Solar System Notes:

Inner Planets:

1. The four planets closest to the sun are the inner or terrestrial planets  The Latin word terra means "Earth".

All have solid surfaces, are similar in size when compared to the gas giants, take short time to orbit the Sun and are relatively close to each other.

2. Astronomical Unit or AU- a unit of measurement equal to the distance between the Earth and Sun (93 million miles or 150 million kilometers).

3. Mercury-smallest and closest to the Sun.  NOT the hottest, one side hot and one side super cold. No moon. ⅓ AU from the Sun

4. Venus- The HOTTEST planet! Covered in thick clouds of poisonous gases that trap the Sun’s heat causing a greenhouse effect.  Almost same size as Earth, its year is longer than its day! Revolves backward,  .8 AU from Sun. No moon.

5. Earth- largest and densest terrestrial planet, one moon, 1 AU from Sun.

6. Mars-4th planet. 2 moons, covered in red dust and looks reddish in telescope.  Has several robot probes on surface. 1.5 AU from Sun. 1.9 Earth year orbit.

7. Asteroid Belt- area between the orbits of Mars and Jupiter. Is filled with asteroids and meteors that orbit the Sun.  

Outer Planets:

8. The four planets that are outside the asteroid belt.  Have no solid surface and are called the Gas Giants. Have several to many moons.

9. Jupiter-largest planet, 5th from Sun, so large that it could contain all of the other seven planets.  Has four large moons that were discovered by Galileo, over 60 moons in all. Is 5.4 AU from Sun, 12 year orbit.

10. Saturn-has rings, least dense of all planets.  6th planet, has over 60 moons, is 10 AU’s from Sun, takes 29 years for orbit.

11. Uranus- 7th planet, over 20 moons, 20 AU from Sun, takes 84 years for one orbit, is tipped over on its side.

12. Neptune-the Blue Planet, 13 moons, 29 AU from Sun, takes 165 years for one orbit.

Other Solar System Objects:

13. Asteroids-a small rocky body that orbits the sun. Asteroids are made up of carbon, rocks, and metals. Most asteroids in our solar system have orbits that lie between Mars and Jupiter in the asteroid belt. Asteroids can be as large as a dwarf planet.

14. Meteroids-broken asteroids, smaller, most are the size of pebbles and dust.

Meteors-meteoroids that are still in space or burning in the atmosphere (shooting stars)

Meteorites-meteoroids that have struck a planet.

15. Comets-giant dirty snowballs.  Orbit the Sun, can be miles in diameter. Develop a glowing tail as they get close to the Sun.  Halleys Comet orbits the Earth every 76 years.

16. Dwarf planets-objects that orbit the Sun but are not large enough to classify as planets.  Ceres, Pluto, Eris, Haumea, and Makemake.

17. Kuiper Belt-area out beyond Pluto, comets come from here.