The
Sun
Chapter 28
Basic Properties
• Composition of sun
0.8%
28%
70%
H
He
O
C 0.3%
Fe 0.2%
Basic Properties
•
•
•
•
•
332,000x mass then earth
695,000 km at equator
6,000°C average temp.
Rotates 1 about every 30 days
Age= ~5.0 billion years old
Structure of the Sun
• 3 Regions
– Core
– Inner Zone
– Atmosphere
The Core
•
•
•
•
~10% of the sun
15,000,000° C
Made up of gas
Because of gravity
the core is 10x denser
than iron
The Core
• Heat in the core causes electrons of the atoms
to roam free
• Exposed nuclei is then changed by nuclear
reactions
• Give a hydrogen fusion reaction
Hydrogen Fusion
• Step 1
– 2 hydrogen nuclei collide and fuse
• Step 2
– One of these protons changes into a neutron
• Step 3
– Another proton combines with the proton-neutron pair, producing
a nucleus of 2 protons and 1 neutron
• Step 4
– 2 of these nuclei collide and fuse
• Step 5
– Resulting cluster throws off 2 protons, leaving behind a nuclei of
2 protons and 2 neutrons
Hydrogen Fusion
• Energy is given off in every step
• Changes more then 600,000,000 of H into He
every sec.
Mass into Energy
• 1905-Albert Einstein
proposes the Theory of
Relativity
• Proposed this before
nuclear physics
• E=mc²
• E represents energy
produced, m represents
mass, and c represents
the speed of light
The Inner Zones
• 2 regions within this zone
– Radiative Zone
– Convective Zone
Radiative Zone
• Zone that surrounds
core
• 2,500,000°C
• Energy moves from
atom to atom in the
form of
electromagnetic
waves, or radiation
Convective Zone
• Zone around radiative
zone
• About 1,000,000°C
• Energy moves by
convection
• Hot gases rise, and
cool gases sink
Sun’s Atmosphere
•
•
•
•
Uppermost region of solar gases
Photosphere
Chromosphere
Corona
Photosphere
• Innermost layer of atmosphere
• Surface of the sun-what we see ~6,000°C
• Grainy appearance-Granulation
– Caused by the rising and sinking of gases from the Convective zone
Chromosphere
• Chromosphere =
Color sphere
• Thin layer of
gases that glows
reddish light
• Temp. ranges
from 4,00050,000°C
• Gases move away
and towards the
photosphere
• May form narrow
jets of gas that
shoot outward
Corona
• Crown of the sun-Outermost layer
• Huge cloud of gas heated by sun’s magnetic field ~2,000,000°C
• Prevents most of the atomic particles from sun escaping into
space
• Atomic particles that escape cause solar wind
Solar Activity
• Gases in sun are in
constant motion
• Energy and gravity
are main reason
• Sun also rotates on
its axis
• Parts of the sun rotate at different speeds
• Equator rotates faster than the poles
– Equator ~25 days
– Poles ~33 days
• Average rotation is 27 days
Sunspots
• Magnetic fields slow
down activity in
convective zone
• Slower convection
means less gas
transfers heat
• This causes cooler
areas on the surface
called sunspots
• Sunspots run in a 11
year cycle
Prominences
• As a result of sunspots, prominences may form
• Huge arches that reach above the surface
• Each one follows a magnetic field path
Solar Flares
• One of the most violent solar disturbances
• Sudden outward eruption of electrically charged atomic
particles
• Cause magnetic storms on earth
• Solar Flare Movie
Auroras
• As a result of these
magnetic storms, the
Aurora Borealis occurs
• Solar particles are
attracted to the poles
by the magnetosphere
• These particles come
in contact with gas
molecules in the upper
atmosphere and
produce the northern
lights
Formation of the Solar System
• Each solar system that forms has four
basic properties
– Patterns of motion among large bodies
– Two major types of planets
– Asteroids and Comets
– Exceptions to the Rules
Formation of the
Solar System
• Solar Nebular Theory
– Theory that describes
the formation of the
solar system
– Accretion of particles
began ≈5 bya
Formation of the Planets
• As the sun was
spinning, small bodies
of matter called
planetismals began
clumping together
• Planetsimals smash
together and form
protoplanets
Formation of the Planets
• These protoplanets gain mass
through accretion
• Different materials in the gas cloud
will condense at different
temperatures
• Rock planets versus gas planets
Formation of the Planets
• Frost Line
– Determines what type of planets will form
– Planets beyond frost line will be gas planets
– Inside of frost
line will be rock
planets
Formation of the Earth
• 3 sources of heat
– Collision of planetismals
– Increasing weight of the outer layers
– Radioactive materials within the earth
The Solid Earth
• Density Stratification
– The young earth was a
giant ball of molten lava
– Heavier elements sink to
the middle of planet
• Caused the earth to
separate into about 3
layers
– Core
– Mantle
– Crust
The Atmosphere
• Earth managed to
capture some H and
He that was in the
solar nebula
• This first atmosphere
was lost to space as a
result of some cosmic
force
Formation of the Atmosphere
• Our present day atmosphere came mostly from
outgassing of materials
• Outgassing is when gas escapes to the surface
from inside
– Volcanoes
Formation of the Oceans
Eventually, enough gases escaped and started to
condense
Some paleoclimatologists have speculated that the
earth rained for ≈25 my
Water would evaporate instantly back into the
atmosphere
Eventually the earth cooled and oceans began to
form