What in the world is it about some of these stars that keeps me glued to the eyepiece for more than an hour at a time? This one I found to be irresistible, magnetic, stunning — heck, it was even charismatic in a chromacolor sort of way. It really was that good.
I have no idea now where I first came across a reference to Xi (ξ) Boötis, but at a visual magnitude of 4.7, it’s one of the many gems of the sky that glow in the dim fourth and fifth magnitude range that escapes easy visual detection — yet it’s relatively easy to pick out of a reasonably dark sky once you’ve identified its location on a star chart. I really wish I knew how many more are twinkling up there in relative obscurity — there must be hundreds.
Fairly easy to locate, it can be found about eight degrees due east of Arcturus, or about the same distance directly south of Izar, since it occupies one corner of an equilateral triangle anchored by all three stars. I was going from memory when I aimed a TV85 at it, and I landed on Omicron (ο) Boötis instead, which absolutely would NOT split. And for good reason, too — it’s only a single star. 🙂
But that dim light came on upstairs soon enough. I looked at a chart, moved a few degrees to the northeast — and when Xi (ξ) hovered into view, my hour of stellar bliss began. Wow.
Xi (ξ) Boötis (Σ 1888) HIP: 72659 SAO: 101250
RA: 14h 51.4m Dec: +19° 06′
***** Magnitudes Separation PA Latest Data
AB: 4.76, 6.95 5.6″ 302° WDS 2015
AC: 4.76, 13.83 69.9″ 342° WDS 2015
AD: 4.76, 11.73 158.6″ 286° WDS 2015
AE: 4.76, 8.65 271.5″ 98° WDS 2015
AF: 4.76, 9.20 337.5″ 37° WDS 2015
Distance: 22.1 Light Years
Spectral Classification: G8 (A), K5 (B)
NOTE: Magnitudes, separations, and PA updated to match current WDS as of 12/2/2016
My instrument of first approach was a 12mm Radian (50x), which prompted me to sit up straight and look closely. At first glance, I saw only a single star, but with a bit of intense staring, the very small dot of the secondary revealed itself.
This was really a splendid sight — the primary was a light shade of glowing red with a touch of orange, and there was just enough white mixed in to lighten up the overall color. The secondary was an intense little spot of light virtually identical in color, but much richer. The contrast between those two colors reeled me in so quickly I didn’t know I had been hooked.
The reported colors on this star have been all over the place. In a 60mm at 25x, Haas describes it as a “bright white star touching a vivid little gray star.” I haven’t seen it in a 60mm scope, but I’m curious as to whether I’ll see the same colors. She credits Webb with “yellow, purplish red,” and Hartung with “yellow and deep orange,” which was at least closer to what I saw. The always quote-worthy Admiral Smyth described it in The Bedford Catalogue as
“A binary star, in the left knee of Boötes; being the northernmost of the four stars forming his leg, and 10° east of Arcturus. “A” 3 ½, orange; “B” 6 ½, purple; the colors in fine contrast.” (p. 328)
And somewhere I saw a reference to it as red and blue.
In comparison to the sun, these two stars are somewhat of a rarity, having both less luminosity and less mass than our star. It’s their relatively close proximity to us that keeps them from being out of reach of my telescope, and is responsible for the dazzling show I saw. More on Xi (ξ) can be found here on Jim Kaler’s Star Site.
But to get back to the current observation —- with the seeing wavering between average (III) and medium poor (II), I couldn’t see any reason not to try a 10mm Radian (60x). That pried the two stars apart just a slight bit more, leaving me hungry for a larger slice of dark sky, so I reached down into my eyepiece box and pulled out an 8mm Radian (75x).
Ahhhhhhh ………… that went a long way toward curing my craving. But as usually happens after appetite appeasement, I developed a strong thirst. So my right arm reached down into the depths of the eyepiece box and came out with a 6mm Radian — and 100x.
What blessed bliss! I traversed that field of view several times, lingering over every visible star in it, and in between traverses, I took another drink of those vibrant colors.
Located about five arc minutes east of the primary is a trio of ninth magnitude stars oriented on a north-south line which kept calling to me. They reminded of me another stellar sight I’ve spent many an evening or morning with, Eta (η) Persei. Like this one, it also has a distinctive reddish glow which is very appealing, and it also has a line of three stars spread out in a row opposite the primary, but on the west side instead. And it’s a multiple star as well ………….
………. which I’ve neglected to mention so far. Stunned as I was by the view, I still couldn’t help but suspect that some of the dim stars surrounding Xi (ξ) could be companions, but the data I had at that moment only provided the statistics for two stars. So the next morning I checked that old standby, the Washington Double Star Catalog, and found Xi (ξ) had another four companions scattered around it! I was able to go back to the sketch I had made and identify all of them except for “C.” At a magnitude of 12.6, it might be within reach of the TV85, but I really think the separation of 71.6″ is close enough for it to drown in the glow of the primary. Shouldn’t be any problem with four inches of aperture or more, though, so I’ll try again on the next clear night. In a six inch scope, it should even be possible to detect some color in the “D,” “E,” and “F” companions. (I did pry “C” free from the glare a few days later, and added the inset at the lower right to the sketch above — see the first comment below).
And I discovered something while I was sketching this star field. I was using a red flashlight with an adjustable dimmer, but as I’ve found many times before, despite keeping the light as low as possible, it still affects my dark adaptation just a bit. Not for long, but enough that when I leaned back over the eyepiece, it took about fifteen to thirty seconds to get back to normal. What I noticed, though, was when I first looked into the eyepiece, the colors of the primary and secondary were richer and the background sky was blacker. I suppose that’s not surprising, considering the slight loss in dark adaptation, but the effect is mesmerizing. If I hadn’t been hooked already, I certainly was now.
So imagine a velvet black background that is as devoid of light as it can be. Glowing at the center of it are two red-orange dots of light — the larger one beaming back at you with a soft and pale radiance, the smaller one gleaming very intensely and richly at very close to the same color. Now try to pull yourself away from it and go on to another star.
But I couldn’t.
Believe me, I tried about a dozen times — but every time I pulled back from the eyepiece and looked up at my next target, I was consumed with a craving for another round of those vibrant reddish-orange photons. So back to the eyepiece again … and again …….. and again ………….. and several more agains.
And when I finally did succeed in overcoming Xi’s (ξ) magnetic pull, it was to take a peek at Izar — another reddish-orange star.
What can I say — I’m probably a few hundred thousand parsecs past hope. 😉