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The Double Stars of M 34

If you aim a telescope about halfway between Algol and Almach, lean over to peer into the port-hole like view of an 8×50 finder, and allow your eyes a few moments to roam around the field of view, you’ll notice a dull but quite obvious glow.  Center that glow in your finder, then bend back to the eyepiece in your telescope and – even at very little magnification – you’ll find a throbbing collection of diamond-like stars looking back at you.  That’s M 34, Monsieur Charles Messier’s thirty-fourth comet-like object.

As open clusters go, it’s not the most dazzling in the sky.  For example, it can’t begin to compete with the grandeur of the nearby Double Cluster, just fifteen degrees further north in its wedged-in slot between Eta (η) Persei and Delta (δ) Cassiopeiae, or with the radiant blue-white beauty of the Pleiades, a more distant twenty-two-and-a-half degrees to the southeast.  But it’s no mid-magnitude mediocrity, either.  It can hold its own against any of the many similar-sized open clusters in the sky, and best of all, it has a rather diverse smorgasbord of double stars.  All you need is a moderate aperture telescope (four inches is about right), a clear night, a comfortable chair, and an inclination to explore at a leisurely pace.

Stellarium screen image with labels added, click on the chart for a larger view.

Stellarium screen image with labels added, click on the chart for a larger view.

To navigate your way to M 34, you first have to locate the extended figure of Perseus in the northern sky. Once you get Perseus pinned down, your next goal is to find second magnitude Algol, the Demon Star, which is situated in Perseus’ southwest corner.  After accomplishing that chore, extend your gaze about twelve degrees west to the red/orange/rust-colored double-starred second magnitude radiance of Almach, holding down the eastern edge of Andromeda.  Then point your telescope at the halfway point between Algol and Almach.  (You’ll be forgiven if you’re drawn to Almach first, though.  It’s inevitable, anyway, so go ahead and take a look – you won’t regret it).

Stellarium screen image once again, click for a closer view.

Stellarium screen image once again, click for a closer view.

M 34 is actually slightly north and east of the line joining Algol and Almach, but an 8×50 finder centered at the mid-way point will easily pick it up because of its average five degree field of view.  In fact, M 34 is just five degrees west of Algol, so you may see Algol parked over at the extreme east edge of the field of view.  I labeled 6.80 magnitude HIP 13393 on the chart above for use as a stepping stone just in case you decide to start this adventure from Algol.  That star is three degrees northwest of Algol, and another two degree hop in the same direction will land you in the middle of M 34.

The best way to develop a taste for the beauty of M 34 is to start with a low power view.  Once your eyes have absorbed its concentrated splendor, you’ll want to increase the magnification in order to begin to put some distance between the many pairs of stars scattered around the view.   Since M 34 is only about half a degree in diameter, you can add quite a bit of magnification and still keep the entire cluster in view.  A 127x view in my six inch f/10 refractor with a 12mm Radian (with its sixty degree apparent field of view, hardly a wide-angle eyepiece) provided a porthole on the sky of slightly less than half a degree, which was just about right.

Now for the question which has been hovering over our heads the whole time: Where do we start?  And it’s a particularly pertinent one, too, since I’ve got a list of eight double stars to pick out of this haphazardly scattered array of stars.

Maybe we had better take a look at the sketch first:

M 34 and a faint glimmer of nebulosity occupy the center of the sketch, and arrayed around the edges are four excerpted areas which identify seven of the eight double stars.  The excerpts are located immediately to the left or the right of the actual position of the stars in the sketch.  East & west are reversed here to match the refractor view.   Click on the sketch for a much better view of it.

M 34 and a faint glimmer of nebulosity occupy the center of the sketch, and arrayed around the edges of the eyepiece view are four excerpted areas which identify seven of the eight double stars. The excerpts are located immediately to the left or the right of the actual position of the stars in the sketch. East & west are reversed here to match the refractor view. Click on the sketch to bring it to life.

We may as well begin at the top and work our way around the sketch in a clockwise direction, so that puts TDS 2338 at the beginning of our circuit.  (There’s another version of the sketch at the end of this post which has all the labels inside the sketch).

TDS 2338       No Hip or SAO numbers
RA: 02h 41.7m   Dec: +42° 53’
Magnitudes: 10.94, 10.96
Separation:   0.6”
Position Angle: 40° (WDS 1991)
Distance: ?????
Spectral Classification: ?????
Notes: Only one observation recorded in the WDS

As you can see from the faint magnitudes and agonizingly close separation, we’re not going to split this one, at least not on this trip.  I included it here mainly for identification purposes, which raises a question as to who the initials TDS belong to.  To be more precise, it’s a what, as in a subset of the Tycho Catalog known as the Tycho Double Star Catalog.

But let’s continue clockwise around the edge of the field to a more cooperative pair, HJ 1123.

HJ 1123 (h 1123)            No HIP    SAO: 38244
RA: 02h 42.0m   Dec: +42° 48’
Magnitudes: 8.39, 8.46
Separation:  20.2”
Position Angle: 249° (WDS 2011)
Distance: ?????
Spectral Classifications: B9, B9

You’ll find these two stars just north of the center point of the sketch, or above and slightly to the right (click here to open the sketch above in a second window), hovering over a trio of eighth and ninth magnitude stars arranged in a delicate arc.  With both stars at virtually the same magnitude and moderately separated, HJ 1123 stands out remarkably well from the surrounding area.

This pair was discovered and measured by Sir John Herschel in 1828 using a twenty foot long reflector equipped with a mirror of eighteen inches in diameter, which he frequently stopped down to twelve inches when viewing double stars.

Click to enlarge.

Click to enlarge.

You can see Herschel’s original observational notes on HJ 1123 if you click on the thumbnail image at the left, and if you look carefully you’ll see he estimated a separation of 15”.  If you compare that with the 20.2” separation in the WDS for 2011, it looks as if Herschel under-estimated the distance.  S. W. Burnham measured HJ 1123 in 1879 at 20.10”, so that appears to be what happened.  Burnham’s measures of it are shown further down the screen, logged as number 1372 in that list.

Next on our clockwise circuit is ES 1506 and HJ 2154, which are located in the east corner of the sketch (bottom right quadrant).

Click to enlarge.

Click to enlarge.

ES 1506         No HIP   SAO: 38259
RA: 02h 42.4m   Dec: +42° 46’
Magnitudes: 8.85, 14.00
Separation:  6.9”
Position Angle: 349° (WDS 2007)
Distance: ?????
Spectral Classification: “A” is B8

T.E. Espin’s 1506th discovery is a bit beyond our reach as a result of the 5.15 magnitudes of difference between the two stars, which means the secondary is just over a hundred times fainter than the primary – and it was already a pretty long stretch anyway because of its feeble fourteenth magnitude puff of light (the source for the thumbnail above can be found here).  And considering those circumstances, the not very distant 6.9 arcseconds of distance is no help either.  So with an acknowledging nod to T.E.Espin’s keen eyesight (he did have an advantage since he used a 24 inch Calver reflector for this observation), we’ll move on to John Herschel again and HJ 2155.

Click to enlarge

Click to enlarge

HJ 2155 (h 2155)             No HIP   SAO: 38271
RA: 02h 42.8m   Dec: +42° 49’
Magnitudes: 8.26, 10.27
Separation:  17.4”
Position Angle: 321° (WDS 2007)
Distance: ?????
Spectral Classifications: B9, A2

You can’t miss this one, parked all alone in distinct view in the east corner of our field of view.  Sir John’s observational data for this pair, which was discovered in 1831, appears in the thumbnail image at the right.  His separation of fifteen arcseconds and position angle of 321.2° are better matches for the most recent WDS data than was the case for HJ 1123 above.   Despite the two magnitudes of difference between the secondary and primary, I had no problem separating the pair at first glance, thanks mainly to the comfortable distance between the two stars.

Next on our way around the circle is a pair that required some real detective work to decode, OΣ 44 and HJ 1124.

OΣ 44 (STT 44)          HIP: 12619   SAO: 38254
RA: 02h 42.2m   Dec: +42° 42’
    Magnitudes       Separation     Position Angle      WDS
AB: 8.26,   8.96              1.40”                    58°               2009
AC: 8.26,   8.32           86.40”                  290°               2011
CD: 8.30,12.30           17.70”                  149°               2007
Distance: 810 Light Years
Spectral Classification: “A” is B9
Notes:  CD is BKO 172

HJ 1124 (h 1124)          HIP: 12606   SAO: 38248
02h 41.6m   Dec: +42° 43’
Magnitudes:  8.0, 11.6
Separation:  17.5”
Position Angle: 150° (WDS 2013)
Distance: ?????
Spectral Classification: B8

You’ll find OΣ 44 imitating an isosceles triangle just below and slightly left of center in the sketch.  What you see appears to be a straightforward triple star, but one of those three stars doesn’t belong to OΣ 44, as you can see in the labeled excerpt of the sketch . . . . . . we’ll get back to that in a moment.

With only half a magnitude of difference between the two stars, it didn’t seem unreasonable to expect to split the tight AB pair.  I tried on two different nights, but both times the seeing conditions were plagued by a persistent east wind that played ill-temperatured havoc with the atmosphere, causing the stars to jump and sparkle, and threatening to wear the shine off the edges of the poor nervous little devils.

I spent at least as much time trying to locate HJ 1124 as I did attempting to separate OΣ 44 AB.   Both programs I used for reference, MegaStar and SkyTools 3, were no help at all.  The first one gave the wrong location for it, and the second one ignored it completely.  Fortunately, even though I had to reach all the way back to 1906 for help, S. W. Burnham was ready and waiting to come to the rescue.

Until 1894, OΣ 44 consisted of only the “A” and “B” pair that J.H. Mädler first measured in 1843.  I’m not sure who extended measures to include “C” in 1894, but Burnham left it out of his description of OΣ 44 in his 1906 catalog.  What he did include was a description of HJ 1124 that put it in a low power field with and preceding OΣ 44, which is shown below in entry number 1373.

Shown in this excerpt from the second volume of Burnham’s 1906 catalog are his descriptions for HJ 1123, HJ 1124 (both are referred to with the prefix “H”), and OΣ 44.  Click on the image for a larger view.

Shown in this excerpt from the second volume of Burnham’s 1906 catalog are his descriptions for HJ 1123, HJ 1124 (both are referred to with the prefix “H”), and OΣ 44. Click on the image for a larger view.

As it turns out, the “C” component of OΣ 44 is actually the primary of HJ 1124, and that third star I described a few paragraphs above as not belonging to OΣ 44, is HJ 1124 “B”.  You can see that clearly in the excerpted diagram of  OΣ 44/HJ 1124 in the sketch above.

Burnham also mentioned Herschel had “much under-estimated” the separation of HJ 1124, which is obvious when you compare Burnham’s 1904 measure of it above (16.62″) with Herschel’s measure of HJ 1124 (6″) shown in the previous thumbnail image included in the discussion of HJ 1123.  I also discovered a Simbad search for HJ 1124 turns up the WDS ID number J02422+4242C, the Tycho number 2853-0238-1, and HD 16719 — all of which are additional identifications common to both HJ 1124 and OΣ 44 C.  So that pretty well pins that puzzle down.

Considering the detective work required to establish all that, it’s no wonder both MegaStar and SkyTools 3 had problems in dealing with HJ 1124.   But that confusion also appears to have led to another mystery which took place in 2007.

Measures were published that year adding another star to OΣ 44, which was labeled BKO 172 CD, and is included in the data above for OΣ 44.   The position angle and separation published for it (149° and 17.70”) virtually matches that of the 2013 WDS measures for HJ 1124 (150° and 17.5”).  The magnitudes for the secondary of each pair (12.30 for BKO 172 D and 11.60 for HJ 1124 B) are close as well, all of which leads to the conclusion those two designations apply to the same pair of stars.

And again, confirmation can be found via a Simbad search, which shows both the “D” member of BKO 172 and the “B” member of HJ 1124 with a common WDS and CCDM identifier, J024244+4242D.  I suspect when the 2007 measure was made for what became BKO 172, owing to the already existing confusion over the correct location of HJ 1124, the person who made those measures didn’t realize that pair of stars had previously been cataloged and labeled by John Herschel in 1828.

And all I was looking for was a pleasant evening with a few companionable double stars in a friendly open cluster . . . . . . .

Take a deep breath now, and we’ll take a quick (and brief) look at the last two pairs in M 34.  Both of them can be found tucked up tight against the western edge of the field of view in the sketch.

HJ 2154 (h 2154)             No HIP   SAO: 38225
RA: 02h 41.2m   Dec: +42° 41’
Magnitudes: 9.49, 10.93
Separation:  10.0”
Position Angle: 140° (WDS 2010)
Distance:  ?????
Spectral Classifications: A0, A5

TDS 2335      No HIP or SAO numbers
RA: 02h 41.3m   Dec: +42° 44’
Magnitudes: 10.5, 12.25
Separation:   2.00”
Position Angle: 182° (WDS 1991)
Distance: ?????
Spectral Classification:  ?????
Notes: Only one observation recorded in the WDS

TDS 2335 is located a short three arc minutes north of HJ 2154, and like it’s higher numbered relative, TDS 2338 that we started this survey with, there have been no observations of it since the Tycho observation of 1991.  It should be possible to split it under good seeing conditions with a 9.25 inch SCT, but I’m still waiting for some atmospheric cooperation.

HJ 2154, on the other hand, was rather obvious in my six inch refractor, and should be within reach of a four inch refractor on a decent night.  Sir John Herschel’s 1831 observation of it is shown above in the thumbnail image appearing under the discussion of HJ 2155, which shows the same separation as the 2010 WDS figures, but a significantly wider position angle of 147°.

You may have noticed there’s a persistent pattern among all of these doubles stars with regard to distance.  Other than OΣ 44, which is estimated to be floating in our galaxy 810 light years beyond us, I came up empty-handed in the search for distances.  Most of the estimated distances I’ve seen for M 34 put it in the range of 1400 to 1800 light years, which if correct, would seem a likely distance for most of the double stars in our list.  On the other hand, the distance attributed to OΣ 44 would indicate it’s either not part of the M 34 cluster or point to a discrepancy of distance in one of the measures.

One thing is for certain, however.   The stars of M34 show very little proper motion, which normally would be a pretty good indication of the cluster’s distance (source):

Click on the image for a larger view.

Click on the image for a larger view.

The minimal proper motion of the primary of OΣ 44, at -008 -001 (.008 arc seconds per year west and .001 arcseconds per year south) fits in to that pattern as well, although that doesn’t necessarily place it in M 34.  Of the other seven stars on our list, only TDS 2335 has the same proper motion as OΣ 44, but the other six show very little motion as well.  So at the least it’s possible all the stars on our list are at about the same distance, regardless of whether they’re enmeshed in M 34 or not.

Which is another mystery to be solved on another day.

Next time out we’ll take a tour through a relatively neglected sector of the sky known for a single outstanding double star . . . . . but as I discovered, that pair has some serious competition.

Clear Skies until then!   😎

This is the same sketch as above, except that the labels are moved into the eyepiece field.   East & west reversed here to match the view in the refractor, click on the sketch for a much better view of it.

This is the same sketch as above, except that the labels are moved into the eyepiece field. East & west are reversed here to match the view in the refractor — click on the sketch for a much better view of it.


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