On a clear winter night in the Northern Hemisphere, face south and look at the sky. You will see one of the brightest and most beautiful of the constellations: Orion (pronounced O'Ryan). It is one of the most easily recognized, best known and widely loved constellations. It is also one of the few star groups that resembles its eponym, although even here a bit of imagination helps. Three fairly bright equi-distant stars in a straight line form his belt; just below, a mass of tiny, shimmering stars are his jeweled dagger. Bright stars make his shoulder, head, knee, and if you are fortunate enough to be around very dark skies, you will also see his upraised arm holding a lion's skin, traced in fairly dim stars that might not be visible from the light-polluted skies above almost all modern cities.
At the opposite end of the sky is Scorpius, one constellation that actually looks like what it represents - a huge scorpion, complete with hooked tail, like an inverted question mark, and a string of stars crossing near the head. These could be legs, claws, or whatever else celestial scorpions might have connected to their neckbones.
One of the countless legends of Orion has it that Diana loved Orion. Her brother, Apollo, was upset over her affair with a mortal, and contrived to have him bitten fatally by Scorpius. Diana's efforts to prevent Orion's death could not overcome her brother's greater power. (Other versions of the myth feature Juno, upset by Orion's boasting, sending Scorpius to do the hit job). But evidently Diana had a few powers of her own. At least, she was able to pull enough strings to have Orion and Scorpius placed at opposite ends of the sky. In the evenings, Scorpius is only visible in summer, Orion in winter. As Orion sets in the west, Scorpius rises in the east. Separated by 180° of sky, Orion will be safe throughout eternity, and he need never fear a bite from Scorpius again.
The constellations of Orion and Scorpius are favorite parts of the sky, not only because they contain bright and beautiful stars, but because things of scientific interest are happening there. For example, the bright, reddish star Betelguese, represents Orion's shoulder. It is one of the largest known stars. We would be in sad shape if somehow Betelguese were to be transported to our solar system, in the position of the sun, for its outer limits would extend about as far as the orbit of Mars. We would not be 93 million miles from our parent star as we are now; the earth's orbit would lie some 30 - 40 million miles beneath the surface of that huge star! Coincidentally, a half-sky away, Scorpius contains another red giant Antares, almost as large as Betelgeuse. Its name means "rival of Ares," the Greek equivalent of Mars.
The bright, bluish star at Orion's knee is Rigel (pronounced "Ree-jell"). It is one of the hottest, most brilliant stars known. Only its great distance, approximately 900 light years, keeps Rigel from dominating our night sky. This star is more than 57,000 times brighter than our sun. If you find sunburn painful, be thankful it's not Rigel-burn!
Near Orion, and to the east, is Sirius (pronounced "Ser-ious"), the brightest star in our night heavens. It looks much brighter to us than Rigel because it is much closer. Sirius is "only" 12 light years away, one of our nearest stellar neighbors.
Sirius is a double star. That means it has a companion star, both orbiting around a common point between them, but its companion is much smaller, fainter, and so close to Sirius that it is easily lost in the glare of its brighter companion, thus very difficult to see - somewhat like trying to read the license plate on an approaching car blinding you with its high beams. But it is an extremely interesting star, being a so-called white dwarf. It is known to be so dense that a single teaspoonful of its material would weight tons!
This is not because it is made of special stuff, but rather, because its gases, familiar enough on earth, are in an unusual physical state. Atoms and molecules as we know them are, like our solar system, made up mostly of empty space. But in white dwarfs the gases are under such intense compression that the particles are jammed together with little space between them. This is a very unstable state; if a teaspoonful of its material could be brought to earth, where the pressure is so much lower, then zing! The molecules would immediately spring out to more normal states. I wouldn't want to be standing very close when this happened. It might be like standing next to a few hydrogen bombs!
Within the jeweled dagger lies the Orion Nebula, an immense cloud of gas (mostly hydrogen). It has been called a "stellar nursery", because many young stars have formed there; others may still be forming. Most of these "young" stars are only a few million years old (for comparison, our sun is approximately 5 - 10 billion years old). Some of these stars may even be as young as 300,000 years. Of course, the term "young" is relative. To my children, even I am old!
It is believed that our own sun and solar system once formed from a cloud of gas very similar to this one. Ergo, the more we learn about this object, the more we are likely to learn about our own history.
* Appeared in The Kenwood Press February 1, 1998
© 1998, by Nathan B. Miron, Ph.D.