exam two questions

Question 1

The most abundant elements in stars are

Answer 1

hydrogen and helium

Question 2

Spectral lines of hydrogen are strongest in _____ stars.

Answer 2

A

Question 3

The spectra of stars show that stars are made

Answer 3

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

Question 4

What are the standard units for luminosity?`

Answer 4

watts

Question 5

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

Answer 5

temperature.

Question 6

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

Answer 6

false

Question 7

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

Answer 7

four times the area of star B

Question 8

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

Answer 8

O is smallest, K is largest

Question 9

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

Answer 9

the diameters of the two component stars

Question 10

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

Answer 10

less massive and approaching us at this moment.

Question 11

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:

Answer 11

240 years

Question 12

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

Answer 12

larger than that of Star B

Question 13

On an H-R diagram, stellar masses

Answer 13

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

Question 14

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

Answer 14

spectral type M2, luminosity class I

Question 15

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

Answer 15

65 light years

Question 16

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

Answer 16

upper right

Question 17

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

Answer 17

5 parsecs

Question 18

What is the primary visible color of an emission nebula?

Answer 18

red due to ionized hydrogen atoms

Question 19

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

Answer 19

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

Question 20

A reflection nebula is caused by

Answer 20

starlight scattered by dust particles.

Question 21

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

Answer 21

infrared

Question 22

Neutral hydrogen is most obvious in the electromagnetic spectrum:

Answer 22

at 21 cm in the radio region.

Question 23

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

Answer 23

emits a radio wave photon

Question 24

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

Answer 24

around ten billion years old

Question 25

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

Answer 25

above and to the right of the main sequence.

Question 26

During a protostar's T Tauri phase, it:

Answer 26

may develop very strong winds

Question 27

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

Answer 27

0.1 to 150 solar masses

Question 28

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

Answer 28

intense ultraviolet radiation coming from a protostar

Question 29

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

Answer 29

emission lines; is ionized by

Question 30

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

Answer 30

horizontally right

Question 31

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

Answer 31

about as much as a large mountain.

Question 32

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

Answer 32

neutrinos.

Question 33

The making of abundant iron nuclei is typical of:

Answer 33

type II supernovae.

Question 34

Pulsars:

Answer 34

spin very rapidly when they're young.

Question 35

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

Answer 35

a Type II supernova

Question 36

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

Answer 36

nova

Question 37

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

Answer 37

be more spread out

Question 38

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

Answer 38

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

Question 39

The spectral sequence in order of decreasing temperature is

Answer 39

OBAFGKM

Question 40

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

Answer 40

bluer

Question 41

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

Answer 41

bluer

Question 42

A star's luminosity is the

Answer 42

total amount of light that the star radiates each second.

Question 43

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

Answer 43

eclipsing binaries.

Question 44

In what range of masses are most stars found?

Answer 44

.1 to 100 solar masses

Question 45

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

Answer 45

radial velocity

Question 46

The most important reason for studying binary stars is to find

Answer 46

the masses of stars.

Question 47

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

Answer 47

3 solar masses

Question 48

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

Answer 48

at the top right.

Question 49

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

Answer 49

smaller and more dense

Question 50

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:

Answer 50

parallax shift

Question 51

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

Answer 51

main sequence

Question 52

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

Answer 52

Star B is hotter than star A.

Question 53

On an H-R diagram, stellar radii

Answer 53

increase diagonally from the lower left to the upper right.

Question 54

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

Answer 54

nebula

Question 55

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

Answer 55

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

Question 56

Interstellar dust consists mostly of

Answer 56

microscopic particles of carbon and silicon.

Question 57

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

Answer 57

molecular clouds

Question 58

What two things are needed to create an emission nebulae?

Answer 58

hot stars and interstellar gas, particularly hydrogen

Question 59

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

Answer 59

an emission nebula

Question 60

Most stars, probably all stars, formed:

Answer 60

in a cluster of stars.

Question 61

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

Answer 61

less massive than the Sun.

Question 62

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

Answer 62

gravitation

Question 63

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

Answer 63

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

Question 64

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

Answer 64

10 million K

Question 65

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

Answer 65

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

Question 66

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

Answer 66

material from winds from these same stars

Question 67

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?

Answer 67

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

Question 68

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

Answer 68

remains roughly constant.

Question 69

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

Answer 69

it builds up a core of inert helium.

Question 70

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

Answer 70

Earth.

Question 71

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

Answer 71

hydrogen and helium.

Question 72

Neutron stars do NOT have:

Answer 72

rotation periods comparable to the Sun's.

Question 73

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

Answer 73

its core collapsing

Question 74

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

Answer 74

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

Question 75

Supernova explosions are important because they seem to be

Answer 75

the main way of releasing heavy atoms into space