Sleuthing in Sight of Sadalmelik: OΣ 460, Σ 2862, and Σ 2855

If it seems like we’ve been here before, it’s because we have – just a month shy of a year ago, when we looked at “The Alpha-Beta-Gamma of Aquarius,” and discussed Homer-era Greek grammarians, urns of olives, and wine. Those who believe double star discussions have to be relegated to dry recitations of arrid statistics haven’t spent a night with a few ancient Greek star gazers.

On that trip, we discovered Sadalmelik, aka Alpha (α) Aquarii, means “lucky stars of the king”.   Some of that luck seems to have spread to a few nearby stars in the rarified void surrounding Sadalmelik (we’re outside the Milky Way here, so star populations are sparse). I accidentally stumbled over the first lucky star, a tantalizing triple, while surveying some of Herr Otto Wilhelm von Struve’s more difficult discoveries, and it didn’t take long to discover his father, Friedrich Georg Wilhelm von Struve, had also found a couple of visually stunning stars. All three of the stars we’re about to look at are within a two degree radius of Sadalmelik, which will serve as our star base.

Stellarium screen image with labels added, click to enlarge.

Aquarius is a dim and meandering constellation spread out over several acres of sky.   You’ll find it below the west edges of Pegasus and Cetus and north of Capricornus.   Focus your attention on the turquoise α (Alpha) in the chart above because we’re not going to wander far from it.

Here are the locations of our three stars, all labeled in tempting turquoise:

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

We’ll going to start in the north and work our way south, so let’s move north to OΣ 460, which is located two degrees due north of Sadalmelik. Use 7.57 magnitude HIP 109044 and 6.99 magnitude HIP 109052 to point you in the correct direction. You’ll find OΣ 460 lying in the center of a dim, but distinctive arc of three stars; 7.24 magnitude HIP 109144 lies on its east side, and 8.39 HIP 108990 brackets it on its west side.

OΣ 460 (STT 460)    HIP: 109064   SAO: 127283
RA: 22h 05.7m  +01° 47’
Magnitudes   AB: 8.40, 12.80    AC: 8.40, 12.10
Separations   AB: 13.80”           AC: 18.80”
Position Angles      AB: 340° (WDS 2003)    AC: 30°  (WDS 2003)
Distance: 867 Light Years (Simbad)
Spectral Classification:   “A” is F0

After several frustrating attempts to split some uncooperative sub-arcsecond pairs, I went in search of this tantalizing triple star as a diversion.   My first glance into the eyepiece showed a single star, but when I averted my vision slightly, both “B” and “C” suddenly materialized from out of the primarial glare, which, after wrestling with stars that refused to separate, was a very welcome sight:

Averted vision beauty! You have to look closely to catch sight of the “B” and “C” components, just as I did when peering into the eyepiece. The primary is a weak shade of white. Notice the two UCAC4 labeled stars, which we’ll come back to shortly. (East & west reversed to match the refractor view, click on the sketch for a better view of the faint components).

I doubled the magnification with a 5mm eyepiece in hopes of pulling “B” and “C” out of the subdued glare of the primary, which resulted in this slightly improved view:

Although they’ve moved up to direct vision objects, you still have to look closely to catch “B” and “C”. (East & west reversed once again, click to improve the view).

(Click to enlarge)

At 304x, I was able to confirm my 152x impression that both “B” and “C” are brighter than the magnitudes shown above from the WDS.   Even though it was an averted vision object at 152x, “B” was too conspicuous in my six inch refractor for a 12.8 magnitude star, especially considering it’s parked within 14” of a primary listed as being four magnitudes brighter.   In fact, when compared with the two UCAC4 labeled stars in the first sketch (here it is again), both of which are in the 11.2 to 11.4 magnitude range, “B” was of about the same brightness, allowing for the glare of the primary. I found “C” was slightly brighter than “B”, perhaps in line with the .7 WDS magnitude difference between them, suggesting a magnitude for C in the range of 10.6.

A quick look at the excerpt above at the right from S.W. Burnham’s 1913 Proper Motion Catalog shows he estimated the magnitude of “B” at 11.7 and “C” at 11.0, which is similar to my estimates. STT 460 is part of a joint survey of Otto Struve’s pairs with high magnitude differentials (delta_M) I’m working on, so it will eventually be suggested to the WDS for magnitude revisions.

A glance at the proper motion of the three stars of OΣ 460 shows they appear to be unrelated, since all three are moving in different directions and at differing rates of speed.

A:  +036 -040   (WDS)         (.033”/year east, .038”/year south)
B:  -031 +142   (WDS)         (.031”/year west, .142”/year north)
C: +027 +001   (WDS)         (.027”/year east, .001”/year north)

Now we’ll drop down to Σ 2862, which lies a bit more than a degree (1° 16’) south and very slightly east of OΣ 460. You’ll find it just 24’ east of 6.99 magnitude HIP 109052. (Here’s our previous chart again).

Σ 2862        HIP: 109186    SAO: 127306
RA: 22 07.1m   Dec: +00° 34’
Magnitudes:  8.04, 8.41
Separation:   2.5”
Position Angle: 95°  (WDS 2011)
Distance: 256 Light Years (Simbad)
Spectral Classification: “A” is F8

Spare beauty in a sparse field is the best way to describe this delicate pair:

The primary and secondary are white, almost touching one another, separated by the width of B.  It always amazes me how frequently surrounding stars arrange themselves into eye-catching geometric configurations – notice the three stars pointing into the west, lined up almost perfectly with one another. The moon was at first quarter when I made this sketch, about 40 degrees to the west, with moisture practically dripping out of the air, so some of the background stars undoubtedly were obscured at the time. (East and west reversed once more, click to improve the view considerably).

This pair of stars was discovered and measured in 1828 by F.G.W. Struve.   The WDS identifies it as a physical double, which appears to be based on the similar proper motions of the two components.   The WDS data shows “A” with a rate of +078 +049 (.078”/yr east, .049”/yr north) and “B” with a rate of +088 +047 (.088”/yr east, .047”/yr north).

Shown below is a list of measures in Thomas Lewis’s book on Struve’s stars, to which I’ve added two additional measures that I pulled from S.W. Burnham’s 1906 catalog (labeled LM and Hu), three from R.G. Atiken’s 1932 catalog, and four which come from WDS data.

Click for another view.

Based on the proper motion of the two stars, there should be very little detectable change in the relative positions of the two components.   The separation measures in the list above are relatively stable in the 2.3” to 2.5” range, but surprisingly the position angle has consistently moved in a northward direction.   That would lead to the conclusion that either the proper motions numbers are slightly off, or that that one of the two stars could be in a very wide orbit around the other. Some of the preliminary GAIA data is available now in Vizier (the catalog code is I/324) so I checked and found that, unlike the WDS, it lists both stars with the same proper motion, +088.7 +046.6, numbers which are at least similar to the WDS.   At any rate, it’s possible these two stars are doing something more than just traveling the through the galaxy in tandem.

Our last star lies a little over a degree (1°7’) south of Sadalmelik (our chart once again). Drop a short 38’ south and slightly west to 5.29 magnitude 32 Aquarii and then another 32’ south and slightly east to reach Σ 2855, using 9.21 magnitude SAO 145857 to guide you. Notice Σ 2855 forms a triangle with two faint stars, 8.51 magnitude HIP 109141 and 8.93 magnitude SAO 145864.

Σ 2855 (STF 2855)    HIP: 109038    SAO: 145859
RA: 22h 05.3m   Dec: -01° 25’
Magnitudes   AB: 8.34, 10.26     AC: 8.34, 10.80
Separations  AB: 25.10”             AC: 85.10”
Position Angles   AB: 305° (WDS 2013)    AC: 117° (WDS 2013)
Distances   A: 494 Light Years    B: 109 Light Years
Spectral Classifications:   “A” is F8, “B” is G

Spare beauty once more, but we also find ourselves entranced again by a captivating geometric configuration:

The primary was a faint white, and easily the brightest star in a sparse field, while “B” and “C” seemed to be intent on getting lined up perfectly. The first quarter moon mentioned above also had something to do with the lack of stars seen in the field. (East & west reversed once more, click for a much better view).

F.G.W. Struve discovered the AB pair in 1828, and I haven’t been able to track down who added the “C” component in 1896.   S.W. Burnham would have been the most likely person, but he didn’t include it in his 1906 or 1913 catalogs, and from what I can determine, Philip Fox and George Hough didn’t measure it either.   I had hoped to get a clue from Aitken’s 1932 catalog, but for some reason he skipped over Σ 2855 entirely.

A look at the distances shown above in the next to last line of data eliminates any question as to whether the AB pair are related, since there’s approximately 385 light years separating the two.   Simbad doesn’t provide a distance for the “C” component, but there is a possibility “A” and “C” are linked physically by proper motion, as the image below shows:

Aladin image with Simbad proper motion data super-imposed. Click to enlarge!

Click to enlarge.

The common motion of “A” and “C” is very obvious, and the proper motion data at the bottom of the images shows the rates of motion are very similar.   “B” is moving more rapidly, which is a function of it being much closer to us.   A look back through the recorded measures is further evidence of the relative motion of “A” and “B”, as you can see the separation (at 25.10″ in 2013) has been narrowing slowly as “B” appears to overtake “A”.   If you happen to be looking up a few thousand years from now, you’ll have the pleasure of attempting to split a very close pair of stars!

Time to go contemplate an urn of Greek olives and a glass of wine, and leave Aquarius to wend its way westward for the remainder of the year.  Our next tour will takes us north to the dense Milky Way star fields of Lacerta, where we’ll see if we can help the Lacertan lizard get a handle on his magnitudes.

Until then, Clear and Stable Skies!   😎

Pouring Starlight from an Aquarian Water Jar: Bu 1515, HJ 5529, and Bu 172 (and a Bow to Zeta Aquarii)

Ahhhhh, there’s nothing like a sip of cold water on a hot summer day . . . . . . . . but if you’re waiting for water to flow from the Aquarian water jar, you’re likely to be well past parched by the time Aquarius hoists his massive framework into the heavens. Still, even though the Aquarian may be a little late for thirsty lips, he nevertheless has one other redeeming quality: a penchant for pouring starlight out of that jar tucked under his right arm.

The Aquarian jar in outline: Eta (η), Zeta (ζ), Pi (π), and Gamma (γ) frame the water jar, while Alpha (α) rests on Aquarius’ right shoulder.  (Stellarium screen image with labels and outline added, click on the image for a larger version).

As an informative aside, the German language has a much more descriptive name for Aquarius: der Wassermann — which, if it isn’t obvious, translates as The Water Man.  At any rate, flowing from The Water Man’s jar are the three main stars of this excursion: Bu 1515 (60 Aqr), HJ 5529 (Kappa/κ Aqr), and Bu 172 (51 Aqr), which are mapped into their respective places on the left side of this chart:

Stellarium screen image with labels added, click to enlarge.

Mainly an autumn constellation, Aquarius hangs around into the beginning of winter provided you get outside when the December dusk descends. But before we look at a the three main attractions for this tour, it would really be inexcusable to pass up an opportunity to take a short peek at the real star of Aquarius, Zeta (ζ).

Zeta Aqr  (55 Aqr)  (Σ 2909)  (H II 7)      HIP: 110960   SAO: 146107
RA: 22h 28.8m   Dec: -00° 01’

Identifier	Magnitudes	Separation	PA	WDS
EBE-1 Aa, Ab:	4.34, ????	0.65″	147.8°	2014
STF 2909  AB:	4.34, 4.49	2.247″	164.9°	2015

Distance:  92 Light Years (Simbad)
Spectral Classifications:  “A” is F3, “B” is F6
Note: Orbital data is here; 2015 separation and PA based on WDS Ephemerides data.

Greg has already covered Zeta (ζ) rather well in a previous post (be sure to continue into the comments section for more discussion), so I’ll keep this brief and to the point: this is one of the genuine gems of the ecliptic.

In a smaller scope, and when Zeta (ζ) is lower in the sky, I’ve caught flashes of lemon and orange from these two stars. The night I caught it for this sketch, Zeta was parked on the meridian, so I captured it at its highest point in the sky. This time, the primary and secondary boasted an attractive white-gold hue, which was just slightly more distinct in the northern member of the pair. (East & west reversed to match the refractor view, click on the sketch for an improved version).

We’ll get this excursion started with Bu 1515, also known as 60 Aquarii.  It’s an easy one to find: starting at fourth magnitude Eta (η) Aquarii, drop a degree and a half south and just slightly west (here’s our previous chart once again). For reference, Bu 1515 is parked halfway between Eta Aqr and 6.15 magnitude HIP 111171.

Bu 1515  (60 Aqr)        HIP: 111394   SAO: 146160
RA: 22h 34.0m   Dec: -01° 34’
Magnitudes   AB: 5.98, 11.54     AC: 5.98, 11.89
Separations  AB: 99.80”            AC: 126.60”
Position Angles   AB: 298° (WDS 2000)    AC: 275°  (WDS 2000)
Distance: 347.5 Light Years (Simbad)
Spectral Classification:  “A” is G6

This is a compact little triple star with a white primary. The “B” and “C” components are faint enough that you have to look closely to catch your first glimpse of them, but once you have them in view, they willingly stay within visual grasp. (East & west reversed, click on the sketch for an improved view).

Anyone familiar with S.W. Burnham’s double star discoveries is aware the title of his 1900 catalog of discoveries, A General Catalogue of 1290 Double Stars Discovered from 1871 to 1899, tops out at Bu 1290 – hardly a surprise, of course . . . . . . . which raises the question of where the numbering for Bu 1515 came from.  Again, it should come as no surprise that Burnham continued to discover double stars after the publication of that catalog, so the numbering continued. (From what I can determine, it ends at Bu 1540). The origin of the Bu 1515 designation, though, is a bit vague.  After my internet roaming failed to turn up an answer, I got in touch with Brian Mason at the USNO/WDS, who not only provided me with an answer, but also a link to the source.

The source is a four page article published in the July 5^th, 1918, issue of The Astronomical Journal, in which Burnham is listed as the author. Although the data in the article is his, the four page article was actually put together by Philip Fox, who had been entrusted by Burnham with a list of unpublished double star measures.

The star that became Bu 1515 is listed at the bottom of the page as 60 Aquarii. Click on the page to ease eye strain.

In 1932, when R.G. Aitken published the successor to Burnham’s 1906 double star catalog, he apparently dropped Burnham’s listing. (The Aitken catalog is referred to today as the ADS – the actual title is New General Catalogue of Double Stars). Nevertheless, the observation remained assigned to Burnham, although with no designation. The Bu 1515 designation first showed up in a 1996 edition of the Washington Double Star Catalog (WDS), which led Brian to conclude it was added by Charles Worley, who first had responsibility for the WDS as we now know it.  As to how that number was arrived it, we may never know.

Before we leave Bu 1515, there’s an unexpected triple star bonus, Bu 77, parked in the south corner of the view.  Here’s the WDS data on this threesome:

Bu 77      No HIP or SAO Numbers
RA: 22h 34.0m   Dec: -01 47’
Magnitudes   AB: 9.31, 9.92    AC: 9.31, 10.80
Separations  AB: 2.60”            AC: 25.30”
Position Angles  AB: 215° (WDS 2010)   AC: 230° (WDS 2010)
Distance:  None found
Spectral Classification:  “A”is F0

I caught the 10.80 magnitude “C” component, but the 9.92 magnitude “B” companion escaped me since I wasn’t aware Bu 77 was in the field until after I had made the sketch above.  S.W. Burnham first captured this triple in 1872 with his six inch f/15 Clark refractor.

Meanwhile, on to another mystery, HJ 5529, aka Kappa (κ) Aquarii.  You’ll find it just short of three degrees south and slightly east of Bu 1515, where it shines distinctly. Here’s our last chart again.

HJ 5529/Kappa Aquarii   (63 Aqr)      HIP: 111710   SAO: 146210
RA: 22h 37.8m   Dec: -04° 14’
Magnitudes as of Sept. 14th, 2014:  5.00,  8.8
Magnitudes as of Dec. 22nd, 2014:  5.18, 12.2
Separation: 87.1”
Position Angle: 256°  (WDS 2010)
Distance: 234 Light Years
Spectral Classification: “A” is K2
Note: High PM for primary: -069 -120 (WDS and Simbad); secondary at +043 +007

The fifth magnitude primary radiates a rather attractive white-orange hue which is more pronounced in photos of it (see the Aladin image below). The secondary, “B”, is the first star immediately to the west (left) of the primary, which is shown more clearly in the inset – and if you look closely, it doesn’t quite live up to the 8.8 magnitude allotted to at the time I made the sketch. (East & west reversed once more, click on the sketch for a better view of the secondary).

Aladin image, click to enlarge.

When I first bent down to the 12mm eyepiece lodged in the diagonal of my six inch refractor, I anticipated a very obvious secondary parked to the west of the primary, but that wasn’t quite what happened.   Instead, I found myself peering into the depths of the west side glare for a glimpse of secondarial light. It took a few seconds, but once I captured it visually, I had little trouble keeping it in view. The surprising absence of a brighter star initially baffled me until I realized it wasn’t my eyesight, but an oversight – of some sort.

But of what sort was the question.

I did some research in Vizier, in both the UCAC4 and Nomad-1 catalogs, which is shown beneath the image below:

There are three tables of data below the sketch – the WDS is first, UCAC4 is next, and Nomad-1 is last. To avoid confusion, I’ve flipped the image to match the visual orientation of the sketch above. Click to see the data more clearly.

The secondary is decidedly fainter than the WDS magnitude of 8.8. On the other hand, the UCAC4 “f” magnitude of 12.124 struck me as too faint (mainly because of the glow coming from the primary), as did the Nomad-1 “Vmag” of 12.180. However, combining the “J” and “K” magnitudes for the secondary in the UCAC4 data resulted in a visual magnitude of 12.111, so despite my reservations, all indications pointed to the 12.1 to 12.2 range. A comparison with nearby TYC 5236-01401-1, which appears slightly brighter in both my sketch and the Aladin color photo just below it, also seemed to point to the 12.1 to 12.2 magnitude range for the secondary, although I still had concerns as to what extent the primary’s glow might be causing the secondary to appear a bit fainter than it actually was.

I aimed my research through cyberspace to reach Bill Hartkopf at the USNO/WDS, who very quickly answered in less than half an hour.  After making similar magnitude comparisons, and looking at images of HJ 5529/Kappa (κ) Aqr on red and blue plates, he leaned toward the Nomad-1 “Vmag” of 12.18. He also made a small change in the magnitude of the primary, from 5.0 to 5.18.

All of which explains why there are two lines of magnitudes listed in the data above for HJ 5529/Kappa (κ) Aquarii.

But there was yet another surprise lurking in the dark, waiting patiently to reach out and grab me when I least expected it.

.
A Case of Mistaken Identity

The proper motion of HJ 5529 A is rather significant at -069 -120 (.069”/year west, .120”/year south) . . . . . . .

The red arrows show the proper motion of both HJ 5529 A and TYC 5236-01401-1. Click to enlarge the Aladin image: note, this image is also inverted to match my sketch.

. . . . . . . which prompted me to see if S.W. Burnham had commented on it in his 1906 catalog. So there I was again, staring semi-somnolently (this time at a computer screen, not into an eyepiece), when I was jolted from lethargy to a loss of words:

Click to enlarge and clear-ify.

“I have never been able to see any trace of the small star in the last thirty years.”

?????

But I certainly saw it — not to mention it being clearly visible in the photos . . . . . . .

When in doubt (or somewhat stunned), go to the source:

HJ 5529 is the last entry. Click for a clearer version.

“An exceedingly minute point strongly suspected.”

Which explains the origin of the quote at the beginning of Burnham’s catalog entry.

But as I looked at John Herschel’s observation more closely, I noticed the position angle and distance were decidedly discordant with the current measures . . . . . . . and then I realized there were no magnitudes shown.

I aimed my new discovery through cyberspace with instructions to land in Bill’s in-box, which it did.  He researched a bit further and found this entry in Burnham’s 1913 Proper Motion Catalog:

Click to enlarge and clear-ify once more.

“ . . . has never been seen since and certainly does not exist.”

Another surprise.

But at least this entry by Burnham included measures of Kappa (κ) Aquarii, which meant Burnham had seen something. In fact, if you compare his measures with the most recent 2010 data in the WDS, you’ll notice a significant difference between the two, which is attributable to the considerable proper motion of the primary.

As to what Herschel was looking at when he assigned a catalog number of 5529, we’ll probably never know.  It’s possible the 12^th magnitude secondary would have been very difficult to detect with the twenty inch mirror Herschel used at the time, but his measures seem to indicate he was looking at another star entirely — and the absence of magnitudes makes it even more impossible to figure out what he might have been looking at.

We may also never know where the 8.8 magnitude of the secondary in the WDS originated. Bill sent me the text file for HJ 5529/Kappa Aqr, which shed no light whatever on the origin of that magnitude. But what it did show is S.W. Burnham was the first person to actually make and publish measures of Kappa (κ) Aquarii. (There was an 1896 measure by P. L. Gauchet, 246.4° and 103.11”, which wasn’t published until 1926). So credit for the double star status of Kappa (κ) Aquarii should go to Burnham, and as for HJ 5529 – wherever and whatever it originally was, it wasn’t Kappa (κ) Aquarii.

Now on to the last of our four stars, in which the ever-present S.W. Burnham also had a hand – and it also is a puzzle of sorts. Bu 172, aka 51 Aquarii, is less than a finder field (8×50) away from Kappa (κ) Aquarii.   Here’s our last chart again, which shows it three and half degrees west and slightly south of Kappa (κ).   A closer look reveals it’s roughly halfway between Kappa (κ) and 5.75 magnitude HIP 110023.   You can also use the three stars surrounding 5.98 magnitude HIP 109466 for a reference point, as well as 5.35 magnitude Rho (ρ) and 4.16 magnitude Theta (θ) Aquarii.

Bu 172 (51 Aqr)            HIP: 110578   SAO: 146067
RA: 22h 24.1m   Dec: -04° 50’

Identifier	Magnitudes	Magnitudes	Separation	Pos’n	WDS
	9/14/2014	12/22/2014		Angle
Bu 172     AB:	6.45,  6.63	6.45,  6.63	0.46″	36°	2014
Bu 172 AB,C:	5.77, 10.10	5.77, 12.20	53.10″	343°	2005
Bu 172 AB,D:	5.77, 10.00	5.77, 11.50	123.30″	191°	2002
Bu 172 AB,E:	5.77,   9.87	5.77,  9.87	130.30″	133°	2002
STU 14 AB,F:	5.88,   8.50	5.77, 11.10	256.80″	3°	2000

Distance: 424 Light Years
Spectral Classification: “A” is B9.5
Notes:  AB,C is H V 95;  AB is binary (orbit is here); AB,C is physical; D and E are optical.

5.77 magnitude AB sits in the center of its retinue of four stellar attendants, casting the spell of its white light over “C” and just barely snaring “D” and “E”.  Lying over four arc minutes to the north, “F” distinctly fails to live up to its 8.50 magnitude reputation. (East & west reversed once more, click on the sketch for a much improved version).

This was too good not to post!  Aladin image, click for the full effect.

Once again I found myself looking at a multiple star with magnitudes that didn’t quite match the published numbers, but this time I was expecting it. Peter Morris had sent me two descriptions of Bu 172 earlier in the year, pointing out “F” was much fainter than the 8.50 magnitude assigned to it, and also calling attention to magnitude discrepancies in the “C” and “D” components. Within a few days of receiving Peter’s second description, I pointed my six inch f/10 refractor at Bu 172 and found his description right on target.

Again I called on Vizier for advice and leaned on the UCAC4 and Nomad-1 catalogs for support:

I also flipped this Aladin image horizontally so it would match my sketch and added the data below the image. Click on the image in order read the data more easily.

My eyes were first drawn to the UCAC4 and Nomad-1 magnitudes for “F” – UCAC4 has it at 10.516 (“f”) and Nomad-1 at 11.050 (“Vmag”), both of which seemed to be in about the right range.   There was a similar range of difference between the two catalogs for “D” (10.890 and 11.500), with Nomad-1’s 11.500 looking like the better choice. I tried a few tricks in order to get Nomad-1 to recognize “C”, but with no luck, so the only values I had were the UCAC4 “f” magnitude of 12.064 and the combined “J” and “K” infrared values, which worked out to a visual magnitude of 12.386.

I had sent this research off to Bill Hartkopf at the same time I sent my findings on HJ 5529, and after some further research, Bill changed the magnitude values for “C”, “D”, and “F” to the numbers shown above in red for the Bu 172 data above.

Apart from the AB pair, the proper motions of the various components of Bu 172 appear to indicate none of them are related physically, especially in the case of “D” (source):

Click on the image for a larger view. NOTE: this is an erect image view (east at the left).

The WDS notes file for Bu 172 describes AB,C as physical, but from looking at the plot above, that doesn’t appear to be the case, although there may well be more involved than I’m aware of.

Click to enlarge the image.

The binary AB pair, which at a separation of 0.46” was beyond my reach, was discovered in 1875 by Burnham with the combination of his eagle-eyes and six inch f/15 Clark refractor. More than likely he detected an elongation rather than a separation (he sent his observation off to Ercole Dembowski for measurement), but even at that, I would love to duplicate his feat – if I could only persuade the seeing to cooperate!   Surprisingly, when Dembowski measured it he came up with the same separation as the WDS Ephemerides shows for 2014, which is a remarkable coincidence. That star has been measured many times, which is evident from Burnham’s list at the right, and the orbital data for it is well established.

The WDS shows the first observation of the AF pair, STU 14, was made in 1893. which may be an indication of a measure made by Burnham, although I can’t find any reference to that star in his catalogs. The three letter identifier refers to K. M. Sturdy, who published in the Webb Society Double Star Circulars in the 1990’s.

That’s it for an interesting and unpredictable look at starlight flowing from der Wasserman’s water jar.  You shouldn’t have to read between the lines too much in order to grasp the message underlying the observations of the last two stars: it’s still quite possible for amateur astronomers to contribute in very significant ways to double star research. Remarkable as it may seem, even in the early 21^st century you can still point a telescope into the sky and find yourself looking at a sprinkling of stars that don’t quite match the published data. When that happens, it’s well worth the time to do a bit more research and report what you find.  You really can make a difference.

Many thanks to many people for help on this one: First to Peter Morris of England for pointing me toward Bu 172, and second to Bill Hartkopf and Brian Mason at the USNO/WDS for help and suggestions on Bu 1515, Bu 172, and HJ 5529.   Thanks also to an internationally flavored group of persistent double star hunters and accomplices who also keep a sharp eye out for magnitude discrepancies: Chris Thuemen (Canada), Dr. Wilfried Knapp (Austria), Steve Smith (Colorado), and Steve McGaughey (Hawaii).

Clear Skies!   😎

The Alpha-Beta-Gamma of Aquarius: α, β, and γ Aquarii

You might call this a kind of A-B-C of Aquarius, since it’s a look at three of the brightest stars in the constellation . . . . . . . except that in Greek the first three alphabetical letters are α,β, and γ — as in alpha, beta, and gamma. In case you don’t stay up late at night wondering about linguistic details, the Greek language has managed to do just fine without the equivalent of the Arabic “c”.  Instead, it leans on Kappa (κ) for the “k” sound and Sigma (σ) for the “s” sound (along with Xi (ξ) and Chi (χ) for additional variations) – subtly suggesting we could dispense with the Arabic “c” just as easily, although that might throw the English language into a torrent of turmoil. (But Kapricornus and Setus have a certain irresistible allure).

At any rate, while Homer-era Greek grammarians were debating linguistic intricacies over glasses of grape and urns of olives, the “g” of Gamma (γ) managed to slip into the slot behind the “b” of Beta (β) . . . . . . . and the rest is ancient history, so to speak.

And you probably thought linguistics was a dry subject.

But to get to the main point, in order to prepare for a few excursions through Aquarius, I did some quick stellar research and discovered several of the brighter stars which make up the Aquarian framework are also double or triple.  So I decided to begin at the beginning of the alphabet . . . . . . . and here we are.

Or to be more specific, this is where we are:

The constellations immediately surrounding Aquarius suffer from a noticeable lack of first magnitude stars, not surprising considering their location beyond the galactic boundaries of the Milky Way.  Fortunately, the diamond-shaped asterism partially outlined here by Alpha (α) and Gamma (γ) Aquarii is distinctive enough to stand out from its dim stellar surroundings. (Stellarium screen image with labels added, click on the chart for a better view).

And here’s a closer look, along with some tongue-twisting Arabic names:

Stellarium screen image with labels added, click to enlarge.

We’ll start at the alphabetical beginning, but first a word of warning to small aperture users.   The companions of the three stars we’re going to look at are all eleventh and twelfth magnitude, and all are handicapped in varying degrees by the third and fourth magnitude glares of the primaries.   A six inch refractor is the minimum required to pry the secondarial and tertiary lights loose from their high-spirited primarial parents.

Alpha (α) Aqr  (34 Aqr) (BUP 232)        HIP: 109074   SAO: 145862
Sadalmelik (lucky stars of the king)
RA: 22h 05.8m   Dec: -00° 19’

Identifier	Magnitudes	Separation	Position Angle	WDS
BUP 232 AB:	2.96, 12.20	110.00″	40°	2008
SKF 1651 AC:	2.96,  2.90	999.90″	239°	2010

Distance:  523 Light Years (Simbad)
Spectral Classification:  “A” is G2
Note: SKF 1651 AC is Beta Aqr, shares common PM with Alpha Aqr

This is one of the easier pairs we’ll look at, thanks to the 12.20 magnitude secondary’s 110” distance from the primary. Even at that, I had to struggle at first to get a glimpse of it, but once I snagged it with averted vision, it was easy to keep in view.  A 40% waxing moon in the sky didn’t do a lot to help the situation, but despite the moonlight I was able to detect a slight gold tinge in the otherwise white primary.  Apart from 8.40 magnitude SAO 145858 in the northwest corner of the field, the rest of the field was populated very faintly. (East & west reversed to match the refractor view, click to get a better view).

But what happened to the 2.90 magnitude “C” component referred to in the data above? The first clue there’s something out of the ordinary with regard to SKF 1651 AC is the strange separation listed for it, 999.90”. Fortunately, a look at the WDS notes for SKF 1651 identifies “C” as Beta (β) Aquarii, which as it happens is located slightly over 10 degrees to the southwest.  That enigmatic 999.90” figure is simply a way of indicating a separation too large to fit into the space allotted for it in the WDS.

So why would you include a star located ten degrees from the primary as a component?  The answer has to do with their shared proper motion.  That prompted me to look up the numbers and compare Simbad plots . . . . . . . and this is what I came up with:

Alpha (α) Aquarii is on the left, Beta (β) Aqr on the right. Also shown in the left panel is Alpha Aqr B and on the right, Beta Aqr C. Click on the image for a more legible view.

As you can see, the primaries of Alpha and Beta Aquarii are undoubtedly moving in the same direction. For the curious, Simbad shows Alpha Aqr with a proper motion of +018.25 -009.39 (.01825”/year east and .00939”/year south) and it lists Beta at +018.77 -008.21. In a case like this, you would expect their distances from where we are to be similar, and they are: 523 light years for Alpha and 537 for Beta – which is reasonably close given the imprecision of parallax based measures at those distances.

One last item to consider for the curious minded is the WDS designation for the AB pairing of Alpha Aqr, BUP 232.   The three letters refer to S.W. Burnham’s 1913 proper motion catalog (Measures of Proper Motion Stars Made with the 40 Inch Refractor of the Yerkes Observatory in the Years 1907 to 1912).  Shown below are his measures and comments on the AB pair from page 71 of that catalog:

Click to enlarge the image.

You can see a slight change taking place between his 1879 and 1907 measurements, which agrees with the directional change indicated by the 2008 WDS numbers. His comment about the motion of the large star (the primary) being “nearly in the direction of the faint companion” is basically correct, since “A” is moving east and “B” is moving west. But when you include the northerly and southerly components, the two stars are actually moving away from each other. The proper motion of Alpha Aqr B, by the way, is -006.7 -007.4 (.0067”/year west and .0074”/year south).

And since we’ve been referring to it frequently, not to mention it being the next letter in the Greek alphabet, we’ll head ten degrees to the southwest and look at Beta (β) Aquarii.  Here’s our second chart again in case you need a navigational reminder.

Beta (β) Aqr  (22 Aqr)  (H V 76)     HIP: 106278   SAO: 145457
Sadalsuud (luckiest of the lucky)
RA: 21h 31.6m    Dec: -05° 34’

Identifier	Magnitudes	Separation	Position Angle	WDS
H 5 76 AB:	2.91, 11.0	37.60″	319°	2013
Bu 75  AC:	2.91, 11.6	61.00″	189°	2013

Distance: 537 Light Years (Simbad)
Spectral Classification:  “A” is G0
Note: Common proper motion with Alpha Aquarii

If you look closely, you can detect a slight yellow trying to escape from the white glow of the primary. That glow made it rather hard to detect both “B” and “C”, with “C” being the toughest of the two dim companions. The 40% full moon was also hovering nearby, adding to the challenge of seeing “C”.

There are two other stars in the field that caught my attention, the first located northwest of “B” and the second southeast of “C”. I decided to see what the UCAC4 showed for magnitudes of those two stars, which generated this image:

Click on the image in order to make the data more legible. Note this is a mirror-reversed image, which matches the orientation of the sketch above.

I’ve labeled the star to the northwest of “B” with a “1”, as well as the corresponding data below the image.  That data shows star “1” with an “f” magnitude of 14.772, which is far too dim.  Allowing for a dimming of “B” because of the primary’s glow, star “1” is at least the same magnitude as “B”, if not slightly brighter.   Southeast of “C”, I labeled two stars (“2” and “3”), but I only saw one of those – more than likely it was star “2”.   Again, it was brighter than “C”, and making allowance for the effect of the primary’s glow on “C”, I would lean toward star “2” being at least as bright as the 11.6 listed for “C” in the WDS.  The UCAC4 data also shows “C” as being fainter than what I saw, but considering the glare, the WDS magnitude of 11.6 is a better match.

The AB pair of Beta (β) Aquarii was discovered by William Herschel on July 20^th, 1782:

A translation of his Latin on the first line places Beta (β) on the Aquarian’s left shoulder, and as you read further he describes both the separation (33.27”) and position angle (55° 48’) as “very inaccurate.”  That last number should include the phrase north preceding, which would make it equivalent to a present day figure of 325° 48’ (source, scroll to the sixth title).

To get a better idea of how accurate Herschel’s estimates were, we can look at Burnham’s entry for Beta Aqr in his 1906 catalog:

(Click on the image for a larger view).

The AB pair is the second entry shown above, and you can see the first observation Burnham includes is that of John Herschel (H), which doesn’t tell us much since it apparently includes a very rough estimate of the separation.   Starting in 1893, the data becomes more consistent and matches well with the 2013 WDS data.

Burnham also includes a comment about “C” being discovered with his six inch refractor (f/15), which occurred in 1871.   His 1898 measure of it was probably made with the 40 inch Yerkes refractor, since “C” was far too dim to measure in the six inch Clark. It looks like the AC pair have shifted noticeably relative to each other since 1893.

Let’s hop back to the east side of Alpha (α) Aquarii now and take a look at the star graced with the third letter of the Greek alphabet, Gamma (γ) Aquarii.   Here’s the second chart once again.

Gamma (γ) Aqr  (48 Aqr)  (HJ 3106)     HIP: 110395   SAO: 146044
Sadachbia (lucky star of the tents)
RA: 22h 21.7m   Dec: -01° 23’
Magnitudes: 3.84, 12.2
Separation:   33.3”
Position Angle: 150° (WDS 2008)
Distance:  164 Light Years (Simbad)
Spectral Classification:  “A” is A0
Notes:  Optical pair based on PM: +130 +008, +000 -015

You gotta look close, but there really is a secondary just below the primary at the 150 degree position – not that I saw it on the first look at this star. There’s a slight touch of yellow in the primary, which showed up despite the moon’s insistent 40% glare. (East & west reversed once more, click on the sketch to see the secondary better).

It took two attempts to pry the 12.2 magnitude secondary loose, the first attempt being defeated by both the moon and Pacific ocean murk.  When I returned for attempt number two, atmospheric clarity had improved enough to allow the secondary to fight its way out of the primarial glare.  The 12mm Radian (127x) provided my first glimpse of the elusive star, and a 6mm AT Plössl (253x) confirmed it wasn’t my imagination working overtime.

The UCAC4 catalog shows the secondary at a magnitude of 12.011, which is basically in agreement with the WDS number.   Considering both the glare from the primary and the secondary’s proximity to it, it’s even possible the secondary may be much as a magnitude brighter.

Click on the image to enlarge it and improve the legibility of the data.

Also shown on the image above is the proper motion of the primary, which both Simbad and the WDS show as +130 +008 (.130”/year east, .008”/year north).   The WDS shows very little motion for the secondary: +000 -015 (the last number is southerly motion).

In fact, if you look at earlier observations of Gamma Aquarii, as in the excerpt below from Burnham’s 1906 catalog, the change in position angle and separation is strikingly obvious.

Click on the image for a more crisp view.

A comparison of the position angles and separations in Burnham’s observations with the 2008 data from the WDS (150° and 33.3”) shows the primary is almost racing through its sector of the galaxy.

Sir John Herschel is credited with being the first observer to detect Gamma Aquarii’s faint secondary, which according to the first date of first observation in the WDS took place in 1831 (source):

Click to improve the clarity of this image also.

The numbers he listed for the separation seem rather unlikely, though, when compared with the numbers published in Burnham’s catalog. And in fact, Herschel’s comment in the right column – “An extraordinary difference of estimates in distance” – points to his being aware there was a problem with the two numbers.

We’re not done yet in Aquarius, so don’t wander off too far.   We’ll continue east in the next tour to look at two more stars in the Aquarian water jar, and then go south for a couple of more.

Clear skies until then! 😎

Special: Neptune’s birthday and a real beauty in the Water Jar

During  the early morning in July you can celebrate Neptune’s birthday and when you tire of that, move a short distance to the water jar and take a long, cool sip of Zeta Aquarii.  For details go here. 

Ice cubes in the water jar – Zeta (ζ) Aquarii and friends

Zeta (ζ) Aquarii   (H II 7) (Σ 2909)       HIP: 110960   SAO: 146107
RA: 22h 28.8m Dec: -00° 01′
Mag: 4.34, 4.49  Sep: 2.3″ PA: 166° (WDS 2013)
Distance: 103 ly
Spectral type: F3 IV-V

(WDS data updated 9/13/2014)

It’s almost Neptune’s birthday, otherwise I would not be prowling around this particular section of sky – it tends to look empty  and the constellations that do fill it use a lot of fourth and fifth magnitude stars and when you connect the dots they seldom  look like their names imply –  but oh what a beauty I have been missing – Zeta (ζ) Aquarii. It’s easy to find, can be split with a 60mm, and yields a closely matched pair with the slightest tint of colors.

But I’m jumping ahead of the game – this year Neptune is in Aquarius and completing it’s first Neptunian “year” – almost 165 years since it’s discovery. You can read all about it here, including star-hopping charts and instructions. But when I went to that section of sky the other night and found  Neptune peeking barely above my tree line – I got thinking about what else might be here and that “water jar,” or “Y” really caught my eye. It is practically dead on the celestial equator and so should be visible to much of the world.

Here’s the general vicinity I’m talking about.

Click image for much larger – readable – version. Looking south on a Summer morning you’ll see the general region that includes our target double. There are only two, bright “guidepost stars” in this region, Altair and Fomalhaut, and except for the  familiar “teapot” the asterisms tend to be made of fourth and fifth magnitude stars and are best seen in binoculars. What I’ve labelled the “Arrowhead” is a good deal of the constellation Capricornus. The pair of stars at the northeastern tip, which includes Deneb Algiedi, are easy to find and a good guide.  The “Circlet” and the “Water Jar” itself can be seen with the naked eye if your skies are reasonably free of light pollution, but are easier targets for binoculars. (Prepared from Starry Nights Pro screen shot.)

It was about 2 am and though the water jar was faint, it was well above my tree line. The whole asterism just fit in my 15X70 binoculars – lower power ones with a wider-field would do better.  Checking the charts I found the central star of this 4-star asterism is a double – not only a double, but one Sissy Haas rates as a “showcase double” and with good reason. Here’s a closer view.

Click chart for a much larger version. I included the insert from the Johann Bayer. Uranometria atlas of 1603 to help you understand why it’s called the “water jar” because there’s no way this asterism look like any water jar I’ve ever seen. (Prepared from Starry Nights Pro screen shot.).

There’s a hint of color here. The brighter one seemed  to hold a slight tint of lemon in the 85mm refractor. The other a hint of grey.  Sissy Haas says they have a pretty color “whitish citrus orange.” In the 60mm I had to crank up the power, got a hairline split, and saw no color.

But here’s what really delights me about Zeta Aquarii.  I see it as part of a wonderful sequence of similar doubles that if viewed in succession would give one a practical lesson in the meaning of “separation.”  The others are Nu Draconis, Gamma Arietis, and Porrima. Along with Zeta Aquarii these four are each made of a pair of stars that are nearly equal in brightness and the pairs each orient in a roughly north/south direction. But they differ signifcantly in separation.

At 63.4 seconds, the 5th magnitude pair in the dragon’s head can be split with binoculars if you can hold them steady enough.  The “Ram’s Eyes,” Gamma Arietis, are a beautiful sight in just about any small telescope being at the breaking point between 4th and 5th magnitude and separated by 7.5 seconds. The Zeta Aquarii pair is just a bit brighter, but more of a challenge. Haas list the spearation as 2.0 seconds. To me they seemed a bit wider than that because I found them so much easier to split than Porrima. Porrima, in the spring of 2011, has given us more of a challenge with a separation of  1.7 seconds and a brightness that puts them right on the borderline between third and fourth magnitude.

Of course, all of these aren’t well placed for observing at the same time, but all could fit into the same July night.  Porrima would be first on the agenda, low in the southwest after sunset and still a challenge object.

Porrima  (Gamma {γ} Virginis), also designated as Σ1670 (STF 1670)
RA: 12h 42m    Dec: -01° 27′
Magnitudes:  3.48, 3.53  (WDS 2009)
Separation:   1.7″  (Spring 2011)
Position Angle:    44° (2010)
Distance:   38 Light Years
Spectral Type: F0, F0

Go here for details.

Sometime after midnight you should get a good shot at the Dragon’s Head and Nu Draconis.

Nu (ν) Draconis

RA: 17h 32m Dec: +55°11′
Mag: 4.88, 4.86 Sep: 63.4″ PA: 311°
Distance: 99 ly
Spectral type: A6, A4

Go here for details.

In the early morning hours Zeta Aquarii is best places. And the for the Ram’s eyes  (Gamma Arietis) ot’s best to wait until just before astronomical twilight begins a couple hours before sunrise. Then it should be well placed in the eastern sky.

Ram’s Eyes  – Mesarthim – (Gamma [γ] Arietis)
RA: 01h 53.5m   Dec: +19° 18′
Mag: 4.5, 4.6   Separation: 7.5″  PA: 0°
Distance: 204 LY
Spectral Classification: B9, Ap

Go here for details.