Parsec

The Parsec is a unit of length that is used when measuring large distances and/or objects in the context of space. Equivalent to 3.262 lightyears, the formula for a parsec arises from the relationship between an Astronomical Unit (AU) and an arc second. Said formula goes as follows:

$1 Pc = \frac{1 AU}{1 arc second}$

Expressing the arc second in the standard unit of radians, we get:

$1 Pc = \frac{1 AU}{\frac{1}{206265 rad}}$

This also means that a Parsec is equal to 206,265 AU. This relationship to the arc second is also where the Parsec gets its other name, parallax second.

To put everything above in perspective, if we were to use meters, we would see that a Parsec is equal to 3.086×10¹⁶ m.