To start with,what the hell is a parsec?

(it's a right triangle)

If the angle on the right is one arcsecond (1/3600 of a degree) then d is one parsec. If the angle is two arcseconds, then d is two parsecs. One parsec = (one AU)/sin(1 arcsecond) * sin(pi/2 - one arcsecond) Nevermind the relationship is only true when the angle is 1 arcsecond.

An astronomical unit is about ninety-three million miles. A parsec turns out to be around 3.26 lightyears. The parsec is the SI unit for astronomical distances so if you were planning to publish any astronomy research using light-years, tough luck.

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