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The Sun and Stars
The Sun
• About 150 million km away from earth
• Supports all life
• The sun is a large star
• A star is a body of electrically charged gas, or plasma,
that emits energy from nuclear reactions taking place in
its core
• The sun has a magnetic field that is generated by
movement deep it its interior
• Four important events occur on the surface of the sun:
sunspots, solar prominence, solar flares and coronal mass
ejections.
Sunspots
• A region on the Sun’s surface that is
cooler than the surrounding areas
• Looks darker than the surrounding
areas
• Indicates areas that the magnetic
field is extremely strong, so the
convection is slow
• Sunspots come and go
• Sunspots are very large, most of
them is larger than Earth’s diameter
Solar Prominences
• A large, low energy, curved,
bright stream of particles
• Curved shape often forms a
complete loop
• Shaped by the Sun’s magnetic
field
• May last for several hours, or
several weeks
Solar Flares
• A high energy, massive explosion at the surface of the Sun
• Sudden release of magnetic energy that often flings hot plasma
into space
• Solar flares can reach their maximum energy level in just a few
minutes and last several hours
• An extremely powerful kind of flare is called a coronal mass
ejection
• When this happens, a large amount of plasma is thrown out into
space at a speed of more than 1000km/hr
• Sometimes, it may be pointed straight at Earth and can reach
Earth about three days later. Our magnetic field protects Earth
and diverts most of the plasma away from the surface
• This causes the auroras (Borealis and Australis)
Layers of the Sun
• Corona - The corona is the outermost layer of the
Sun’s atmosphere, starting at about 2100 km above
the solar surface. The temperature in the corona is
500,000C
• Chromosphere - emits a reddish glow as superheated hydrogen burns off.
• Photosphere – lowest layer of atmosphere. It is
about 500 kilometers thick. This layer is where the
sun's energy is released as light and where solar
flares occur. Because of the distance from the Sun
to Earth, light reaches our planet in about eight
minutes.