solar system

Solar System

conjunctionThe Astronomical Unit
  Bode's Rule
What Is A Planet?
Comparison of Planet Properties

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


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?

  e.g., Is Pluto a planet?

       In the 1990s, many "asteroids" or "cometary nuclei" approaching 1/4 Pluto's size were
       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.

  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:

  Gravitational Constant: G = 6.67 × 10-11 N·m2/kg2
  Astronomical Unit:   1 AU = 1.49 × 1011 m
  Velocity Of Light:  c = 3.00 × 106 m/s
  Mass Of Sun:    M¤ = 2.00 × 1030 kg
  Radius Of Sun:   R¤ = 6.96 × 108 m
  Mass of Earth:   MÅ = 5.98 × 1024 kg
  Radius Of Earth:   RÅ = 6.38 × 106 m

A Survey Of The Planets: Mercury

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



A Survey Of The Planets: Venus

Venus data

Venus image

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

                          A Survey Of The Planets: Earth

Earth dataEarth image

Notes: Liquid Water In
  Abundance, Life!

Earth's Moon

Earth's moon

Moon Data:
                                      3475.6 Km  (2159.7 miles)
                Rotational period
                                      27.322 days
                Sidereal revolution period
                                      27.322 days
                Sinodic revolution period
                Mass (Earth=1)
                Volume (Earth=1)
                Gravity (Earth=1)
                Mean distance from Earth
                                      384,400 Km  (238,862 miles)
                Minimum distance from
                                      356,410 Km  (221,469 miles)
                Maximum distance from
                                      406,697 Km  (252,717 miles)

A Survey Of The Planets: Mars

Mars data

Mars image

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


A Survey Of The Planets: Jupiter

Jupiter data

Notes: Largest Planet, "Mini
  Solar System", Fast Rotation.


A Survey Of The Planets: Saturn

Saturn data

Saturn image

Notes: Very Low Density.




A Survey Of The Planets: Uranus

Uranus data

Uranus image

Notes: Rotates On Its Side!




 A Survey Of The Planets: Neptune

Neptune data

Neptune image

Notes: Fantastic Blue




A Survey Of The Planets: Pluto

Pluto data

Pluto image

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



The Solar System: Minor Bodies
an asteroidThere 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.

  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

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