Thursday, October 21, 2010

Winter's in the Southern Sky

6:50 a.m. Already the starlight from our nearby planetary space heater is washing out the light of more distant stellar fires. Practice these last few years is now the only means I have of picking out old friends in the bluing sky. But I can see them now and know that they'll be moving unseen across the sky all morning as we go on with our daily activities.

I count, at first, sixteen or seventeen visible stars in the great Winter Hexagon this morning. Soon the coming Sun fades out all but the brightest, the eight stars that give this configuration its name and define its shape. Remarkable to me has been this new lesson that the darker the night, the more difficult it is to find stars, or rather, to pick out a particular star. Just as it's easier to find a familiar face in a small group than in a crowd, getting to know the stars in moonlight or dawn trains my eye and improves my chances of finding them in darker skies.

As the World Turns
To compound the challenge, my spatial sense of what happens in the sky during daylight or when I'm asleep is developing only slowly. I have a real problem visualizing the whole rotation business. For example, last night at bedtime, the eastern sky looked something like this. No problem with Cassiopeia, she's circumpolar and always a good guide. As my eyes adjusted, I was able to pick out the fainter stars of Perseus just below her. Huh?

But then what in the universe is this next bright star, just above the horizon? And, off to its right, the orange one just cresting the hogback? Nothing looked right, despite the faint cluster above "orange" that could only be... the Pleiades. (Somehow it was easier to see them than to make out the closer stars that would have instantly told me who "orange" was!)

I know you're all ahead of me here, and I should know, no matter what, that if the "handle" of the Pleiades (which looks a little like a miniature Big Dipper) points to an orange star, that star has got to be... Aldebaran!

And that means Star-So-Bright must be Capella, in the constellation Auriga. My friendly face, the Winter Hexagon, is just peeking above the horizon and is somewhat disoriented (or, clearly, I am!). It's these puzzles that make figuring out the night sky so much fun.

Back to the Hexagon
But this morning the Big Sky Geometer is "right" side up, even if only a few of its stars remain visible in the dawn. The discovery of the Winter Hexagon* was, for me, a great stride forward in placing myself, finding my way around, in starry skies. Let's take a quick look at what else is out there.

*Introduced to me by astronomer Aileen O'Donoghue, in her lovely autobiography, The Sky is Not a Ceiling.

If we can just darken the sky a bit, and we accomplish this by getting up a half-hour earlier, we look for the Winter Hexagon and see more clearly its components—the six constellations whose brightest stars outline the figure. Each constellation has, of course, many more stars than I can show here.

Castor and Pollux, the twins of Gemini, dangle their feet toward the center of the hexagon. Capella, the She-goat, is joined now by her kids and several other stars. Continuing clockwise, we meet Aldebaran, now accompanied by the Hyades, a true open cluster of stars so near to us (150 light-years) that it spreads into a bigger area than the tightly bound (and more distant at 400 light-years) Pleiades.

Then of course, Orion—everyone's favorite, always recognizable—strides across the celestial equator and dominates winter skies here in the Northern Hemisphere. Innumerable stars, globular clusters, and several nebulae, especially in his "belt" and "sword," provide a lot of entertainment for observers. At his feet, behind my neighbors' house, lies Lepus the Hare, and behind Orion trails his faithful dog, Canis Major with bright Sirius, the brightest star in the winter sky. Around the final corner, Procyon (in Canis minor, another dog) completes the hexagon.

In a few more hours, I'll try to picture the invisible Winter Hexagon hanging above the western horizon, rotated another click and preparing to set. That's the exact position in which I found our summer sky-map, the Summer Triangle (see Watcher's excellent post for more on this one) several dark nights ago.

That's the framework, but even with practice I can't help being startled when I go out early to wave The Husband off to work, as I did one day recently, and find a dark sky so sprinkled with stars it literally leaves me breathless. Then all the names I've been struggling to learn leave me completely and only wonder is left behind.


Dave Coulter said...

Nice post. I'll bet you guys have nice clear skies out there!

Sally said...

Well, not the last few days, but I'm keeping my fingers crossed for more good viewing!

Thanks for stopping by, Dave!