Careful measurements of the parallaxes of stars reveal their distances

• Distances to the nearer stars can be determined by parallax, the apparent shift of a star against the background stars observed as the Earth moves along its orbit

• Parallax measurements made from orbit, above the blurring effects of the atmosphere, are much more accurate than those made with Earth-based telescopes

• Stellar parallaxes can only be measured for stars within a few hundred parsecs