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A John Herschel Odyssey in Canis Major: h 3934, h3938, and h 3945

So there we were, me and my 80mm Mizar, sitting quietly in the moonlight. The sky was magnificently crisp, the stars were twinkling with adolescent enthusiasm, a rapturous host of beautiful fluffy white clouds were arrayed randomly above me — and I was mentally preparing myself for an invigorating evening of sucker hole roulette.  You probably know the routine:  find the most wide open space of sky you can (get ready to spin the roulette wheel), aim your scope at a target in the middle of it (spin the wheel now), get lined up (it’s slowing down already), focus the image (it’s really slowing down now), and then guess how long it will be before the clouds invade your field of view (the wheel is barely moving at all now).  Usually it takes no more than a fraction of a second after you find the focus (yep, just heard the marble drop).  Fun stuff if you have the patience for being fleeced repeatedly.  (It doesn’t matter where the marble drops, you won’t win).

But as the evening wore on, the clouds became less common and the sucker holes began to get larger and more long-lasting.  So I stuck with it, zeroing in on a target and staying with it for as long as I could see it.  At some point – I think it was about the time my fingers had turned to ice and my toes were as hard as permafrost – I spied a huge swath of clear sky in Canis Major.  And that was when I remembered the Winter Albireo, thanks to a recent email and sketch from Steve McGee.

So I grabbed my well-worn copy of Sky and Telescope’s Pocket Sky Atlas, flipped to chart number 27, and star-hopped around the coastal pines to it.

I didn’t mention the coastal pines?  They’re a family of inter-woven and close-knit fir trees living across the street from my second story deck — there are about a dozen of them — that project eighty feet into the air, blocking most of my view of the southern sky below a declination of minus ten degrees or so. I keep waiting for a winter wind to take them down, but no luck so far. Anyway, since the Winter Albireo lies at a declination of minus twenty-three degrees, that meant I had replaced the art of sucker-hole-hopping with a challenging game of fir-tree-finesse.   So with mother earth escorting them through the lace-like framework of pine needle branches, I spent the next hour catching views of three of John Herschel’s 1837 discoveries.

** ** ** ** ** ** ** ** ** ** **** ** ** ** ** ** ** ** ** ** ** *** ** *** ** ** ** ** ** ** ** ** ** **

It was November 13th, 1833 when Sir John, with firm intentions of completing a survey of the southern skies, packed up his astronomical hardware (including a five inch refractor and an 18.25” reflector) and boarded the East India Company’s Mount Stewart Elphinstone, bound for The Cape of Good Hope.  During his sojourn there, he made a large number of double star observations, which are preserved for posterity on pages 171 to 242 of the book that resulted from that trip, Results of Astronomical Observations Made During the Years 1834, 5, 6, 7, 8 at the Cape of Good Hope; Being the Completion of a Telescopic Survey of the Whole Surface of the Visible Heavens, Commenced in 1825. That long-titled book, which was published in London in 1847, has fortunately found its way into the public domain and can be found here.

And we’re here to take a look at three of those stars now, beginning with h 3945, sometimes referred to as the Winter Albireo.

 One navigational method of carving a path through the sky to our first target is to triangulate your way to it by using Delta (δ) and Omicron-2 (O2) Canis Majoris.  Another effective approach is to draw a line from Omicron-1 through Omicron-2 and extend it in the same direction for the same distance, which will bring you out just a few photons north of h 3945.  (Stellarium screen image with labels added, click to enlarge).

One navigational method of carving a path through the sky to our first target is to triangulate your way to it by using Delta (δ) and Omicron-2 (O2) Canis Majoris. Another effective approach is to draw a line from Omicron-1 through Omicron-2 and extend it in the same direction for the same distance, which will bring you out just a few photons north of h 3945. (Stellarium screen image with labels added, click to enlarge).

h 3945    (BC is SHY 508)    HIP: 35210    SAO: 173349
RA: 07h 16.6m   Dec: – 23° 19’
Magnitudes   AB: 5.00, 5.84    BC: 5.84, 6.76
Separations  AB:26.40”           BC: 999.90”
Position Angle:  52° (WDS 2008)   165°  (WDS 1999)
Distance: 6273 Light Years
Spectral Classification: K4, A5

Before we get too far, I should mention you’ll find the stars catalogued by John Herschel carry a prefix of “HJ” in the Washington Double Star Catalog (WDS).  But the older lower case “h” is still used on many charts, so there’s no telling which style you’ll run across.  I prefer the historical aura of the lower case format, which was originally used to differentiate the younger Herschel (h), Sir John, from the senior Herschel (H), Sir William, an effective visual form of paternal recognition if ever there was one.

I first bumped into h 3945 by accident several years ago when I was exploring the star fields east of Canis Major for open clusters.  I think I had wandered north to it after ogling NGC 2362, a tight little cluster of stunning beauty surrounding Tau (τ) Canis Majoris which just happens to include another John Herschel discovery, h 3948.  That one is a complex quadruple star that also includes two additional sub-arc second companions, and with a bit of cooperation from the winter skies, it may be the subject of a another post.

But for now, let’s go see why h 3945 picked up the Winter Albireo designation:

And it should be obvious!  This colorful sketch was done by Steve McGee and is used with his kind permission. The apparent field of view is about 45’, based on a comparison with MegaStar.  (East and west are reversed here to match the refractor view, click for a larger version).

And it should be obvious! This colorful sketch was done by Steve McGee and is used with his kind permission. The apparent field of view here is about 45’. (East and west are reversed here to match the refractor view, click for a larger version).

 Outlined in yellow are all three of the Herschel stars described in this post.  (Click to enlarge the view).

Outlined in yellow are all three of the Herschel stars described in this post. (Click to enlarge the view).

I don’t have the least clue as to who was first to describe h 3945 as the Winter Albireo, but as the colors in Steve’s sketch show, it was inevitable.  Haas describes it as “bright citrus orange” and “royal blue” (p. 38), and the Night Sky Observers’ Guide describes it as “intense orange and blue” (Vol 1, p. 88).  In his 1894 Celestial Objects for Common Telescopes, the Reverend T. W. Webb was considerably more impressed: “fiery red, greenish blue . . . Magnificent pair.” (64)  And even John Herschel, normally rather reticent with descriptive notes, recorded the colors he saw in two separate observations, as can be seen at the bottom of the page at the right:

Not only is h 3945 deserving of comparison to Albireo, it also measures up well with Almach — but despite that, it does disappoint on occasion.  I think it’s mainly a northern hemisphere thing, a result of the colorful pair’s relatively low position in the southern sky, which tends to diffuse the colors considerably when haze is present.

On the night I tracked it down with my 80mm Mizar, the sky was crisp and transparent, but the moon, waxing at about 60% of full, was bright enough to turn the orange tinge very pale, and the blue was barely detectable.  So if you’re not impressed, go back on a better night – and to give the color a chance to  work its magic, go with four inches of aperture or more if you can.  My first view of it was in a four inch refractor, and that initial image still flickers to life every now and then in my double-starred memory.

STScI Photo with labels added.  (East & west reversed,

STScI Photo with labels added. (East & west reversed,

There’s supposed to be a 6.76 magnitude third component, SHY 508, which is shown in the data line above with a position angle of 165 degrees at a distance of 999.90” (16.7’).  The problem is it’s not there — not in Steve’s sketch, not in my copy of MegaStar, and not in the STScI photo at the left.

As you can see, I’ve labeled two possible candidates in the STScI photo.  The fainter of the two, GSC 6537:2093, is at the correct PA and distance, but at a magnitude of 10.8, it’s too dim.  The only star in the immediate area that comes close to matching the magnitude recorded for SHY 508 is 6.30 magnitude HIP 35132 / SAO 173319 / HD 56341, but at a PA of about 200 degrees and a distance of slightly less than 30 arc minutes, it’s in the wrong place.  So – another mystery for the books.  Or perhaps it’s just “SHY.”  🙄

Time to remove the mystery hat and clamber off to the north now, and to aid our navigation we’ll employ another chart:

As you can see, we don’t have far to go.  In fact, with the Winter Albireo centered in your finder, our next star is easy to spot.  Look for two stars of similar brightness about a degree to the northwest – the first is our next target, h 3938, and slightly beyond it in the same direction is 5.95 magnitude HIP 34914.  (Stellarium screen image with labels added, click for a larger view).

As you can see, we don’t have far to go. In fact, with the Winter Albireo centered in your finder, our next star is easy to spot. Look for two stars of similar brightness about a degree to the northwest – the first is our next target, h 3938, and slightly beyond it in the same direction is 5.95 magnitude HIP 34914. (Stellarium screen image with labels added, click for a larger view).

h 3938                HIP: 34940   SAO: 173247
RA: 07h 13.8m   Dec: – 22° 54’
Magnitudes: 6.32, 9.10
Separation:  19.4”
Position Angle: 250°  (WDS 1999)
Distance: 1576 Light Years
Spectral Classification: B2, G5

Besides playing hide-and-seek with the interfering framework of pine needles, I was also contending with rather poor seeing once again, easily as bad as the worst shown on this chart.  And there were other factors of frustration as well.  The first was the 2.8 magnitude difference between the two stars, the second was the sunlight reflecting recklessly from 60% of the moon’s surface, and the third was the challenge the 9.1 magnitudes of secondarial light posed to an 80mm lens operating at 60x — more magnification just led to a muddled view.  So despite the reasonably wide separation of 19.4”, I had to look long and hard to corner my quarry — it was averted vision or no vision.   Fortunately, it didn’t take all that much visual averting to see the secondary, but it was very ghost-like at first.  It easily could have been a creation of my imagination on first sighting, so I kept coming back to it as I made my sketch:

You won’t need averted vision to see the secondary here, but clicking on the chart will enlarge the view and make things easier.  (East & west reversed to match the refractor view).

You won’t need averted vision to see the secondary here, but clicking on the sketch will enlarge the view and make things easier. (East & west reversed to match the refractor view).

I really think this pair of stars is crying out for more aperture.  It was certainly a challenge with the 80mm scope — an additional twenty millimeters would be a much better choice.  Both stars were essentially colorless under the observing conditions I was contending with, but if you look up in the NNW corner of the sketch, you’ll see a sixth magnitude star that has a very pronounced orange tint to it – that’s HIP 34914, a class K4 star at a distance of 780 light years, which we saw earlier in our finder.

h 3934  (BC is RST 4840)    HIP: 34718   SAO: 173152
RA: 07h 13.3m   Dec: – 21° 48’
Magnitudes    A,BC: 6.91, 8.49     BC: 8.60, 10.80
Separations   A,BC: 13.7”      BC: 0.60”
Position Angles   A,BC: 235° (WDS 1999)   BC: 270° (WDS 1949)
Distance: ?????
Spectral Classification: B5, B9

Now, with our previous pair still centered in your finder, if you use HIP 34914 as a pointer (here’s the chart above), you’ll find h 3934 shining as a 6.9 magnitude star at three times the distance separating h 3938 and HIP 34914.

And again, I had to avert my vision to catch a glimpse of the 8.49 magnitude secondary (we’ll skip “C” since it’s well out of reach for 99.99% of us):

Very similar to the previous sketch, with a little less distance between the two stars.  (East & west reversed, click for a larger view).

Very similar to the previous sketch, with a little less distance between the two stars. (East & west reversed, click for a larger view).

The magnitude difference is only 1.58 between this primary-secondary pair, but they’re six arc seconds closer than our previous Herschel duo, which pretty much gobbles up what would otherwise be an advantage.  In fact, the secondary here was every bit as eager to avoid my vision as that of h 3938.  Again, I heard a voice echoing in the moonlight – more aperture!  And sure enough, when I went looking for other observations of these two Herschel discoveries, I found Haas had come to the same conclusion:

h 3934: “150mm, 36x: Nice view.  A bright, easy pair at the end of a curved line of dim stars.  It’s a pure white star and an ash white, split by only a small gap.”

And our previous star —

h 3938: “125mm, 50x: Lovely combination. A bright white star with a small nebulous companion, split just wide enough for the companion to be easily seen while striking in contrast.”  (p. 38 for both)

** ** ** ** ** ** ** ** ** ** **** ** ** ** ** ** ** ** ** ** ** *** ** *** ** ** ** ** ** ** ** ** ** **

And that was about enough for me on this particular night.  Apparently intermission was over since the clouds were drifting back into their places in the sky in groups, the wind was winding itself up for another blustery show, and a persistent image of steaming hot tea was dancing in my head.

With any luck at all, next time out we’ll see if we can dig h 3948 out that open cluster surrounding Tau Canis Majoris.

Clear Skies!

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7 Responses

  1. John, Thanks for posting on this very interesting group of stars. I’m still trying to get that drift to the West “quite rightly,” for a Mellow Yellow. I had great fun making the sketch, though. It was Chris Thuemen who pointed me to this pair while he was here for the Maui International Double Star Conference. The wind was tough that night and it was a challenge making the sketch. We had just looked at Tau CMa in NGC 2362 and Chris said, “Hava look at THIS!” I star hopped up to it an BINGO! Good fun.

  2. Great write up John!

    Haven’t visited that neck of the sky before. You’re right though; different systems look better in smaller ‘scopes than larger. What’s amazing is that small and large achromats seem to me to be about equally efficient at prizing them out!

    Best wishes,

    Neil.

  3. Hi John!
    As Steve indicated about our last night at the summit of Haleakala, I was simply wandering around Canis Major when the notion to re-visit h 3945 came upon me. I had been in this area 3 years previous and do not remember the vivid colours of the AB pair. As you noted, much of the reduced colour rendering is likely due to the increased atmosphere that we northerners have to look through to observe this pair. Being at 10,000′ elevation and at 33 degrees north latitude, the conditions were significantly different. As I moved from telrad to eyepiece, I simply exclaimed “Wow, look at this Steve”. “Albireo of the South”. The pair is dimmer than Albireo and with greater separation that allow the orange and blue companions to be unaffected by the others brightness.

    I have seen a number of other pairs with this same vivid colour combination, but the names elude me at the moment. I will have to dig back into my records and create a list for you to explore.

    I have a question regarding the “C” component. Do you have any thoughts as to why, or better still, how a star with such a large separation would be considered or thought to be a companion. Would this star even have been observed in the same fov through the 18.5″ reflector that Herschel was using to create his catalogue?

    Another great read, John!!

    Cheers, Chris.

    • Thanks for the comments, Chris, Neil, and Steve (aka Mellow Yellow???) 😎

      On Chris’s question, the “C” component of the BC pairing is moving parallel to the “C” component according to the proper motion figures in the WDS, -031 for “B” compared to -029 in RA for “C”, and +042 for “B” and +041 for “C” in Dec. Those figures can be seen here. So it appears a common physical (proper) motion was suspected.

      Interestingly, “B” is not physically related to “A.” So we have a primary-secondary pair that are line-of-sight, and a BC pairing that is suspected of being linked through parallel proper motion, yet the “C” star is no longer visible at it’s 1999 magnitude or location!

      NOW — comes another mystery. The WDS notes files at the above link includes this comment: “SHY 508 BC: HIP 35213 + HIP 35578.” I looked up the coordinates for HIP 35578 and found it’s assigned a RA of 07h 20m 32.5s and a Dec of -26* 42′ 01″ — and that not only puts its four minutes EAST and 3.5 degrees SOUTH of h 3945 (aka Winter Albireo), it puts it two degrees SOUTH of Tau Canis Majoris! It does have the 6.76 magnitude assigned to the “C” component of SHY 508, however. If you have Sky Safari, enter HD 35578 in the search function and you’ll get the data on it — center it, and you’ll see it appear on your screen south of Tau.

      So in answer to Chris’s second question, it certainly would not have been visible in John Herschel’s reflector, nor at a distance of three degrees, would he have seen it in the same field in his five inch refractor.

      None of this makes any sense. There’s a mistake in the initial observation of SHY 508 “C” — either a mistaken star or an error in coordinates.

      P.S.: I’ve sent a request to Brian Mason at the WDS for info on SHY 508. I have a suspicion that separation of 999.90″ for the BC pair is meant to convey an anomously large distance, as opposed to the actual distance. That figure strikes me as rather odd.

      John 😕

  4. Hi John!
    Correct me if I am wrong, but are not the vast majority of stars in the galaxy moving generally together…therefore linked…even gravitationally. I am having difficulty, given my virtually total ignorance of the subject, remember, I’m just a dumb photographer…LOL. The whole notion of double star discovery in the early days; I’m having difficulty understanding how, and even if, the early observers managed to established a connectedness between stars, or was it more based on close proximity and a good guess. Given the typically slow movement of stars in general (of course there are the exceptions), I can’t see how enough data for the typical double star could have been amassed by these early observers to establish whether these were true binaries or simply optical doubles. I guess what I am really hoping for is the existance of a book or article that, for the layman like myself, provides an indepth description of the processes and theories that the early observers/cataloguers used to guide their observations/activity…and even more basic than that, what prompted the discipline of double star observing , measuring, recording…etc, in the first place. I am sure there are many of us that could use a double star primer.

    Getting back to our distant “C” component, proper motion, from my limited knowledge, does not mean these stars are necessarily gravitionally bound and even less that they are in a orbital dance. I just find it extremely odd that this kind of separation would have resulted in someone being able to establish a connection.

    Of course the science and measuring techniques of today clearly show the special relation that groups of stars (2 to whatever #) posess; the new research of exo-planets being an off-shoot of this activity, I find I am missing all the early “raison d’etre” for the this branch of observation.

    Thankfully, I don’t lie awake all night trying to answer these questions…but I do dream of my next photo opp!!

    Cheers, Chris.

    • Chris,

      I don’t know of any single source that covers all the aspects of double stars and the intricacies of determining relations between a given pair of stars. One place to start is the Wikipedia entry on double stars — that will provide you with some definitions at least.

      Aside from the obvious connection between stars with orbital relationships (true binaries), there are others that are suspected of being physical pairs, and there are various reasons for coming to that conclusion.

      As an example of one of those reasons, I tracked down a paper co-written by the “SHY” of SHY 508 (his name is Ed Shaya),which was published in December of 2010 — you’ll find the paper here. Much of it will go over the heads of most of us, but the basic gist of the paper is he and his co-writer did a study that searched for stars which had once been orbital companions, but for one reason or another (such as interactions with passing stars or galactic tidal forces) had separated over time. The goal of the study was to identify those stars by looking at their movement (proper or otherwise) and using statistical methods to determine the likelihood of their having once been linked to other stars — and they were looking at distances between the two stars in excess of 1 parsec (3.26 Light Years), which corresponds in some cases to several degrees apart from our vantage point. And that may well explain SHY 508.

      At any rate, the article will give you some insight into one of the more complicated aspects of double star research, which from what I gather is an offshoot of stellar formation, and also involves brown dwarfs and large exo-planets.

      As to the motion of stars, yes, they tend to move with the orbital direction of the galaxy, but in addition, most all stars have a component of motion which is separate from that of the galaxy, and that’s what is referred to with the term proper motion. Keep in mind, the sun and the star you’re looking at are both moving (shifting positions) in relation to one another. Another way to say that is the closer a star is to our sun, the more it will seem to move as opposed to a star thousands of light years away. Stars with high proper motion are very likely to be relatively close to us. Again, you might take a look at the Wikipedia entry for proper motion.

      John

      • Hi John!
        Thanks for that. That was very useful. So I did a bit of surfing and came across a periodical called, “The Asterism” in particular Vol. XVIII No.5, Feb. 2007. It’s lead article is aptly called, “Double Star Observation” and was authored by Clif Ashcraft. According to Clif, he whole endeavor of double star observation is actually a very simple concept…it’s all about the mass…knowing stellar mass provides a whole array of data about individual stars. Without the knowledge of stellar mass we would not have astro physics. So it is obvious that the painstaking work that went into double star measurements and orbit calculations was probably the single most critical and important activity in astronomy.

        The article is well written for the layman. Here is one little tidbit from the article…to the best of Clif’s knowledge, the record holder for double star measurements is Dr. Van den Bos with the almost unbelieveable measurement total of 71,929. Wowsers!! Clif goes on to note that during his university days in 1963, while working on a course project on Mt. Hamilton, he accidently happened onto Dr. Van den Bos in the midst of his measures. It appears that the good doctor enjoyed classical music while engaged at his work.

        I feel better know that I have this very basic understanding of the why. It now puts the whole subject of double stars on a very sound footing. One really has to hand it to these early astronomers for the quality and sheer volume of their collective works. For those of you who have access to Aprils issue of “Astronomy” there is a fascinating article about the life and times of Sir John Herschel. An excellet read.

        Cheers, Chris.

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