Solar System

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Solar System

Note: Earth Science Australia is not an astronomy site.
This content is meant to stimulate interest from an earth science perspective.
Many excellent astronomy site are available...see Links page..

      see also Kepler's Laws of Planetary Motion...
      see also The Eight Motions of the Earth...
      see also The Sun...
      see also the Stars...
The Astronomical Unit
Bode's Rule
What Is A Planet?
Former Planet Pluto and the Plutinos
The Solar System: Minor Bodies
Comparison of Planet Properties
       see also Meteorites...
       see also Comets...

inner planets

Before the true distance of the Earth from the Sun was known, and what the true distances in the Solar System were, relative distances were measured by the Astronomical Unit. It still is the most meaningful way to understand the scale of the Solar System

The Astronomical Unit:

The mean distance of the Earth from the Sun.  This distance is defined to be 1 A.U.

Astronomical Unit


solar system

crossection of solarsystem

Conjunctions and Orbits

planetary conjunctions     earth / moon orbits

Bode's Rule

In 1772, the German astronomer Johann Bode found an empirical rule, dubbed Bode's Rule, that does a remarkable job of "predicting" planetary positions in the Solar System.
1. Write down a sequence of 4s, one for each planet except Neptune, including one for the asteroids.
  2. Add the sequence 0, 3, 6, 12, 24, ….
  3. Divide these numbers by 10.
The result is the relative distance of each object from the Sun, to a surprising degree of accuracy!

Bode's Law

What Is A Planet?

We all have heard that the Sun has nine planets circling around it, but what exactly is a planet?
Planet: A non-stellar body larger than a certain size (roughly 1,000 to 3,000 km), orbiting around a star as its primary host.
A List Of Important Numbers/Constants:

A Survey Of The Planets: Mercury


Mercury data
Notes:  Very Small Magnetic Field, Past Cratering, Inter-Crater Plains - Past Geologic Activity.

A Survey Of The Planets: Venus


Venus data
Notes: Thick Atmosphere, Little/No Magnetic Field, Evidence of Past/Present Geological Activity.

A Survey Of The Planets: Earth


Earth data
Notes: Liquid Water In
  Abundance, Life!

Earth's Moon


Moon Data:

Diameter 3475.6 Km  (2159.7 miles)
Rotational period 27.322 days
Sidereal revolution period 27.322 days
Sinodic revolution period 29d12h44m2,9s
Mass (Earth=1) 0.0123
Volume (Earth=1) 0.0203
Gravity (Earth=1) 0.1653
Mean distance from Earth 384,400 Km  (238,862 miles)
Minimum distance from Earth 356,410 Km  (221,469 miles)
Maximum distance from 406,697 Km  (252,717 miles)

A Survey Of The Planets: Mars


Mars infographic

Above graphic shows Mars's and Earth's orbits around the Sun.
Mars data

Notes: Evidence Of Abundant
Water In The Past, Spectacular Geological Features.

A Survey Of The Planets: Jupiter


Jupiter's asteroids

Jupiter data
Notes: Largest Planet, "Mini Solar System", Fast Rotation

Ganymede - a moon of Jupiter

Ganymede, Jupiter Moon

Moons with Atmospheres...

moons with atmospheres

A Survey Of The Planets: Saturn


Saturn data
Notes: Very Low Density.

Moon: Titan

atmosphere of Titan

A Survey Of The Planets: Uranus


Uranus data
Notes: Rotates On Its Side!

A Survey Of The Planets: Neptune


Neptune data

Notes: Fantastic Blue Color!

A Survey Of The Planets: Former Planet Pluto and the Plutinos

Pluto is no longer a planet
In the 1990s, many "asteroids" or "cometary nuclei" approaching 1/4 Pluto's size were discovered.
Pluto crosses Neptune's orbit, like an asteroid or a comet.
Pluto is only 1/2 the size of our own Moon. 
Seven planetary satellites are larger than Pluto.
Pluto has a highly inclined orbit.


Pluto data

Notes: "Oddball" Planetoid - Small Size For Location, Highly  Inclined Orbit.

The Plutinos - Pluto-like Planetoids

The Plutinos

The Solar System: Minor Bodies

Dwarf Planet Ceres

Dwarf Planet Ceres


an asteroid

location of asteroid belt

There is a lot of debris in the solar system, including meteoroids, asteroids and comets.
Asteroids:  A small planetary body composed mostly of rock or metals; most orbit in the asteroid belt between Mars and Jupiter.  All known asteroids have diameters less than 1,000 km.  Lower size limit often taken to be about 10 m.  Many unaltered since their formation - give clues to Solar System formation.

Trans-Neptunian Objects


Kuiper Belt and Oort Cloud

Kuiper Belt and Oort Cloud

Orcus Motion

Orcus motion

Outer Solar System

Meteoroids:  A small, extraterrestrial, solid body.  Term usually used for bodies smaller than a
  kilometer, and frequently millimeters, in size.  Objects destined to become meteors.
Comets:  An ice-rich planetesimal that can emit an observable gaseous halo when its ice is warmed by the Sun.  Most comets spend their time in the outer Solar System, making it difficult to distinguish them from normal asteroids.

Comparison of Planet Properties

Comparison of planet values

planet atmospheres