| Term: | Parsec |
| Definition: |
A basic unit of astronomical distances, corresponding to a trigonometric parallax of one second of arc. In other words, it is the distance at which one astronomical unit (the mean radius of the Earth's orbit) subtends an angle of 1 arcsecond. 1 pc = 3.2616 light-years = 206,265 astronomical units = 30.857 x 10^12 km. |