24.3 The Sun
Structure of the Sun
Earth’s primary source of energy
Divide the sun into 4 parts
Solar interior
The visible surface (photosphere)
2 atmospheric layers (chromosphere
& corona)
Structure of the Sun
Photosphere (light ball) (Sun’s surface)
Radiates most of the sunlight we see
Layer of gas
Grainy texture
Granules that are surrounded by narrow dark
regions (size of TX)
Each granule survives 10-20 mins
Up and down movement is called boiling
(convection)
90 % H 110 % Helium
Absorption spectrum
Continued…
Chromosphere (above photosphere)
Thin layer of hot gases
Observable only a few moments during a
solar eclipse (or by a special instrument that
blocks out light from the photosphere)
Hot incandescent gases under LP = emission
spectrum
Continued…
Corona (crown)
Outermost portion of the solar atmosphere
Visible only when the photosphere is covered
Solar wind
Magnetic field prevents solar wind from
reaching our surface
Radiates less energy bc of its very low density
The Active Sun
Sunspots (dark regions on the surface of the
photosphere)
Appear darker bc of their temp. which is
about 1500 K less than that of the surrounding
solar surface
Prominences (huge cloudlike structures
consisting of chromospheric gases
Look like gaint arches
Ionized gases trapped by magnetic fields that
extend from regions of intense solar activity
Continued…
Solar Flares (brief outbursts that
normally last about an hr & appear as
a sudden brightening of the region
above a sunspot
During their existence they release
enormous amounts of energy (UV,
Radio, & X-ray radiation)
Auroras (northern lights & southern
lights)
The Solar Interior
Nuclear fusion (converts 4 H nuclei into the
nucleus of a helium atom)
Lots of energy is released
Energy is released bc some matter is actually
converted to energy
Energy is in the form of high-energy photons
that work their way toward the solar surface
The photons are absorbed and reemitted
many times until they reach a layer just
below the photosphere
REVIEW
What is the structure of the sun?
Which layer of the sun can be thought of
as its surface?
Are the same number of sunspots always
present on the sun? Why or why not?
How much longer will the sun likely exist in
its present state?
How does the sun produce energy?
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