all planets (terrestrial &
Jovian) orbit Sun counterclockwise
system extends to ~ 10,000 AU
(Oort cloud)
most orbits ~ circular & close to ecliptic
plane
planetary motions follow Keplers
laws
1 AU
= 1.5 x 1013 cm (or 149,597,870 km)
solar system formed 4.6 Byrs ago in a
rotating,
circumstellar disk of
gas and dust
follow evolution by observing
sources at different epochs