1. Small Solar System Bodies
Asteroids, Comets and Plutons

2. Asteroids: Definition
Asteroids are small rocky objects that orbit the Sun.
Most are located in the asteroid belt between Mars and Jupiter.
They range in size from 10 to 1000 km across.
Approximately 10, 000 asteroids in total, the total mass is less than the mass of Earth’s Moon.

3. Asteroids: Ceres
The first discovered asteroid was Ceres, discovered in 1801 by Guiseppe Piazzi.
Ceres is the largest object in the asteroid belt.

6. Asteroids: Origins
Two theories regarding the formation of the asteroid belt:
1) The belt is the remnant of a planet that broke up long ago.
2) The belt is made of fragments that never managed to form a planet.

7. Asteroids: Origins
The second theory is more commonly accepted (not enough mass to constitute a planet; chemical composition is too diverse).

8. Asteroids: Other Notables
Some moons may be captured asteroids (e.g. Deimos and Phobos).
Other locations for asteroids include:
1) Near Earth Asteroids
2) Trojans (before and behind Jupiter)
3) Centaurs in the outer solar system

9. Comets: Definition
A comet is a body of frozen mass with a highly elliptical orbit of the Sun.
Often considered to be a dirty snowball.

11. Comets: Composition
Comets are composed mainly of frozen ice, frozen carbon dioxide and dust. They may contain methane gas, ammonia and organic materials.
They may also contain metals, rock and gasses picked up as they travel.

12. Comets: Composition
Comets are composed of a solid nucleus. As it approaches the Sun, it can develop a cloudy atmosphere called a coma, and two tails.

13. Comets: Tails A comets orbit the Sun, they develop two tails.
The tails always point away from the Sun.
The ion tail is composed of gasses ionized by the Sun and affected by its magnetic field.
The dust tail is composed of dust that has been pushed out of the coma by the Sun’s radiation.

17. Comets: Locations
Comets with orbital periods of more than 200 years likely come from the Oort cloud. Comets with shorter periods likely come from the Kuiper belt.

18. The Kuiper Belt
The Kuiper belt is a disk of small icy bodies that extends from approximately 30 AU to 50 AU.
Kuiper belt objects include short period comets, and perhaps Triton, Pluto and Charon and Quaoar.

23. The Oort Cloud
The Oort cloud is a large spherical cloud surrounding the solar system. It is composed of icy bodies.
The cloud ranges from to AU.
It is sometimes called the Opik-Oort cloud.

25. Plutons
Pluto is no longer a planet.

26. Plutons
Pluto is now the head of its own category, Plutons or dwarf planets.
A dwarf planet is any round object that has not cleared the neighborhood around its orbit and is not a satellite.