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AStronomy > exam two questions > Flashcards

exam two questions Flashcards

1
Q

The most abundant elements in stars are

A

hydrogen and helium

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2
Q

Spectral lines of hydrogen are strongest in _____ stars.

A

A

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3
Q

The spectra of stars show that stars are made

A

of the same atoms as the Earth but in different amounts.

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4
Q

What are the standard units for luminosity?`

A

watts

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5
Q

Knowing only the color of a star, we can estimate the star’s

A

temperature.

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6
Q

The most abundant chemical elements in a star’s atmosphere always give the strongest spectral lines in the star’s visible spectrum.

A

false

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7
Q

If star A has twice the radius of star B, the surface area of star A is

A

four times the area of star B

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8
Q

Three stars each radiate the same amount of energy per second. They are of spectral types O (bluish), G (yellow), and K (orange). Rank them in order of their radii

A

O is smallest, K is largest

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9
Q

Analysis of the light curve of an eclipsing binary star may give the astronomer information about

A

the diameters of the two component stars

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10
Q

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

A

less massive and approaching us at this moment.

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11
Q

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

240 years

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12
Q

If Star A is closer to us than Star B, then Star A’s parallax angle is

A

larger than that of Star B

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13
Q

On an H-R diagram, stellar masses

A

can be determined for main-sequence stars but not for other types of stars.

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14
Q

Each choice below lists a spectral type and luminosity class for a star. Which one is a red supergiant?

A

spectral type M2, luminosity class I

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15
Q

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

A

65 light years

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16
Q

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

A

upper right

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17
Q

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

A

5 parsecs

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18
Q

What is the primary visible color of an emission nebula?

A

red due to ionized hydrogen atoms

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19
Q

Ionization of hydrogen in H II regions is most visible at:

A

656.3 nm, Balmer alpha line for 3-2 electron transition.

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20
Q

A reflection nebula is caused by

A

starlight scattered by dust particles.

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21
Q

If you wanted to observe stars behind a molecular cloud, in what wavelength of light would you most likely observe?

A

infrared

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22
Q

Neutral hydrogen is most obvious in the electromagnetic spectrum:

A

at 21 cm in the radio region.

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23
Q

When an electron in H changes its spin from the same to the opposite direction as the proton, it:

A

emits a radio wave photon

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24
Q

All globular clusters in our Milky Way are about how old?

A

around ten billion years old

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25
Q

On an H-R diagram, a protostar would be:

A

above and to the right of the main sequence.

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26
Q

During a protostar’s T Tauri phase, it:

A

may develop very strong winds

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27
Q

What is the approximate range of masses that newborn main-sequence stars can have?

A

0.1 to 150 solar masses

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28
Q

Which of the following phenomena is not commonly associated with the star formation process?

A

intense ultraviolet radiation coming from a protostar

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29
Q

The spectrum of a planetary nebula shows ___ because it ____ its central star

A

emission lines; is ionized by

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30
Q

which of the following best describes the evolutionary track followed on the H-R diagram for the most massive stars?

A

horizontally right

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31
Q

If you had something the size of a sugar cube that was made of neutron star matter, it would weigh

A

about as much as a large mountain.

32
Q

Most of the energy of the supernova is carried outward via a flood of:

A

neutrinos.

33
Q

The making of abundant iron nuclei is typical of:

A

type II supernovae.

34
Q

Pulsars:

A

spin very rapidly when they’re young.

35
Q

Which of these does NOT depend on a close binary system to occur?

A

a Type II supernova

36
Q

A surface explosion on a white dwarf, caused by falling matter from the atmosphere of its binary companion, creates what kind of object?

A

nova

37
Q

If a star is rapidly rotating on its axis, its rotation can cause lines in its spectrum to

A

be more spread out

38
Q

Assuming that we can measure the apparent brightness of a star, what does the inverse square law for light allow us to do?

A

Calculate the star’s luminosity if we know its distance, or calculate its distance if we know its luminosity.

39
Q

The spectral sequence in order of decreasing temperature is

A

OBAFGKM

40
Q

A star whose surface is hotter than another star’s appears

A

bluer

41
Q

In general, the narrower the spectral line of a star:

A

bluer

42
Q

A star’s luminosity is the

A

total amount of light that the star radiates each second.

43
Q

The radius of a star can be determined from knowledge of its luminosity and surface temperature. Radii can also be measured directly for the components of

A

eclipsing binaries.

44
Q

In what range of masses are most stars found?

A

.1 to 100 solar masses

45
Q

A spectroscopic binary is a double star showing a periodic variation in

A

radial velocity

46
Q

The most important reason for studying binary stars is to find

A

the masses of stars.

47
Q

A hypothetical visual binary is observed to have a period of 3 years and a semi major axis of 3 A.U. The sum of the masses for the system

A

3 solar masses

48
Q

On the H-R diagram, red supergiants like Betelguese lie:

A

at the top right.

49
Q

A main sequence star at spectral type K0 is _____ than a K0 giant star

A

smaller and more dense

50
Q

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

parallax shift

51
Q

most of the stars on the H-R diagram belong to which group?

A

main sequence

52
Q

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 B is hotter than star A.

53
Q

On an H-R diagram, stellar radii

A

increase diagonally from the lower left to the upper right.

54
Q

A “fuzzy” dark or light patch in the sky is called a:

A

nebula

55
Q

What effect do even thin clouds of dust have on light passing through them?

A

It dims and reddens the light of all more distant stars.

56
Q

Interstellar dust consists mostly of

A

microscopic particles of carbon and silicon.

57
Q

What are the very cold (about 20 K), dense clouds of gas thought to be the most massive objects in the Galaxy called?

A

molecular clouds

58
Q

What two things are needed to create an emission nebulae?

A

hot stars and interstellar gas, particularly hydrogen

59
Q

A large gas cloud in the interstellar medium that contains several type O and B stars would appear to us as:

A

an emission nebula

60
Q

Most stars, probably all stars, formed:

A

in a cluster of stars.

61
Q

The vast majority of stars in a newly formed star cluster are

A

less massive than the Sun.

62
Q

What is the force that keeps a main sequence star from blowing apart?

A

gravitation

63
Q

A typical protostar may be several thousand times more luminous than the Sun. What is the source of this energy?

A

from the release of gravitational energy as the protostar continues to shrink

64
Q

Approximately what core temperature is required before hydrogen fusion can begin in a star?

A

10 million K

65
Q

No stars have been found with masses greater than 300 times our Sun because

A

they would generate so much power that they would blow themselves apart.

66
Q

What is the source of the large dust shells seen around some red giants and red supergiants?

A

material from winds from these same stars

67
Q

Which of the following statements about stages of nuclear burning (i.e., first-stage hydrogen burning, second-stage helium burning, etc.) in a massive star is not true?

A

Each successive stage lasts for approximately the same amount of time.

68
Q

As a 10 solar mass star leaves the main sequence on its way to becoming a red supergiant, its luminosity:

A

remains roughly constant.

69
Q

A solar mass star will evolve off the main sequence when:

A

it builds up a core of inert helium.

70
Q

The core of a highly evolved high mass star is a little larger than:

A

Earth.

71
Q

Nearly all the elements found in nature were formed inside stars, EXCEPT for:

A

hydrogen and helium.

72
Q

Neutron stars do NOT have:

A

rotation periods comparable to the Sun’s.

73
Q

When a high-mass star becomes a supernova, it is probably a result of

A

its core collapsing

74
Q

Which of the following statements about electron degeneracy pressure and neutron degeneracy pressure is true?

A

Electron degeneracy pressure is the main source of pressure in white dwarfs, while neutron degeneracy pressure is the main source of pressure in neutron stars

75
Q

Supernova explosions are important because they seem to be

A

the main way of releasing heavy atoms into space

AStronomy (9 decks)

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