Transcript Earth, Moon, and Sun

Earth, Moon, and Sun
Astronomy Unit
Earth in Space
• Astronomy- the study of the moon, stars,
and other objects in space
• Axis- an imaginary line that passes
through Earth’s center and the North and
South poles, about which Earth rotates
• Rotation- the spinning motion of a planet
about its axis
• Earth’s rotation on its axis causes day and
night.
• Revolution- movement of one object
around another object
• One complete revolution around the sun is
called a year.
• Orbit- the path of an object as it revolves
around another object in space
Seasons on Earth
• If Earth’s axis were straight up and down
relative to the sun, temperatures would
remain fairly constant. There would be no
seasons.
• Earth has seasons because its axis is
tilted as it moves around the sun.
• Latitude- measurement of
distance from the equator,
expressed in degrees
north or south
• Solstice- the two days of the year on which
the noon sun is directly overhead at either
23.5 degrees south or north
• When the noon sun is overhead at 23.5
degrees south, it’s winter in the northern
hemisphere.
• When the noon sun is overhead at 23.5
degrees north, it’s summer in the northern
hemisphere.
• Equinox- the days of the year on which
neither hemisphere is tilted toward or away
from the sun
• Vernal equinox- day of the
year (March 21) that
marks the beginning of
spring in the northern
hemisphere
• Autumnal equinox- day of the year
(September 23) that marks the beginning
of fall on the northern hemisphere
• Seasonal changes affects living things in
the United States.
• In spring and summer, the sun shines for
more hours each day and the sun is higher
in the sky.
• The warmer days allow plants to grow
leaves and flowers.
• In the fall and winter, the nights get longer
and plants stop growing and lose their
leaves and flowers.
The Sun’s Interior
• The interior of the sun is like a giant
furnace.
• The sun produces energy from nuclear
fusion.
• Nuclear fusion- process by which hydrogen
atoms join together to form helium,
releasing energy.
• This occurs only under conditions of
extremely high temperatures and pressure.
Nuclear
fusion
occurs in
the sun’s
core, the
central
part of the
sun.
The Sun’s Atmosphere
• The sun’s atmosphere has 3 layers: the
photosphere, the chromosphere, and the
corona.
• Photosphere- inner layer of the sun that
makes light
• Chromosphere- glow that comes from the
middle layer of the sun during a total solar
eclipse
• Corona- outer layer of the sun that
glows like a white halo around the sun
• Solar wind- a stream of electrically
charged particles produced by the sun’s
corona
• Features on or above the sun’s surface
include sunspots, prominences, and solar
flares.
• Sunspots- areas of
gas on the sun that
are cooler than the
gases around them
• Cooler gases don’t give off
as much light as hotter
gases, which is why
sunspots look darker than
the rest of the photosphere.
• Prominences- reddish loops of gas
• Solar flares- an explosion of hydrogen gas from
the sun’s surface that
occurs when loops in
sunspot regions suddenly
connect
Comparing Earth to the Sun
• The diameter of the Sun is 1,392,000 km,
while the equatorial diameter of the Earth
is 12,756 km. Compared to the Earth the
Sun is HUGE.
Comparing the Earth to the
Moon
The average distance between Earth and
Moon is approximately 30 times Earth's
diameter.
Comparing the Sun to the Moon
• The Sun is 400 times the Moon's diameter
and 400 times as far away. That means
the Sun and Moon appear to be the same
size when viewed from Earth.