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95 Herculis and a Small Jewel, OΣ 341 (STT 341)

Ninety-five Herculis is one of those stars I’ve frequently come across in my reading but had never looked at, despite the numbers of times I’ve made a mental a note to do that.  My memory machinery finally functioned at high speed one evening, prompting me to take a look — and when I did, I was also rewarded with a spectacular stellar gem in the form OΣ 341, also known as STT 341.

Slide out to the east along the line of stars that run from Delta (δ) Herculis to Omicron (ο) Herculis and then drop south seven degrees to 95 Herculis. (Stellarium screen image with labels added, click on the chart for a larger view)

95 Herculis (Σ 2264)       HIP: 88267     SAO: 85648
RA: 18h 01.5m   Dec: +21° 36′
Mag: 4.9, 5.2   Sep: 6.3″   PA: 257°  (WDS 2010)
Distance: 470 Light Years
Spectral Classification: A5, G8

The easiest way to get to 95 Herculis is to follow the directions on the first chart above, which has you starting at Delta (δ), a beautiful multiple star well worth spending some time with,  and following the line of stars that lead east from it to Omicron (ο).  When you reach that point, turn to the south and continue about seven degrees, which is about one and a half fields of view in most 8×50 finders.  The next chart (below) gives you a close up view of the area you’re headed towards, and shows 95 Herculis in relation to its neighbors — 98, 102, 101, and 96.

A closer look at the 95 Herculis/OΣ 341 area. (Stellarium screen image with labels added, click to enlarge)

Two glowing white globes with a tinge of yellow that really stand out against the background of a black sky. (Click on the sketch for a larger view)

In my 76mm Tasco refractor at 48x, 95 Herculis is two sharply defined bright white dots of light which are just touching one another.  At 133x, they separate very well, and I noticed that the western component is just slightly smaller than the other one.  They both appeared to me to be primarily white with just a tinge of yellow on closer examination. Haas describes them as “pure gold,” and Admiral Smyth saw — I hope you’re sitting down when you read this — “light apple green” and “cherry red.”  Obviously, none of these color descriptions are close to each other, so I’ll look again — but without colored lenses in my eyepieces, I really don’t expect I’ll see apple green or cherry red.

These are huge stars.  The “A” component is 6.8 times the diameter of our sun and is 167 times more luminous; the “B” component, the larger of the two, has a diameter 19.4 times that of the sun and is 194 times more luminous.  But since this pair of stars is a distant 470 light years from us, you won’t need sun glasses of filters!  (Data from Jim Kaler’s web site)

The following night I took another look with two larger refractors, a four and a five inch.  At low magnification, 55x in the four inch and 59x in the five inch, they were cleanly split, but still very close.  The two glowing white globes really stand out against the background of a black sky.

OΣ 341   (STT 341)      HIP: 88637     SAO: 85723
RA: 18h 05.8m   Dec: +21° 27′
Mag – AB-C:  7.6,   9.8   Sep: 27.8″   PA: 175°
Mag – AE:      7.3, 10.3   Sep: 66.1″   PA:  38°
Mag – AF:      7.4, 11.0   Sep:  112″   PA: 356°
Mag – AG:     7.4,   7.6   Sep:  133″    PA: 239°
Distance:      123 Light Years
Spectral Classification: M1 (for AB)

If you go back to the second chart above, you’ll see our next star lies about half a degree to the east of 95 Herculis.  It’s very obvious in a finder, and depending on what eyepiece you’re using on 95 Herculis, you may see this one over at the eastern edge of the field.

This is a beautiful multiple system of five stars.  There are also a few stars of similar brightnesses near it that almost look like they belong to this system, but they just happen to be in the vicinity.  This system is best seen with three inches or more of aperture, although having located them in the four and five inch refractors, all of the faint components were visible in the 76mm with averted vision at 60x — any more magnification than that tended to increase the glare from the primary and make them harder to see.

In the four inch at 55x the system almost looks like a very small cluster, as was the case in the five inch at 59x.  Increasing the magnification in the four inch to 88x didn’t result in a major change in appearance, but it did put some distance between the “C” and “E” components and the primary.  Surprisingly, even though it’s only an inch greater in aperture, the image was noticeably brighter at 59x.  The four inch is an APO, the five inch an achro, and I much preferred the image in the five — which just confirms my opinion that achros deserve a lot more respect than they get!

OΣ 341 (STT 341). East and west are reversed here to match the view in a refactor. (STScI Photo with labels added, click to enlarge)

The three faint components are grouped closely around the primary in a kind of arc, while the “G” component is off all by itself to the south, although there is a tenth or eleventh magnitude star just to it’s southwest which looks like it’s part of the system, but isn’t.  Normally, in a multiple system, the second brightest star follows in alphabetical order, which in this case would be the letter “C,” so I’m not sure what caused it to be designated “G.”  Both “AB” and “G” appeared white to me, and of course the others were just too faint for detecting color.  Haas again saw color where I didn’t — she describes the primary as “peach white.”

These observations were made under dark skies on July 6th and 7th, 2010, at about 0100.

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3 Responses

  1. July 21st, 2011 – 2300

    I was enticed back to 95 Herculis tonight for two reasons, the first being that I wanted to get a sketch of the area to add to this post . . . . . and the other having to do with Admiral Smyth’s “colorful” description of it. As I mentioned above, he reported seeing “apple green” and “cherry red.”

    So I looked long and hard last night, and frankly, I just can’t see it. When I defocused a bit on both stars, the slight tinge of yellow I’ve seen before was slightly more obvious. If I had been looking through some haze, or caught these two stars closer to the horizon (they were just west of the meridian when I made the sketch), it might have been possible for that yellow tinge to cause both stars to slide toward the red side of the spectrum.

    But not “cherry” red, and certainly not green.

    Although I suppose if a person saw red in one, the other might take on a green tinge.

    However — in his description of the 95 Herculis system referenced above, Kaler states the “A” component is a class A5 star, while “B” is a G8, making it slightly cooler. But, as he also states, when its infrared illumination is taken into account, “B” is the more luminous of the two stars — 194 times brighter than our own star, versus 167 times for “A”. So on that basis, it would seem unlikely that the color of the secondary would be influenced by the brightness of the primary.

    And yet, here’s what the Cambridge Double Star Atlas reports for 95 Herculis:

    Lovely twin suns with amazing ‘apple-green & cherry-red’ tints — which look exactly like that!” (p. 17)

    Now a good comparison would be the nearby — and by the way, totally ignored — 100 Herculis, located five degrees north of 95 Herculis. That system is two stars of equal magnitudes, 5.8, separated by fourteen arcseconds. Aside from being slightly wider, they’re almost identical in appearance to 95 Herculis. And both stars are classed as A3.

    And Smyth, as well as other observers, report both of them as pale white. Which is what I see as well.

    So it remains a stellar mystery to me just exactly what, or how, two such rich colors — apple green and cherry red — can be seen in the two stars that are the 95 Herculis system.

    But I’ll keep checking back. I would love to see it.

    And if I do, you’ll probably hear me, regardless of where you happen to be on this planet, when — and if — it happens.

    Of if you see it, by all means add a comment here and let us know!

    Meanwhile, as for 100 Herculis being totally ignored — stand by. It won’t be for long. 😉

  2. Are you sitting down John?

    I went to 95 Herculis tonight with the TV 101. I did NOT have Smyth’s description in mind. In fact, what I had in mind was the two white stars of 100 Herculis and I thought that was what I was seeking. So i nearly fell off my observing chair as I popped in a 5mm eyepiece to split it (109X) and said “wow! red and green! Make a note.” Only then did I remember Smyth and went in and checked the description in Haas.

    Yes – that is a lovely description – a perfect description of what I saw. Of course, it depends on what kind of cherries you have in mind. I can see where cocktail drinkers and sundae eaters could be confused. Those are the wrong cherries. When I was a kid we had two cherries trees in our yard flanking an apple tree which produced lovely green apples that barely made it to yellow when they were ripe.

    The cherry trees were the sour type – not the big, fat red ones they put on top of an ice cream sundaes. I spent many hours climbing that trees and tying little strips of white cloth near the ripening cheeries – which started out green and slowly went to a red of about the hue of this star. My efforts were rewarded because my mother preserved those cherries and all winter long I had peanut butter and cherry preserve sandwiches and the most delicious cherry pies. And the apples in the tree next to it were “apple green.” So in this case, I am 100% with the captain – definetly “light apple green and cherry red” but sour cherry red.

    And yes, 100 Herculis is a wonderful find. Perhaps I should pull together a special listing of “twins – stars that like 100 Herculis are exactly – or almost exactly – the same magnitude? In the 4-inch it split delicately at 22X and was real nice at 42X. Thanks for steering me towards these two – and now I have to go back and take a look at OΣ 341!

  3. Fortunately I was sitting down when I read Greg’s preceding comment on observing red and green in 95 Herculis. That same night, I went out and tried my best, but I came up empty handed. I had better luck with Delta Herculis, glimpsing hints of red and green in those two stars, though.

    And then, a few days later when I was working on the 100 Herculis post, I opened volume two of Burnham’s Celestial Handbook to the section on Hercules to see what information he might have on it, and instead came across a fascinating bit of history on 95 Herculis. At the top of p. 972 of my edition, he includes this quote regarding the colors of the primary and secondary of 95 Herculis, from a 1905 book by Anges Clerke, The System of the Stars:

    Familiar with them as vividly tinted objects, Professor Piazzi Smyth was astonished, on pointing his telescope toward them from the Peak of Teneriffe, July 29, 1856, to perceive them both white. In the following year, nevertheless, they shone as before in ‘apple green and cherry red’, and were so observed by Admiral Smyth, Dawes, and others. Captain Higgins actually watched these colors fade and then revive in 1862-63, in the course of about a year; but no trace of them has been seen of late; the stars of 95 Herculis are now of an identical pale yellow . . . The history of these stars goes back to 1780 when Herschel observed them as bluish-white and white; J. Herschel and South called them ‘bluish-white and reddish’ in 1824; Struve, 1828-32, greenish yellow and reddish yellow, in precise agreement with Pickering’s appraisement in 1878. Thus the magnificent tints of orange and green which Secchi admired in 1855 and Piazzi Smyth missed in 1856, were of a transitory character.”

    Burnham takes up the discussion in the next paragraph:

    To which the modern observer can add only the question: ‘transitory . . . or illusionary?’ Despite the mass of reports and the reliability of the observers, it seems quite unlikely that color changes of such rapidity could be physically real. Star colors, even in the case of strong contrast pairs, are delicate and elusive; disagreements among the most experienced observers seem the rule rather than the exception. In any case, similar changes have been reported for many other well-known pairs including Gamma Leonis, 70 Ophiuchi, Delta Herculis, Gamma Delphini, and Zeta Cancri. None of these stars have shown any noticeable spectral changes which would, necessarily, accompany any real change in color.” (Burnham’s Celestial Handbook:An Observer’s Guide to the Universe Beyond the Solar System, by Robert Burnham, Jr. Dover Edition, 1978, Volume 2, p. 972)

    Just to be clear, I see no reason whatever to doubt the veracity of any of the reports of red and green. I really suspect there is an atmospheric influence of some kind which in some way affects the colors that are seen.

    But I think Greg summed it up best in an email to me about the Burnham discussion: “Weird, to say the least.”

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