

Which star in the figure below is closest to Earth?

A) star A
B) star B
C) The two stars are the same distance.
D) not enough information

Question 6

The star named Capella has an apparent magnitude of 0 while the star named Polaris has an apparent magnitude of 2,which means that Capella appears ________ Polaris in the night sky.

A) brighter than
B) as bright as
C) dimmer than

Question 7

Parallax is used to directly measure:

A) distance.
B) velocity.
C) luminosity.
D) mass.

Question 8

When an electron moves from a higher energy level in an atom to a lower energy level:

A) the atom is ionized.
B) a continuous spectrum is emitted.
C) a photon is emitted.
D) a photon is absorbed.

Question 9

How is the distance to a star related to its parallax?

A) Distance is directly proportional to parallax.
B) Distance is inversely proportional to parallax.
C) Distance is directly proportional to parallax squared.
D) Distance is inversely proportional to parallax squared.

Question 10

What is the difference between brightness and luminosity?

A) These are different names for the same property.
B) Luminosity is how bright the star appears to us; brightness is how much light it emits.
C) Brightness is how bright the star appears to us; luminosity is how much light it emits.
D) Luminosity measures size; brightness measures temperature.

Question 11

Star A is a red star.Star B is a blue star.Which is hotter?

A) star A
B) star B
C) We also need to know the luminosities of the stars to determine their temperatures.
D) Color is not related to temperature at all.

Question 12

Which sequence correctly lists the spectral classes of stars in order of decreasing temperature (from hottest to coolest)?

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

Question 13

If a star's measured parallax is 0.1 arcsec,what is its distance?

A) 1 pc
B) 5 pc
C) 10 pc
D) 50 pc

Question 14

How many arcseconds are there in a degree?

A) 60
B) 360
C) 3,600
D) 6,000

Question 15

Two similar stars have the same temperature.If star A is four times brighter than star B,then:

A) star B is two times farther away than star A.
B) star B is four times farther away than star A.
C) star B and star A lie at the same distance from us.
D) It is impossible to determine their relative distances from the information given.

Question 16

The spectral class of a star is related to its:

A) luminosity.
B) temperature.
C) radius.
D) mass.

Question 17

What spectral class is the Sun?

A) A0
B) G2
C) F5
D) M3

Question 18

Stars generally exhibit:

A) an absorption spectrum.
B) a continuous spectrum.
C) an emission spectrum.
D) both emission and absorption spectra.

Question 19

To measure the parallax of the most distant stars measurable,we would make two measurements of the star's position separated by:

A) 6 hours.
B) 12 hours.
C) 6 months.
D) 12 months.

Question 20

If a star's distance is 100 pc,what is its parallax?

A) 0.01 arcsec
B) 0.05 arcsec
C) 0.1 arcsec
D) 0.5 arcsec

Question 21

On a typical H-R diagram,where are the largest stars located?

A) in the upper left corner
B) in the upper right corner
C) in the lower left corner
D) in the lower right corner

Question 22

You discover a binary star system in which star A has a velocity of 10 km/s and star B has a velocity of 30 km/s.Which one of the following mass combinations is physically possible?

A) Star A is 3 M¤ and star B is 1 M¤.
B) Star A is 1 M¤ and star B is 0.3 M¤.
C) Star A is 1 M¤ and star B is 3 M¤.
D) Star A is 2 M¤ and star B is 0.5 M¤.

Question 23

Stars X and Y are 5 AU apart from each other.Star X is four times as massive as star Y.The center of mass of this system is ________ AU away from star X and ________ AU away from star Y.

A) 1; 4
B) 2; 3
C) 3; 2
D) 4; 1

Question 24

Examine the figure below.On a typical H-R diagram,what are the stars that have the hottest surface temperatures and the smallest radii?

A) red giants
B) blue giants
C) red dwarfs
D) white dwarfs

Question 25

A star classified as a K0III star is:

A) a giant that is cooler than the Sun.
B) a supergiant that is hotter than the Sun.
C) a main-sequence star that is hotter than the Sun.
D) a subgiant that is cooler than the Sun.

Question 26

Eclipsing binary systems:

A) orbit in the plane of the sky.
B) exhibit large radial velocity shifts.
C) contain equal mass stars.
D) contain stars that pass in front of one another during their orbit.

Question 27

Examine the figure below.On a typical H-R diagram,where are main-sequence stars that have the hottest surface temperatures located?

A) in the upper left corner
B) in the upper right corner
C) in the lower left corner
D) in the lower right corner

Question 28

The one property of a main-sequence star that determines all its other properties is its:

A) luminosity.
B) mass.
C) temperature.
D) spectral type.

Question 29

Examine the figure below.On a typical H-R diagram,where are main-sequence stars that have the coolest surface temperatures located?

A) in the upper left corner
B) in the upper right corner
C) in the lower left corner
D) in the lower right corner

Question 30

The slower-moving star in a binary is:

A) the less massive star.
B) the more massive star.
C) the hotter star.
D) the more distant of the two stars.

Question 31

The Hertzsprung-Russell (H-R)diagram (see figure below)is a graph of:

A) mass versus brightness for stars.
B) size versus mass for stars.
C) luminosity versus surface temperature for stars.
D) mass versus spectral type for stars.

Question 32

The luminosity class of a star is related to its:

A) distance.
B) temperature.
C) radius.
D) mass.

Question 33

Which of the following properties is never plotted on the horizontal axis of an H-R diagram?

A) color
B) luminosity
C) temperature
D) spectral class

Question 34

Stars of similar temperatures but different sizes will have:

A) similar luminosities but different masses.
B) similar masses but different distances.
C) different spectral types but similar luminosities.
D) similar spectral types but different luminosities.

Question 35

In a binary star system that contains stars with 10 M¤ and 5 M¤,the velocity of the 10 M¤ star will be ________ times the velocity of the 5 M¤ star.

A) 0.2
B) 0.5
C) 1
D) 2

Question 36

All of the following are useful in determining the masses of stars in a binary system EXCEPT:

A) the period of the orbits of the two stars.
B) the average separation between the two stars.
C) the luminosities of the two stars.
D) the velocities of the two stars.

Question 37

The stars that have the largest radii are classified as:

A) giants.
B) ultragiants.
C) supergiants.
D) dwarfs.

Question 38

Applying Kepler's third law to a binary star system allows us to determine:

A) the mass of each star.
B) the system's total mass.
C) the system's distance.
D) the system's brightness.

Question 39

Why do O- and B-type stars have weaker hydrogen absorption lines than A-type stars?

A) O- and B-type stars are cooler than A-type stars.
B) A larger fraction of the surface hydrogen atoms in O- and B-type stars is ionized.
C) O- and B-type stars have converted much more of their hydrogen into heavier elements.
D) A-type stars have a higher mass than O- and B-type stars, and they have more hydrogen.

Question 40

Roughly what percentage of stars are main-sequence stars?

A) 10 percent
B) 40 percent
C) 60 percent
D) 90 percent

Question 41

A star with a stellar parallax of 0.035 arcsec is at a distance of how many parsecs?

Question 42

What is the main property of a main-sequence star that determines nearly all its other properties?

Question 43

How do astronomers use spectra to determine the composition of a star?

Question 44

In what ways are energy states of an atom like books occupying shelves in a bookcase?

Question 45

Using information from the figure below,explain why star 2 is the more massive star of the eclipsing binary pair?

Question 46

Examine the figure below.Along the main sequence,how do the luminosity,temperature,radius,and mass of stars change as you go from the upper-left to the lower-right corners of the H-R diagram?

Question 47

You observe a binary star system and find that star 1 has a velocity of 10 m/s while star 2 has a velocity of 40 m/s.What is the ratio of masses of the two stars (M₁/M₂)?

Question 48

Explain how we can use spectroscopic parallax to determine the distance to a star farther away than a few hundred light-years.

Question 49

If given the image alone in the figure below,what further information might be required to determine that the stars are a visual binary system?

Question 50

Describe the luminosity classes found on the H-R diagram below.

Question 51

What are the two main chemical elements that make up the Sun? How much of the mass of the Sun is composed of elements other than these two?

Question 52

Why do we see black lines in an absorption spectrum if the absorbed photons are (almost)instantaneously reemitted by the atoms in the cloud?

Question 53

What is the spectral type of stars that have the strongest hydrogen absorption lines? Why do stars that are hotter than these have weaker hydrogen lines?

Question 54

How is the unit of length known as a parsec defined?

Question 55

Describe how brightness,luminosity,and distance are related.

Question 56

How are atoms excited,and why do they decay?

Question 57

You observe a binary star system and find that star 1 has a velocity of 20 m/s while star 2 has a velocity of 40 m/s.What is the ratio of masses of the two stars (M₁/M₂)? If star 2 has a mass of 2 solar masses what is the mass of star 1?