The Sun 24.3
A typical star powered by nuclear reactions
Mostly the
(fusion of hydrogen to form helium)
Which releases energy
Structure of the sun
1. Solar
Atmosphere
2. Solar interior
(core)
Solar Interior
a) Core - Where
nuclear fusion of
hydrogen into
helium occurs
c) Convection Zone –
Area of convection
where energy is
being transferred
away from the
core
b) Radiation Zone – energy
moves outward as
electromagnetic radiation
The Sun’s interior
• The sun produces energy by
nuclear fusion
• During nuclear fusion
– 4 hydrogen (4.032 atomic
mass, 4 X 1.008) are changed
(converted) into 1 helium
(4.003 atomic mass)
– Energy is released – tiny
missing mass is converted into
energy according to Einstein’s
equation
The Sun’s interior cont…
• each second
– Sun consumes ~ 600
million tons of hydrogen
– Converting ~ 4 million tons
into energy
– As hydrogen is consumed,
helium is produced
forming the solar core
• Core is continually growing
in size
• ~ 100 billion years of fuel
left
• The sun will remain it’s
currents size ~ 10 billion
years before it grows in size
and eventually consumes
Earth
Solar atmosphere
a) Photosphere
• Layer of gas and is the
visible surface of the sun
• ~ 90% hydrogen
• ~ 10% helium
• 500 kilometers thick
• Appearance of boiling with
up and down movements
of gas
• convection of gas transfers
energy
• Tiny amounts of other
elements
b) Chromosphere
• Thin red layer of hot
gases under low
pressure
• Few thousand
kilometers thick
• Found above the
photosphere
c) Corona
• Outermost layer
of the solar
atmosphere with low
density
• layer of ionized
gases
produce solar
winds as protons
and electrons
escape from the
gravity of the sun
sunspots
• Dark areas on the
surface of the
photosphere
• Areas with
temperatures less
than surrounding
area
• # of sunspots
varies in an 11
year cycle
Prominences
Solar Flares
• Huge cloudlike
arches of gases
• Explosive outbursts of sudden
brightening above sunspot clusters
• Release high amounts of solar energy
 Ultraviolet
 Radio
 X-ray