Located at the very northern tip of the constellation of Boötes is a small triangle of stars which represents the shepherd’s club. It’s up so high and so close to the end of the Big Dipper’s handle that it almost seems as if Boötes is about to give Alkaid, the star at the tip of that handle, a good whack (take a look at the map of Boötes at the bottom of this post to see what I’m referring to). These three stars (Lambda (λ), Theta (θ), and Kappa (κ)), along with Iota (ι), form an asterism which the ancient Arabs designated as Al Aulad al Dhibah, the “Young of the Hyena.” Which is appropriate, because during my efforts to pry the 12.6 magnitude companion out of the glare of Iota “A,” I thought I heard laughter coming from up there.
But I’m getting ahead of myself. Let’s tackle Kappa (κ) first.
Kappa (κ) Bootis (Asellus Tertius) (Σ 1821) (H III 11) HIP: 69481 SAO: 29046
RA: 14h 13.5m Dec: +51° 47′
Magnitudes: 4.5, 6.6
Position Angle: 236° (WDS 2011)
Distance: 196 Light Years
Spectral Types: A7, F1
At low magnification you’ll find that Kappa (κ) shares the field with Iota (ι). This pair of stars is an arresting sight in the eyepiece because they’re almost a mirror image of each other, as the dimmer companions are located on roughly the opposite sides of the primary. In a 60mm scope they’re a pleasant sight at 40x.
The primary, frequently referred to on star maps as Kappa-1, is a bright blue, and the secondary, Kappa-2, is white, and based on spectroscopic analysis, also seems to have a companion. Admiral William Smyth’s nineteenth century observation matches mine, but Haas describes them as white and silver. At any rate, we agree on the rest of her description of them as a “showcase pair.”
The Arabic name, Asellus Tertius, translates as the “third donkey.” Iota (ι) is the second donkey, and since I know you’re dying for the rest of this, Theta (Θ) is the first donkey.
At 13.3″ apart, this is a relatively wide pair, so I found it to be easy enough split in a 152mm scope, and it wasn’t much of a challenge in a 63mm refractor, although the view was more pleasing because the stars were closer together.
And on to Iota (ι), donkey number two ………
Iota (ι) Bootis (Asellus Secundus) (Σ I 26) (H V 9) HIP: 69713 SAO: 29071
RA: 14h 16.2m Dec: +51° 22′
Magnitudes A: 4.8 B: 7.4 C:12.6
Separation AB: 38.8″ AC: 92.8″
Position angle AB: 33° (WDS 2011) AC: 187° (WDS 2000)
Distance: 97 Light Years
Spectral Types: A: A7 B: K0V
First the colors. I saw the “A” and “B” components as yellow and blue-white, Haas describes them as “gloss white and a nebulous star,” and once again, Smyth and I are close: “pale yellow, creamy white.”
But count yourself fortunate to see the very faint third component, let alone figure out what color it is. I did my best to coax it into view with a 63mm refractor, but with no success. I gave it another try with a 152mm refractor, and with averted vision at 76x, I was just able to detect it at times – higher magnification did nothing to improve it – so it’s hardly any wonder that I had no luck with the 63mm. The glare of the other two stars is just enough to make detection of the 12.6 magnitude companion a real challenge, and as the inset in the sketch above shows, it’s hardly more than a faint point of light. More aperture and less moisture in the air would help, no doubt, but the extra aperture was in the house and the moisture was a bit beyond my realm of influence. Although the echo off the surrounding hills of that young laughing hyena made me wonder how much influence it might have.
But I also found that detection of 7.4 magnitude “B” was a bit tricky in the 63mm refractor. And again, it was because of the glare from the 4.8 magnitude primary. At times, it was easy to see, at others, it could only be detected with averted vision.
At any rate, this pair of doubles – or one double and an elusive triple – is really an attractive sight. And with three donkeys and a young hyena close by to provide a good laugh or two, you won’t feel like you’re out there in the dark all by yourself.
Credit goes to Jim Kaler’s web site for information on the names of these two stars. My observations were made on June 5th, 2010, and the sketch was done just over a year later, on June 25, 2011.