Reference table
Astronomical distances
Astronomical unit, light-year and parsec all describe a length, just in very different steps. The table shows one unit of each in all the others.
| 1 unit | Kilometres | Astronomical units | Light-years | Parsecs | Light-seconds |
|---|---|---|---|---|---|
| 1 ls | 299,792.458 km | 0.00200399 AE | 3.168809e-8 Lj | 9.715612e-9 pc | 1 ls |
| 1 AE | 149,597,870.69999999 km | 1 AE | 0.00001581 Lj | 0.00000485 pc | 499.00478384 ls |
| 1 Lj | 9,460,730,472,580.80078125 km | 63,241.07708427 AE | 1 Lj | 0.30660139 pc | 31,557,600 ls |
| 1 pc | 30,856,775,814,913.671875 km | 206,264.8062471 AE | 3.26156378 Lj | 1 pc | 102,927,125.05433899 ls |
The light-year is the distance light travels in vacuum in one Julian year (365.25 days), not a measure of time. The parsec is the distance at which the Earth's orbital radius subtends one arcsecond; it is about 3.26 light-years. All three are defined by exact constants rather than measurements.