General orientation to the Solar System IV

The Asteroid Belt

Asteroid Ida from NASA.
Items of interest

Note: Many minor bodies are smaller the detection threshold of our instruments and only become apparent when they collide with something.

The Jupiter system

Jupiter : (right with Earth for scale)

The planets to scale from The RASC Calgary Centre

Items of interest

The Galilean satellites

Io, Europa, Ganymede, Callisto, Earth and the Moon to scale.

Jupiter has 79 known satellites, whose orbits' semimajor axes range up to 0.203 AU. Most of their mass, however, is concentrated in the four large "galilean" moons discovered by Galileo Galilei in 1613 (Above, with Earth and Moon for scale) that orbit close to Jupiter. (The rest are "potatoes.") Their discovery was a crucial step forward in the establishment of science as a profession and way of thought, as they demonstrated that there was definitely something in the solar system that defied church doctrine and conventional wisdom by circling something other than the Earth. These moons are major worlds in their own rights, sharply distinct from one another and from other moons. They are very interesting, with surfaces that range from utterly boring to ferociously dynamic. Because the Jupiter system is well beyond the snow line for water and CO2 can condense as solids, all but Io contain significant amounts of these "ices".

Galilean Thumbnails:

Galilean orbits from Wikipedia.

Orbital resonances:

Now for an oddity: The inner three Galilean moons interact with one another gravitationally to produce resonances - simple numerical ratios between their orbital periods:

Key concepts and vocabulary.