Parsec
An astronomical unit of distance equal to the distance at which a star exhibits a trigonometric parallax angle of exactly one arcsecond (1″).
Governing formula
1 pc = 1 AU / tan(1″) ≈ 3.2616 ly ≈ 3.0857 × 10¹⁶ m
SI unit
Parsecs (pc, kpc, Mpc)
In depth
Short for 'Parallax of one Arcsecond'. Derived from Earth's orbital baseline (1 AU). Kiloparsecs (kpc) measure galaxy dimensions; Megaparsecs (Mpc) measure intergalactic cosmic distances.
Examples in the real world
The center of the Milky Way galaxy located approximately 8.2 kiloparsecs (~27,000 light-years) from Earth.