1 megaparsec is a distance, equal to 1 million parsecs.
1 parsec is the distance of about 3.26 light years. It's the distance from us that an
object is if ... in six months, when the Earth moves from one side of its orbit to the
other side ... the object 1 parsec away appears to shift its position against the
'distant background' objects by 1 second = 1/3,600 of a degree.