Download Characteristics of the Sun

CHARACTERISTICS OF THE SUN
Video Summary
Our Sun is an ordinary star—just one of
billions of stars in our galaxy alone.
However, as our own star, the Sun holds
special status for us and is essential to
our existence. The Sun’s gravity holds the
solar system together, and nuclear fusion
within the Sun supplies the energy for life
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on Earth. Without the Sun, Earth would
be a drastically different place. In this video segment adapted from NASA, learn
some basic facts about our Sun.
Topics Covered:
Recommended for Grades 3-12
– Earth and Space Science: Earth in the Universe
Media Type: QuickTime Video
Video Length: 1m 28s
Permitted use: Download, Share, Remix
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Discussion Questions
 Compare our Sun with other stars in terms of size and temperature.
 What is the Sun’s role in the solar system?
 What does the narrator mean when she says that the sunlight you see
actually left the Sun 8.5 minutes ago?
 The Sun is about 150 million kilometers away from Earth. How does that
compare to the distance of other stars?
Background Essay
The Sun, our star, is at the center of the solar system and critical to our existence. Without
the energy supplied by the Sun, Earth would be a cold and inhospitable planet—it would
have no liquid water, no weather, and no life. The Sun contains approximately 99% of
the mass of the entire solar system and its gravity holds the solar system together. More
than one hundred Earths could line up across the Sun’s diameter, and over one million
Earths could fit inside it.
Characteristics of the Sun
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However, compared with other stars, the Sun is rather ordinary. It is about in the middle
of the ranges for star size and brightness. Many of the stars that you can see in the night
sky are actually bigger and brighter than the Sun—they only appear smaller because they
are much farther away. However, there are also many stars dimmer than the Sun that are
too faint to be seen from Earth. In fact, these dim stars are by far the most common stars
in the galaxy. Thus, despite the Sun being in the middle range for all possible types of
stars, when considering the total population of stars in the galaxy, the Sun is larger and
brighter than most.
Like all stars, the Sun is made of hot gases. It doesn’t have a solid surface, but its surface
is defined by the photosphere—distinctly visible from a distance—which has a temperature
of about 5,800 K (9980°F). The photosphere looks granular because of convection cells
of hot gas within the Sun, similar to those on the surface of boiling water. The
photosphere sometimes displays dark blemishes called sunspots, which are caused by the
Sun’s magnetic field. Above the photosphere are a thin layer called the chromosphere
and the outermost layer of the Sun, the corona, a wispy and extremely hot layer with a
temperature of a few million Kelvin. The Sun is very active and produces events such as
solar flares, coronal holes, and coronal mass ejections.
The Sun is composed of about 75% hydrogen, 25% helium, and trace amounts of heavier
elements. At its core, the Sun’s temperature reaches over 15 million K (27 million°F) and
its pressure is over 200 billion times the pressure at Earth’s surface. At these temperatures
and pressures, hydrogen is converted into helium in the process of nuclear fusion. The
energy created in the core travels outward toward the Sun’s surface and is radiated as
light. This energy takes about 8.5 minutes to reach Earth, which orbits about 150 million
kilometers (93 million miles) from the Sun.
To learn more about nuclear fusion, check out The Elements: Forged in Stars.
To learn more about the Sun’s magnetic field, check out Solar Magnetism.
To learn more about the Sun’s effects on Earth, check out Solar Wind’s Effect on Earth.
Lesson Plans Using This Resource:
– Our Super Star
Professional Development Courses Using This Resource:
– Teaching Earth and Space Science
– Earth in Time and Space
Curricular Standards Correlations:
NSES, Project 2061, MCREL, and state standards correlations available at
www.teachersdomain.org. (Free registration required for your specific state standards correlated to this resource.)
Characteristics of the Sun
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© 2007 WGBH Educational Foundation. All rights reserved.
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Source: NASA/Goddard Space Flight Center
Materials used courtesy of:
NASA/Goddard Space Flight Center
Collection developed and produced for Teachers’ Domain by:
Collection funded by:
”Teachers‘ Domain is proud to be a Pathways portal to the National Science Digital Library.”
Characteristics of the Sun
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© 2007 WGBH Educational Foundation. All rights reserved.
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