Download presentation
Presentation is loading. Please wait.
1
Stars Chap. 30 The Sun 30.1 Measuring Stars 30.2
Stellar Evolution 30.3
2
The Sun 30.1 Objectives explore the structure of the Sun
describe the solar activity cycle and how the Sun affects the Earth compare the different types of spectra
3
How do we learn about it?
4
How do we learn about it? Using solar observatories
Dunn Solar Telescope Sacramento Peak, NM
5
How do we learn about it? Using solar observatories Using satellites
Solar Heliospheric Observatory (SOHO)
6
Properties
7
Properties Radius The Sun has a very large radius Sun: 695,000 km
Earth: 6,400 km
8
Properties Mass The Sun has a very large radius
The Sun is very massive Mass Sun: 2.0 x 1030 kg Earth: 6.0 x 1024 kg
9
Properties The Sun has a very large radius The Sun is very massive
The density is similar to that of the gas giant planets.
10
Properties The Sun has a very large radius The Sun is very massive
The density is similar to that of the gas giant planets. Outer portion is not very dense
11
Properties The Sun has a very large radius The Sun is very massive
The density is similar to that of the gas giant planets. Outer portion is not very dense Inner portion is much denser
12
Properties The Sun has a very large radius The Sun is very massive
The density is similar to that of the gas giant planets. Physical state of matter:
13
Properties The Sun has a very large radius The Sun is very massive
The density is similar to that of the gas giant planets. Physical state of matter: plasma.
14
Layers of Atmosphere
15
Layers of Atmosphere Photosphere
16
Layers of Atmosphere Photosphere Lowest layer Only about 400 km thick
Average temp: 5800 K Emits light we can see
17
Layers of Atmosphere Photosphere Chromosphere
18
Layers of Atmosphere Photosphere Chromosphere
Thicker layer (about 2500 km) Hotter (average temp: 30,000 K) Difficult to see, except during eclipse
19
Layers of Atmosphere Photosphere Chromosphere Corona
20
Layers of Atmosphere Photosphere Chromosphere Corona Outermost layer
Extends several million km Very hot (1 to 2 million K)
21
Solar Activity Caused when sun’s magnetic field interrupts its atmosphere
22
Solar Activity Solar Wind
23
Solar Activity Solar Wind
Charged particles from sun traveling at high speeds (400 km/s)
24
Solar Activity Solar Wind
Charged particles from sun traveling at high speeds (400 km/s) Deflected by our magnetic field
25
Solar Activity Solar Wind
Charged particles from sun traveling at high speeds (400 km/s) Deflected by our magnetic field Causes auroras
26
Solar Activity Solar Wind Sun Spots
27
Solar Activity Solar Wind Sun Spots Appear on photosphere
28
Solar Activity Solar Wind Sun Spots Appear on photosphere
Look dark because they are cooler
29
Solar Activity Solar Wind Sun Spots Appear on photosphere
Look dark because they are cooler Associated with solar wind
30
Solar Activity Solar Wind Sun Spots Solar Flares
31
Solar Activity Solar Wind Sun Spots Solar Flares
Violent eruptions from surface
32
Solar Activity Solar Wind Sun Spots Solar Flares
Violent eruptions from surface Occur in corona
33
Solar Activity Solar Wind Sun Spots Solar Flares
Violent eruptions from surface Occur in corona Some the size of Earth
34
Solar Activity Solar Prominence
35
Solar Activity Solar Prominence Less violent than flares
36
Solar Activity Solar Prominence Less violent than flares
Cool sheets of gas that condense from corona
37
Solar Activity Solar Prominence Less violent than flares
Cool sheets of gas that condense from corona Some rain back material on surface
38
Interior of Sun
39
Interior of Sun Core
40
Interior of Sun Core Site of fusion (energy production)
Density of 160 g/cm3 (15 x denser than lead) Temperature of about 15 million K Extends 25% to outside
41
Interior of Sun Core Radiative Zone
42
Interior of Sun Core Radiative Zone Extends another 60% to outside
Temp. is about 2 million K Passes energy (photons) from atom to atom
43
Interior of Sun Core Radiative Zone Convective Zone
44
Interior of Sun Core Radiative Zone Convective Zone Final 15%
Energy is carried via moving gas volumes Temp. is about 5700 K
45
Fusion
46
Fusion Joining of nuclei
47
Fusion Joining of nuclei Occurs at very high temp./pressure
48
Fusion Joining of nuclei Occurs at very high temp./pressure
Opposite of fission
49
Fusion E = mc2 Joining of nuclei Occurs at very high temp./pressure
Opposite of fission Mass is lost during process E = mc2
50
Fusion 1354 J/m2 Joining of nuclei Occurs at very high temp./pressure
Opposite of fission Mass is lost during process Tremendous amount of energy produced 1354 J/m2
51
Three types of Spectra
52
Three types of Spectra Continuous spectra
Shows all the colors with no breaks
53
Three types of Spectra Continuous spectra Emission spectra
Only certain lines produced (depending on elements present
54
Three types of Spectra Continuous spectra Emission spectra
Absorption spectra Light passes through a gas and some of it is absorbed (leaving dark, ‘missing’ sections)
55
Composition of Sun
56
Composition of Sun Hydrogen (70%)
57
Composition of Sun Hydrogen (70%) Helium (28%)
58
Composition of Sun Hydrogen (70%) Helium (28%) Trace elements
(O, C, Ne, Fe, N, Si, Mg, S)
59
The End
60
Measuring the Stars – 30.2 Objectives
describe star distribution and distance classify the types of stars summarize the interrelated properties of stars
61
Groups of stars Pleiades
62
Groups of stars Constellations
Groups of stars named after animals/mythological creatures
63
Groups of stars Constellations Orion
64
Groups of stars Constellations Betelgeuse Rigel Orion
65
Groups of stars Constellations Star Clusters
A group of stars that are bound by gravity
66
Groups of stars Constellations Star Clusters Open cluster Pleiades
Stars are loosely bound by gravity
67
Groups of stars Constellations Star Clusters Open cluster
Globular cluster M13, in Hercules Tightly bound stars, relatively close together
69
Groups of stars Constellations Star Clusters Binaries
Algol – a blue dwarf Two stars that are gravitationally bound.
70
Stellar Positions and Distances
71
Stellar Positions and Distances
Stellar distance
72
Stellar Positions and Distances
Stellar distance Light year (ly) The distance traveled by light in one year.
73
Calculate this! Light travels at a speed of 300,000 km/s. How many miles is a light year?
74
Calculate this! Proxima Centauri is 4.24 light years. How many kilometers is this star?
75
Stellar Positions and Distances
Stellar distance Light year (ly) Parsec (pc) The distance of a star when it appears to shift one second of a degree due to parallax. 1 pc = 3.26 ly.
76
Stellar Positions and Distances
Stellar distance Light year (ly) Parsec (pc) Parallax The apparent shift in position of an object as the observer’s location changes
77
Calculate this! The brightest star in the sky (besides the Sun) is Sirius. It is 2.6 pc from Earth. How long does it take light from Sirius to reach us?
78
Stellar Positions and Distances
Other Properties of Stars
79
Stellar Positions and Distances
Other Properties of Stars Apparent Magnitude How bright a star appears. (affected by luminosity and distance)
80
Magnitude The lower the number the brighter the object.
Each value increase equates to about decrease in brightness.
81
Magnitude of celestial objects
82
Stellar Positions and Distances
Other Properties of Stars Apparent Magnitude Absolute Magnitude How bright a star would appear at 10 pc. (This can be calculated if you know the actual distance.)
83
Stellar Positions and Distances
Other Properties of Stars Apparent Magnitude Absolute Magnitude Luminosity The energy output from the surface of a star. Can be measured in joules/second or watts.
84
Stellar Positions and Distances
Other Properties of Stars Apparent Magnitude Absolute Magnitude Luminosity Spectra of Stars The types (colors) of light given off
85
Stellar Positions and Distances
Other Properties of Stars Apparent Magnitude Absolute Magnitude Luminosity Spectra of Stars Determined by temperature Cooler stars have more lines in spectra
86
Stellar Positions and Distances
Other Properties of Stars Apparent Magnitude Absolute Magnitude Luminosity Spectra of Stars Determined by temperature Given a letter & number ranking O5, A4, A5, G2 (sun), etc.
88
Stellar Positions and Distances
Other Properties of Stars Apparent Magnitude Absolute Magnitude Luminosity Spectra of Stars Determined by temperature Given a letter & number ranking Light spectra can shift due to motion
89
Stellar Positions and Distances
Other Properties of Stars Apparent Magnitude Absolute Magnitude Luminosity Spectra of Stars H-R diagram (Hertzsprung-Russell) Used to classify stars based on spectra & magnitude
91
The End
92
Stellar Evolution – 30.3 Objectives
Explain how astronomers learn about the internal structure of stars Describe how the Sun will change during its lifetime and how it will end Compare the evolutions of stars of different masses
93
Introduction
94
Introduction A star is balances two forces
95
Introduction A star is balances two forces Inward force:
96
Introduction A star is balances two forces Inward force: gravity
Outward force: _________________
97
Introduction A star is balances two forces Inward force: gravity
Outward force: fusion and radiation
98
Introduction Structure of a star depends on:
99
Introduction Structure of a star depends on: Composition
Elements a star is made of
100
Introduction Structure of a star depends on: Composition Mass
The total amount of material in a star
101
Introduction Structure of a star depends on: Composition Mass
Gravity Pull inward which is balanced by force outward
102
Introduction Structure of a star depends on: Composition Mass
Gravity Temperature Higher temperature counter higher gravity.
103
Introduction Structure of a star depends on: Composition Mass
Gravity Temperature Rate of Fusion When temperatures increase so do reaction rates.
104
Introduction Structure of a star depends on: Composition Mass
Luminosity Gravity Temperature Rate of Fusion Star produces more energy, and is brighter.
105
Fusion Energy producing reaction in stars
106
Fusion Main sequence stars Most stars fall in this category
107
Fusion Main sequence stars Start by fusing H + H to He
108
Fusion Main sequence stars Start by fusing H + H to He
He + He + He to C
109
Fusion Main sequence stars Start by fusing H + H to He
He + He + He to C He + C to oxygen
110
Fusion Main sequence stars Start by fusing H + H to He
He + He + He to C He + C to oxygen He + O to neon
111
Fusion Main sequence stars Start by fusing H + H to He
He + He + He to C He + C to oxygen He + O to neon He + Ne to magnesium
112
Fusion Main sequence stars Start by fusing H + H to He
He + He + He to C He + C to oxygen He + O to neon He + Ne to magnesium This stops at iron because fusion of larger elements is no longer favorable.
113
Life cycle of Sun
114
Life cycle of Sun Star formation
115
Life cycle of Sun Star formation
Nebula collapses on itself from its own gravity Orion Nebula Nebula is an interstellar cloud of gas and dust
116
Life cycle of Sun Star formation
Nebula collapses on itself from its own gravity Protostar forms in center of disk shape, emitting lots of infrared light
117
Life cycle of Sun Fusion begins. . .
118
Life cycle of Sun Fusion begins. . .
when minimum temperature is reached
119
Life cycle of Sun Fusion begins. . .
when minimum temperature is reached this often illuminates surrounding gases Rosette Nebula
120
Life cycle of Sun Fusion begins. . .
when minimum temperature is reached this often illuminates surrounding gases star enters main-sequence phase – primarily converting H to He.
121
True or False? Large main-sequence stars last longer than smaller main-sequence stars.
122
True or False? Large main-sequence stars last longer than smaller main-sequence stars. False – larger stars get hotter, and use their fuel up faster.
123
Life cycle of Sun Becoming a Red Giant
Betelgeuse A larger, cooler star that is very luminous.
124
Life cycle of Sun Becoming a Red Giant
After about 10 billion years, hydrogen is used up
125
Life cycle of Sun Becoming a Red Giant
After about 10 billion years, hydrogen is used up Core of star is made of He
126
Life cycle of Sun Becoming a Red Giant
After about 10 billion years, hydrogen is used up Core of star is made of He Layer of gas surrounding core does fusion, causing gases to expand and cool
127
Life cycle of Sun Becoming a Red Giant
After about 10 billion years, hydrogen is used up Core of star is made of He Layer of gas surrounding core does fusion, causing gases to expand and cool Outer layers are driven away due to decrease in surface gravity
128
Life cycle of Sun Becoming a Red Giant
After about 10 billion years, hydrogen is used up Core of star is made of He Layer of gas surrounding core does fusion, causing gases to expand and cool Outer layers are driven away due to decrease in surface gravity He in core reacts to form C
129
Life cycle of Sun Becoming a White Dwarf
130
Life cycle of Sun Becoming a White Dwarf
Star is not big enough to further react carbon
131
Life cycle of Sun Becoming a White Dwarf
Star is not big enough to further react carbon Gases surrounding star expend and are driven off
132
Life cycle of Sun Becoming a White Dwarf
Star is not big enough to further react carbon Gases surrounding star expend and are driven off Core remains as small, hot, earth- sized object
133
Life cycle of Sun Becoming a White Dwarf
Star is not big enough to further react carbon Gases surrounding star expend and are driven off Core remains as small, hot, earth- sized object This star is made of carbon
134
Massive Stars Monocerotis
135
Massive Stars Same beginning – but hydrogen fusion happens quickly
136
Massive Stars Same beginning – but hydrogen fusion happens quickly
Star expands and contracts to repeatedly, forming variety of elements (not bigger than Fe)
137
Massive Stars Same beginning – but hydrogen fusion happens quickly
Star expands and contracts to repeatedly, forming variety of elements (not bigger than Fe) Mass if lost by stellar wind
138
Massive Stars Size determines fate
139
Massive Stars Size determines fate
If star’s mass is < 1.4 x Sun’s size it becomes a white dwarf.
140
Massive Stars Size determines fate
If star’s mass is < 1.4 x Sun’s size it becomes a white dwarf. If star’s mass is > 1.4 x Sun’s size it’s gravity pulls gases inward, merging protons and electrons in
141
Massive Stars Size determines fate
If star’s mass is < 1.4 x Sun’s size it becomes a white dwarf. If star’s mass is > 1.4 x Sun’s size it’s gravity pulls gases inward, merging protons and electrons in neutrons.
142
Massive Stars Size determines fate
If star’s mass is < 1.4 x Sun’s size it becomes a white dwarf. If star’s mass is > 1.4 x Sun’s size it’s gravity pulls gases inward, merging protons and electrons in neutrons. These are neutron stars
143
Massive Stars Size determines fate
If star’s mass is < 1.4 x Sun’s size it becomes a white dwarf. If star’s mass is > 1.4 x Sun’s size it’s gravity pulls gases inward, merging protons and electrons in neutrons. These are neutron stars They are very dense – 3x Sun’s mass squeezed into 10 km radius.
144
Massive Stars Size determines fate
If star’s mass is < 1.4 x Sun’s size it becomes a white dwarf. If star’s mass is > 1.4 x Sun’s size it’s gravity pulls gases inward, merging protons and electrons in neutrons. These are neutron stars They are very dense – 3x Sun’s mass squeezed into 10 km radius. Particles from outer layer bounce off neutron star creating supernova
145
Massive Stars Size determines fate
If star’s mass is < 1.4 x Sun’s size it becomes a white dwarf. If star’s mass is > 1.4 x Sun’s size it’s gravity pulls gases inward, merging protons and electrons in neutrons. If star’s mass is 3 x Sun’s size it becomes a black hole.
146
The End
Similar presentations
