Mastering Astronomy Timed quiz 4 Flashcards Preview

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Flashcards in Mastering Astronomy Timed quiz 4 Deck (54)
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1

Approximately, what basic composition are all stars born with?

90 percent hydrogen, 10 percent helium, no more than 1 percent heavier elements
one-quarter hydrogen, three-quarters helium, no more than 2 percent heavier elements
three-quarters hydrogen, one-quarter helium, no more than 2 percent heavier elements
98 percent hydrogen, 2 percent helium
half hydrogen, half helium, no more than 2 percent heavier elements

three-quarters hydrogen, one-quarter helium, no more than 2 percent heavier elements

2

Since all stars begin their lives with the same basic composition, what characteristic most determines how they will differ?

mass they are formed with
time they are formed
location where they are formed
color they are formed with
luminosity they are formed with

mass they were formed with

3

What are the standard units for luminosity?

joules
Newtons
kilograms
watts per second
watts

watts

4

What are the standard units for apparent brightness?

Newtons
watts
watts per square meter
joules
watts per second

watts per square meter

5

Which of the following correctly states the luminosity-distance formula?

distance =
apparent brightness = luminosity × 4π × (distance)2
luminosity =
apparent brightness =

apparent brightness = luminosity / 4pie x (distance)^2

6

Why do astronomers often measure the visible-light apparent brightness instead of the total apparent brightness of a star?

Astronomers are lazy.
All stars put out most of their light in the visible range of the spectrum.
They are identical for most stars.
Most stars do not put out light in other ranges of the spectrum.
In order to measure the total apparent brightness of a star, you must measure its brightness in all wavelengths, and this is difficult to do. The only wavelengths you can measure from the surface of Earth are visible and radio wavelengths.

In order to measure the total apparent brightness of a star, you must measure its brightness in all wavelengths, and this is difficult to do. The only wavelengths you can measure from the surface of Earth are visible and radio wavelengths.

7

The most distant stars we can measure stellar parallax for are approximately

5,000 parsecs away.
halfway across the Milky Way Galaxy.
50 parsecs away.
500 parsecs away.
in the Andromeda Galaxy.

50 parsecs away.

8

Which of the following statements about apparent and absolute magnitudes is true?

A star with apparent magnitude 1 is brighter than one with apparent magnitude 2.
A star's absolute magnitude is the apparent magnitude it would have if it were at a distance of 10 parsecs from Earth.
The absolute magnitude of a star is another measure of its luminosity.
The magnitude system that we use now is based on a system used by the ancient Greeks over 2,000 years ago that classified stars by how bright they appeared.
All of the above are true.

all of the above are true

9

The spectral sequence sorts stars according to

surface temperature.
mass.
radius.
core temperature.
luminosity.

surface temperature

10

The spectral sequence in order of decreasing temperature is

OBAFGKM.
BAGFKMO.
OBAGFKM.
ABFGKMO.
OFBAGKM.

OBAFGKM

11

Why is the spectral sequence of stars not alphabetical?

Because there is still uncertainty over what generates the energy in stellar cores.
The original alphabetical labeling did not correspond to surface temperature and thus had to be reordered.
Because it refers to stellar masses and these were difficult to measure accurately.
The letters refer to the initials of the original discovers.
They were chosen to fit a mnemonic.

The original alphabetical labeling did not correspond to surface temperature and thus had to be reordered.

12

Which of the following statements about spectral types of stars is true?

The spectral type of a star can be used to determine its color.
A star with spectral type F2 is hotter than a star with spectral type F3.
A star with spectral type A is cooler than a star with spectral type B.
The spectral type of a star can be used to determine its surface temperature.
All of the above are true.

all of the above are true

13

Which of the following persons reorganized the spectral classification scheme into the one we use today and personally classified over 400,000 stars?

Annie Jump Cannon
Williamina Fleming
Henry Draper
Cecilia Payne-Gaposchkin
Edward Pickering

Annie Jump Cannon

14

On a Hertzsprung-Russell diagram, where would we find stars that are cool and luminous?

upper right
lower right
upper left
lower left

Upper right

15

On a Hertzsprung-Russell diagram, where would we find stars that have the largest radii?

upper right
lower right
upper left
lower left

Upper right

16

On a Hertzsprung-Russell diagram, where on the main sequence would we find stars that have the greatest mass?

upper right
lower right
upper left
lower left

Upper left

17

On a Hertzsprung-Russell diagram, where would we find red giant stars?

upper right
lower right
upper left
lower left

Upper right

18

You observe a star in the disk of the Milky Way, and you want to plot the star on an H-R diagram. You will need to determine all of the following, except the

spectral type of the star.
apparent brightness of the star in our sky.
distance to the star.
rotation rate of the star.

Rotation rate of the star

19

A star of spectral type G lives approximately how long on the main sequence?

100 million years
10,000 years
10 billion years
1 million years
1,000 years

10 billion years

20

Which of the following luminosity classes refers to stars on the main sequence?

II
V
III
I
IV

V

21

Cluster ages can be determined from

main sequence turnoff.
main sequence fitting.
visual binaries.
pulsating variable stars.
spectroscopic binaries.

main sequence turnoff.

22

In order to understand star clusters, we need to be able to estimate their ages. What technique do scientists use for this?

radioisotope dating
finding the main-sequence turnoff point of the stars
measuring its parallax
calculating orbital parameters using Kepler's Laws
counting the planets that have formed around the largest stars

finding the main-sequence turnoff point of the stars

23

What do astronomers mean when they say that we are all "star stuff"?

that life would be impossible without energy from the Sun
that the carbon, oxygen, and many elements essential to life were created by nucleosynthesis in stellar cores
that Earth formed at the same time as the Sun
that the Universe contains billions of stars
that the Sun formed from the interstellar medium: the "stuff" between the stars

that the carbon, oxygen, and many elements essential to life were created by nucleosynthesis in stellar cores

24

All of the following are involved in carrying energy outward from a star's core except

radiative diffusion.
convection.
neutrinos.
conduction.

conduction.

25

Which stars have convective cores?

high-mass stars
intermediate-mass stars
low-mass stars
all of the above
none of the above

High mass stars

26

What is happening inside a star while it expands into a subgiant?

It is fusing hydrogen into helium in a shell outside the core.
It is fusing helium into carbon in a shell outside the core.
It is not fusing any element; it is contracting and heating up.
It is fusing helium into carbon in the core.
It is fusing hydrogen into helium in the core.

It is fusing hydrogen into helium in a shell outside the core.

27

Compared to the star it evolved from, a red giant is

cooler and brighter.
the same temperature and brightness.
hotter and dimmer.
hotter and brighter.
cooler and dimmer.

cooler and brighter.

28

At approximately what temperature can helium fusion occur?

a few million K
100 million K
100 billion K
100,000 K
1 million K

100 million K

29

The helium fusion process results in the production of

carbon.
oxygen.
nitrogen.
iron.
hydrogen.

carbon.

30

Which of the following sequences correctly describes the stages of life for a low-mass star?

white dwarf, main-sequence, red giant, protostar
protostar, main-sequence, white dwarf, red giant
protostar, red giant, main-sequence, white dwarf
protostar, main-sequence, red giant, white dwarf
red giant, protostar, main-sequence, white dwarf

protostar, main-sequence, red giant, white dwarf