question_answer 20)

A parsec is a convenient unit of length on the astronomical scale. It is the distance of an object that will show a parallax of 1" (second) of arc from opposite ends of a baseline equal to the distance from the earth to the sun. How much is parsec in terms of metres ? 

Answer:

One parsec is the distance at which an arc of length 1 AU makes an angle of 1 second of an arc. As                . Here                       of   Order of magnitude of parsec = 16.