PARALLAXES AND PARSECS



motion: TOC for Knowledge Concepts, Exercises, and Solutions

One useful mathematical relation to remember is the inverse relationship between distance and parallactic angle: 1 ????????(angle in arcseconds) = --------------------- (distance in parsecs) So, for example, if the parallax of a distant object, measured using Earth's orbit as a baseline: is 1 arcsecond, then the distance is 1 parsec, is 2 arcseconds, " " 1/2 parsec, is 3 arcseconds, " " 1/3 parsec, is 1/2 arcsecond, " " 2 parsecs, is 1/3 arcsecond, " " 3 parsecs, is 1/9 arcsecond, " " 9 parsecs, and so on. This relationship is merely a coincidence of how a parsec is defined.

