WHAT IS A PARSEC?
A parsec is a unit of distance that’s often used by astronomers as an alternative to the light year, just as kilometres can be used as an alternative to miles. One parsec is approximately 3.26 light years, or almost 19 trillion miles. To that extent, it’s easy enough to answer the question. But understanding just how a parsec is defined, and why it’s used, is a little harder.