remember THREE (3) important astronomical lengths:
|
UNIT astronomical unit light year parsec |
ABBREV. AU ly pc |
DEFINITION avg. Earth - Sun dist. dist. light travels in 1 yr 1 AU subtends 1'' at 1 pc |
DISTANCE 156 x 106 km 1013 km 3.1 ly |
MISCELLANEOUS interplanetary length scale (3 x 105 km/s)x(3.15 x 107s) interstellar length scale |
Other distances used are variants of these three:
intragalactic scale is kpc (kilo- = 1000)
intergalactic scale is Mpc (mega- = 106)
FYI, everything you always wanted to know about metric prefixes:
You don't need to memorize these, just keep them in mind, and keep this
sheet!