Small Solar System Bodies Asteroids, Comets and Plutons

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.

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

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.

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

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

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.

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.

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.

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.

                                                                                                                                                                                              

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.

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.

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 50 000 to 100 000 AU. It is sometimes called the Opik-Oort cloud.

Plutons Pluto is no longer a planet.

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.