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?