Wrenched Orion—Part 1

I wrote recently about how the stars appear to be points of light scattered on a distant sphere above us. Our eye perceives this phenomenon as if the stars are all the same (great) distance from us, when, in fact, their distance varies. As a result, the constellations appear to us to be two-dimensional planar figures, when they are really three-dimensional objects.

The two-dimensional shape we perceive is a result of viewing a constellation from only one point in space: Earth. If we could move to another point in space, the constellation would appear very different.

Let's consider a simple example. Suppose we had an imaginary constellation of eight stars arranged in a way that they formed the corners of a perfect cube. Here's how a three-dimensional cube is represented:

From a particular point in space eight stars might look like this:

If we used our imaginations (as the ancients did, to create the constellations), we might connect the stars (dots) and see this: It's a cube!

But we might also imagine these eight stars (from this same location in space) to form an object like this:

or even this:

Depending on our culture, we could discern many different objects from these eight stars, depending on how we imagine them to be connected.

But it gets even more fascinating. Suppose we were able to travel vast distances through space. Our perspective of the “cubic” arrangement of these eight stars would change. What if we were to travel to a location where we viewed the cube face-on. It would look like this:

where each of the four stars is hiding another one behind it. 

How the civilizations at this location would perceive this “cubic” constellation, we can only guess. But it's a reminder that the constellations we see have their three-dimensional stars arranged in a pattern that is unique to us, at our location in space.

More on Orion next time...

Awesome Orion

December and January usher in the most brilliant constellation in the heavens: Orion the Great Hunter, AKA the Celestial Warrior. It is also low in the southeastern sky, so every person on Earth—northern or southern hemisphere—is able to gaze upon this most sparkling and recognizable constellation. Some people might argue that the Big Dipper is the most conspicuous constellation. Maybe so, but the Dipper doesn’t stop me in my tracks quite like Orion does when I step outside on a cold, clear winter's night and become dazzled every time I see it.

Most of the celestial constellations bring to mind quite different images in different cultures and different eras, but Orion has consistently been interpreted as a warrior boldly flashing his shield, if not some other similar mythical heroic figure. There is no constellation that has brighter stars than Orion. It contains two of the seven most luminous stars in the sky, and the heaven’s brightest star of all—Sirius—lies close by.

Orion was prominent in the minds of the ancients. The Egyptians considered it to be the incarnation of their great god of the afterworld, Osiris. In the Bible’s Book of Job, when God berates Job for his lack of humility, he says, “Can you bind the chains of the Pleiades or loose Orion’s belt?” (The Pleiades is another spectacular winter sight right next to Orion: an open cluster of young stars that is also known as the Seven Sisters.)

When observing Orion with the naked eye, one notes some 15-20 stars that outline the Great Hunter’s form. A detailed examination with a good backyard telescope will reveal over 200 stars—most of which are double and multiple suns. (Most stars we can see are not single bodies like our sun, but are double systems, and even multiple stars.)

The two brightest stars in Orion are Betelgeuse (BET-el-jews) and Rigel (RYE-jel). Betelgeuse is the largest star we can see with the naked eye. It’s a red giant and is one of the few stars one can look at and tell that it’s not really white, but an orangish-red. It is more than 600 times the size of our sun and some 10,000 times brighter. It could go supernova at any moment. When it does (keep an eye out!), it will be as bright as the full moon and even visible in the daytime. But it might also might not happen for another 1,000 years. Nearby Rigel is no dim bulb—being 50 times the size of our sun. Betelgeuse can be found in Orion’s shoulder and Rigel (meaning “foot of Orion”) at one of his feet.

Orion’s belt is the real eye catcher for me. It is made up of three identical brilliant blue stars, perfectly aligned and equally spaced. Some 1500 years ago the Arabs were the world’s premier astronomers and many of the heaven’s most notable stars carry Arab names. Orion’s belt Arabic names are Mintaka (“the belt”), Alnilam (“the belt of pearls”), and Alnitak (“the girdle”).

The most special sight of all in the Orion constellation is the “fuzzy star” in the middle of the sword that hangs from his belt. It’s not a star at all, but a gorgeous nebula; AKA the Great Nebula in Orion. It’s a massive cloud of gas and dust that is 20 times the size of our solar system. Denser portions of the cloud are in the process of collapsing and forming new stars—some just babies, a mere few million years old!

To the naked eye under a dark sky, the Orion nebula can be seen not as a point of light (like all stars), but a wee bit of a blurry blob. With a pair of binoculars the nebula appears as a tiny white cloud, but in time exposures from large telescopes, it shows its real colors: a swirl of red, blue, and violet.

I find it fascinating to come to know some of the specifics details and origins of Orion the Great Hunter and his star-birthing nebulous sword, but it’s not at all requisite to be cognizant of these facts, in order to gaze upon this constellation on a winter’s night and become captivated by its beauty. One needn’t know anything about Orion to be thrilled by this stellar sight.

How Many Sisters?

There is no better time for gazing at the heavens than in mid winter. Directly overhead, about 9 pm, are three bright star clusters and constellations: Orion, the Hyades, and the Pleiades. Part of the show are the super stars Sirius and Betelgeuse.

Orion the Hunter holds up his shield, warding off Taurus the Bull (containing the Hyades star cluster), who in turn defends the Seven Sisters of the Pleiades. Following close on Orion’s heels is Canis Major (Great Dog), whose bright nose is Sirius, the brightest star in our sky. Inset into Orion’s shoulder is giant red Betelgeuse. Each one of these objects is notable on its own. Together they are a light show that surpasses Las Vegas.

The Hyades is a group of a half dozen stars shaped like a V. It’s a true cluster—in that all of its stars are related. (In contrast, the stars of the Big Dipper, although they appear to be grouped, are disconnected and at vast distances from one another. They just appear to be aligned, from our vantage point.)

Orion contains some of the brightest stars in the northern hemisphere. His belt is three vivid blue stars that grab your eye. The shoulder star Betelgeuse is ancient; it's over 50,000 times brighter than our Sun and 500 times its size. If it were put where our Sun is, it would engulf the Earth and Mars.

Hanging from Orion’s dazzling belt is a sword of three stars. But the middle one is not a star; it’s the Orion Nebula—an immense cloud of interstellar gas, which is the blown-out leftovers of an ancient supernova. Today the clumps of gas are coalescing into new stars It’s a hot and active star nursery.

Yipping at Orion is Canis Major. The dog’s nose, Sirius, is the brightest star in our sky—24 times brighter than our Sun. Although Sirius appears to be an intense point of light to the naked eye, it is really a double (binary) star. Half the stars in our Milky Way are binary stars, but most can’t be separated with the naked eye. The Egyptians cast Sirius as one of their key stars. Its appearance each year heralded the flooding of the Nile.

Finally there’s the Pleiades. Pretty little Pleiades. It has a mystical, magical quality to it. It resembles a miniature teapot; sort of like a tiny Dipper. Its alternative name—the Seven Sisters—is Subaru in Japanese. Take a look at that car’s logo and get an idea of how the cluster appears.

When I look at the Pleiades I see six stars, not seven. So where does the name Seven Sisters come from? Greek mythology describes the seven daughters of Atlas being turned into stars by Zeus. So Pleiades got its label.

Some people have claimed seeing as many as 16 stars in the Pleiades cluster. I suspect it’s a little like a macho game of “Mine’s bigger than yours.” He who sees more stars is the winner. But there’s a way to beat all the braggers. Take up a pair of binoculars and you can see dozens of stars in Pleiades. Big telescopes register as many as 3000 young stars in the cluster—all a brilliant blue.

I can’t stand outside very long on mid winter nights, looking up at these stellar favorites of mine. The cold sinks too deep into my old bones. But I’m always stopped dead in my tracks by the sight of them, as I cross the yard. It’s delight that never tires.