If there is one constellation that most people can identify, it’s Orion — the hunter. He strides boldly across the night sky, a club in one hand, a shield in the other. He is strikingly visible on these cold winter evenings. Step outside around 8 p.m. and look a little south of east. (He rises earlier as winter goes on.) You can’t miss him; look for the three stars of his belt.
Orion is not just a spectacular constellation. Within his boundaries you’ll find several gems of the night sky including two of the brightest stars we have. Look for blue-white Rigel marking his left knee (or foot, according to some depictions in which he’s kneeling). It is 860 light-years away and is actually a quadruple star system: four stars that orbit each other in complex ways. Rigel is the biggest and brightest of the four. Its name comes to us from Arab astronomers of the Middle Ages. They knew Orion as Jauzah and this star as Rijl Jauzah al Yusra, the left leg of Jauzah.
Next, look to Orion’s right shoulder. There you’ll see red Betelgeuse. Again, we have Arab astronomers to thank for this funny sounding name, which you may pronounce “beetle-juice” or, as I prefer, “betel-geis.” However you say it, it’s a fascinating star. Betelgeuse is a supergiant that has almost exhausted its nuclear fuel and is nearing the end of its life. Stars like this expand to enormous size as their surfaces cool (red indicates a cooler surface temperature than blue-white Rigel, though at 5,840° F Betelgeuse is still quite hot). When red supergiants finally consume all the fuel at their cores, they collapse under the weight of their own gravity, exploding in a supernova.
Astronomers predict that Betelgeuse will explode within the next 140,000 years — a long time for humans to think about, but an eyeblink of cosmic time. It could be tonight or a very long time from now. When Betelgeuse blows, it will outshine everything else in the night sky for months and even be visible in the daytime. But don’t worry, it won’t harm us. We’re safe here, 500 light-years away.
Now move on to the sword that hangs from Orion’s belt. Look for three stars that form a line diagonally down from the belt. Now look closer. The middle star may look fuzzy or hazy. That’s because it’s not a star but a nebula, a faintly glowing cloud of hydrogen gas and dust 24 light-years across. The Orion Nebula (also known as Messier 42 or simply M42) is a stellar nursery, a place where new stars form. Their light illuminates the cloud of raw materials from which they grew. Our Sun was born in a similar nebula, long ago dissipated by the fierce radiation of the very stars it spawned. If you have binoculars, steady them on a railing or tree branch and aim them at M42. You’ll see a small faint blueish cloud with tiny stars embedded in it. These are newly formed stars within the nebula.
I enjoy pointing out M42 to people, as it’s one of only a handful of deep-sky objects visible to the unaided eye. Deep-sky objects are generally anything in the night sky that isn’t a planet, moon, comet, asteroid, or star. These include galaxies and nebulae of different types. Another naked-eye deep-sky object is the Andromeda Galaxy, which I wrote about in the Sept. 28, 2023 issue.
Most cultures past and present recognize the constellation Orion in one way or another. He has been a shepherd, a deer, a dancer, a harpooneer, a hand, a god, and, to the ancient Greeks and others, a hunter. The myth of Orion has several variations, too. As in most Greek myths, things end badly for the mortals involved, including Orion. In some versions, Orion was a horrible human being, guilty of terrible deeds; but all agreed he was an excellent hunter. So, Zeus placed him in the night sky, forever on the hunt.
As the glittering Summer Triangle marks summer in the northern hemisphere, so Orion denotes winter and the constant revolution of both seasons and stars. I encourage you to brave the cold and venture outside. Whatever you see in Orion (I like the cosmic dancer of the ancient Hindus), his stars are bright and colorful and M42 is a deep look back to our own origins, 4.5 billion years ago. Besides all that, winter nights, when free of clouds, are wonderful for stargazing. Clear skies!
