Parsec
unit of length used in astronomy
A parsec is a unit of distance used in astronomy. It is the distance that light travels in 3.26 years, or just under 31 trillion kilometres (about 19 trillion miles).
| Parsec | |
|---|---|
 A parsec is the distance from the Sun to an astronomical object which has a parallax angle of one arcsecond. (the diagram is not to scale). | |
| General information | |
| Unit system | astronomical units |
| Unit of | length |
| Symbol | pc |
| Conversions | |
| 1 pc in ... | ... is equal to ... |
| SI units | 3.0857×1016 m |
| imperial & US units | 1.9174×1013 mi |
| other astronomical | 2.0626×105 AU |
| units | 3.26156 ly |
This is from the definition: a parsec is the distance from the Sun to an object which has a parallax angle of one arcsecond. The technique used in the calculation is trigonometry.
It takes 3.26 years for the light to come from a parsec away.
