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16-1 (PART 2) | A SOLAR SYSTEM
IS BORN
THE BIRTH OF A STAR
• As the planets are forming, gas and
dust near the center of the solar
nebula grow dense.
• In the center the hydrogen atoms
begin to fuse.
• Fusion creates energy that pushes
outward. The star begins to shine.
• A star is born and a new solar system
is formed.
THE STRUCTURE OF THE SUN
• Corona: Uppermost part of the
atmosphere; millions of miles
thick
• Chromosphere: orange-red
layer of atmosphere; thousands
of miles thick
• Photosphere: the lower
atmosphere and what we see
• Core: where nuclear fusion
occurs
ENERGY PRODUCTION IN THE SUN
• The sun has been
shining for about 4.6
billion years
• Tiny amounts of matter
can produce huge
amounts of energy
NUCLEAR FUSION
• Nuclear fusion is the
process by which two or
more low-mass nuclei fuse
to form another nucleus
• When hydrogen nuclei
fuse, they form helium and
ignition begins
CONDITIONS REQUIRED FOR FUSION
• Under normal conditions, hydrogen atoms never get close
enough to join
• In the center of the sun, the temperature and pressure are
very high
• This forces the atoms to collide, causing hydrogen to fuse
MEASURING INTERPLANETARY DISTANCES
• One way scientists measure distances in space is by using
astronomical units (AU)
• One AU is the average distance between the Earth and the
sun, which is 150,000,000 km
ANOTHER WAY
• Another way to measure distances is by using the speed of
light
• A light-minute is how far light travels in one minute, which
is 18,000,000 km
• Distance in the solar system can also be measured in lighthours or light-years