Our Solar System
Characteristics
• our solar system is in the Milky Way galaxy
• composed of the Sun (yellow dwarf) and
everything that orbits it
– sun is 99.8% of the mass
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Planets: 0.135%
Comets: 0.01% ?
Satellites: 0.00005%
Minor Planets: 0.0000002% ?
Meteoroids: 0.0000001% ?
– sun’s gravity keeps the planets in orbit
– around 135 satellites are orbiting the
planets in our solar system
• a satellite is an object in orbit around a larger
mass
Formation
• about 4.6 billion years old
– probably began as a nebula-- a large cloud
of dust in space
– collapsed into a large, rotating, diskshaped cloud
– continued to collapse and the material in
the middle became hot and dense (the
Sun)
– planets begin to form by accretion where
particles collide and stick together
because of gravity
• the planets, moons, and asteroids of our
solar system orbit the Sun in about the same
angle called the ecliptic plane
Earth’s temperature
• tends to be hotter at
the equator because
the sun’s energy is
perpendicular to the
earth and therefore
more concentrated
• Earth’s seasons are caused by the tilt
(23.5º) of the earth on its axis
• the pole tilted towards the sun is hotter and
the days longer
– more direct
sunlight and
higher
temperatures
The Moon
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only natural satellite of Earth
has no atmosphere
gravity is about 1/6 of Earth
light comes from the Sun that is reflected off
the Moon's surface.
• moon’s gravity pulls on earth’s water creating
high and low tides.
• phases of the moon
– appears to be different shapes depending
on its position relative to earth
– waxing is when the moon is “getting”
bigger
– waning is when the moon is “getting”
smaller
Eclipses
• occurs when one object moves into
the shadow cast by another object
– solar eclipse
• moon blocks out the sun from
reaching an area on earth
– lunar eclipse
• earth blocks the sun from reaching the
moon