1. To ASTRONOMY….. and beyond!

2. What we will be discovering:
 Structures of the solar system
 The Sun-Earth-Moon System
 The Planets and their Moons
 Asteroids, Comets, and Meteoroids
 Stars and Galaxies

3. Axis and Period of Rotation
Axis of Rotation
Period of Rotation
 an imaginary line that
 The time it takes for one
runs through the center
of the planet. (The planet
rotates around this line.)
rotation around the axis
to occur. (one day)

4. Period of Revolution and Ellipse
Period of Revolution
Ellipse
 The time it takes a planet
 Oval shaped. (example:
to move completely
around the sun. (one year)
Earth’s orbit around the
sun is an oval or ellipse.)
 ALL planets have
elliptical orbits around
the sun (Kepler’s first
law)

5. AU’s and LY’s
Astronomical Unit
Light Year
 The average distance
 The distance that light
from Earth to the Sun.
 1 AU = 149,600,000km
travels in a vacuum in one
Julian year. (365.25 days)
 Typically used to measure
distances on a galactic
scale.
 1 ly = apx 10 trillion km

6. Now, because I know you’re interested…
Revolution and Rotation
periods of the planets:
Planet
P of rotation
P of revolution
Mercury
59 days
88 days
Venus
243 days
255 days
Earth
24 hours
365 days
Mars
24 hours
687 days
Jupiter
10 hours
11.9 years
Saturn
11 hours
29.5 years
Uranus
17 hours
84 years
Neptune
16 hours
165 years

7. The reason for the seasons!
 The yearly cycle of the seasons is caused
by the tilt of Earth’s axis as it revolves
around the sun.
 Depending on which hemisphere is tilted
towards the sun, they will be experiencing
summer and the one tilted away will be
experiencing winter.
 The equator always experiences warm
weather because it’s always tilted toward
the sun!

8. Earth + Revolution = Seasons

9. The Equinoxes
 The earth experiences 2 equinoxes- one
in March and one in September.
 An equinox is when neither end of the
Earth’s axis is tilted toward the sun,
therefore, both hemispheres are receiving
an equal amount of sunlight and energy!
 Day and night are equal in length during
the actual equinox (March 21 and
September 22)

10. The Solstices
 The solstices are the times of year when
the direct sunlight is farthest north or
south of the equator.
 The summer solstice occurs for us on
June 21 (this is the winter solstice for the
southern hemisphere)
 The winter solstice occurs for us on
December 21 (this is the summer solstice
for the southern hemisphere)