表示天體間距離的單位
parsec n : a unit of astronomical length based on the distance from Earth at which stellar parallax is 1 second of arc; equivalent to 3.262 light years [syn: {secpar}]
PARSEC Extensible language with PL/I-like syntax, derived from PROTEUS. "PARSEC User's Manual", Bolt Beranek & Newman (Dec 1972).