Hey, sky fans! Happy Friday! Another week down, and, just like that, it’s nearly mid-September. I can already see some leaves on the driveways across the street.
You know, when I was out looking for the Moon, Mars, and Saturn the other night, I got a look at the Summer Triangle, which is very high overhead these days. For the last couple of months, it’s been climbing higher through the eastern skies. Now, it’s going straight over the top of the ol’ sky dome (not to be confused with the SkyDome, sports fans), on its way to the western horizon before we know it.
Last month, while I was traveling in New Hampshire with my family, I snapped this photo.
I had to do some trickery with a tripod and a fence in order to get it to arc backward enough to get the whole thing in. “Why didn’t you just turn the camera around and shoot it from the other direction?” my daughter asked as we stared and talked.
Anyhow, the sky was wonderful there, deep and dark. There were so many stars that it was disorienting, like being lost in a town you know well. The stars that seem like isolated islands of light when I’m home, like lone campfires seen from the window of a cross-country overnight flight, blended in among the rest. Fortunately, the Milky Way, which you can barely make out cutting diagonally from the upper right to the lower left of this photo, was there to help. There are so few places left, and the stats keep getting worse, where the Milky Way is visible, that any time I can see it fixes even the most terrible day.
The Summer Triangle isn’t an actual constellation; it’s an asterism, a distinct and recognizable but informal group of stars. Its stars are the brightest in three constellations: Deneb is in Cygnus, the swan; Altair is in Aquila, the eagle; and Vega, which is the fifth brightest star in the entire night sky, is in Lyra, the lyre or harp. I love the idea of summer nights spent with those two birds soaring overhead into the night. They’re part of what makes summer summer to me.
These stars are completely unrelated to each other or any other stars in the night sky. In fact, most stars you can see with the naked eye aren’t related to each other at all. Asterisms like the Summer Triangle, and constellations typically aren’t related to each other. It’s only because of our point of view on them, because they’re so bright, and because of our amazing skill at finding patterns that they look like they’re together. A well-known exception to this is the Big Dipper, whose stars are traveling together.
Also, because of our view of the sky, all of the stars in it just appear to be out there, scattered across a giant black sheet. Unless you see an airplane or a particularly bright satellite (ISS, I’m looking at you), or the Moon, everything just seems to be… there. If you were able to step away from Earth far enough to start to see some depth, get a different perspective on these stars, you’d see things change. In fact, if you were able to get far enough away, you’d see the Summer Triangle, not as a triangle at all, but as more of a line of three bright stars among many others, extending away from Earth, farther and farther toward the deepest parts of the galaxy.
Altair and Vega are 17 and 25 light years away, so around 100 trillion and 150 trillion miles at 6 trillion to the light year. That’s pretty close, though, right across town, cosmically speaking.
Deneb though, is somewhere between about 1500 and 2500 light years away! That’s…. like… 16…seven… really far! In fact, it’s one of those most distant stars you can see with the naked eye, really pushing the boundaries of how far your eye can see without help. Imagine, though, the Deneb you’re seeing tonight, the light you’ll be see, is the Deneb that existed in 6th century, or maybe a thousand years before that. Those photons spent all that time traveling across unspeakable emptiness unhindered, unblocked, and unabsorbed the whole way, until it got to your eye. I don’t know about you, but it’s amazing and calming to think of how remote the chances of your eye and that photon meeting are. Yet, they did.
But these bright stars aren’t the only things there. We know lots about these famous stars. Vega is one of the most studied stars in the sky. Altair is in one of my favorite books from when I was a kid. For a minute, let’s think about something different.
Consider the other ones, the unlabeled ones, the dimmer ones. Consider the anonymous stars. They’re all listed and cataloged, but most of them aren’t named. I love to look up and think about what’s out there, and think about not just what we know, but also what we don’t, and imagine what we’ll learn one day. For the most part, we don’t know anything about these stars. Astronomers, who, thankfully, spend their lives working on these things, sure. You and me, though?
What’s going on at HIP 98526*, which you can see, faintly, just up and to the left of Altair? Who knows? What about further? The more distant stars? The ones you need a telescope to see? The ones beyond the ones you need a telescope to see? What about the ones that are tens of thousands of light years away? They’re so far that we can’t even see them as stars; they blend together into the long band of brightness that we see as the Milky Way.
There are so many stars, so much to see, and so many incredible things to learn. Is tonight the night. I know I’ll be outside. Thanks, as always, for stopping by.
Clear skies, and have a great weekend, everyone!
* HIP 98526 happens to be only about 600 LY away, a third as far as Deneb, yet we can barely see it. Deneb is really luminous; it puts out a lot of light.