Seeing Distance

Looking at the night sky full of stars, it is nearly impossible to gauge the distance to stars. Some of the dimmest stars, invisible to the naked eye, are our next-door neighbors, while some of the brightest stars in the sky reside far beyond our own neighborhood.

In the example below, we have selected Pi 3 Orionis, which is one of the closer, easily visible stars in the familiar constellation, Orion. In Hood Tools, we select "Sky Map" and click on the patch of sky where we find "Orion including Rigel and Betelgeuse."

Sky Map closeup of Orion with Pi 3 Orionis selected as the "Focus" star. The Sky as We Know It The Sky Map closeup shows Orion as we usually see it. This is the natural, or "brightness," view. The two brightest stars, Betelgeuse in the shoulder, and Rigel at the foot, help make Orion one of the most recognizeable constellations in the sky. As you will soon see, without prior knowledge, we can only guess at the distances to each individual star.

The Sky Map closeup, Distance mode reveals visually how far each star is. Distance Mode Clicking on "Distance" viewing mode reveals many close stars which are invisible to the naked eye (mostly red dwarfs), and it shows that some of the brighter stars are the most distant. Betelgeuse (Alpha Orionis, the brightest) shows only as a dot. Rigel, (Beta Orionis, second brightest), is only a little closer, but still very remote. Pi 3 Orionis, though far dimmer than the more recognizeable stars of Orion, stands far closer. In fact, Pi 3 Orionis is one of the Solar neighborhood stars.