Transcript Section 18.3

Astronomy
Chapter Eighteen: Earth, the
Moon, and the Sun
• 18.1 The Earth and Its Moon
• 18.2 Earth Cycles
• 18.3 The Sun
Investigation 18B
Earth’s Seasons
• What causes the seasons?
18.3 The Sun
• The Sun is a star.
• A star is a giant, hot
ball of gas held
together by gravity.
• The Sun is mediumsized compared with
other stars in the
universe.
Approximately 1 million
planet Earths could fit
inside the Sun!
18.3 The Sun
• Gravity squeezes the
atoms in the core of a
star so tightly that they
fuse together in a
reaction called nuclear
fusion.
• In the process, huge
amounts of energy are
given off.
18.3 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.
18.3 Features of the sun
• Occasionally, large
“loops” of gas
called prominences
can be seen
jumping up from
groups of sunspots.
18.3 Features of the sun
• Solar wind is an
electrically charged
mixture of protons and
electrons.
• Auroras, called the
northern lights, occur
when layers of our
atmosphere are
energized by solar winds.
Research Connection
Solar Observatory
• The staff of Big Bear
Solar Observatory
study the sun, solar
phenomena, and the
solar atmosphere.
Activity
Distance from Earth to the Sun
• Scientists have been
studying the sun, its
behavior and its
relationship to the
Earth.
• Graph the month of the
year versus the
distance of Earth to the
Sun using a
spreadsheet program.