While many of the stars of Orion are among the brightest in the night sky, those in his shield are fainter. They are labeled with the Greek letter pi followed by numbers, from top to bottom. The brightest, pi-3, is similar to the Sun, and appears relatively bright only because it's just 26 light-years away. Orion is high in the south on February evenings.
Orion is one of the most beautiful constellations, and one of the easiest to find. Tonight, for example, it’s well up in the south at nightfall. Look for a tall box of four bright stars, with a slash of three stars across its middle.
But not all of Orion’s stars are quite so easy to find. Off the top right corner of the box, for example, is a curving lineup of six stars. Depending on whose diagrams you look at, it represents either a shield or a dead lion held in the hunter’s outstretched arm.
The stars are all designated with the Greek letter pi, and from north to south they’re numbered 1 to 6.
The brightest star in the shield is at its middle — Pi-3. It looks bright mainly because it’s close by — just 26 light-years away. In fact, a couple of hundred thousand years ago it was only about half as far as that, so it would have looked much brighter in Earth’s night sky. Pi-3 is similar to the Sun. It’s a bit bigger, brighter, and heavier than the Sun, but still a close match for our own star.
The stars that line up to the south of Pi-3 — Pi-4 and -5 — look slightly fainter, but they’re actually far more impressive. Each is well over a thousand light-years away. And each consists of at least two brilliant, massive stars — stars that make Pi-3 look like a flashlight shining next to a spotlight.
So look carefully for the hunter’s curving shield — a set of stars that’s truly “outside the box.”
Script by Damond Benningfield, Copyright 2011
For more skywatching tips, astronomy news, and much more, read StarDate magazine.