Okay, now that the sky has significantly changed over the past month, let’s take a look at “upcoming attractions”.
There are three prominent stars that constitute what’s known as the “Summer Triangle”: Altair, of the constellation Aquila; Deneb, of Cygnus; and Vega, of Lyra. When these three are directly overhead, they form a huge triangle that is the guide to finding numerous celestial gems. Incidentally, only first-magnitude stars have proper names. The remaining stars are categorized, in descending order of magnitude, by Greek nomenclatures: Delta, Epsilon, etc.
Vega is the flagship star of the constellation Lyra (the harp, although it’s always reminded me more of a shopping cart). There is a gorgeous double star in the equilateral mini-triangle “handlebars” of this shopping cart: Epsilon Lyra. It’s a relatively tough double to “split”, ergo a great barometer of your telescope’s resolution capability and the quality of its optics. Something else resides in this “shopping basket”: M57, or the Ring Nebula…this one’s not a beginner object, but surprisingly easy to find once you’ve located it for the first time. You’ve almost surely seen a picture of it: a gorgeous oval, with brilliant red and yellow color. No less than Captain Kirk, of the Starship Enterprise, thought enough of it to have a color photo on the bridge of his ship!
The Ring Nebula sports a vast array of beautiful colors in pictures, but looks like a ghostly grey doughnut through the average backyard telescope. It’s very tiny, situated almost exactly between the stars that form the “front end” of the shopping cart. Low magnification shows it as a small, grey “blob”…changing to a high-power eyepiece begins to show the smoky interior of the “hole”, plus that the nebula is oval in shape. Again, don’t expect color! The cones in our eyeballs-our color receptors-aren’t sensitive enough to be stimulated by the faint hues these Deep Sky Objects (DSOs) emit. The Ring Nebula is a prime example of a planetary nebula, one in which the original star exploded, and violently cast off its outer “shell”; hence the ring. It’s ever so slowly changing shape, but because of the sheer distance and vast size, we earthlings don’t discern the change over a lifetime. Think about just how distant and large that object has to be, for such a “gaseous anomaly” to appear stable to us.
Moving a few degrees away, we stop at a star named Albireo, which is the “head” of Cygnus, a.k.a. the “Northern Cross”. Can you make out the shape? The bright star of this neighborhood, again a part of the Summer Triangle, is Deneb. When we zoom in on Albireo, at the opposite end of the “cross”, we are in for a pleasant surprise: it’s not only a brilliant double star, but the two emit faint color! What’s particularly striking about this pair is that one is orange, and the other blue (that’s right; these actually exhibit color through a telescope!). The duo is easily resolved through virtually any amateur instrument.
Now shift your binoculars or telescope a few degrees away from Albireo, and you’ll spot another gem: M27, or the Dumbbell Nebula (I didn’t name these attractions; please bear that in mind). In the above rendering of the “trinity”, M27 is almost exactly positioned opposite M57, albeit on the other side of Albireo (it’s located above the word “Sagitta” in the top illustration). Like the nearby Ring Nebula, this one resembles something other than what it’s named for…at least for moi: M27 reminds me of an apple core. This one’s also a planetary nebula…in this case, we’re gazing at one “sideways”: think of a six-inch slice of garden hose, about an inch in diameter. Given M27’s shape, we’re looking at this truncated piece of hose from the side. In the case of the Ring Nebula-M57-we’re holding it so that we’re looking into the hose. Somewhere across the Milky Way “neighborhood” in which we reside, E.T.’s seeing the Ring from his sideways perspective, yet the Dumbbell straight on! Interesting hypothetical to ponder…
The Dumbbell is one of the brightest, easiest objects to see. It’s a delight for beginners…again, just a few degrees from the “head” star, the aforementioned Albireo, of Cygnus. Draw an imaginary line, from M57 through Albireo, to the vicinity opposite the Ring Nebula, and start hunting. It won’t be nearly as tricky to locate as the tiny ring.
Speaking of degrees, make a fist, and extend it upward to the sky. The width of your fist represents about ten degrees of the sky your hand is obscuring. Five degrees would be the span from your thumb to the knuckle that’s your…yeah, that finger. That’s about as much as you typically see, gazing through a pair of binoculars. A telescope’s field of view is about one-maybe two-degrees of sky.
The third star of this stellar trinity is Altair, in the constellation of Aquila, a.k.a. The Eagle. Altair didn’t get dealt any significant cards: no attractions to speak of. It’s in a lonely parsec of sky. It does, however, boast one planet, Altair 4, formerly home of The Krell, Dr. Morbius’s research indicates.
Just kidding about Altair 4 and its erstwhile inhabitants! Giving my age away, I am.
I’ll cover the more elusive attractions of this region next time.