Download Composition of the Sun

Structure of the Sun
Chapter 29
The Sun’s Energy
Section 1
Composition of the Sun
 Using a device called a spectrograph, scientists break up
the sun’s light into a spectrum.
 Dark lines form in the spectra of stars when gases in the
stars’ outer layers absorb specific wavelengths of the light
that passes through the layers.
 By studying the spectrum of a star, scientists can
determine the amounts of elements that are present in a
star’s atmosphere.
Composition of the Sun
Because each element produces a unique pattern of
spectral lines, astronomers can match the spectral
lines of starlight to those of Earth’s elements, and
identify the elements in the star’s atmosphere.
Both hydrogen and helium occur in the sun.
About 75% of the sun’s mass is hydrogen, and
hydrogen and helium together make up about
99% of the sun’s mass.
The sun’s spectrum reveals that the sun contains
traces of almost all other chemical elements.
Nuclear Fusion
Nuclear fusion occurs inside the sun.
Nuclei of hydrogen atoms are the primary fuel
for the sun’s fusion.
Nuclear fusion produces most of the suns’ energy
and consists of three steps.
Nuclear Fusion
In the first step, two hydrogen nuclei, or protons,
collide and fuse.
– In this step, the positive charge of one of the protons is
neutralized as that proton emits a particle called a
positron.
As a result, the proton becomes a neutron and
changes the original two protons into a protonneutron pair.
Nuclear Fusion
In the second step, another proton combines with
this proton-neutron pair to produce a nucleus
made up of two protons and one neutron.
In the third step, two nuclei made up of two
protons and one neutron collide and fuse.
As this fusion happens, two protons are released.
The remaining two protons and two neutrons are
fused together and form a helium nucleus. At
each step, energy is released
Nuclear Fusion
The Final Product
One of the final products of the fusion of
hydrogen in the sun is always a helium nucleus.
The helium nucleus has about 0.7% less mass
than the hydrogen nuclei that combined to form it
do. The lost mass is converted into energy during
the series of fusion reactions that forms helium.
The energy released during the three steps of
nuclear fusion causes the sun to shine and gives
Mass Changing into Energy
 The sun’s energy comes from fusion, and the mass that is
lost during fusion becomes energy.
 In 1905, Albert Einstein proposed that a small amount of
matter yields a large amount of energy.
 This proposal was part of Einstein’s special theory of
relativity.
 This theory included the equation:
E = mc2
Mass Changing into Energy
In Einstein’s equation E = mc2,
– E represents energy produced;
– m represents the mass;
– c represents the speed of light, which is about
300,000 km/s.
Einstein’s equation can be used to calculate
the amount of energy produced from a
given amount of matter.
Spot Question
How did the equation E = mc2 help
scientists understand the energy of the sun?
Einstein’s equation helped scientists
understand the source of the sun’s energy. The
equation explained how the sun could produce
huge amounts of energy without burning up.
The Core
The parts of the sun include the core, the
radiative zone, and the convective zone.
At the center of the sun is the core.
– The core makes up 25% of the sun’s total diameter of
1,390,000 km.
– The temperature of the core is about 15,000,000
kmºC.
The core is made up entirely of ionized gas, and
is 10 times as dense as iron.
The Radiative Zone
The radiative zone of the sun surrounds the core.
The temperature of the radiative zone ranges
from about 2,000,000ºC to 7,000,000 ºC .
In the radiative zone, energy moves outward in
the form of electromagnetic waves
The Convective Zone
The convective zone surrounds the
radiative zone.
– The temperature of the convective zone is
about 2,000,000ºC.
Energy produced in the core moves
through this zone by convection.
Convection is the transfer of energy
The Sun
The Sun’s Atmosphere
The sun’s atmosphere surrounds the convective
zone of the sun’s core.
Because the sun is made of gases, the term
atmosphere refers to the uppermost region of
solar gases.
The sun’s atmosphere has three layers: the
photosphere, the chromosphere, and the corona.
The Photosphere
Photosphere means “sphere of light.” The
photosphere of the sun is the innermost layer of
the sun’s atmosphere.
– It is the visible surface of the sun
The photosphere is made of gases that have risen
from the convective zone.
– The temperature in the photosphere is about 6,000ºC.
Much of the energy given off from the
photosphere is in the form of visible light.
Spot Question
What layers make up the sun’s atmosphere?
The sun’s atmosphere consists of the
photosphere, the chromosphere, and the
corona.
The Chromosphere
The chromosphere lies just above the
photosphere.
– The chromosphere’s temperature ranges from
4,000°C to 50,000 °C.
Also known as the “Color Sphere”.
The Chromosphere
The Sun’s Outer Parts
The corona is a huge region of gas that has a
temperature above 1,000,000ºC.
As the corona expands, electrons and electrically
charged particles called ions stream out into
space.
These particles make up solar wind, which flows
outward from the sun to the rest of the solar
system
Corona
Section 2 Solar Activity
Sunspots
Sunspot are dark area cooler areas of the
photosphere
Magnetic fields cause convection to slow in parts
of the convective zone.
This causes a less energy to go from the core to
the photosphere.
Less energy makes these regions of the
photosphere are considerably cooler.
Cooler areas appear darker than their surrounding
regions.
The Sunspot Cycle
Observations of sunspots have shown that the sun
rotates.
The numbers and positions of sunspots vary in a
cycle that lasts about 11 years.
Sunspots initially appear in groups about midway
between the sun’s equator and poles.
The # will peak at about 100 of more sunspots.
After the peak, the number of sunspots begins to
decrease until it reaches a minimum
The Sunspot Cycle
Solar Ejections
The solar-activity cycle is caused by the
changing solar magnetic field.
This cycle is characterized by increases
and decreases in various types of solar
activity, including solar ejections.
Solar ejections are events in which the sun
emits atomic particles.
Solar Ejections: Prominences
Solar ejections include prominences, solar
flares, and coronal mass ejections.
Prominences are huge arches of glowing
gases that follow the curved lines of the
magnetic force from a region of one
magnetic force to a region of the opposite
magnetic.
Solar Ejections: Solar Flares
Solar flares are the most violent of all solar
disturbances.
Solar flares release the energy stored in the
strong magnetic fields of sunspots
Solar Ejections:
Coronal Mass Ejections
Some of the particles from a solar flare escape
into space, increasing the strength of the solar
wind.
Particles also escape as coronal mass ejections.
The particles in the ejection can cause
disturbances to Earth’s magnetic field.
These disturbances have been known to interfere
with radio communications, satellites, and even
cause blackouts
Auroras
Auroras are the result of the interaction
between the solar wind and Earth’s
magnetosphere.
Auroras are usually seen close to Earth’s
magnetic poles because electrically
charged particles are guided toward earth’s
magnetic poles by Earth’s magnetosphere.
Auroras
Depending on the pole there are near they are
called different things. North Pole= aurora
borealis or northern light. South Pole= aurora
australis or southern lights.
Auroras are most frequent just after peak sunspot
cycles
In the United States auroras are visible about 5
times per year, however in Alaska auroras can be
seen almost every clear night. Astronauts can
even see auroras in orbit.