Download Stars - Sun

The Sun
• The Sun is a giant, hot ball of
gas held together by gravity.
• The Sun is a medium-sized
compared with other stars in
the universe.
• Main sequence star
Approximately 1 million
planet Earths could fit
inside the Sun!
The Sun
• Gravity squeezes the
density of a star so tightly
in the core that the
electrons are stripped
away and the bare nuclei
of atoms almost touch
each other.
• Nuclear fusion occurs.
The Sun
• In the process, huge
amounts of energy are
given off.
• Because of its mass,
the Sun’s gravitational
force is strong enough
to hold the entire solar
system in orbit.
Anatomy of the sun
• The apparent surface of
the Sun that we can see
from a distance is called
the photosphere, which
means “sphere of light.”
• Just above it is the
chromosphere.
• This is a very hot layer of
plasma, a high-energy
state of matter.
Anatomy of the sun
•
•
The corona is the outermost
layer of the sun’s
atmosphere, extending
millions of kilometers
beyond the sun.
Sunspots are areas of gas
that are cooler than the
gases around them.
Features of the sun
• Occasionally, large “loops”
of gas called prominences
can be seen jumping up
from groups of sunspots.
Features of the sun
• Solar wind is an
electrically charged
mixture of protons and
electrons that cause
magnetic storms.
• Auroras, called the
northern lights, occur
when layers of our
atmosphere are
energized by solar
winds.
Solar energy
• Solar energy is a term that refers to radiant
energy from the Sun.
• The radiant energy of the Sun reaches Earth in
the form of electromagnetic waves.
• We can use solar energy to heat buildings and
generate electricity.
More about the Sun’s energy
• In 1905, Albert Einstein proposed that matter can
be converted into energy.
• His famous equation shows how huge amounts of
energy can be created from a smaller mass.
27.2 Temperature and color
• If you look closely at the stars on a clear night,
you might see a slight reddish or bluish tint to
some stars.
• This is because their surface temperatures are
different.
27.2 Temperature and color
• The color of light is related to its energy.
• White light is a mixture of all colors at equal brightness.
More about the Sun’s energy
• The amount of this energy
from the Sun that reaches
the outer edge of Earth’s
atmosphere is known as
the solar constant.
• The accepted value is
1,386 watts per square
meter (W/m2), or about
thirteen 100-watt light
bulbs per square meter of
surface.
Brightness and luminosity
• For a distant source of light like a star, the brightness
decreases as the inverse square of the distance.
The Sun
http://astrosun2.astro.cornell.edu/academics/courses/astro201/hr_diagram.htm
http://aspire.cosmic-ray.org/labs/star_life/hr_interactive.html