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Marvelous Marfik, an Ophiuchan Jewel

Now you can call it Marfik, or you can call it Marfic, but don’t call it Marfak  — which calls Cassiopeia home twice, as in Marfak East (Theta/θ) and Mafak West (Mu/μ).  And you sure don’t want to call it Marsic, which is also known as Kappa (κ) Herculis, and is sometimes spelled Marfak as well.  And please don’t call it Mirfak, better known as Alpha (α) Persei, or you’ll be searching for a winter star in the summer time.  I hope I’m making myself perfectly clear here.  😉

And who says those eleventh century Arabian star naming guys didn’t have a sense of humor.

So why don’t we call Marvelous Marfik Lambda (λ) Ophiuchi instead and save ourselves a lot of confusion.  Of course you could call it Σ 2055 — as in STF 2055 — or you could adopt William Herschel‘s name for it, H I 83.  But I’ll stay with Lambda (λ) and leave it at that.

And how, you might wonder, did I find my way into this confusion?  The more pertinent question would actually be how did I find my way out — but since I’m still stuck on this star, I can’t answer that one yet.   The answer to the first question is that I discovered Marfik — sorry, Lambda (λ) — when I was looking at data on Marsic, meaning Kappa (κ) Herculis.

And as they say, the rest is history.   Or at least it will be once I finally finish what follows.

But what do you say we go find this thing.

You’ll find Marfik/Lambda (λ) Ophiuchi on the west side of the very irregular six-sided polygon that forms the framework of Ophiuchus. Look for its 3.9 magnitude light halfway between two very distinctive pairs of stars, 3.2 magnitude Kappa (κ) and 4.4 magnitude Iota (ι) to the northeast of Marfik, and 3.2 magnitude Epsilon (ε) and 2.7 magnitude Delta (δ) to its southwest.  (Stellarium screen image with labels added, click to enlarge).

Marfik  (Marfic) (Σ 2055)  (AB is H I 83)         HIP: 80883    SAO: 121658
RA: 16h 30.9m   Dec: +01° 59′
Magnitudes  AB: 4.15, 5.15    AB,C: 3.82, 11.0    AD: 4.15, 9.8
Separation   AB: 1.40″             AB,C: 119.60″              AD: 308.1″
Pos’n Angles:  AB: 40° (WDS 2013)   AB,C: 169° (WDS 2013)   AD: 247° (WDS 2002)
Spectral Classification: A0 for both “A” and “B”
Distance: 166 Light Years
Status:  AB gravitationally attached, orbit is closing slowly, and can be seen here; “C” is physically related.

This one is not for the faint of heart armed with a small aperture refractor, but then again, that’s probably more a reflection of my not having the seeing conditions I need to split the claustrophobic AB pair.  Still, it needs at least four inches of aperture, regradless of your seeing.

But don’t think for a minute that I’m trying to discourage four inch refractor afficianados  —-  not one bit.  That was my instrument of first approach — in fact it was my first two instruments of approach — and I darn near got a split, poor seeing and all, in each of them.

Approach number one was with a TV102 I recently rescued from it’s parched Utah environment.  Actually, I was giving it a lengthy test run with a Feathertouch micro-focuser I had installed on it, and hunting down Marfik was a spur of the moment decision.   I was handicapped times two — first by the customary uncooperative seeing, and second by a surplus of late Spring murk which has over-stayed its temporary visit by several weeks too many already.  A 5mm Radian view (176x) was the limit of what I could coax from the sky that night, and even the faint 11.0 magnitude “C” component was an averted vision affair.  I hate to wish summer gone, but I sure could use a bit of crisp autumn air to clean up the view overhead.

Eleven nights later I called my Skylight 100mm f/13 from its reclining position on it’s red blanket covered rack in high hopes it could deliver on this tough pair.  And it came darn close.

I started with a 10mm Radian (130x) and was rocked back in my chair when I found myself looking at a pair of distinct dots of yellow-white light that were welded together — I really didn’t expect anything more than a bit of elongation at that magnification.  I inched ahead slowly with an 8mm Radian (163x) and could see each round dot of light a bit more clearly, but still not separately, or as Sir William Herschel sometimes described that configuration, “one behind the other.”  So then I reached for a 6mm Radian (217x) and sat still for a while to see what I could catch in between bounces.

The seeing was almost decent — probably a few tenths of a notch on the negative side of a three (III) — but I really needed something just a bit better.  If it had been in my power to crank it up a few tenths to the other side of a III, I would have gladly done it.  Maybe, just maybe, I caught the merest hair of a hairline split, but there was just too much movement in the eyepiece to be sure.  I gave both a 5mm (260x) and a 4mm Radian (325x) their chance to succeed, but they lost the battle to the seeing.  I just couldn’t hold the image still for long enough in the 5mm view, and the 4mm view would only briefly come close to anything like a fleeing focus.

So I was back again, three nights later, with my over-length D&G five inch f/15 refractor, and so was the mirthless murk.  And even worse seeing.  I can save us a lot of time by summing up that effort in one word — absolutley-and-completely-and-totally-futile. I saw more of the heavens on the other two nights in each of the four inch refractors.

And the following night I was all set up with the Skylight 100mm f/13 refractor again — scope on the mount, eyepiece in the diagonal, all prepared to line everything up on Polaris — when the clouds surrounded me and made a mad rushing and swirling dance for the zenith.  And they got there in not much more than a minute.

Rats!   Fooled again!   For about the fifteen thousandth time I do believe.

Since we’re getting nowhere here, let’s look at a sketch instead:

This is William Herschel’s “one behind the other” configuration. One of these days I hope to find the black slice of sky that’s rumored to be between those two stars. (East & west reversed, click for a larger view).

North is at the top, west is at the left, matching the sketch above.  (Aladin image)

Now the quality about Marfik/Lambda (λ) that really intrigues me is its color.  It’s yellow, but it’s white.  By that I mean it’s a very unique shade of yellow but the white is unmistakable.  If you think about what a clear glass of medium strength lemonade would look like with a high afternoon summer sun shining through from the side of the glass, you would just about have it.  That color is absolutely impossible to miss in the finder of your scope after you’ve located it the first time.  And I’m referring to both the secondary and the primary — they radiate the same wavelength of color, plus or minus one or two microns.  If you click on the Aladin image at the right to enlarge it, what you’ll see is a pretty good approximation of the color I observed.

I mentioned William Herschel’s H I 83 catalog number above because the discovery credit is all his.  He happened on it on March 9th, 1783 (“A very beautiful and close double star“), but didn’t see the yellow tint I saw in the two stars, instead describing the primary as white and the secondary as blue, “both fine colours.”  (Source: go to the 1784 Catalog at the bottom of the first page.)   He didn’t hold back on the magnification, either, using 460x and 932x on the pair, but then according to his measurements, the primary and secondary were only separated by .50 arc seconds.  Admiral Smyth credits Herschel with describing this pair as very close and difficult to measure except when, in Sir William’s words, “the star will be quiet.” —–  certainly a unique way to put it, but one I utterly understand.  And, If I had to bet, I would bet the high magnifications he used had at least some effect on the “colours”.

Friedrich Georg Wilhelm von Struve took his first full measure of Lambda (λ) Ophiuchi in 1825, and came up with a separation of .84″.  Admiral Smyth looked at it in 1834, 1836, 1839, and 1842, and came up with consistent measurements alternating between 1.0″ and 1.1″ — and he also saw the pair as white and blue, but he included a “smalt” tone with his blue (p. 365 of The Bedford Catalogue).  And Sissy Haas, bless her double star soul, is right with me on this one: “125mm, 200x: Stunning pair!  A brilliant star touched by a bright star; both look lemon yellow.

So you have to wonder about that blue seen by William Herschel and Admiral Smyth — or perhaps I should reverse that and say you have to wonder about that yellow Ms. Haas and I saw.  After all, the A0 spectral classification puts both stars firmly in the blue white category, so Herschel and Smyth were really on the right track.  But that odd color of yellow I saw is certainly unique in my experience, and it was there every single time I looked at it.   And it’s very obviously there in the Aladin photo above, too.

The spectral classification that follows A0 is F, which is white, and it’s only when you get to the next cooler classification, G, that yellow-white enters the picture.  So I’m not sure what to think.  But, as has been said by many observers, there’s no explaining star colors sometimes — you would do better to predict the weather three months in advance.  So I’ll let Sir William have the last word here on star “colouration.”

Here I must remark, that different eyes may perhaps differ a little in their estimations.  I have, for instance, found, that the little star which is near α Herculis, by some to whom I have shewn it has been called green, and by others blue. Nor will this appear extraordinary when we recollect that there are blues and greens which are very often, particularly by candle-light, mistaken for each other. The situation will also affect the colour a little, making a white star appear pale red when the altitude is not sufficient to clear it of the vapours. It is difficult to find a criterion of the colours of stars, though I might in general observe that Aldebaran appears red, Lyra [Vega] white, and so on;  but when I call the stars garnet, red, pale red, pale rose-colour, white inclining to red, white, white inclining to blue, blueish white, blue, greenish, green, dusky, I wish rather to refer to the double stars themselves to explain what is meant by those terms.”

From p. 2 of William Herschel Double Star Catalog

Even here, I have to step back and think about Sir William’s “red.”   The red he uses to describe Aldebaran is what I would call reddish-orange, certainly a strong tint of orange at the very least.  Obviously beauty is not the only quality which dwells in the eye of the beholder.  Perhaps each wavelength is uniquely our own once it’s processed by our mental machinery.

Whatever the case,  I just have one thing left to say:  I’ll be back  …………….  and I’ll get a clear black space between these two stars if it’s the last thing I do this summer!

Clear and “colourful‘ skies!  😛

(WDS data updated 7/27/2014)

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7 Responses

  1. Hi John. Excellent report on an often overlooked bright double. I tried Marfik last June in average seeing using a 90mm F8.8 achromat. 200x was required to show the individual airy disks just touching during brief steady moments. The components were very tight and most of the time the seeing only allowed elongation. However the position angle was fairly easy to determine even when the seeing only allowed elongation. With 1.4″ and a 1 magnitude difference between the components this is indeed a real challenge in smaller apertures.

    Karl

  2. That sounds pretty much like my experience with Marfik, Karl. It’s not too tough to get enough elongation to detect the position angle, but going beyond that to a dark slice of sky is my plan one of these sessions.

    If you had fun with that one, take a look at the AB pairing of Xi (ξ) Scorpii (0.99″), which I just posted. Managing only the elongation of that one will be an achievement in and of itself!

    John

    • Well, I’ve been back, as I promised in the next-to-last paragraph above, and I got what I would call a dancing almost split — dancing because Marfik/Lambda Oph wouldn’t hold still at all, and almost split because I could see two touching dots of light.

      I believe the good Reverend Dawes would call that resolved, but I sure can’t call it split.

      My weapons of choice were my five inch f/15 D&G refractor and a 10mm Radian, which yielded up 191 diameters of magnification. Really, that was too much for the conditions, but anything less was too little.

      I have not surrendered! I will be back again!

      John

      P.S. — that odd and beautiful shade of yellow was still there, too.

      • Hi John,
        Last night was my first look at Marfik and what a lovely
        sight it is. The seeing was pretty good after a few rain
        showers during the day, I was using my 150mm reflector
        and the Zeiss eyepieces. At 165x I could just see the
        two stars almost touching not quite split I then dropped
        the 6mm eyepiece to give me 275x and straight away I
        got a nice clean split. I have to say last night I could not
        detect any trace of yellow in them, to me the primary was
        white and secondary had a trace of blue. I only had about
        10 minutes before it went behind a large tree to end my
        view for the night so another session is required maybe I
        will get a clear night soon to see if I can detect any yellow
        in it.

        Pat.

  3. Hi Pat,

    Glad you reminded me of Marfik — I’ll take a look at it with a six inch refractor tonight if I get a chance. If I don’t see yellow again, I’ll be surprised, but that white and blue seems to be persistent in many of the observations described in the post.

    There’s gotta be a reason, but darned if I know what it is. Reflector vs. refractor might be part of it, but I suspect atmospheric conditions (what Wm. Herschel referred to as “vapours) are at least equally important.

    It’s almost 10 PM and I hear the stars calling —

    Cheers!

    John

    P.S. — just updated the AB and AB,C data to the 2013 WDS info (no change yet in the AD data).

  4. Just had two nights in a row to look at Marfik and unfortunately the seeing wasn’t much help at all. Wm. Herschel’s “vaporous humours” were busy vaporizing and their sense of humor is questionable, to say the least. I had glimpses of a split a few times — and I was using a six inch f/10 refractor (!) — but the seeing was so poor that a precise focus was impossible at 152x (10mm Radian), plus the focus kept changing. When I could see two well-defined orbs, they were very Porrima-like.

    As for color, under those conditions, it would be hard to call anything definitive. What I saw was mainly white with a weak hint of yellow — in other words, a pale imitation of what I’ve seen previously.

    Gotta get better seeing soon!

    John

    • Nothing but clouds here for the last 3 nights so at least
      you were better than me.

      Pat.

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