Transcript The Solar System Ch. 28

The Solar System
Solar System Models
• geocentric model:
model of the solar system
that states that the Earth
is the center of the solar
system
– believed until 1600’s
• heliocentric model: model
of the solar system that
states that the sun is the
center of the solar system
and the planets revolve
around it
• the stars don’t seem to move in
our sky; planets do because they
are much closer than stars
• planets move in an eastward
movement
• sometimes planets appear to move
in a backward movement, this is
called retrograde motion
• a loop occurs because each planet
travels around the sun at
different speeds
Watch retrograde motion!
http://www.astro.uiuc.edu/projects/data/Retrograde/index.html
• The path a planet follows
around the sun is called its
orbit
Kepler’s Laws of Planetary Motion
• 1st law : planets orbit the sun
in a path called an ellipse
aphelion
perhelion
• astonomical
unit: the
average
distance
between the
earth and
the sun
– 150 million
km
• 2nd law: planets move fastest
when they are closest to the sun
in their orbits
• 3rd law: the farther away a
planet orbits, the longer the
planet takes to revolve around
the sun
• revolution: movement of the
Earth around the sun
– takes 365.24 days (1 year)
• rotation: spinning of Earth on its
axis
– takes 24 hours (1 day)
– rotates counterclockwise
the Earth is tilted 23 ½ °on its
axis. Either the Northern
Hemisphere or Southern
Hemisphere tilts towards the sun
• hemisphere that tilts towards
the sun has summer (more
direct sunlight
• hemisphere that tilts away from
the sun  has winter (less direct
sunlight)
• summer solstice: longest sunlight
hours of the year-June 21st-first day
of summer
• winter solstice: shortest sunlight
hours of the year- Dec. 21st- first day
of winter
• spring equinox: equal amounts of
day/night hours- March 21st- first day
of spring
• fall equinox: equal amounts of
day/night hours- Sept. 21st- first day
of fall
• precession:
slow circular
motion of the
Earth’s axis as
it turns in
space that
traces a circle
in space every
26 thousand
years
• INNER PLANETS
– also known as
the terrestrial
planets
– dense, small,
have solid
rocky
surfaces,
metal cores
• OUTER PLANET
– also known as the Jovian Planets
– less dense, large, gaseous, thick
atmosphere
To remember the order of the
planets, just remember this
sentence…
“My Very Eager Mother
Just Served Us Nine
Pizzas”
Other Objects in the Solar
System
• comet: composed of dust,
rock, frozen water, and gas
1. nucleus: glows by reflected sunlight
2. coma: hazy cloud that surrounds the
nucleus
3. tail: gas and dust that always points
away from the sun
Halley’s Comet
Hale-Bopp
Comet
• asteroid: solid, rock-like mass,
irregular in shape
• orbit the
sun- most
orbit
between
Mars and
Jupiter in
the
asteroid
belt
• Ceres is the largest asteroid
• meteoroid: rock or icy fragment
moving through space
– can be large as a boulder or as
small as sand
• meteor: light made by
meteoroid as it passes through
Earth’s atmosphere
• meteorite: a meteoroid that
lands on Earth
– can be stone, iron, or stony-iron
– most burn up before striking the surface
stone
meteorite
iron
meteorite
stony-iron
meteorite
• if they strike the Earth, they
form impact craters (this is
rare!)