Rain. Lots of it. Infinite amounts almost. October had 18.5 inches of it – all of which arrived in the last two weeks of the month — and November was abundantly blessed with 15.40 inches more. And December is already rolling right along, filling my five inch capacity rain gauge in just the first few days. So double-stars have been relegated to the much drier confines of an astronomical closet for the time being.
But –- just before the revenge of the rain gods arrived, which was shortly after I escaped from my tribulations in Triangulum –– I managed a quick trip into Taurus in search of an elusive multiple star I’ve pursued off and on since last spring.
Chris Thuemen mentioned this multiple star many months ago in an observation he recorded in his double star imaging site. His photos of it revealed something along the lines of a dumbbell-(as in weight lifting apparatus)-shaped asterism. It’s basically a pair of widely separated fourth and fifth magnitude stars with a very closely spaced pair of tenth magnitude stars conveniently placed about halfway between the brighter pair, plus a pair of barely there 13th/14th magnitude stars flitting around the fringes.
That pair in the middle is a genuine enigma – meaning it’s a very perplexing pair to pry apart. The two stars are separated by a moderately close 5.3 seconds of arc, which shouldn’t really be too tough to distinguish in a six inch refractor. But every time I approached them, they distinguished themselves conspicuously by completely refusing to cooperate.
Follow me and see for yourself:
Σ 541/Σ I 9 (STF 541/STFA 9) HIP: 20635 SAO: 76601
A = Kappa-1 or 65 Tau B = Kappa-2 or 67 Tau
AB = H VI 8 CD = HJL 1034 CD = J 2722
RA: 04h 25.4m Dec: + 22° 18′
. Magnitudes Separation Position Angle WDS
AB: 4.2, 5.3 340.7″ 173° 2011
A, CD: 4.2, 9.5 176.4″ 176° 2000
AE: 4.2, 13.2 145.0″ 268° 2000
B, CD: 5.3, 9.5 159.9″ 351° 1997
BF: 5.3, 13.7 108.5″ 215° 2010
CD: 10.6, 10.0 5.3″ 330° 2011
Distance: 153 Light Years
Spectral Classification: All are A7
Note: A & B are members of the Hyades Cluster
As you can see, there are almost as many names attached to this multiple star as there are stars in the Hyades cluster. If the data above seems a bit perplexing or overwhelming, the thing to do is take it in small doses to start with. You can swallow the whole thing when we’re done here. But let’s get a look at the labeled version of this shimmering sextuplet before we go any further:
First, the wide pair that you’ll see graciously staring back at you in your finder or in a wide-field eyepiece is Kappa-1 and Kappa-2 Tauri, which are also designated with Flamsteed’s catalog numbers, 65 and 67 Tauri.
Next, Sir William Herschel was here on October 6th, 1779, and cataloged the wide Flamsteed pair as H VI 8. The Washington Double Star Catalog (WDS) connects the H VI 8 designation to the A,CD pair, but Herschel specifically linked his observation to Flamsteed’s 65 and 67 Tauri, and added this comment: “Double. At a considerable distance.”
Then, Sir William’s son, Sir John Herschel, paid a visit to the CD pair and recorded it in his 1830-31 catalog as h 1034 (or HJ, or HJL). Again, this is at variance with the WDS information, which assigns HJL 1034 to the AB pair. However, Sir John assigned magnitudes of ten and eleven to the two stars he looked at, and also added this comment: “Neat. Exactly in the parallel.” – which certainly points to the two faint stars in the middle, “C” and “D.”
And the J 2722 designation applied to the CD pair is a reference to the work of Robert Jonckheere, who became famous for classifying double stars fainter than tenth magnitude.
Last, but not least, are the two Struve designations, Σ 541 (STF 541) and Σ I 9 (STFA 9). The first number comes from F.G.W. Struve’s 1827 Catalogus Novus Stellarum Duplicium; the second number is from his first supplement to that catalog. The Σ 541 catalog number appears to have been applied to the CD pair – it’s listed with magnitudes of 9 and 10, and is described this way: “Media inter κ1 et κ2 Tauri.” – which is pretty clear, even to this non-Latin literate star gazer (see the thumbnail at the right of page 14 from the above catalog). Struve’s second catalog number, Σ I 9, apparently refers to the wider AB pair — and I’ve had no luck whatever attempting to track down a copy of that volume.
At any rate, the WDS has wisely combined the confusing designations under one unifying umbrella, Σ 541, as you can see in the notes section of this link.
But the initial fog generated by all those catalog designations goes stellar hand in stellar hand with the fog surrounding the defiantly difficult CD pair, hovering innocently halfway between the Kappa (κ) twins. I lost count of the number of times I tried to sneak up on this pair, each time with little success. A big part of the reason for my un-success was the seeing was unaccountably cursed every single time I made my approach. By the time they finally trundled out of view in the west last spring, I had come to the conclusion these two faint stars were never going to allow a prying apart lever to be wedged solidly between them. I waved good-bye with a sigh of relief and muttered something about good riddance, too.
But when I caught sight of Taurus climbing over the roof of my house in the early morning hours of September, I took up my pursuit once more – and discovered the curse was still there. Finally, after uselessly uttering most of the same phrases I had learned in the spring, by the middle of November, despite continued poor seeing, I managed to get a night that provided several solidly convincing glimpses of separation between the two stars.
So I grabbed a pad and committed the view to paper. And it’s a good thing I did, too, because there hasn’t been a single clear night since. Did I mention a curse?
In my many prior attempts at distinguishing “C” from “D”, I was always able to see a slight hint of duality in the two stars, but never anything that could quite be called a successful split. This time, I found the slice of intervening dark sky I knew was there all along – but just barely, and it really wasn’t what you would call dark, either.
The problem is – and no doubt it was part of the reason my earlier attempts were frustrated – is there’s too much glare here. The Kappa (κ) twins are the culprits, throwing their 4.2 and 5.3 magnitudes of A7 white light all over the field with unrestrained enthusiastic abandon. The bulk of their wildly radiating photons seem to collide halfway between the two glaring stars, which happens to be right above the diminutive beady little heads of the CD pair. It’s like looking through a rain-soaked windshield on a dark and stormy night at oncoming headlights and trying to pick out the faint phantom-like outlines of the shapes hidden behind them. Maybe I would have met with success sooner if I had worn dark glasses. 😎
But I got ‘em – so enough of this carping and complaining. And as I’m now reminding myself – it wasn’t raining that night, either!
Then there are those 13th magnitude companions, “E” and “F.” The first one is the more lively (a very relative term) of the two, boasting a half magnitude advantage at 13.2. And although that half magnitude doesn’t represent much difference, at this level of lackluster illumination, the 13.7 magnitude “F” companion was subsisting at the extreme limit of what I could pick out from behind Kappa-2’s 5.3 magnitude glaring scowl. But with persistence and repeated applications of averted vision – very strained by the time I was done, I might add – I got both of them as well.
There are other 13th magnitude dots of light near both “E” and “F”, which raised the level of difficulty a couple of astronomical notches, mainly because they kept popping in and out of view — which is what “E” and “F” were doing, too, of course. So for a while I wasn’t sure which stars were which. If you’ve ever strained your eyes over a narrow-field short eye-relief eyepiece, attempting to see faint hints of almost-not-even-there-grayed-out-traces-of-light, you’ll know how hard it can be to pinpoint their locations. It quickly becomes a game of celestial hide-and-seek: There it is! – no,it’s over there – wait, it’s back here again – no it’s not, it’s here now – etc., etc., etc. Fortunately I had notes with me of their position angles and distances, which was a huge help in pinning down those elusively illuminated traces of light.
So give this tempting little Taurian sextuplet a try sometime. I recommend a minimum of six inches of aperture for the CD pair, although if you have less moisture to deal with above your head, you might find five inches will work. Or if you’re really smart, and paid careful attention to the lessons to be learned here, you’ll stick with an 80mm refractor and just admire the view.
Clear Skies, or something of that sort.