1. Our Solar System
Chapter 28

2. Formation of the Solar System
28.1

3. A collapsing interstellar cloud
Stars and planets form from interstellar clouds
They appear dark because of dust blocking out the light
The light can cause it to glow, or even become heated
Starts and solar systems are “born” this way
Collapse accelerates
The collapse of this cloud is slow, but it accelerates and becomes denser at the center

4. This collapse and spin results in a flattening at the equatorial plane
Matter condenses
Our solar system may hav eformed this way when temperature and pressure cause hydrogen to fuse into helium
The temperature differential allowed for different elements to concentrate in different areas around the sun
This is why the inner planets are rocky and have a higher melting point
Outer ones are less dense and made of ice and gas

5. Planetesimals
Much like coalescence, the planetesimals combined to get larger in many cases to become the known planets.
Gas giants form
Jupiter was the first to form
Icy planetesimals combined to form it
Its mass (gravity) caused it to collect much of the debris
The others formed the same way, but Jupiter took most of the extraneous material

6. Terrestrial planets form
the merging of planetesimals in the inner portion of the disk
Made of materials that resist vaporization
Most of the gaseous material and “smaller stuff” consumed by the sun, hence fewer satellites.
Debris
All of the “junk” left over
Some became comets
Some ejected from solar system or destroyed in collisions
The asteroid belt between mars and Jupiter is the rest

7. Modeling the Solar system
Initially the geocentric theory stated that everything moved around the earth.
Retrograde motion led astronomers to find a different explanation
The heliocentric model (Copernicus) put the sun at the center and planets in orbit around it.
Proximity to the sun caused planets to move at different speeds
This explained retrograde

8. Kepler’s Laws 1st law is that planets move in elliptical orbits
The sun was at 1 focus
The semi-major axis (half the length of the major axis) is where we get the AU (astronomical unit) distance many distances are measured in
This is more math that I want to get into!
The eccentricity of the orbit is how “squashed” the orbit is
2nd law is an equal area is swept out in equal amounts of time (although the orbital distance may be different)
3rd law he defined the size of the ellipse and the orbital period (year)

9. Gravity Gravity is the attractive force between 2 objects
It is affected by mass and distance
Gravity is what determines the orbit planets follow
Newton’s explanation of gravity supported Kepler’s laws of planetary motion.

10. The Inner Planets
28.2

11. Terrestrial Planets these are the 4 inner planets
similar densities to Earth
solid rocky surfaces

12. Mercury closest to the sun 1/3 Earth’s size no moons
2 Mercury Years is 3 Mercury days
Atmosphere
O2 and Sodium
replenished daily by the sun

13. Surface Interior covered with craters and plains
the plains formed much like the maria on the moon
the craters are smaller with less ejecta
Interior
the density suggests a dense core similar to the Earth
the magnetic field suggests its partially molten

14. Venus
Has no moons
the brightest planet because of proximity and albedo 75%
Thick atmosphere doesn’t allow for direct observation
probes and satellites have provided radar images of 98% of the surface

15. The Outer Planets
28.3

16. The Gas Giants
These planets include: Jupiter, Saturn, Uranus and Neptune
All larger than Earth by times

17. Jupiter The largest planet 1/10 of the sun and 11X Earth’s
Better than 70% of the planetary mass of the solar system
52% albedo
Has a banded appearance
“the great spot” is a storm that has lasted for better than 300 years

18. Density is relatively low for its size
The is because of it composition (H and He in gas or liquid form.
Rotation
Shortest day in the solar system about 10hrs
This fast spin distorts the shape
This also contributes to its banded appearance
Belts are low lying dark-colored clouds
Zones are high light-colored clouds
Moons
More than 60, but some are very small

19. Mostly composed of ice and rock
Gravity assist

20. Saturn Second largest planet in the solar system
Atmosphere and interior
Slightly smaller than Jupiter
Density less than water… it would float!
Rings
Much broader and brighter than other planets’
7 major rings made up of ringlets
Gravity keeps the rings in place

21. Moons 55 moons Titan, the largest is bigger than Mercury
Odd among moons because of content with dense atmosphere and methane’s existence in 3 states

22. Uranus 4x larger and 15Xmass of the Earth Atmosphere Moons and Rings
Bluish appearance cause by methane gas
Clouds are similar in appearance to the surface
Liquid surface with a small solid core
Moons and Rings
At least 27 moons and faint rings

23. Rotation The rings are dark and almost not observed
Almost a top to bottom rotation
Poles vacillate between 42 years of darkness and light

24. Neptune Atmosphere Moons and Rings
Smaller and denser than Uranus but 4XEarth
Similar in color to Uranus (twins??) but does have some color variation on surface
Belts and zones give it texture
Moons and Rings
13 moons Triton being the largest
Triton has retrograde orbit
Also has nitrogen geysers when heated by the sun
Rings are invisible from Earth but exist