Q&A: General Astronomy and Space Science
Why is that for 1 parsec such an odd value has been
chosen(i.e. 3.26 light years)? For other measurement units we
generally have values such as 10,100 or something like
The use of a parsec as the unit of length stems from the way
in which astronomers measure the distance to nearby stars.
One parsec is the distance at which the parallax of a star is
equal to one arc second.
As the Earth orbits the Sun, the nearer stars appear to
shift against the background of distant stars. To see how
this works, hold your finger up at arm's length in front of
an object about ten feet away's length The parallax
of a star is apparent shift of its position due to the orbit
of the Earth around the Sun.