When Orion strides into the skyscape each year I feel like I’m greeting an old friend, and I’m reminded of the first time I ever saw him. Standing on the sidewalk in front of my childhood home in Oregon, my mom showed me how to chain together the stars that outlined the hunter’s belt and sword. This was the first constellation I learned, and it still produces a sense of awe that we are so very, very small in the galactic scheme of things. Although daunting, I also find it weirdly freeing to try to wrap my brain around things completely un-Earthbound; the nature of the universe is so vast it swallows my worldly worries whole.
Orion is a great starter constellation because he’s easy to find and is composed of a number of very bright stars of varying colors, plus a famous nebula (star nursery). Rising in the east about 8 pm, he can be seen clearly overhead by 10 pm, and sticks around from November through April. Orion also acts as a helpful guide from which you can identify other surrounding stars and constellations.
Look for three equally spaced stars that form Orion’s belt, then three stars “hanging” from the left of the belt that form his sword (one of these stars is actually the nebula, but I’ll get to that in a minute). On very clear nights you can see the three stars that make up his comparatively tiny head, an arc of stars to the right that form a shield, and his raised right arm (on our left) holding a club.
The most easily identifiable star in Orion is Betelgeuse, which marks his right shoulder (to our left). One of the brightest stars in the winter sky, it is a red giant. Aptly named, it is both reddish in color and large beyond our ability to even measure accurately (its ever-changing surface gases make it difficult to pinpoint its distance from Earth, and therefore difficult to size). Notice differences in the colors of stars, which indicate varying surface temperatures.
The inset arrow points to red giant Betelgeuse. (Photo courtesy of NASA.)
Solar System Ambassador and McMurray Middle School science teacher Evan Justin, a veteran amateur astronomer, helped me get a grasp on the big B. Betelgeuse is 667 Earth suns across, about 20 of our sun’s mass, and about 1.6 billion of our suns (by volume) could tuck neatly into its magnificence.
“It’s red because it has ballooned so much it’s losing energy to space faster, so it has a lower temperature,” Justin explained. “When a star uses up its primary fuel—hydrogen— it starts fusing less energy-efficient atoms together, so multiple sorts of fusion are going on in its core, and all that surface area means the star gets cooler.”
Justin said it’s like putting a wok on the hot burner of an electric stove. The heat spreads out fairly evenly across the wok’s surface. Now put a wok as big as your house on the hot burner and the wok will not be as hot at its edges. Since Betelgeuse’s surface area is so enormous, the energy coming from its core is widely spread out, making it cooler overall. (Okay, relatively cooler—its surface temperature is “only” about 5,000 degrees F.)
One day within the next 100,000 years or so, scientists say Betelgeuse will go supernova, meaning it will eat up all the energy at its core and implode.
“That concussive impact of the core causes a portion of it to be thrust out into space,” Justin says. “A supernova is the first step of a new solar system—it’s a real phoenix kind of thing.” (This implosion could have already happened, but because Betelgeuse is 640 light years away it will take 640 years for us to see it from Earth.) When Betelgeuse goes supernova, it will be so bright as to be visible during the day as a “day star.” In A.D. 185, the Crab Nebula’s supernova event was recorded on tortoise shells by the Chinese—it was visible for about a week as a bright daytime star.
Compare Betelgeuse with blue-white Rigel, Orion’s left foot (on our right) with a surface temperature upwards of 23,000 degrees F. (For contrast, our sun is a yellow star with a surface temperature around 11,000 degrees F.) Rigel is a supergiant—the sixth brightest star in the sky, it is 57,000 times brighter than our sun.
Orion is also known for containing a remarkable deep-sky object. Can you see how the middle of his sword is a little fuzzy? That’s because it’s not a star, but the Great Orion Nebula: thousands of lights years across of exploded stars.
The Great Orion Nebula. (Photo courtesy of NASA.)
“It challenges our theories to have collections of nebulae this large,” Justin said. “Hundreds of solar systems are being born there—he has a stellar nursery in the middle of his belt.”
This is where binoculars come in handy. Justin explains that binocular lenses act as funnels, concentrating light into your eyes and allowing your color sensors to transmit more detail to your brain. He recommends a wide lens with low magnification (greater than 20 mm and up to 120 mm). “Wide lenses allow you to see the sky through the eyes of a super eagle,” he says.
Through Justin’s telescope, the Great Orion Nebula appears delicate and diaphanous in 3D. “You can see different colors; it’s like an amoeba with definite texture and depth,” he says.
If you’re interested in taking a closer look at Orion, and you’d like to see the nebula in 3D, Justin will bring out his telescope for free star parties. Call him or email him, 206-919-8553 or ejustin@vashonsd.org, to set up a time for your family or small group (weekends and school breaks are best).
Whatever you do, bundle up and look up. Winter is prime time for stargazing because it gets dark earlier and more moisture content in the lower atmosphere makes the sky clearer. This time of year Earth is facing toward the outer edge of the Milky Way, where there are fewer stars. (In the summer we face the brighter center of the galaxy, with billions of stars creating a lighted haze). Islanders also benefit from darker skies because we lack the constant glow of city light pollution.
To learn more about the night sky, visit the Vashon Library’s science section. The Kids Book of the Night Sky and the National Geographic Backyard Guide to the Night Sky are good places to start. And The Starlore Handbook spins yarns about the myths and symbols associated with each constellation. You can carry a star map in your pocket with the cell-phone app Star Walk, which provides a real-time picture of what you’re looking at in the night sky, and can direct you to objects of interest.
There are hundreds of websites that are also helpful; a few of Justin’s favorites are
Sky and Telescope magazine
NASA SkyView—virtual telescope
Munich Astro Archive Constellations
See what you can discover tonight…