Small Solar System Bodies Asteroids Comets and Plutons

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.