Download Summing up the solar system

SUMMING UP THE SOLAR
SYSTEM
Formation of the Solar System
 Nebular Hypothesis– 12 billion years ago a
giant nebula (cloud of gas & dust) rotated
quickly, shrank, & compressed creating the
sun and a planetary disc. As time passed, the
disc condensed into small planets.
 4.6 billion years ago, most planets had formed,
including Earth!
Models for Our S.S.
 Aristotle & Ptolemy 90-168 A.D. geocentric
model of our S.S.  Earth is at the center
 Copernicus 1473-1543 A.D. heliocentric model
for our S.S.  Sun is at the center
 Kepler Explained the motions of planets with
3 laws– observed planet orbits from different
places on Earth
Kepler’s 1st Law
 Elliptical Orbits not Circular, with the Sun at
one foci
Ellipse Geometry
You do not have to copy this slide
Major Axis
Foci
Minor Axis
Eccentricity=How oval is it?
Kepler’s 2nd Law
 Perihelion- planet’s closest
distance to Sun in orbit
 Moves faster than @ aphelion
 Aphelion- planet’s farthest
distance from Sun
 2nd Law- “Equal Area
Law” b/c the planet has to
move faster closer to the
sun to get an area equal to
that of an area furthest
from the sun
Click below for an Animation!
http://www.physicsclassroom.co
m/mmedia/circmot/ksl.cfm
Kepler’s 2nd Law: When a planet is closer
to the Sun, it moves faster
Kepler’s 3rd Law
 The more distant a planet’s orbit is from the
Sun, the slower it moves
 Compares planets to one another
 Period- time for one complete orbit around
sun
 Let’s see all three in action
Measuring Distances in our S.S.
 Astronomical Unit
(AU) the distance
from Earth to the Sun
(150 million kilometers
OR 93 million miles)
 Things within our solar
system are measure in
A.U.’s
Other areas within our S.S.
1. The Kuiper Belt: [30-55 AUs] 1000s of
objects s.a. dwarf planets and balls of
ice/dust/gas (comets or “dirty snowballs”)some get hurled towards the sun

comet’s tail always points AWAY from the sun
b/c of the solar wind
2. Oort Cloud: [5,000-100,000 AUs] way past
the Kuiper belt & Pluto; millions of comets
that do not orbit the sun
S.S. FACTS
1. Inner planets- “terrestrial” planets
2. Outer planets- “gas giants” or “Jovian planets”
3. Saturn would float in a bowl of water (density
is <1.0 g/cm³)
4. All outer planets have rings
5. Venus revolves around the sun quicker than it
rotates on its axis (Its day is longer than its
year!)
6. Venus is our “sister planet” b/c of its size and
density
7. Venus is also known as the “morning star” b/c
we can see it in the western sky in the morning
S.S. FACTS
8. Venus is the hottest planet b/c of a runaway
9.
10.
11.
12.
Greenhouse Effect (too much gas!)
Uranus rotates on its side (spins like a
bowling ball)
Neptune used to have a dark spot, like
Jupiter, which was also thought to be a
storm
Uranus & Neptune are about the same size
Jupiter is the largest planet
Size of planets in order
from largest to smallest
1.
2.
3.
4.
5.
6.
7.
8.
9.
Jupiter
Saturn
Uranus
Neptune
Earth
Venus
Mars
Mercury
Pluto (not a planet)
Why was pluto downgraded
to a ‘dwarf planet’?
1. Too small ~1 mile across
2. Doesn’t fit the categories of “terrestrial” or
“gas” planet- predominantly ice & resides in
Kuiper belt (like a comet)
3. Not always the 9th planet– its orbit is so
eccentric that it crosses Neptune’s orbital
path every 228 years & spends ~20 years
being closer to the Sun than Neptune