Astro Sfa 105 Ch 11 Stars

Front 1

What do all stars have in common with each other?

Back 1

1. all form in great clouds of gas and dust
2. each one begins its life with roughly the same composition

Front 2

At the beginning of a star's life, what is roughly its composition?

Back 2

1. 3/4 = hydrogen
2. 1/4 = helium
3. >2% elements heavier than helium

Front 3

What does the brightness of a star depend on?

Back 3

1. distance
2. amount of light the star emits

Front 4

Name the 3 stars that make up the 3 corners of the winter triangle we can observe with our eyes?

Back 4

1. Procyon
2. Sirius
3. Betelgeuse

Front 5

To the naked eye, the stars Procyon and Betelgeuse appear equally bright in our sky. Which star, Procyon and Betelgeuse, actually emits more light and why?

Back 5

Betelgeuse, it actually emits @ 5,000 times as much light as Procyon

Front 6

What is the term for how bright stars look in our sky?

Back 6

Apparent brightness

Front 7

But what is actually meant by "apparent brightness"?

Back 7

The amount of power reaching us per unit area.

Front 8

What is the total amount of power that a star emits into space?

Back 8

Luminosity

Front 9

T or F
Luminosity varies. Apparent brightness remains the same.

Back 9

False,
Luminosity does not vary.
Apparent brightness can vary based on distance.

Front 10

In mathematical terms, what is the inverse square law of light?

Back 10

apparent luminosity/(div)
= 2
brightness 4pi X (radius)

Front 11

In general terms, what is the inverse square law of light?

Back 11

Amount of light received per unit area decreases with increasing distance by the square of the distance.

Front 12

What are the standard units of luminosity?

Back 12

Watts

Front 13

What are the units of apparent brightness?

Back 13

Watts per square meter

Front 14

What is the most direct way to measure a star's distance?

Back 14

Stellar parallax

Front 15

What is the term for the small annual shifts in a star's apparent position caused by Earth motion around the Sun?

Back 15

Stellar parallax

Front 16

How do astronomers measure stellar parallax?

Back 16

Comparing the observation of a nearby star made 6 months apart.

Front 17

What is the term for the angle formed by drawing the difference in a star's shift?

Back 17

Parallax angle

Front 18

T or F
More distant stars have smaller parallax angles.

Back 18

True

Front 19

How far away can we accurately measure parallax?

Back 19

Not much further than what we call our local solar neighborhood in the Milky Way

Front 20

What is the term for the parallax angle of 1 arcsecond?

Back 20

1 parsec

Front 21

What is the abbrev. for parsec?

Back 21

pc

Front 22

What is the distance of 1 parsec in terms of light years?

Back 22

1 parsec = 3.26 light years

Front 23

T or F
All stars have parallax angels of less than 1 arcsecond.

Back 23

True

Front 24

What was the first reliable way to measure the distances to the stars?

Back 24

Parallax

Front 25

How is the luminiosity of the Sun expressed?

Back 25

L
sun

Front 26

What is the nearest star

Back 26

Proxima centauri

Front 27

T or F
Stars come in a wide range of luminosities

Back 27

True

Front 28

T or F
Our Sun is one of the dimmest stars.

Back 28

False,
Our Sun is somewhere in the middle of the range of luminosities.

Front 29

How is the dimmest stars'approximate luminosities expressed

Back 29

@ 1/10,000 times the Sun or

-4
10 L
Sun

Front 30

How is the brightest stars' approximate luminosities expressed?

Back 30

1 million times the Sun or

6
10
Sun

Front 31

What is another way to refer to a star's apparent brightness?

Back 31

Apparent magnitude

Front 32

What is another way to refer to a star's luminosity?

Back 32

Absolute magnitude

Front 33

Who originated the magnitude system for barightness and luminiosity of stars?

Back 33

Ancient Greek,
Hipparchus

Front 34

What is the apparent magnitude of the brightest stars?

Back 34

Lower numbers for the apparent magnitude,
For ex., the brightest star's
apparent magnitude is the first magnitude or magnitude 1

Front 35

What is the apparent magitude of the dimmest stars?

Back 35

Higher numbers for the apparent magnitude,
For ex., the faintest visible stars are the sixth magnitude or magnitude 6

Front 36

Which way does the magnitude scale run?

Back 36

Backwards

Front 37

What is the precise definition of magnitude differences?

Back 37

Each difference of five magnitudes represents a factor of 100 in brightness,

Front 38

How many times brighter is a magnitude 1 star than a magnitude 6 star?

Back 38

100 times

Front 39

How many times brighter is a magnitude 3 star than magnitude 8 star?

Back 39

100 times.

Front 40

What is the brightest star in the night sky?

Back 40

Sirius

Front 41

What is the precise definition of absolute magnitudes?

Back 41

It is the apparent magnitude it would have if it were at a distance of 10 parsecs or 32.6 light years from Earth

Front 42

What is the distance of 1 parsec?

Back 42

3.26 light years

Front 43

What is the distance of 10 parsecs?

Back 43

32.6 light years

Front 44

Which temperature of a star is directly measurable, interior or surface?

Back 44

surface temperature is directly measurable

Front 45

Name the 2 ways surface temperature is measured?

Back 45

1. star's color
2. star's spectrum

Front 46

T or F
Stars come in almost every color of the rainbow.

Back 46

True

Front 47

Is a red star cooler than a yellow star?

Back 47

Yes

Front 48

Is a blue star cooler than a yellow star?

Back 48

No,
A yellow star is cooler than a blue star

Front 49

What causes stars to come in different colors?

Back 49

Stars emit thermal radiation and thermal radiation spectrum depends only on the temperature of the object that emits it.

Front 50

Which way is more accurate to determine the surface temperature of a star, spectral lines or colors?

Back 50

Spectral lines

Front 51

The hottest stars with the bluest colors are called what spectral?

Back 51

Type O

Front 52

What are the spectral types for stars in descending surface temperature?

Back 52

1. O Oh
2. B Be
3. A A
4. F Fine
5. G Girl/Guy
6. K Kiss
7. M Me
8. L
9. T

Front 53

What is the mneumonic (memory) device that is commonly used to remember the spectral types of stars

Back 53

Oh Be A Fine Girl/Guy Kiss Me

Front 54

How many subcategories is each spectral type subdivided into?

Back 54

10
For ex.,
B0, B1, B2. B9

Front 55

The larger the number in the subcategory, the ________ the star.

Back 55

The larger the number in the subcategory, the cooler the star

Front 56

What spectral type is our Sun?

Back 56

G2 which means it is slightly hotter than a G3 but cooler than a G1.

Front 57

The range of surface temperatures for stars is much _______ than the range of luminosities.

Back 57

The range of surface temperatures for stars is much NARROWER than the range of luminosities.

Front 58

What spectral type are the coolest stars?

Back 58

Spectral type M

Front 59

T or F
Cool red stars are much more common than hot, blue stars.

Back 59

True

Front 60

Where and when did the current system of stellar classification begin?

Back 60

At Harvard College

Front 61

What did Pickering use as computers as he studied and classified stellar spectra?

Back 61

Women students from Wellesley and Radcliffe

Front 62

What did Williamina Fleming do?

Back 62

She classified over 10,000 stars

Front 63

How did Williamina Fleming classify stars according to stellar spectra?

Back 63

According to the strength of their hydrogen lines,
Type A was assigned to the strongest hydrogen lines
Type O was was assigned to the weakest hydrogen lines.

Front 64

T or F
Classification of stellar lines according to hydrogen proved to be accurate.

Back 64

False,
Classification based solely on hydrogen line was inadequate.

Front 65

Who was the person whose stellar spectral classification was finally adapted?

Back 65

Annie Jump Cannon

Front 66

What causes the differences in spectral line from star to star?

Back 66

Changes in the ionization level of the emitting atoms

Front 67

Why do O stars have weak hydrogen lines?

Back 67

At their surface temperatures, nearly all their hydrogen is ionized. Without an electron to "jump" between energy levels, ionized hydrogen can neither emit nor absorb its usual specific wavelengths of light.

Front 68

Who wrote "the most brilliant Ph.D. thesis ever written in astronomy"?

Back 68

Cecilia Payne-Gaposchkin

Front 69

Of the 3, mass, surface temperature, and luminosity, which is the most difficult to measure?

Back 69

Mass

Front 70

What is the most dependable method for "weighing" a star?

Back 70

Newton's version of Kepler's 3rd law.

Front 71

What is the criteria for using Kepler's 3rd law to measure the mass of a star?

Back 71

It must be a binary star system where 2 stars continually orbit one another.

Front 72

How many stars orbit a companion star?

Back 72

@ one half or 1/2.

Front 73

List the 3 classes of binary star systems:

Back 73

1. visual binary
2. eclipsing binary
3. spectroscopic binary system

Front 74

What is the term given to a pair of star that we can see distinctly as the stars orbit each other?

Back 74

Visual binary

Front 75

What is the term for a pair of stars that orbit in the plane of our line of sight?

Back 75

Eclipsing binary because when neither star is eclipsed, we the combined light of both stars, and
when one star eclipses the other, the apparent brightness of the system drops because some of the light is blocked from our view.

Front 76

What is the term for a graph of apparent brightness against time?

Back 76

light curve

Front 77

What is the most famous example of an eclipsing binary system?

Back 77

Algol

Front 78

What is the name for the diagrams that continue to be central to the study of stars?

Back 78

Hertzsprung-Russell diagrams
(H-R) diagrams

Front 79

In an H-R diagram, what is represented in the horizontal axis?

Back 79

stellar surface temperature

Front 80

What did Hertzsprung and Russell base their stellar surface temperatures on?

Back 80

spectral sequence OBAFGKM

Front 81

In an H-R diagram, what is represented in the vertical axis?

Back 81

a star's luminosity

Front 82

On an H-R diagram, which direction do temperatures decrease?

Back 82

Towards the right

Front 83

On an H-R diagram, which direction do temperatures increase?

Back 83

Towards the left

Front 84

On an H-R diagram, which direction does luminosity increase?

Back 84

upward

Front 85

On an H-R diagram, where is the location of stars that are hot and luminous?

Back 85

Upper left

Front 86

On an H-R diagram, where is the location of stars that are cool and luminous?

Back 86

Upper right

Front 87

On an H-R diagram, where is the location of stars that are cool and dim?

Back 87

Lower right

Front 88

On an H-R diagram, where is the location of stars that are hot and dim?

Back 88

Lower left

Front 89

Name the 2 characteristics that luminosity is based on?

Back 89

1. surface temperature
2. surface radii

Front 90

If 2 stars have the same surface temperature, how can one be more luminous?

Back 90

Only if it is larger in size.

Front 91

List the 4 major groups of stars based on the H-R diagram:

Back 91

1. main sequence stars
2. supergiants
3. giants
4. white drawfs

Front 92

What type of stars fall somewhere along the main sequence of the H-R diagram, the prominent streak running from the upper left to the lower right?

Back 92

Main sequence stars

Front 93

What are the stare in the upper right of the H-R diagram because they are very large in addition to being very bright?

Back 93

Supergiants

Front 94

What are the stars that are somewhat smaller in radius and lower in luminosity, but still much larger and brighter than main-sequence stars of the same spectral type?

Back 94

Giants

Front 95

What are the stars near the lower left that are small in radius and appear white in color because of their high temperatures

Back 95

white drawfs

Front 96

What is the symbol used to assign each star to a luminosity class?

Back 96

roman numerals I - V

Front 97

What is the term used to describe the region of the H-R diagram in which the star falls?

Back 97

Luminosity class

Front 98

What is the luminosity class for supergiants?

Back 98

I

Front 99

What is the luminosity class for giants?

Back 99

III

Front 100

What is the luminosity class for main sequence stars?

Back 100

V

Front 101

What are the luminosity classes for intermediate to the other stars?

Back 101

II and IV

Front 102

T or F
White drawfs fall outside the luminosity classification system and are often assigned the luminosity class "wd".

Back 102

True

Front 103

What is the complete classification of our Sun?

Back 103

G2 V.

Front 104

What does G2 mean for our Sun's complete classification?

Back 104

It is yellow-white in color

Front 105

What does V mean for our Sun's complete classification

Back 105

V means it is a hydrogen-burning, main-sequence star.

Front 106

Where do most of the stars we observe fall in the classification of the H-R diagram?

Back 106

Main sequence

Front 107

T or F
On the H-R diagram, stellar masses decrease downward along the main sequence.

Back 107

True

Front 108

T or F
Many more stars fall on the lower end of the main sequence than on the upper end, therefore low mass stars are more common that high mass stars.

Back 108

True

Front 109

What is the most important attribute of a hydrogen burning star?

Back 109

Mass

Front 110

What is the stellar luminosity class of bright giants?

Back 110

II

Front 111

What is the stellar luminosity class of subgiants?

Back 111

IV

Front 112

What type of stars follow a simple relationship between mass, temperature, and luminosity?

Back 112

Main Sequence stars

Front 113

T or F
A star is born with a limited suppl of core hydrogen and therefore can remain as a hydrogen-fusing main-sequence star for only a limted time.

Back 113

True

Front 114

Name the 2 reasons the study of star clusters is important:

Back 114

1. All the stars in a cluster at about the same distance from the EArth
2. All the stars in a cluster formed at @ the same time (within a few million years of one another

Front 115

T or F
Stars usually form in groups

Back 115

True

Front 116

What is the term for a congregation of stars?

Back 116

Star clusters

Front 117

List the 2 basic types of star clusters:

Back 117

1. open clusters
2. globular clusters

Front 118

Where doe most of the stars, gas, and dust in the Milky Way lie?

Back 118

In the relatively flat galactic disk

Front 119

What is the term for the region above and below the galactic disk of the Milky Way?

Back 119

The Halo

Front 120

Where are open cluster star clusters always located?

Back 120

in the disk of the galaxy

Front 121

Are stars in open cluster star clusters old or young?

Back 121

open cluster stars are young

Front 122

Name the most famous open cluster?

Back 122

Pleiades also known as
The Seven Sisters also known as
Subaru in japanese

Front 123

T or F
Only 6 of the Seven Sisters is visible to the naked eye.

Back 123

True

Front 124

Where are most globular clusters located?

Back 124

In the halo of the galaxy

Front 125

Approximately how many stars are in open clusters?

Back 125

several thousand stars.

Front 126

How many stars are in globular clusters?

Back 126

can contain more than a million

Front 127

Which star clusters are typically concentrated in a tight ball 60 -150 light years across?

Back 127

Globular clusters

(globular-ball like)

Front 128

How is the Pleiades star cluster different from the typical main sequence?

Back 128

The Pleiades' stars on the diagram trail to the right of the main sequence at the upper end, instead of to the left

Front 129

What do we learn about the Pleiades star cluster from its H-R diagram trailing to the right?

Back 129

The hot, short-lived stars of spectral type O are missing from the main sequence indicating that the Pleiades is old enough for its main-sequence O stars to have already ended their hydrogen-burning lives.

Front 130

What is the term for the precise point on the H-R diagram at which the Pleiades' main sequence diverges from the standard main sequence is?

Back 130

Main-sequence turnoff point.

Front 131

When comparing star clusters on H-R diagrams, we learn that the age of the cluster is equal to__________

Back 131

The age of the cluster = the lifetime of stars at its main sequence turnoff point

Front 132

What is the most powerful tool for evaluating the ages of star clusters?

Back 132

identifying the main-sequence turnoff point

Front 133

T or F
The stars at the main-sequence turnoff points in globular clusters are usually more massive than our Sun.

Back 133

FALSE
The stars at the main-sequence turnoff points in globular clusters are usually less massive than our Sun.

Front 134

What is the approximate age of globular star clusters?

Back 134

13 billion year old

Front 135

What are the oldest known object in Milky Way galaxy?

Back 135

Globular star clusters

Front 136

When did the first stars begin to form?

Back 136

When the Universe was @ 1 billion years old

Front 137

What is the cluster's age = to?

Back 137

The hydrogen-burning lifetime of the hottest, most luminous stars that remain on the main sequence.