1. The Planets
Ali Nork

2. Planetary Revolution Planets revolve counterclockwise around Sun
Planets revolve on a common plane called the ecliptic
Pluto’s orbit is tipped 17.2°
Other planets tipped no more than 3.4°

3. Planetary Rotation Almost all planet rotate counterclockwise, but
Venus rotates backwards (retrograde)
Uranus and Pluto rotate on sides w/ equator perpendicular to orbit

4. Inner Planets Terrestrial, or “earthlike” Mercury, Venus, Earth, Mars
Closer to sun
Small diameter/mass
Density greater than water (3-5g/cm3)
Rocky crust, dense mantle
Very dense core w/ Fe and Ni

5. Inner planets cont’d…. Impact craters
Few moons (actually- Mercury and Venus have no moons)
Less atmosphere
Animation here

6. Outer Planets Jovian planets- Jupiter-like
Gas giants- Jupiter, Saturn, Uranus, Neptune
Huge compared to Earth
Large mass, low density (<1.75g/cm3)
Mostly gaseous (H and He)

7. Outer Planets cont’d…. Have rings
Have many moons- Jupiter (67), Saturn (62), Uranus (27), Neptune (14)
Separated from terrestrial planets by the Asteroid Belt

8. What’s Up With Pluto? Was considered a planet for 76 years
2006- reclassified as a dwarf planet
Mostly ice
Very small (1/20 the mass of Mercury)
Has 3 moons (Charon, Nix and Hydra)
Highly eccentric (elliptical) orbit which crosses Neptune’s

10. Origin of the Solar System
Solar nebula model- ss formed out of an eastwardly rotating interstellar cloud 5 billion years ago
Dust and gas cloud (mostly H and He)
Cloud condensed due to gravity; speed of rotation increased; became flattened
Densest area in middle became the sun

11. Disk eventually cooled; different elements and compounds condensed depending on distance from sun
Tiny grains of condensing material accumulated and collided; eventually formed planetismals (“baby planets”)
Jupiter was the first large planet to form in outer ss; probably prevented other outer planets from growing larger
Asteroid belt (interplanetary debris between Mars and Jupiter) remains b/c Jupiter’s gravity prevented it from creating a planet

12. Planetary Formation
Terrestrial planets formed where temps were very high and metals and silicates could form solids
Jovian planets formed at lower temps where gas became ice
No planets in asteroid belt b/c Jupiter is so massive and its gravity disturbed planet formation
Larger mass enables planets to hang onto particles in rings; less impacted by solar wind (far away from sun)

13. Planetary Satellites
Moons are natural planetary satellites that revolve around a planet
Some cool moon facts:
Jupiter’s moon Ganymede is the largest one in our solar system
Saturn’s moon Titan has a mostly nitrogen atmosphere and has liquid hydrocarbon lakes; also has water ice
Mars has 2 tiny moons (Phobos and Deimos) which may be captured asteroids

14. Ganymede

15. Titan

16. Phobos and Deimos

17. Voyager I “family portrait”
-Taken in 1990 after Voyager I and II left Pluto’s orbit

18. Asteroids
Rocky masses that revolve around Sun; usually between Mars and Jupiter
Debris left over by a planet that failed to from (about 2.8 AU from Sun)
Need a telescope to view them
Largest is Ceres (578 mi wide)

19. Comets
Nucleus of ice and debris; coma is gas surrounded by nucleus

20. Comets cont’d… Tail points away from sun and is caused by solar wind
Long, eccentric orbit which goes outside the 9 (or 8) planets
Orbital periods can be long or short
Comet Shoemaker-Levy 9 slammed into Jupiter’s atmosphere in 1994

21. Kuiper Belt Located beyond planet Neptune
Home to over 700,000 icy, small objects (Pluto, Quaoar)
Sometimes objects are redirected towards the sun (disturbed by gravity of one of the gas giants)

22. Oort Cloud Home to many comets Located 50,000 AU from the sun
Outer edge defines the boundary of our solar system
Members include Sedna and various comets

25. Meteoroids Rocky, icy fragment in space
Range in size from small sand particles to boulders
Meteor (shooting star) is light produced when enters Earth’s atmosphere due to friction
Meteorite is meteoroid that has struck Earth’s surface
May produce impact craters

26. Meteoroids cont’d…
Meteoroids can’t be seen, but meteors can b/c of light produced
Maybe formed from impacts between asteroids
Micrometeoroids- tiny fragments that often hit Earth
Can travel at high speeds and damage spacecraft