Summer is almost over.
It would be awfully wrong of me to end the summer without discussing the last star of the Summer Triangle. Makes sense, right?
Ahhhh: Altair. What could I say about my stellar friend in the sky? Turns out not much of anything! Off the top of my head I know a few facts about Altair, but that’s about it. Altair happens to be one of them fancy stars I use to navigate the sky with. Vega is another one of them fancy stars.
Altair is pretty easy to find, especially if you are able to locate Deneb and Vega. From my location (EST), if I were to go outside around dusk, all I have to do is crank my head to the sky—The Summer Triangle will already be well above the horizon around 7:30-8:00pm. Make sure you consider your specific latitude (Altair rises at various times, depending on location).
Altair…what is there to say about Altair? I’ll give you the tale of the tape:
Constellation: Aquila (eagle)
Distance: About 16.7 Light Years
Mass: 1.8 times the sun
Luminosity: 11 times the sun
Apparent Magnitude: 0.77
Honorable Mention: 12 brightest star in the sky
One of the facts I happened to know about Altair is that this particular star is a fast rotator. Don’t ask me why I know that because, in all honesty, I don’t know. Like I stated—I have no real interest in Altair—I use the star to get to somewhere else in the sky. Very polite, I know.
What was I saying? Right! Rotation. Altair’s equator rotates at about 286 km/s (149.1 m/s). This high-speed rotation has caused Altair to stretch at its poles, causing the star to slightly deform into an oblate geometry. This sweat inducing rotation occurs every 9 hours. The sun’s equator takes almost a full month (about 25 days) to complete a full rotation. Gee, when I say it like that, Altair is really bustin‘ a move. Gotta love differential rotation!
I thought Altair was a variable star, but I had to double-check. My assumption is correct, but it turns out that Altair’s brightness doe’s not change that much—only less than a thousandth of a magnitude. For those that are interested: Altair is classified as a Delta Scuti variable star.
You can see this oblong, Delta Scuti, fast-rotating star, for yourself, if you happen to reside north of the equator (or on). You don’t need any fancy maps! Only a little training.
Alright—allow me to put on my wizard hat. Do you remember this image? We used it to locate Deneb and Vega in previous training sessions. You’re one star away from becoming a Summer Triangle Master. Yes… that’s an official title. Feel free to retrain yourself if you are a little rusty: here and here.
Since I’m a nice guy, I’ll help you out. I had to cast a few spells upon this image to make my point as clear as humanly possible. The illusionary white lines trace out each side of the Summer Triangle. You see those green blobs? Those highlight each star that represents the vertices of the Summer Triangle. You need to be at least a level 25 wizard to pull off a stunt like this—don’t laugh.
You see the green blob allllll the way toward the bottom right of the frame? That star emprisoned within that green blob is Altair. Take a nice, long look.
**SHALAKALABAZAAM** Now you see it, now you don’t! Ta-da! I dispelled my previous illusions. Here’s where the real training begins. Try to locate all three stars of the Summer Triangle—especially Altair.
Are you done? Fantastic! Remember: if you lie, you only screw yourself. Cherish these words of wisdom: Train with respect and your training will respect you. Oh, and don’t forget this: effort in is effort out.
If you are having trouble locating the Summer Triangle, I’ll whisper a few secrets that might enlighten you:
Look BIG. I’m not talking about you in particular, I’m talking about the sky. Images of the sky tend to make it look smaller than it actually is. Remember to look at large portions of the sky and don’t concentrate on small areas.
Look for Vega. Vega is the brightest of all three stars that make up the Summer Triangle. Its location in the sky also makes it very convenient to simply crank your head up and look for the brightest star you see. After you locate Vega—Deneb and Altair should be fairly easy to locate.
Check the time. If you go outside too late, it’s possible the Summer Triangle might have drifted below your horizon line.
Sky too cluttered. If you happen to be observing near many trees or buildings, it’s possible these objects could obscure your view.
You live in the southern hemisphere. Those that reside south of the equator are not privy to the Summer Triangle. Sorry.
Stellar Orientation. As Earth orbits the sun, constellations will shift position in the sky relative to Polaris (North Star). The Summer Triangle’s orientation in the sky will change, depending where Earth is in its orbit.
Remember: It’s called the Summer Triangle for a reason. If you go outside during the middle of winter and try to locate this stellar geometry—you’re going to have issues.
Well? What do you think? Our exploration into the Summer Triangle is finally complete (for now). What you do with this knowledge is your choice—use it wisely. For the rest of your life you’ll be prepared to take on the northern summer sky with obscene confidence.
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