Chapter 28.2 Stars and Their Characteristics

1
Chapter 28.2 Stars and Their Characteristics
2
If we imagined that the distance from the Earth
to the Sun was 1 Centimeter..
Sun
Earth
1 Centimeter
3
How far away do you think the next nearest star
would be???
?
4
How far away do you think the next nearest star
would be???
2.5 Kilometers
1.5 miles
5
In real distance, the next closest star would be
300,000 times the distance form the Earth to the
Sun, or
Earth
Proxima Centauri
Sun
39 Trillion miles (thats 4.24 Light Years!)
6
What does 39 trillion miles look like????
Objects in Space are so far apart that units of
measurement used on Earth are not useful.
7
Would you use inches to tell someone how far it
is between Los Angeles and New York City? Why not?
8
On Earth units of measurement such as kms. or
miles work well.
California, for example, is only a few thousand
kms. From Maine.
Approx. 4,000 kms.
9
In the Universe, however, the kilometer is just
too small to be useful. For example, the distance
to the next nearest big galaxy, the Andromeda
Galaxy, is 21,000,000,000,000,000,000 km. This is
a number so large that it becomes hard to write
and hard to interpret. So astronomers use other
units of distance.
Andromeda Spiral Galaxy
Earth
21,000,000,000, 000,000,000 kms
10
The basic unit of measurement of distance inside
of our solar system is the
Astronomic Unit
11
An Astronomic Unit is equal to the distance from
the Sun to the Earth, which is about 93 million
miles.
Earth
93 million miles
Sun
12
Planets inside Earths orbit have distances from
the Sun of less than 1 AU.
(Mercury is .4 AUs from the Sun.)
.4 AUs
Sun
Mercury
13
Planets outside the orbit of the Earth have
distances from the Sun of greater than 1 AU.
(Mars is 1.5 AUs and Pluto is 39 AUs from the
Sun.)
14
But, Astronomic Units are too small for measuring
distances outside of our own Solar System.
15
The closest star to the Sun, Proxima Centauri,
would be more than 300,000 AUs from our star,
and thats the closest!
16
Astronomers use
Light Years
to measure distances outside our Solar System.
17
A Light-Year is a unit of Distance.
A Light Year is equal to the distance that light
can travel in one Earth year. A Light Year is
equal to 5.3 trillion miles. Use of Light Years
makes the units used in measuring distances in
Space smaller, but small is pushing it!
18
The Speed of Light is 186,000 miles per second.
Peeoooummmmmmm!!!
That is almost 8 times around the Earth in 1
second!
19
The Crab supernova remnant is about 4,000
light-years away.


20
The Milky Way Galaxy is about 150,000
light-years across.
21
The Andromeda Galaxy is 2.3 million light-years
away.
22
The Virgo Galaxy Cluster is 45 million light-
years away.
23
The most distant Supernova is 10 billion
light-years away.
24
The most distant Galaxy Cluster is 12 billion
Light-years away.
25
The most distant Galaxy is 13 billion light-
years away.
26
The background radiation from the big-bang is 14
billion light-years away.
27
(No Transcript)
28
Types of Stars and Their Organization in Space
29
How are Stars and Planets different?

• They differ in a lot of ways, but for the moment,
  we will focus on the fact that
• Stars emit light, due to nuclear fusion in their
  center, while planets only reflect light.

30
Binary Systems

• Solar systems contain at least one star, and can
  contain three or more

2
3
1
31
Six Star Binary System
32
Star Cluster contain from tens and hundreds to
millions of stars.
Pleiades Seven- Sisters
33
Open Cluster-Galactic center behind
34
Open Cluster-150 stars
35
Large Globular cluster-millions of stars
36
Center of Globular cluster-Note star density
37
Spiral Galaxies contain billions of stars.
Globular Clusters of old Stars
Open Clusters of new Stars
38
Elliptical Galaxy- Many billions
All old Globular Clusters
39
What is a Star???
40
A Star is a self-luminous (it is giving off
light as opposed to reflecting it) sphere of gas
that is undergoing Nuclear Fusion in its center.
41
Not all stars are the same. In fact, they vary in
many ways.
42
Stars Vary in Brightness.
Magnitude-How bright an object in Space is, or
appears to be. Luminosity- Luminosity is the
true brightness of an Individual unit of a star.
The Luminosity of a Star depends on a stars
temperature.
3
5
5
3
3
A.
B.
5
5
3
3
3
3
3
Which star is hotter? Which is brighter?
43
Absolute Magnitude- Absolute Magnitude is a
measurement of the true brightnessof stars as
if all stars were viewed from the same distance.
The Absolute Magnitude of a star depends on its
Volume and Luminosity.
1
1
A.
B.
3
3
1
3
1
1
1
3
3
3
1
1
1
1
3
3
1
1
1
Which star is larger? Which is brighter?
44
Apparent Magnitude- Apparent Magnitude is a how
bright a star appears to be from Earth. The
Apparent Magnitude of a star is affected by
Absolute- Magnitude (Volume x Luminosity) and
Distance from Observer.
Betelgeuse, one of the brightest stars in the
Universe, does not appear to be as bright as our
Sun, because of its distance from us compared to
the Suns distance.
45
Stars also vary in their mass, density and
volume, interior and surface temperature, rate of
fuel-consumption, color, Main Sequence life-span,
what they do when they die and what they become
after they die.
46
Stellar Mass
When comparing the masses of different stars, we
will use the mass of our star, the Sun, as the
standard. A star that is identical to ours would
be a star of 1 Solar Mass.
47
Stars vary in mass from a fraction of 1 solar
mass, up to 50 times the mass of our Sun, or 50
Solar Masses.
Red Dwarf star
50 solar mass star
The Sun
48
Stars vary even more in their volume/density
49
Sun
50
Number represents xSun volume
51
(No Transcript)
52
(No Transcript)
53
(No Transcript)
54
(No Transcript)
55
(No Transcript)
56
White Dwarf
Earth
57
(No Transcript)
58
(No Transcript)
59
(No Transcript)
60
Variation in Black Hole Sizes
61
Star Density
62
Stars vary in their Main Sequence and Giant
life-span
63
Surface Temperature (K)
Luminosity (Solar Units)
Time on Main Sequence Line (Million Years)
5 10 15 20
25 Solar Mass
Some Properties of Main Sequence Stars
64
Stars vary in what they become when they are no
longer fusing Hydrogen.
Blue Supergiant
65
Red Supergiant
Betelgeuse
Orions Belt
Orion Nebula
Rigel
66
Stars vary in how they die
Supernova explosion
67
Supernova
68
Supernova
69
(No Transcript)
70
(No Transcript)
71
(No Transcript)
72
(No Transcript)
73
(No Transcript)
74
Native American Petroglyph recording Supernova
explosion
75
Planetary Nebula
76
(No Transcript)
77
(No Transcript)
78
(No Transcript)
79
(No Transcript)
80
(No Transcript)
81
(No Transcript)
82
(No Transcript)
83
(No Transcript)
84
(No Transcript)
85
Stars vary in what they become when they die
(Run out of material that can be fused to create
outward pressure).
White Dwarf in Binary System
86
White Dwarfs
87
(No Transcript)
88
(No Transcript)
89
(No Transcript)
90
White Dwarf in Binary System
91
(No Transcript)
92
White Dwarfs in Globular Cluster
93
(No Transcript)
94
Neutron Stars
95
(No Transcript)
96
(No Transcript)
97
Neutron Star
98
Pulsars
99
Binary Pulsar
100
(No Transcript)
101
(No Transcript)
102
(No Transcript)
103
(No Transcript)
104
(No Transcript)
105
(No Transcript)
106
(No Transcript)
107
(No Transcript)
108
(No Transcript)
109
Pulsar Cone
110
(No Transcript)
111
Black Holes
112
(No Transcript)
113
(No Transcript)
114
(No Transcript)
115
(No Transcript)
116
(No Transcript)
117
(No Transcript)
118
(No Transcript)
119
(No Transcript)
120
(No Transcript)
121
(No Transcript)
122
Volume
Life-Span
Density
Temperature
A stars mass determines every other
characteristic of the star that we mentioned
earlier.
Rate of Fuel consumption
How it dies
123
HR Diagram
124
(No Transcript)
125
Luminosity
Surface Temperature
126
(No Transcript)
127
(No Transcript)
128
(No Transcript)
129
(No Transcript)
130
Main Sequence
Main Sequence Line Core Fusion of H at constant
rate Volume directly related to mass
131
(No Transcript)
132
(No Transcript)
133
(No Transcript)
134
.
.
25-50 M
sun
Masses/Luminosity of Main Sequence Stars
135
(No Transcript)
136
(No Transcript)
137
Giants
Core fusion of He
138
(No Transcript)
139
(No Transcript)
140
(No Transcript)
141
Supergiants
.
.
.
Supergiants
142
(No Transcript)
143
(No Transcript)
144
(No Transcript)
145
White Dwarfs
White Dwarfs
Dead Star High temps. Due to compression
146
(No Transcript)
147
(No Transcript)
148
(No Transcript)
149
Black Holes, Pulsars and Neutron- Stars are not
identified on the HR Diagram because they are
either very dim or do not give off energy in the
visible wavelengths.
150
Star Life Cycles
151
As we have discussed, stars are not all the
same. All of the characteristics of a star are
determined by their mass. Stars with different
masses have different life cycles.
152
Based upon their masses, stars can follow three
main pathways and fit into three candidate
groups during the course of their lives.
153
These groups include

• White Dwarf Candidates (less than one solar
  mass to 15 solar masses)
• Neutron Star and Pulsar Candidates (16 to 30
  solar masses)
• Black Hole Candidates (Greater than 30 Solar
  Masses)

154
(No Transcript)
155
(No Transcript)
156
White Dwarf Candidates
157
Pulsar and Neutron Star Candidates
Supergiant
158
(No Transcript)
159
Pulsar
160
Black Hole Candidates
Supergiant
161
Black Holes
162
(No Transcript)
163
(No Transcript)
164
(No Transcript)