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Splitting stars – for us and for you!

We are experienced amateur astronomers who especially enjoy viewing double stars with long-focus refractors.  This journal is a record of our observations, but we also hope it will serve as a guide to you to help you plan observing sessions and choose double stars you want to observe.  In the column to the left you’ll find a drop down menu listing the doubles in this blog by constellation – and to the right there’s a list of our 10 most recent observations. Finally, you have two other choices:

  • First, you can read  our observations of a double and leave your own observations of that same star as a comment.
  • Second, you can subscribe to this blog so that you get email notifications when we add a star to it. Just check out the links in the right-hand column.

We’d love to hear from you regarding your own observations of the same doubles.

A Closer Look at Eta (η) Lyrae, Including SHJ 289, HLM 19, and SEI 584

Relegated to a blue-white existence well beyond the Lyrae-ian framework, Eta (η) Lyrae beams its fourth magnitude photons at us from about seven degrees due east of Vega, the jewel in the constellation’s crown. Fortunately it isn’t relegated to total stellar isolation, thanks to a surrounding trio of fainter double stars with cooperative separations. In fact, those stars all inhabit the same field of view with Eta (η), providing the observer with a rare four-for-the-price-of-one visual bonanza.

Stellarium screen image with labels added, click to enlarge.

Stellarium screen image with labels added, click to enlarge.

Eta (η) Lyrae was a popular item with the early double-star detectives of the late 18th and early 19th century.  All of them were quick to capture Eta (η) in a telescope, with the result that each of their names became attached to it in the form of the four cryptic catalog designations listed at the end of the title line below.

Eta (η) Lyrae  (Aladfar)  (20 Lyrae)  (Mayer 61)  (H IV 2) (SHJ 291)  (Σ 2487)
HIP: 94481    SAO: 68010
RA: 19h 13.8m   Dec: +39° 09’
Magnitudes    AB: 4.38, 8.58    AC: 4.38, 11.42
Separations   AB: 28.30”          AC: 162.10”
Position Angles   AB: 79° (WDS 2013)   AC: 151° (WDS 2013)
Distance:  1388 Light Years (Simbad)
Spectral Classification:  “A” is B2.5, “B” is A0
NOTE: The catalog designations above, from Mayer 61 to (Σ 2487), refer to the AB pair.

Before we take a look at the historical record, which will include an attempt at decoding William Herschel’s H IV 2 observation of Eta (η), let’s take a peek:

The primary is best described as very white, although it’s also winked at me with a yellow hue on a few previous occasions. “B” stands out quite distinctly despite being four magnitudes fainter than the primary, and “C”, an 1880 addition which is three magnitudes fainter than “B, shines weakly from just outside the southern edge of the primary’s glare. Also seen in the inset at the right are the trio of double stars referred to above. (East & west reversed to match the refractor view, click on the sketch for a much better view).

The primary is best described as very white, although it’s also winked at me with a yellow hue on a few previous occasions. “B” stands out quite distinctly despite being four magnitudes fainter than the primary, and “C”, an 1880 addition which is three magnitudes fainter than “B, shines weakly from just outside the southern edge of the primary’s glare. Also seen in the inset at the right are two of the three double stars referred to above. (East & west reversed to match the refractor view, click on the sketch for a much better view).

Because of its remote location 1388 light years from us, Eta (η) lacks the wanderlust which is typical of stars located within fifty light years or so of planet earth. That’s borne out by the Simbad and WDS proper motion data for both the primary (-001 -001, which is .001”/year west and .001”/year south) and the secondary (+003 +007, or .003”/year east and .007”/year north).   In other words, you would need to hang around for about a thousand years before noticing a barely perceptible difference – and I can think of a lot of things I would rather do over the next thousand years.

But at least Christian Mayer got us started down that road with the inclusion of Eta (η) in his 1779 double star catalog, Tabula Nova Stellarum Duplicium.  Eight more stars were added in a 1781 revision, resulting in Eta (η) Lyrae being designated as Mayer 61, which the resourceful astronomer measured with a separation of 28.3” and a position angle of 81°.

Sir William Herschel turned his telescope to Eta (η) Lyrae on August 29th, 1779, and recorded this observation in his 1782 catalog (twelfth title from the top):

Wm Herschel on Eta Lyrae

The separation of 25.4” he measured was slightly less than Mayer’s figure, while his position angle of 31° 51’ south preceding works out to a puzzling 238° 9’.  Neil English and I have wrestled with Sir William’s Latin on the first line of the observation with little luck – whatever it means, it’s as much a puzzle as the position angle, which was also noticed by Sirs John Herschel and James South on June 16th, 1823 (source for their 1824 catalog, last title on the page):

Click to enlarge.

Click to enlarge.

The stellar Herschel-South duo made two separate measures of Eta (η) Lyrae on the same night, one with a 3.75 inch Dolland refractor (see p. 11 of the 1824 catalog) and the other with a five inch Tulley refractor (the “chef d’oeuvre of that eminent artist”, p.12 of the catalog), which are referred to in their report in terms of their lengths, five-feet and seven-feet, respectively.   Those two instruments are described in detail on pp. 4-14 of their catalog.

Click to enlarge.

Click to enlarge.

When averaged together, the result is a separation of 29.34” and a position angle of 5° 58’ north following, which equates to a present day figure of 84° 2’.   If you look at the individual measures obtained with the two telescopes, you’ll see a noticeable difference between them in separation and position angle.   Also included in their report is an 1819 position angle measure of Eta (η) Lyrae by F.G.W. Struve, 5° 30’ north following, which is our present day 84° 30’.   Struve measured the position angle again in 1830 at 85°, and that time included a separation of 27.90”.   Additional measures up through 1900 are shown at the right, in an excerpt from Thomas Lewis’s book on Struve’s double stars.

It doesn’t happen frequently, but occasionally a position angle gets measured erroneously from the fainter of two stars, instead of from the brighter of the pair.   But that doesn’t explain William Herschel’s position angle for Eta (η) Lyrae of 238° 9’, since adding 180° to the Herschel-South-Struve PA of 84° from 1819 and 1823 results in a figure of 264°.  John Herschel and James South came to the conclusion they and Sir William were measuring different stars, pointing out Struve’s 1819 position angle was essentially in agreement with theirs. Yet when I look at William Herschel’s 1782 catalog entry, his description of the two stars as being “considerably unequal”, as well as his reference to “three other stars in view” (probably referring to the two eighth magnitude stars and one tenth magnitude star arranged in a slight curving arc to the south of Eta (η) Lyrae, the middle one of which is SHJ 289), I don’t get the impression Sir William was looking at a different star.   His separation of 25.4” also supports that impression.

We’ll chalk the puzzling position angle up to what may have been the result of an unusually stimulating and vibrant stellar ether spread invisibly over William Herschel and his telescope on that August night in 1779.   We’ll never know otherwise, so that’s a good place to leave this mystery.

The Surrounding Double Star Trio

Click to enlarge.

Click to enlarge.

The brightest of the threesome of doubles surrounding Eta (η) Lyrae, SHJ 289, was cataloged by John Herschel and James South on June 16th, 1823, the same night they measured Eta.   Once again, as they did with Eta (η), they measured SHJ 289 once with each of their two refractors, resulting in an averaged separation of 40.4” and an averaged position angle of 32° 18’ north following, which translates into a present day figure of 57° 42’.   Those numbers compare favorably with the 2013 data in the WDS shown below. (Here’s the sketch above).

SHJ 289  (H V 42)     No HIP Number   SAO: 68003
RA: 19h 13.5m   Dec: +39° 02’
Magnitudes: 8.01, 8.71
Separation:  39.2”
Position Angle: 56°  (WDS 2013)
No reliable distance known
Spectral Classification:  Ap (“p” refers to “unspecified peculiarity” – see Sky and Telescope here)
Note:  The HIP number shown in Stelladoppie is wrong.

William Herschel measured this pair on September 25th, 1781 (about two years after his measure of Eta (η) Lyrae), and cataloged it as H V 42:

Wm Herschel on SHJ 289

He came up with a separation of 38.8” and a position angle of 26° 18’ north following, or as we would say today, 63° 42’, the last figure differing notably from the Herschel-South measure. It’s surprising that these two stars carry the SHJ designation instead of William Herschel’s H V 42 designation, since Sir William provided the first measures for it.   Normally that’s the criteria for determining what prefix is attached to star, but as in this case, there are exceptions to the rule.

Simbad doesn’t list a parallax for either of the SHJ 289 components, but Stelladoppie reports a distance of 11,248 light years, which is too distant to be accurate if based on parallax. The most recent proper motion data from the URAT1 survey lends support to the idea that the two stars are rather distant from us, with motions reported for A of -007.3 +001.8 (.0073”/yr west, .0018”/yr north) and for B of -005.6 +001.2 (.0056”/yr west, .0012”/yr north). Translated into everyday language, the inherent motion of the two stars barely qualifies as a crawl.

Located 5.75′ due west of Eta (η) Lyrae is another pair of stars known as HLM 19 (here’s the sketch above once again).

HLM 19    No HIP or SAO
RA: 19h 13.2m   Dec: +39° 08’
Magnitudes: 11.30, 11.87
Separation:   12.4”
Position Angle: 330° (WDS 2013)
No distance or spectral classification

The three letter prefix for these two stars belongs to Edwin Holmes, who discovered them sometime around 1900. According to this article by T.E. Espin, some of the position angles in the stars discovered by Holmes were in error, so he and M.A. Ellison made more precise measures in the early 1920’s. The first date of measure for HLM 19 in the WDS is 1922 (11.8”, 332°), which Espin made, and can be seen at the bottom of the first page of the article in the link above.

Holmes is also known for his 1892 discovery of the comet known as 17P/Holmes, which put on a spectacular display in the autumn of 2007.   Holmes’ account of his discovery can be read here, and there’s also a detailed biography of him here.

Located 7’ northeast of Eta η Lyrae is the last of the trio of surrounding double stars, SEI 584 (here’s our earlier sketch once more):

SEI 584    No HIP or SAO Numbers
RA: 19h 14.3m   Dec: 39° 11’
Magnitudes: 10.74, 11.60
Separation:   25.2”
Position Angle: 118°  (WDS 2010)
No distance or spectral class

The SEI in SEI 584 belongs to Julius Scheiner, who was a pioneer in astrophotography and spectral analysis. A biography of him by Edwin Frost is available here.

No distance or spectral class is available for this pair of stars, but as was the case with SHJ 289, the URAT1 proper motion data indicates they’re located a respectable distance from us.

Click to enlarge.

Click to make the date more legible.

Translated, the proper motion numbers are telling us A is moving east at a rate of .0061” per year and south .0074” per year, while B is moving east at the rate of .0015” per year and south at the rate of .0159” per year, which again is a relative crawl compared to stars located within fifty light years or so from us.  Judging by the motion of A relative to B, it doesn’t appear the two stars are gravitationally linked.

That’s it for this trip through Lyra — not sure yet where the next stopping point is, so stay tuned.

Until then, clear and stable skies!  :cool:

From 68 Herculis (OΣ 328) to 72 Herculis and Beyond to H N 5

If you look at a star atlas (for example, chart number 52 of Sky & Telescope’s Pocket Sky Atlas), just a few degrees east of the Herculean keystone you’ll find a pair of fifth magnitude stars dominating a relatively barren star-scape. They’re 68 and 72 Herculis, the first a rather difficult pair which I found to be surprisingly less difficult to split than it should have been, and the second surrounded by a multitude of scattered components. In between these two stellar sign posts are additional faint double and multiple stars, some of which offer interesting places to pause and ponder while negotiating the interstellar interval between 72 and 68 Herculis.  And we’ll make an additional short hop through the darkness east of 72 Herculis to wrestle with the mysterious HN 5.

Here’s a wide view of the location:

Stellarium screen image with labels added, click to enlarge the image.

Stellarium screen image with labels added, click to enlarge the image.

And here’s a close-up of the area:

This is an Aladin image of the area with all the double and multiple stars in the immediate area of 68 and 72 Herculis labeled.   Click for a larger image.

This is an Aladin image of the area with all the double and multiple stars in the immediate area of 68 and 72 Herculis labeled. Click for a larger image.

We’ll start with 68 Herculis, aka OΣ 328, which, as our first chart above shows, lies midway between Pi (π) and Epsilon (ε) Herculis, and about two degrees east of the line which connects those two stars.

68 Herculis  (OΣ 328/STT 328)      HIP: 84513   SAO: 65913
RA: 17h 17.3m   Dec: +33° 06’
Magnitudes: 4.8, 10.2
Separation:  4.2”
Position Angle: 59°  (WDS 2001)
Distance: 665 Light Years (Simbad)
Spectral Classification: “A” is B 1.5

When I first saw the magnitudes of the primary and secondary, along with the separation, my first thought was that it would be pointless to try to resolve this pair with either my six inch refractor or 9.25 inch SCT. My experience has been that a pair of stars with a magnitude differential of four (usually referred to as the Delta_m) with a four arc second separation is right at the extreme visual limits of both the six and the 9.25 inch scopes.  This pair has a Delta_m of 5.4, which should have put it out of reach.

But when I saw the amazing photo below taken by Steve Smith, I reconsidered:

West is at the left to match the refractor image in the sketch below.   Click to improve the view!   (Photos used with the kind permission of Steve Smith).

West is at the left to match the refractor image in the sketch below. Click to see the secondary more clearly.  (Photos used with the kind permission of Steve Smith).

So armed with a slight ray of hope and a couple of photon absorbing Plössls, I pointed the six inch f/10 refractor up toward the zenith and took a seat.  The seeing that night was average (III on this scale), but near the top of the sky it was slightly better (something close to a IV on that same scale) — although for very short periods of time it was actually quite steady.  I had no luck with a 10mm Radian (152x), which was no surprise, and after several minutes of patient waiting, also struck out with a 6mm Astro-Tech Plössl (253x).  For whatever reason, that eyepiece does a rather good job of suppressing the glare around a primary, so I didn’t expect to do any better with the next step up in magnification.

The choice for that step fell on a 4mm Astro-Tech Plössl (380x), which isn’t quite as effective with the glare — but if you don’t try, you’ll never know.  After something like ten minutes of careful study, I managed to catch a slight elongation in the primary at the correct PA with averted vision.  Then suddenly a faint, but very distinct, point of light popped into view, lingered for a tantalizing second or two, and disappeared.  After another couple of minutes, it re-appeared for slightly longer, and then vanished.  I went back to the 6mm for a few minutes to relieve my strained eyes, didn’t see anything, went back to the 4mm once again for a few more minutes, but still failed to see any sign of the elusive secondary.

Unlike the averted vision elongation of the primary, which was rather smeared and unfocused, the faint point of light I saw was quite clear, even though it was also an averted vision object.   This sketch provides a reasonably good idea of what I saw, but keep in mind, the image was nowhere near as steady as what you see here:

First, enlarge the image to see the secondary, and then imagine trying to hold that faint point of light in view with averted vision while it bounces around at something like ten or fifteen times per second!   East and west are reversed to match the refractor view.

First, enlarge the image to see the secondary, and then imagine trying to hold that faint point of light in view with averted vision while it bounces around at something like ten or fifteen times per second!  East and west are reversed to match the refractor view.

Click to enlarge.

Click to enlarge.

While looking up the data on this star, I noticed it was a variable – in fact, the S&T Pocket Atlas identifies it as u Herculis. (NOTE: there’s also a U Herculis – upper case “U” – which is not 68 Herculis).  A search on the AAVSO site for “68 Her” turned up the data at the right, which shows it’s an eclipsing variable (click on the question mark at the right side of the “Variability type” line) with a variation in magnitude from 4.69 to 5.37 over a cycle of 2.05 days.  The light curve for 68 Her shows the dimmest part of the cycle is rather brief, so the odds of catching the pair at maximum elongation are pretty good.  It’s also quite possible the secondary is a bit brighter than the 10.2 magnitude listed for it in the WDS, which would make it slightly easier to see.

However, I noticed James Kaler places the distance between the two stars at .07 astronomical units, which amounts to fourteen times the sun’s radius.  If that’s the case, there’s another star involved here in addition to the one Steve photographed and I saw.  The 4.2″ separation of the pair at a distance of 665 light years means they’re much farther apart than fourteen solar radii.   The WDS, by the way, makes no mention of a third component.

Next stop is 72 Herculis, which lies a degree southeast of 68 Herculis (here’s our second chart again).

72 Herculis       HIP 84862   SAO 65963
RA: 17h 20.7m   Dec: +32° 28’

Identifier    Magnitudes   Separation    PA WDS
DOR 1  AB:    5.45, 10.78      308.10″   340°  2002
ARN 14 AD:    5.45,   9.01      396.40″    60°  2013
ARN 14 AE:    5.45, 10.36      302.20″    51°  2002
ARN 14 AF:    5.45, 10.37      383.20″   104°  2002
DOR 1  BC:  10.78, 13.30         6.20″   247°  2002

Distance: 46.7 Light Years (Simbad)
Spectral Classification:  “A” is G0

This is what you might call a far-flung sextuplet of mostly faint stars. The inset at the right of the sketch shows all of the members, with the exception of the unresolvable “C”. Note the 12.6 magnitude star located between “A” and “F” which hasn’t been included in the system. You’ll also notice two more double stars in the field of view, GBC 28 and BU 630, which we’ll come back to shortly. (East & west reversed, click on the sketch for an improved view).

This is what you might call a far-flung sextuplet of mostly faint stars. The inset at the right of the sketch shows all of the members, with the exception of the unresolvable “C”. Note the 12.6 magnitude star located between “A” and “F” which hasn’t been included in the system. You’ll also notice two more double stars in the field of view, GBC 28 and BU 630, which we’ll come back to shortly. (East & west reversed, click on the sketch for an improved view).

Click to enlarge the page.

Click to enlarge the page.

The first thing that intrigued me about 72 Herculis was its three letter identifier, DOR.   The references and discoverer codes in the WDS show DOR stands for Dorpat Observatory, referring to the observatory at Dorpat (now Tartu) in Estonia which was under the control of F.G.W. Struve until the mid 1830’s.   Confusing the issue is the first observation date in the WDS, 1853, which is almost twenty years after Struve left Dorpat for the Pulkovo Observatory, located south of St. Petersburg in Russia.   A check of Burnham’s 1906 double star catalog shows him referring to 72 Herculis as σ 544, and a check of Burnham’s list of references (p. vii) shows the lower case Greek letter “σ” (Sigma) refers to Dorpat Observations, Vol III, which was originally entitled Catalogus 795 stellarum duplicium, published in 1822 by F.G.W. Struve.

Since many of the more obscure Dorpat publications aren’t available on the internet, I didn’t expect to find Catalogus 795 stellarum duplicium, but fortunately it was available through Google books, and the result is the page you see above.   The third column lists Struve’s estimate of the magnitude of the primary, and the next two are the right ascension and declination – which means there were no measures of PA and separation published in this catalog.   At the bottom of the page is a perplexing note referring to the asterisked “a)” in the first column.   Since I don’t have a Latin background, I ran the sentence through Google’s translator, which garbled it badly.   Other translation engines didn’t do any better, so I checked with Neil English, author of several books on astronomy, who is well versed in Latin.  His translation is “I did not find the separation of 72 Herculis to have increased as/where it ought to have.”  That raised another question, which we’ll circle back to shortly.

Like its neighbor, 68 Herculis, 72 Herculis is also a variable star, although with a narrow range of magnitudes, 5.38 to 5.45.   Unlike its neighbor, though, 72 Herculis is much closer to us (over 600 light years closer, in fact), which is reflected in its rather high rate of proper motion.

The image is from Aladin – click to enlarge and to make the date below more legible.

The image is from Aladin – click to enlarge and to make the date below more legible.

The arrows shown on the photo are from Simbad, while the data below the photo comes from NOMAD (there’s very little difference in the proper motion rates listed in the two catalogs).  The data shown for “A” shows it moving east at .135”/year and south at a much faster rate of 1.041”/year (rounded off to three decimal places), which makes it a relative speed demon in comparison to most stars.

As you can see by just looking at the arrows, 72 Herculis A is a foreground star that’s moving relatively rapidly against the backdrop of its components, which are obviously unrelated to it.  Their inclusion provides reference points for establishing and verifying the rapid motion of 72 Herculis A.  With the aid of Simbad’s data and Aladin’s epoch plotting tool, I was able to put together this plot which shows the motion of 72 Herculis A in relation to the five components from 1800 to 2000:

Aladin image once again, click to enlarge!

Aladin image once again, click to enlarge!

If you had turned a telescope on 72 Herculis in 1800 (or in approximately 1822 as F.G.W. Struve did), 72 Her A and B would have been a more convincing visual pair, with a separation of 114” versus the 2002 WDS measure of 308.10” – quite a difference, to say the least.  Not quite warp speed, but still pretty darned impressive.

That takes us back to Struve’s comment about the separation of 72 Herculis not having increased as it should have.  Did he realize 72 Herculis A had a high rate of proper motion?  It’s highly unlikely, since there would have needed to be some previous observations of it.  Neither William Herschel or Christian Mayer include 72 Herculis in their catalogs, so Struve’s comment is still difficult to understand.

The Interstellar Interval

In between 68 and 72 Herculis are a handful of double and multiple stars that can be used to test your visual acuity and patience, two of which are shown in the sketch above of 72 Herculis.   Here’s a chart, taken from Aladin, with each of the stars identified and their data shown below:

Click to enlarge and to make the text below the image legible.

Click to enlarge and to make the text below the image legible.

I looked at all of these and had some degree of luck with each one, with the exception of POP 222 – with a 3.8 magnitude differential and a faint 12.32 magnitude secondary, plus the poor seeing, it was beyond reach that night.   One word of caution if you look this one up in Stelledoppie: as of this writing, the HIP and BD numbers shown for it are in error – they actually refer to HU 1185 (WDS 17591+3228) instead of POP 222.

GCB 28 was a tough one to separate, given the faint magnitudes and tight separations, but I managed several phantom-like averted vision glimpses of two of the three stars at 380x (using a 4mm TMB Planetary II).  The “B” component is located about one arc second northeast of the primary, putting it beyond reach due to the poor seeing.  I also needed 380x to detect an elongation in BU 630.  BU 45, on the other hand, was easily visible at 84x as an impossibly small and tight twin dots of light.  I included it at its approximate location in the bottom left corner of the sketch of SEI 542 shown below:

This pair (in the center of the field of view) can also be seen in the Aladin image above as two separate stars – at a separation of 28.80”, they’re easily resolved, provided you have enough aperture to pick out the 12.2 magnitude secondary.   (East & west reversed once again to match the refractor view).

This pair (in the center of the field of view) can also be seen in the Aladin image above as two separate stars.  At a separation of 28.80”, they’re easily resolved, provided you have enough aperture to pick out the 12.2 magnitude secondary.  (East & west reversed once again to match the refractor view).

Also shown at the bottom left of the SEI 542 sketch is BU 628, another pair that was well beyond my optical reach due to its separation of 0.5”.  However, this one is a true binary with a reasonably well determined orbit, which can be seen here.

The Mysterious HN 5

Our last stop on this tour is HN 5, which is located 51’ east and slightly south of 72 Herculis.  If you position 72 Her at the north edge of your field of view and nudge your scope to the east, the “A” and “D” components of HN 5 will pop into view. Here’s an Aladin photo, which shows both components clearly, and if you look closely, you’ll see “B” and “C” parked on opposite sides of “A”.

Aladin image with labels added, click to enlarge.

Aladin image with labels added, click to enlarge.

HN 5      HIP: 85191   SAO: 66016
RA: 17h 24.6m   Dec: +32° 15’

Identifier Magnitudes Separation   PA WDS
HN 5 AB: 8.65, 12.50       24.6″  356°  2002
HN 5 AC: 8.65, 12.20       37.3″  181°  2002
HN 5 AD: 8.65,   8.98     151.1″   15°  2003

Distance: 692 Light Years (Simbad)
Spectral Classes:  “A” is K5, “D” is M2

Both “A” and “D” have a yellow-orange-gold tint if you look closely, which would be more pronounced if the two stars were brighter.   I had to look carefully to get my first glimpse of “B” and “C”, both of which were averted vision objects. I found “C” popped into view first because it’s a bit further from the primary – under better seeing conditions, it should be possible to see it with direct vision. Judging from their tendency to be slightly elusive, the magnitudes listed for them in the WDS appear to be about right.   (East & west reversed once again, click on the sketch for a better view).

Both “A” and “D” have a yellow-orange-gold tint if you look closely, which would be more pronounced if the two stars were brighter.  I had to look carefully to get my first glimpse of “B” and “C”, both of which were averted vision objects.  I found “C” popped into view first because it’s a bit further from the primary – under better seeing conditions, it should be possible to see it with direct vision. Judging from their tendency to be slightly elusive, the magnitudes listed for them in the WDS appear to be about right.  (East & west reversed once again, click on the sketch for a better view).

So why the title above describing HN 5 as mysterious?   First, let’s take a look at Herschel’s description of if it in his 1822 catalog (source):

Click to enlarge

Click to enlarge

Herschel’s account shows he discovered this group of star in 1784, but apparently too late to get them into his 1784 catalog. The mystery here lies in his reference to the position of the stars he was looking at.  He seems to place 58 (Epsilon) Herculis to the north at a distance of 1° 22’ (no idea why he included “f. 22′ 42” ahead of 1° 22’), but the problem is HN 5 is located five degree east and 1 degree north of 58 Herculis.  When I ran his coordinates through a precession calculator, the resulting coordinates for 2000 are very close to those in the WDS for that date.  So it would appear he was looking in the correct location, but then there’s that diagram of the stars which he included – it doesn’t come close to matching the configuration of HN 5.  I’ve tried flipping and rotating my sketch to match the orientation of the Newtonian scope he used, but still can’t come up with a match for his sketch unless I include stars considerably fainter than HN 5 “A” and “D”.

However, when I looked 1° 22’ south of 58 (Epsilon) Herculis, I found 7.86 magnitude HIP 83152, which is located at a distance 1° 23’.  Just to its northwest is a distinctive parallelogram of eleventh magnitude stars, the center of which is 1° 20’ from 58 (Epsilon) Herculis:

Aladin image once again, click to enlarge.

Aladin image once again, click to enlarge.

Their configuration is very similar to those in Herschel’s diagram, but they aren’t oriented at the same angle.  Herschel normally observed at the meridian, so it’s unlikely he would have changed the orientation of his sketch from the actual appearance of the four stars.

At any rate, the HN 5 he saw is not the group of stars currently designated as HN 5.  In fact, it appears S.W. Burnham was the first to measure all four of the stars which currently make up HN 5, as shown in the excerpt below from his 1906 catalog:

Click to enlarge.

Click to enlarge.

Notice his comment “identified and measured”, which would indicate he was specifically trying to identify the stars at the location provided by William Herschel.

Of course, it’s always possible proper motion would distort the positions of stars, although it’s highly unlikely there would have been enough to change their appearance drastically between 1772 and 1903/1905.  But just for the sake of looking, here’s what I found:

Click to enlarge.

Click to enlarge.

That data shows “A” moving west at the rate of .010”/year and south .021”/year, while “D” is moving west at the rate of .003”/year and north at .018”/year, which is nowhere near enough to cause a drastic change in the orientation of the four stars.  And “C” and “D” are moving even less.

So we’ll probably never know what Sir William Herschel was looking at when he cataloged HN 5.  Once again, the solution to another stellar mystery remains locked up in the black vault of interstellar space.

Back soon with another stellar adventure.   Until then, clear skies!   :cool:

Beta (β) and Zeta (ζ) Lyrae: A Closer Look — and a TAR 3 Tale

I hate to quote myself – but what the heck, at least it has the merit of saving time:

Stellarium screen image with labels added, click to enlarge.

Stellarium screen image with labels added, click to enlarge.

“One of the things that has always amazed me about the constellation Lyra is all but one of the stars that make up its outline are multiple systems of stars. You can start in the north with Vega (a triple with magnitudes of 0.0, 9.5, 9.5, and separations of 78″ and 118″) and from there move northeast to Epsilon (ε),  then south to the parallelogram where you come to Zeta (ζ) in the northwest corner.  To the east of it is Delta (δ) and the beautiful open cluster Steph 1 –  and over in the southwest corner you find Beta (β), also known as Sheliak.  Gamma (γ), in the lower southeast corner is the exception, but if you look at in a scope, you’ll find a difficult double just to the west of it, BU 648 (magnitudes of 5.4 and 8.0,  separated by 1.3″).”

I wrote that five years ago – which hardly seems possible now – but it’s hard to improve on that paragraph as an apt description of the duplicitous nature of the six stars which frame the framework of Lyra. Eta (η) Lyrae, which is well outside the Lyrical parallelogram, was also included in that post – not quite sure why – but we’ll leave it out this time and come back to it again in a future post since it also deserves more attention than it received last time.

This time we’ll start at Sheliak/Beta (β), which based on the data below, appears more intimidating than it really is.  Our observations will be limited to “A”, “B”, “E”, and “F”, since the others are beyond our telescopic reach.

Beta (β) Lyrae (Sheliak) (10 Lyrae)          HIP: 92420    SAO: 67451
RA: 18h 50.1m   Dec: +33° 22’

Identifier       Magnitudes      Separation    PA    WDS
RBR 11 Aa, Ab:       3.60,   8.20           0.50″   176°    2002
CIA 3    Aa 1,2:       3.60,   4.00           ????     70°    2007
STFA 39    AB:       3.63,   6.69          45.70″   148°    2014
BU 293      AC:       3.63, 13.00          47.10″   247°    2007
BU 293      AD:       3.63, 14.30          64.40″     68°    2007
BU 293      AE:       3.63, 10.14          66.30″   318°    2012
BU 293      AF:       3.63, 10.62          86.90″     19°    2012
BU 293      BE:       6.69, 10.13         112.50″   332°    2007
BU 293      BF:       6.69, 10.62         120.80″       2°    2007
BU 293      EF:      10.14, 10.62           79.30″     66°    2007

Distance: 882 Light Years (Simbad)
Spectral Classifications:  “A” is B8, “B” is B5, “C” is B2, “E and “F” are G5
Note: STFA 39 is also H V 3, SHJ 281, and STTA 175; CIA 3 is an eclipsing binary.

You can’t miss the AB pair, given their cooperative magnitudes and separation.   “E” and “F” aren’t too tough, either, since their distances from the primary allow their comparatively weak 10.14 and 10.62 magnitudes a chance to shine through the yellow-white primarial glare.   I had hoped to spot 13th magnitude “C”, but it was lost to the glare.   “D”, at a magnitude of 14.30, was well out of reach for my six inch refractor. (East & west are reversed in the sketch to match the refractor view, click to enlarge the image to see the surrounding pairs more easily).

You can’t miss the AB pair, given their cooperative magnitudes and separation. “E” and “F” aren’t too tough, either, since their distances from the primary allow their comparatively weak 10.14 and 10.62 magnitudes a chance to shine through the yellow-white primarial glare. I had hoped to spot 13th magnitude “C”, but it was lost to the glare. “D”, at a magnitude of 14.30, was well out of reach for my six inch refractor. (East & west are reversed in the sketch to match the refractor view, click to enlarge the image to see the surrounding pairs more easily).

The AB pair was first observed by William Herschel on August 29th, 1779 (he saw the same four stars I saw), and cataloged as H V 3  (source):

Wm. Herschel on Beta Lyrae

Click to enlarge.

Click to enlarge.

Beta (β) Lyrae appears to have received a lot of attention in the early years of double star astronomy. In addition to William Herschel’s observation, the observing duo of John Herschel and James South cataloged it as SHJ 281 in 1821, followed by F.G.W. Struve and his son, Otto, who added it to the supplements of their catalogs (STFA 39 in 1835 and STTA 175 in 1840, respectively).  In 1878, S.W. Burnham added the 13th magnitude “C” component as BU 293 while using the 26 inch refractor at the U.S. Naval Observatory in Washington, D.C. (still in use), and R.G. Aitken added the 14th magnitude “D” component in 1898 while wielding the 36 inch refractor at Lick Observatory (also still in use).

I noticed the reference to the John Herschel-James South catalog (Sh 281) at the bottom of Burnham’s record of Beta (β) (shown at right – source), so I pulled up their observation and found the two intrepid observers had included comments at the bottom of their notes on what is now “E” (they refer to it as “C”) and “F” (referred to as “D”).

Click to enlarge.

Click to enlarge.

It appears they used Struve’s data on the two stars, probably because they were too faint for them to measure with the 3.75” inch refractor they were using.

Surrounding Beta Lyrae/Sheliak are three additional pairs of stars, which are identified in the southern half of the sketch above.   HJ 1349 is an 1830 John Herschel discovery and Σ 2407 is an F.G.W. Struve discovery from some time prior to 1827:

HJ 1349     No HIP Number     SAO: 67415
RA: 18h 48.8m    Dec: +33° 19’
Magnitude:  8.29, 10.7
Separation:  29.8”
Position Angle: 92°  (WDS 2008)
Distance: 1148 Light Years (Stelledoppie)
Spectral Classification: G0

Σ 2407      No HIP Number    SAO: 67433
RA: 18h 49.5m    Dec: +33° 16’
Magnitudes: 8.98, 11.4
Separation:  29.7”
Position Angle: 207°   (WDS 2002)
Distance: ?????
Spectral Classification: K2

By far the most interesting of the trio – you would never guess it from the faint face it puts forward – is TAR 3:

TAR 3     No HIP or SAO Numbers
RA: 18h 50.6m   Dec: +33° 13’

   Identifier     Magnitudes    Separation    PA   WDS
TAR 3    AB:    10.53, 11.00        14.80″   305°   2008
BKO 54 AD:    10.53, 13.60        14.40″   192°   2002
TAR3     BC:    11.00, 12.00         3.20″   217°   2002

No Distance or spectral class
Note:  The cross-referenced BD, HD, and HIP identifications numbers for TAR 3 in Stelledoppie are incorrect and refer to a single star in Cygnus.   The correct BD number is +33 3228.

The AB and BC pair were discovered by Kenneth J. Tarrant in 1886. Information on Mr. Tarrant is scarce, but I managed to discover he was an amateur astronomer in England who used a ten inch Calver reflector to make a series of double star measures which were subsequently published in the Astronomische Nachrichten between 1888 and 1893. I found his observational record for the star which became TAR 3 in an 1889 issue, which is shown in the top half of the image below:

I’ve added Burnham’s observation below Tarrant’s for the sake of comparison. Click to enlarge the image.

I’ve added Burnham’s observation below Tarrant’s for the sake of comparison. Click to enlarge the image.

If you look closely, you’ll notice quite a bit of difference in Tarrant’s measures when compared with the 2002/2008 WDS data. The same is true of Burnham’s data (source), which also differs noticeably from Tarrant’s measures. Suspecting the main reason for the significant differences was a high rate of proper motion for “A” and “B”, I took a look at the data and found a surprise.  The rate of proper motion is fairly minor, but because the two stars are moving in opposite directions, the small rate of motion is magnified, resulting in significant changes in position angle and separation over the past one hundred years.

The proper motion data shows A is moving west at the rate of 0.19”/year and south at .038”/year, while B is moving west at the rate of .010”/year and north .024”/year.  Click to enlarge the image.

The proper motion data shows A is moving west at the rate of 0.19”/year and south at .038”/year, while B is moving west at the rate of .010”/year and north .024”/year. Click to enlarge the image.

Click to enlarge.

Click to enlarge.

Curious about what the measures between 1886 and 2008 might show, I sent a request for the text file on TAR 3 to Bill Hartkopf at the U.S. Naval Observatory (USNO). That led to the discovery that the two most recent measures of the AB pair depart noticeably from the trend of the 1886/87 through 2002 measures. I’ve listed all of the measures from the text file at the right.

I ran two sets of coordinates through a spreadsheet which returns the separation and position angles for a given pair of stars and confirmed the anomaly in the 2005 and 2008 measures in the WDS. Plugging the coordinates from the USNO’s NOMAD catalog into the spreadsheet resulted in a separation for the AB pair of 15.56” and a position angle of 310.56°.   The more recent coordinates provided by the URAT1 survey resulted in a separation of 15.48” and a position angle of 310.28°.

So now that we have TAR 3 under control, we’ll move on to Zeta (ζ) Lyrae, which also needed a bit of observational attention (here’s our chart once more). Again, the data makes things appear more complicated than they are.  Fortunately a telescopic view is considerably less confusing.

Zeta-1 Lyrae  (6 Lyrae) (BU 968)    HIP: 91971   SAO: 67321
Zeta-2 Lyrae  (7 Lyrae) (STFA 38)   HIP: 91973   SAO: 67324
RA: 18h 44.8m   Dec: +37° 36’  (WDS ID coordinates for Zeta1)

   Identifier     Magnitudes     Separation    PA    WDS
BU 968   AB:     4.34, 15.80         22.30″     50°    2012
BU 968   AC:     4.34, 13.30         48.90″   270°    2012
STFA 38 AD:     4.34,   5.62         43.70″   150°    2014
BU 968   AE:     4.34, 13.50         62.50″   298°    2012
FYM 42  AF:     4.34, 13.70         77.50″   330°    2012

Distance:  “A” is 156.1 Light Years,  “B” is 155.5 Light Years (Simbad)
Spectral Classifications: “A” is Am, “D” is F0
Note: AD is also H V 2 and SHJ 279; High probability AD is physical.

 Both A and D spread a pleasant gold-white glow over the scene, but that glow also obscures both 15.80 magnitude “B” (it would take a LARGE telescope to see that one), 13.30 magnitude “C”, and 13.70 magnitude “F”. At the time I looked at “E”, it was listed at a magnitude of 11.50, but I could only see it with averted vision, which suggested it was considerably fainter than 11.5. It has since been changed to 13.50, which is discussed below. (East & west reversed once again, click on the sketch for a better view).

Both A and D spread a pleasant gold-white glow over the scene, but that glow also obscures both 15.80 magnitude “B” (it would take a LARGE telescope to see that one), 13.30 magnitude “C”, and 13.70 magnitude “F”. At the time I looked at “E”, it was listed at a magnitude of 11.50, but I could only see it with averted vision, which suggested it was considerably fainter than 11.5. It has since been changed to 13.50, which is discussed below. (East & west reversed once again, click on the sketch for a better view).

Zeta (ζ) Lyrae attracted the same parade of observers as did Beta (β) Lyrae, which can be seen if you look closely at the identifiers in the data above.   Once again, William Herschel was here first – actually, on the same night as his observation above of Beta (β) .  He cataloged it as H V 2 (source):

Wm. Herschel on Zeta Lyrae

Click to enlarge.

Click to enlarge.

Herschel uses the Flamsteed number 6 to identify Zeta (ζ), but he’s actually referring to both 6 and 7, which is now the AD pair.  That pair was also measured and observed by John Herschel and James South on June 5th, 1823 (SHJ 279); by F.G.W. Struve in 1835 (STFA 38); by Otto Struve in 1840 (STTA 173), and by S.W. Burnham in 1880 and 1889 (BU 968).

Burnham’s observations and entry in his 1900 catalog (shown at right) contain considerable detail on the individual components, including magnitude estimations.  You can see his estimates in the right hand column (identified by β) as well as those of R.G. Aitken (identified with A).  They differ by a magnitude on “A and B”, by .8 of a magnitude on “A and C”, and by 1.6 magnitudes on “A and E”.   It’s interesting to note that where Burnham saw “B” as being a full magnitude fainter than Aitken did, their experience was reversed on “C”, with Burnham seeing it as .8 magnitude brighter than Aitken.

Getting back to the magnitude of “E”, based on my experience at the telescope, Aitken’s estimate of 13.0 seemed more likely than Burnham’s of 11.4.  In fact, the photometric data from both the Nomad-1 and UCAC4 catalogs (shown below under the Aladin image of Zeta Lyrae) indicates “E” is in the 13.0 to 13.5 range, which would make it just slightly brighter than “F” at 13.80.

 Click to make the data below the image more legible. The top panel of data is the WDS record prior to the change in magnitudes of “E” and “F”.

Click to make the data below the image more legible. The top panel of data is the WDS record prior to the change in magnitudes of “E” and “F”.  “C”, which eluded me visually, is also hidden in the glow of the primary in this photo.

I passed that information on to Bill Hartkopf at the USNO/WDS, who looked at both “E” and “F” and concluded “E” should be listed at a magnitude of 13.50, which is the NOMAD Vmag shown in the data below the Aladin image.   “F” was changed from a magnitude of 13.80 to 13.70, which also matches the NOMAD Vmag.

So here’s proof once again that visual observations of amateur astronomers can still make significant contributions in this era of CCD’s and automated telescopes!

Our next trip will lead us to a few stellar mysteries in Hercules, so stay tuned.

Until then, Clear Skies.   :cool:

A Stellar Stroll through Southern Lynx, Part 2: 38 Lyn, Σ 1338, and 10 UMa

When we last left Lynx, we were lingering over the mysterious tug-of-war taking place between the two components of Σ 1333.   Ahead of us, just a degree and a half north of that pair, a consecutively numbered mystery, Σ 1334 (aka 38 Lyncis), is impatiently beckoning us to investigate an issue of an entirely different magnitude.

Just to get you oriented before we start, here’s an overview of where we’re headed:

Stellarium screen image with labels added, click to enlarge the chart.

Stellarium screen image with labels added, click to enlarge the chart.

And here’s a close-up view of the area we’re going to tackle on this tour:

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

All three of the stars for this tour are labeled in tantalizing turquoise.  Stellarium screen image with labels added, click for a larger view.

38 Lyn  (Σ 1334) (AB is H I 9)       HIP: 45688   SAO: 61391
RA: 09h 18.8m   Dec: +36° 48’

Identifier  Magnitudes Separation  PA WDS
STF 1334 AB:  3.92,   6.09       2.60″ 224°  2013
DRS 44 AE:  3.92, 14.70     99.50″   52°  2002
CHR 173 Ba, Bb:  6.09,  ????       0.20″ 266°  2004
STF 1334 BC:  6.09, 12.50     79.50″ 217°  2002
STF 1334 BD:  6.09, 12.46    174.50″ 261°  2002

Distance: 125 Light Years (Simbad)
Spectral Classifications:  “A” is A1,  “B” is A4,  “E” is A3

As the data above shows, this is a complicated star. We’re going to simplify it considerably, though, since two of the stars shown above, “E” and “Bb” are well beyond our reach.   That leaves us with “A” through “D”, which is still more than enough to keep us occupied for several paragraphs.

The primary was a color I’ll describe as “without-a-doubt white” and “C” and “D” were way to faint for detecting color in my six inch refractor ( I’ve lettered the components in the inset at the right). “C” was difficult to see because of the AB glare, but the wider separation of “D” allowed it to be seen with less effort.   The AB pair is barely separated at the low magnification shown here. (East & west reversed here to match the refractor view, click on the sketch to improve the view).

The primary was a color I’ll describe as “without-a-doubt white” and “C” and “D” were way too faint for detecting color in my six inch refractor ( I’ve lettered the components in the inset at the right). “C” was difficult to see because of the AB glare, but the wider separation of “D” allowed it to be seen with less effort. The AB pair is barely separated at the low magnification shown here. (East & west reversed here to match the refractor view, click on the sketch to improve the view).

The AB pair eluded me when I first looked at in the 84x view shown above, so I switched to a 253x view, resulting in the shimmering image shown below (the eyepiece view was nowhere near as crisp as the sketch).  As is frequently the case, once I had captured the difficult secondary at high magnification, I was able to go back and catch a glimpse of it at a lower magnification.

This is one of those views you dream about, mainly because they’re so rare, at least in my seeing-challenged neighborhood. The sight of that small white dot of vibrating secondarial light was thing of pure beauty. East & west reversed again, click to enlarge!

This is one of those views you dream about, mainly because they’re so rare, at least in my seeing-challenged neighborhood. The sight of that small white dot of vibrating secondarial light was a thing of pure beauty.  East & west reversed again, click to enlarge!

As you look at the two sketches, you can see “C” and “D” are similar in magnitude, which is reflected in the 12.50 and 12.46 magnitudes shown in the data above for the two stars.  But when I first looked at the two components, the WDS data showed “C” with a magnitude of 10.30.  I could clearly see that wasn’t the case, so I scrutinized the two stars carefully for a couple of nights and never could determine which of the two had the edge in brightness.  The “without-a-doubt-white” glare from the AB pair didn’t make the comparison any easier.

In a case like this, the first thing I do is go to the NOMAD-1 and UCAC4 catalogs to see if magnitudes are listed for the stars in question.  What I was hoping to find was a visual magnitude for “C”.

The 10.30 magnitude for “C” is outlined in red in the WDS data, which was current in early March of 2015. Click to enlarge the image in order to read the data more easily.   Note: this is a mirror image (refractor) view.

The 10.30 magnitude for “C” is outlined in red in the WDS data, which was current in early March of 2015. Click to enlarge the image in order to read the data more easily. Note: this is a mirror image (refractor) view.

There are three tables of data below the image, starting with the WDS data of early March, 2015, followed by the NOMAD-1 and UCAC4 data.  NOMAD-1 shows “C” with a Vmag of 12.520, whereas the UCAC4 table shows no Vmag listed for that component (both boxes are highlighted in yellow).  But UCAC4 shows an f.mag of 12.066 for “C”, so between that number and the NOMAD data, the most likely magnitude for “C” falls somewhere between 12.0 and 12.5.  It’s also possible to combine the UCAC4 J and K magnitude values in such a way as to produce a visual magnitude, so I ran that data through a spreadsheet used for that purpose and came up with a visual equivalent of 12.295 for “C”.

Armed with that data, I sent a message to Bill Hartkopf at the USNO/WDS.  After looking at his sources, Bill decided on the 12.5 Nomad-1 magnitude, which is now a part of the permanent data.  The old magnitude for “C” of 10.30 comes from an estimate made by S.W. Burnham in 1909, which leaves me in the uncomfortable position of having intervened in the work of an acknowledged master.  Just in case he’s watching, my apologies!

As long as we’re here, we may as well look at the proper motion data for 38 Lyn, which will explain another mystery I haven’t mentioned yet:

This is an erect image view -- click to enlarge!

This is an erect image view — click to enlarge!

If you were wondering why a 14.70 magnitude star at a distance of one and a half arc minutes from the primary was added to this system, the explanation lies in the similar proper motions of “A” and “E”.  No proper motion is shown in Simbad for “B”, but since past measures show very little change in the separation of the AB pair, there may be a physical link of some kind between the two stars.

We’re going to continue moving north now (with a slight tilt to the east), this time for a distance of 1° 27’, which will bring us to Σ 1338. As you move in that direction, 7.52 magnitude HIP 45788 helps to point the way. (Here’s our second chart again).   This is a difficult little devil, so bring some patience and a high-powered ocular!

Σ 1338          HIP: 45858   SAO: 61411
RA: 09h 21.0m   Dec: +38° 11’
Magnitudes   AB: 6.72, 7.08    AB,C: 6.12, 12.59
Separations  AB: 1.005”          AB,C: 144”
Position Angles   AB: 312.9° (WDS 2015 Ephemerides)   AB,C: 166° (WDS 2009)
Distance: 139 Light Years  (Simbad)
Spectral Classifications:  “A” is F2, “B” is F4

The tight separation of the AB pairing of this star makes it a real challenge, but fortunately each star is similar enough in magnification to offset part of the difficulty. After looking at the separation and realizing a low magnification would be pointless, I reached into my eyepiece box to grab a 6mm eyepiece and was rewarded with two glowing white globes separated by a slice of black sky.   “C” (south of the AB pair at the left edge of the sketch) was easy to see at 152x, but the AB pair was reduced to a shimmering figure-8 at that magnification.   (East & west reversed, click on the sketch for a better look).

The tight separation of “A” and “B” makes them a real challenge, but fortunately each star is similar enough in magnification to offset part of the difficulty.  After looking at the separation and realizing a low magnification would be pointless, I reached into my eyepiece box to grab a 6mm eyepiece (253x) and was rewarded with two glowing white globes separated by a slice of black sky.  “C” (south of the AB pair at the left edge of the sketch) was easy to see at 152x, but the AB pair was reduced to a shimmering figure-8 at that magnification. (East & west reversed, click on the sketch for a better look).

Friedrich Georg Wilhelm Struve discovered the AB pair in 1829 and over the ensuing years numerous measurements of it were made in an effort to determine whether they were an orbital pair.  The right hand column of the attachment below (from Thomas Lewis’s book on Struve’s double stars) lists a total of forty-five measurements made between Struve’s first one in 1829 and four separate measures in 1900.

Click to enlarge!

Click to enlarge!

The left side of the attachment, which comes from the second volume of S.W. Burnham’s 1906 double star catalog, includes an 1898 measure by Hussey as well as a 1903 measure.   Also shown is a plot by Burnham of the change in position angle and separation between 1829 and 1903.

Jumping ahead to 2015, we have the advantage of more data (not to mention improved technology) which results in enough time and precision to generate this orbital plot for the AB pair of Σ 1338:

Click to enlarge the image.

Click to enlarge the image.

Data from the WDS Ephemerides is shown at the left, and in the information at the top of the plot you can see the quality of the orbit is graded as a “3”, meaning it’s considered to be reasonably accurate.   That data also shows the two stars will be at their closest point in 2023 (periastron), although the change in separation between now and then will be minimal.

Last, but certainly not least, is the intriguing 10 UMa, now located in Lynx as a result of some not so subtle stellar shifting.   Our second chart shows it northwest of Σ 1338 at a distance of about five degrees (5° 18’ to be precise).

10 UMa         HIP: 44248   SAO: 42642
RA: 09h 00.6m    Dec: +41° 47’

Identifier Magnitudes Separation  PA WDS
KUI 37 AB: 4.18,   6.48       0.50″ 231°  2012
STT 566 AB,C: 4.03, 10.36     99.70″ 184°  2004
BUP 122 AB,D: 4.03, 12.08    173.00″ 104°  2013
STT 566 AB,E: 4.03, 11.19    260.40″ 101°  2012

Distance: 52 Light Years (Simbad)
Spectral Classifications:  AB is F3+K0V

You have to take some time to look at this array of stars because the primary has a tendency to overwhelm the surrounding companions.   But if you look closely, “C”, “D”, and “E” start to assert themselves, and as they do, the subtle beauty of the scene begins to capture you. As a bonus, there’s a faintly mysterious star wedged between “D” and “E” that has been neglected for some reason while the other members were added to this system. (East & west reversed once more, click on the sketch to get the full effect).

You have to take some time to look at this array of stars because the primary has a tendency to overwhelm the surrounding companions. But if you look closely, “C”, “D”, and “E” start to assert themselves, and as they do, the subtle beauty of the scene begins to capture you. As a bonus, there’s a faintly mysterious star wedged between “D” and “E” that has been neglected for some reason while the other members were added to this system. (East & west reversed once more, click on the sketch to get the full effect).

The first thing that needs to be said about this complex star is it needs another name.  Of course, like most stars, it has several identities, among them being HIP 44248, SAO 42642, HD 76943, HR 3579, and BD +42 1956 — none of which roll off the tip of your tongue – plus there are another forty-five designations (scroll towards the bottom of that page) in Simbad. A fourth magnitude star that’s easily visible in reasonably dark skies deserves a definite designation, so I suggest we call it STT 566 (OΣΣ 566) since that’s the first double star designation assigned to it as a consequence of Otto Wilhelm von Struve’s discovery of the AB,C pair in 1851.

Click to enlarge!

Click to enlarge!

That pair was the original AB pair until 1935, when Gerard Kuiper discovered the tight 6.48 magnitude companion of the primary. Herr von Struve also added what is now the “E” component in 1851 (at the time it was labeled “C”), and S.W. Burnham threw in the “D” companion in 1908 (he labeled it “a”), adding his measures to an earlier measure in 1893 by Donner.

As I was looking at the measurements for the various components in the excerpt from Burnham’s 1913 Proper Motion Catalog shown at the right, I noticed some rather surprising differences in separations and position angles from the current WDS numbers. For example, what is now the AB,C pair was measured by Struve in 1851 at 260.32° and 150.33”, whereas the 2012 WDS data is 184°and 99.70”.   Even Burnham’s 1908 measures of 119.74° and 141.87” for what is now the AB,D pair differs significantly from the 2012 WDS measures of 104° and 173”. All is not stationary in the heavens, as we’ve discovered on more than a few occasions.

Here’s why:

Click to enlarge.

Click to enlarge.

It seems the AB pair is in a real hurry to get to wherever it’s going. When you boil Simbad’s proper motion numbers (shown below the image) down to basics, they reveal AB is racing westward at the rate of .47” per year and toward the south at the rate of .2” per year. The net effect of those two components of motion is a straight line motion across the sky of approximately 2.5” per year – which adds up quickly in fifty and one hundred year periods.

Here’s the same chart as above, but this time with the position of AB shown in 1851, 1908, 2000, and 2030:

Click for the larger view.

Click for the larger view.

As you look at it, you can see why the separation of the AB,C pair was wider in 1851 when Otto Struve measured it, and also why the AB,D pair was closer in 1908 when S.W. Burnham applied a micrometer to it. Keeping in mind the distance of the AB pair from where we see it is 52 light years – rather close on a galactic scale – more than likely what we’re seeing is the motion of a foreground star against the backdrop of more distant stars.

The AB pair, by the way, has a reasonably well-defined 21 year orbit:

Click to enlarge.

Click to enlarge.

This is a WDS orbital diagram, which comes from the Stelledoppie page for 10 UMa.   If you look at that page, you’ll see another orbital plot above the WDS plot, as well as the WDS Ephemerides data from 2000 to 2030.

And to tie up the last intriguing thread, we’re left with the tale of how 10 UMa came to be in Lynx.  In his brief account of 10 UMa, James Kaler mentions a re-drawing of the constellation boundaries which occurred in the 1920’s.  One of the results was 10 UMa suddenly found itself lying in Lynx.  Actually, re-drawing is a misleading description of what took place. Until that time, the boundaries of the constellations were frequently vague and variable, depending on which atlas was being consulted.  Ian Ridpath has a more detailed explanation of what prompted the decision to re-plot the heavens here.

Update 6/01/2015: I had noticed the magnitudes listed in the WDS for “D” and “E” seemed a bit too bright, especially when compared with “C”, so I checked both the NOMAD-1 and UCAC4 catalogs and found fainter values listed for each of them that were more in line with what I saw.   I sent a message to Bill Hartkopf once again at the USNO/WDS, and he’s changed the magnitude of “D” from 10.80 to 12.082 and “E” has been changed from 10.50 to 11.186.   Those values are based on the APASS data for those two stars, which are the magnitudes listed under the heading “VMag” in the UCAC4 Catalog.   In the chart below, the WDS magnitudes are outlined in red, and the UCAC4 Vmag numbers are outlined in yellow.

Click to enlarge and make the data more legible.

Click to enlarge and make the data more legible.

That’s it for Lynx this year, but there’s a lot more in this faint and extended constellation worth tracking down, so look for more next year.   Not sure where the next tour will take us since the weather in these parts has been less than cooperative lately, so stay tuned.

Until then, Clear Skies!   :cool:

A Stellar Stroll through Southern Lynx, Part 1: Alpha Lyn, HJ 2491, and Σ 1333

It’s long, it’s spread out, and it’s dim – all of which I suspect are reasons you never hear or read much about Lynx, as well as reasons most people don’t visit it. At any rate, it’s never been all that high on my list of locations for ferreting out sources of dueling photons. But I promised myself this would be the year to visit the lesser frequented constellations, and having already spent two sessions in Leo Minor (the first is here and second here), Lynx was a natural progression since the south end of it lies just west of the lesser Leo.

Stellarium screen image with labels added, click to enlarge.

Stellarium screen image with labels added, click to enlarge.

Despite its dim nature, Lynx is not really all that difficult to pin down because it’s sandwiched between Ursa Major’s feet to the east and northeast (labeled on the map above), and Gemini’s Castor and Pollux to the southwest. From the southeast side of Lynx, a line drawn from Algieba in Leo through Mu (μ) Leonis will point you almost directly to Alpha Lyncis, which is where we’re going to start.

Here’s a close-up view which identifies two of the three stars we’re going to look at:

Don’t let that 10 UMa designation throw you. We’ll get to that in part two, but trust me, it’s correct! (Stellarium screen image with labels added, click for a larger view).

Don’t let that 10 UMa designation throw you. We’ll get to that in part two, but trust me, it’s correct! (Stellarium screen image with labels added, click for a larger view).

Alpha Lyncis  (40 Lyn)  (H IV 55)  (SHJ 369)     HIP: 45860   SAO: 61414
RA: 09h 21.3m   Dec: +34° 26’

Identifier Magnitudes Separation  PA WDS
STT   571 AB: 3.29,  8.83    222.20″  42° 2008
STF 1342 BC: 8.83, 11.10      16.60″ 313° 2012

Distance: 203 Light Years (Simbad)
Spectral Classifications: “A” is K7, “B” is A2
Notes:   BC is also H IV 55 and SHJ 369

The primary is a rather attractive shade of orange.   The BC pair is obvious, but even in a six inch refractor, their duality is a bit elusive due to C’s faintness and the 2.27 magnitudes of difference between the two stars. (Click on the sketch to bring the image to life. East & west reversed to match the refractor view).

The primary is a rather attractive shade of orange. The BC pair is obvious, but even in a six inch refractor, their duality is a bit elusive due to C’s faintness and the 2.27 magnitudes of difference between the two stars. (Click on the sketch to bring the image to life. East & west reversed to match the refractor view).

Also shown in the sketch is a faint and shadowy pair, GRV 784, with magnitudes of 12.78 and 13.62, separated by 20.2” at a PA of 98° (WDS 2001). I managed to latch onto the secondary with averted vision, so I suspect it may be a few tenths of a magnitude brighter than the WDS’s listing of 13.62.

I stumbled into a real maze of confusion in the historical literature on this star that took a short eon to sort out. It started with the discovery that William Herschel had identified H III 84 as 40 Lyn in his 1784 catalog of double stars (sixth title from top).  Meanwhile, in the second volume of his 1906 catalog, S.W. Burnham pointed out H III 84 actually refers to SHJ 369/Σ 1340, which is located fourteen degrees north of Alpha (40 Lyn) in Ursa Major. Compounding confusion with more confusion, in his entry for H IV 55 (which correctly refers to 40 Lyn) in the same 1784 catalog, Sir William described what is now the BC pair of Alpha (40 Lyn) as being “3 1/2 minutes north and following 41st Lyncis.” But 41 Lyn is also in Ursa Major and is located eleven degrees north of Alpha Lyn (it’s also a double star, S 598). Both SHJ 369/Σ 1340 and S 598 are shown on the first chart above due north of Alpha (40 Lyn).  More than likely Herschel meant to refer to 40 Lyn, for which that description would be correct, instead of 41 Lyn.

Copies of Herschel’s and Burnham’s catalog entries are shown below, along with John Herschel and James South’s description of SHJ 369 in their 1824 catalog (last title on the page).

Click to enlarge!

Click to enlarge!

As to what caused the error with H III 84, it’s possible the version of Flamsteed’s atlas which Herschel was using at the time had an error or at least was confusing. Also a possible source of the confusion is the fluid constellation boundaries in this area (in case you were wondering how 41 Lyn ended up in Ursa Major).  Another example of the changing boundaries is a star we’ll look at in part two of this tour, 10 UMa, which is firmly in Lynx now. James Kaler’s entry on 10 UMa contains a bit of information on boundary changes which took place in 1920.  And it’s also possible Herschel was tired and didn’t catch the mistakes, which is certainly something anyone who’s sat behind a telescope at 3 AM can understand.

One other aspect of Alpha Lyn (40 Lyn) worth noting is its proper motion, which is significant for a star located 203 light years from planet earth. The Simbad chart below shows the “C” component moving parallel to the primary, but at a much slower rate, while the “B” component is moving even more slowly on a slightly different path.

Rates of motion are A: -224 +015 (.224”/yr west. /.015”/yr north), B: -007 -004 (.007”/yr west, .004”/yr south), and C: -019 +002 (.019”/yr west, .002”/yr north).   All data comes from Simbad, click to enlarge.

Rates of motion are A: -224 +015 (.224”/yr west. /.015”/yr north), B: -007 -004 (.007”/yr west, .004”/yr south), and C: -019 +002 (.019”/yr west, .002”/yr north). All data comes from Simbad, click to enlarge.

On to our next star, which requires a new chart because it’s dim and a bit elusive.

Stellarium screen image, click to enlarge.

Stellarium screen image, click to enlarge.

To reach it, we’ll need to locate 5.98 magnitude HIP 45412, which is west and very slightly north of Alpha Lyn at a distance of 1° 13’.   A line drawn from Alpha Lyn to HIP 45412 will include HJ 2491 at about two-thirds of the distance to HIP 45412, or 54’.  There are two stars south of HJ 2491 which can be used to triangulate its location, 9.8 magnitude TYC 02496-0655 1 and 10.6 magnitude TYC 02496-1219 1.

HJ 2491     No HIP or SAO Numbers
RA: 09h 16.7m    Dec: +34° 31’
Magnitudes: 11.41, 11.50
Separation:  15.20”
Position Angle: 202°  (WDS 2012)
No distance or spectral class available

You have to look close to see this pair!   Six inches of aperture is ideal for these two stars, five should work, but in a four inch refractor they would be difficult to resolve. As you can see, this is a very faint field and it didn’t help that clouds came in and interfered with the transparency as I was making this sketch. (East & west reversed, click on the image to improve the view).

You have to look close (and enlarge the sketch!) to see this pair.  Six inches of aperture is ideal for these two stars, five should work, but resolution in a four inch refractor would be a tough task. As you can see, this is a very faint field and it didn’t help that clouds came in and interfered with the transparency as I was making this sketch. (East & west reversed again to match the refractor view).

John Herschel discovered this pair sometime around 1830 and was more descriptive with it than normal (source):

Click to enlarge.

Click to enlarge.

There’s not much data on this pair of stars apart from what’s listed above and some proper motion statistics. The Aladin image below of HJ 2491 includes the PM data from both the NOMAD-1 and the UCAC-4 catalogs, which shows some slight differences, but overall indicates the possibility of some kind of physical relation between the two stars.  Simbad only shows the proper motion for A, which is why there’s a directional arrow for it and none for B.  If you look closely at the data, you’ll also see the Nomad and UCAC4 catalogs differ slightly on the direction and rate of movement of B in declination (pmDE).

Note this image has east and west in their normal places, as opposed to the refractor mirror image in my sketch.   Click to enlarge the view.

Note this image has east and west in their normal places, as opposed to the refractor mirror image in my sketch. Click to enlarge the view.

We’ll move on to the third star in this tour, Σ 1333, which is slightly more than a degree (1° 7’) north and slightly west of Alpha (40 Lyn).   Here’s our second chart for reference.

Σ 1333  (H I 31)       HIP: 45661   SAO: 61387
RA: 09h 18.4m   Dec: +35° 22’
Magnitudes: 6.63, 6.69
Separation: 1.8”
Position Angle: 51°  (WDS 2013)
Distance: 283 Light Years (Simbad)
Spectral Classifications:  “A”is A8, “B” is A5

This is a tight pair, but not all that difficult to split because the two components are very close to being the same magnitude. Both stars are white. I was able to detect a hint of black space between them at 152x, but as the inset at the right shows, more magnification does an admirable job of putting space between them. (East & west reversed again, click on the sketch for a much better version).

This is a tight pair, but not all that difficult to split because the two components are very close to being the same magnitude. Both stars are white. I was able to detect a hint of black space between them at 152x, but as the inset at the right shows, more magnification does an admirable job of putting space between them. (East & west reversed again, click on the sketch for a much better version).

This is another William Herschel discovery, dating to March 5th, 1782, and again he refers to 41 Lyn when he means 40 Lyn. In fact, he also refers to 39 Lyn on the first line of his catalog entry (the Latin on the first line of the excerpt below translates as “Between 41 and 39 Lyncis”), which is obviously 38 Lyn on our chart.  So either the copy of the Flamsteed atlas Herschel was using had the wrong numbers assigned to the two stars or he used the wrong numbers by mistake (source for catalog excerpt below).

Wm. Herschel on STF 1333

But then he throws in a mysterious reference to Eta (η) Ursae Majoris, which is the star at the east tip of the Big Dipper asterism’s handle, near the border with Boötes and Canes Venatici.  I’ve looked at two editions of Flamsteed’s Atlas Coelestis and in both of them there’s a star south of Kappa UMa (located above the center of our first chart on the Great Bear’s front paw) labeled “η”, which appears to be what is now referred to as 10 UMa – which is now in Lynx as a result of the change in constellation boundaries mentioned earlier.  There are no outlines of constellation boundaries in either of the atlases I looked at, so it’s difficult at times to tell what constellation a given star is part of — and no doubt that situation has caused some confusion in the past.

There’s one other aspect of this pair of stars which caught my attention as I was pulling together the data on it. Shown below is an Aladin image of STF 1333 with Simbad’s proper motion data attached at the bottom, and on the right of the image is a list of measures from Thomas Lewis’s book on Struve’s double stars:

Click to enlarge the image.

Click to enlarge the image.

A close look at Simbad’s proper motion numbers shows both A and B with the same proper motion, yet as Lewis’s data shows the distance between the two stars is widening. The WDS also shows both stars with the same proper motion, while Nomad and UCAC4 only list proper motion data for A.

If you scan the measures in the excerpt from Lewis you’ll see some noticeable inconsistencies in both position angle and separation. Despite the inconsistency, it’s very apparent the two stars are moving relative to each other, which raises two questions: why doesn’t the proper motion data show that, and (stemming from the inconsistency in measures) is there some kind of gravitational interaction occurring between the two stars?

I sent a request to Bill Hartkopf at the USNO/WDS to get the text file for Σ 1333, which provided me with the additional measures made between the end of Lewis’s data in 1903 and the last WDS entry of 2014.  I discovered this pair of stars has received a lot of attention over the past two centuries – the total number of measures in the text file is 226, which provides a wealth of data.  I put both the position angle and separation measures on a graph and came up with this:

Click to enlarge.

Click to enlarge.

As is evident from the jagged lines on both charts, the inconsistency in measures continued throughout the twentieth century.  A couple of things are obvious: first, the two stars are gradually moving farther apart, and second, if you ignore the peaks and valleys in the graphs, there appears to be a fairly consistent and small fluctuation in both PA and separation.

From the increasing separation of the stars, it’s clear the primary and secondary have slightly different proper motions.  And that wobble, or slight fluctuation in PA and separation, hints at either the possibility of an orbit, or at least, at some kind of physical interaction occurring between the two stars.  Bill ran a solution of the data which suggested an orbital period of approximately 3800 years, but also with a larger error range.  The actual chance of this being an orbital pair is actually very slight, but nevertheless, it’s a plausible explanation for the fluctuation visible in the graphs.

Along with all the data in the WDS text file for Σ 1333, there is also a large number of bibliographic references.  It’s possible that buried within all those references is a paper which addresses this issue.

Stellar mysteries!  Sometimes you need more tools and time than Sherlock Holmes ever even thought about!

Next time, we’ll continue moving north in Lynx, so until then,

Clear Skies!   :cool:

A Book! Tales from the Golden Age of Astronomy

It gives me more than just a little pleasure — actually, to be honest, it thrills me right to the tips of my focus fingers — to announce that I’ll be combining with noted astronomy author Neil English on a new book which will be entitled Tales from the Golden Age of Astronomy: A Celebration of Visual Astronomers from Galileo to Moore.  We’ll cover the history of visual astronomy starting at roughly 1600 up through the late twentieth century.  Our focus will be on a few of the well known visual observers, many of whom are frequently referred to in this blog, and as we work our way through the book, we’ll bring in a cast of roughly forty or fifty supporting characters, many of whom have also been discussed at one time or another in this blog.   Completion is tentatively set for October of 2016, with publication sometime after that.

Neil and I wrote a piece on S.W. Burnham, certainly a major figure in visual astronomy, which appeared on his blog in September of 2013.   Reading it will give you an idea as to what we have in mind — it’s available at this link.

Among the titles of Neil’s books are Choosing and Using a Refracting Telescope (published in 2011), Choosing and Using a Dobsonian Telescope (2011), Classic Telescopes (2013), and Grab ‘n Go Astronomy (2014).   Neil also wrote The Guide to Mars for Pole Publications, which publishes the British astronomy magazine Astronomy Now, for which he has also written several articles.

As a preview, here’s a look at what will appear on the back cover:

From the first time humankind cast its collective gaze into the dark sky above, a never-ending fascination with the moon and stars has been a defining characteristic of our species.  Curiosity concerning the mysterious events and objects in the night sky led to constant speculation and conjecture, resulting in a diverse collection of myths and theories that became deeply woven into the fabric of our many cultures.

But for most of recorded history, mankind’s vision of the heavens was limited by the acuity of the naked eye.  That era reached its culmination with the Danish astronomer Tycho Brahe’s late sixteenth century attempts at a detailed catalog of the heavens based on systematic visual observation.  Brahe passed from the scene just as the seventeenth century began, only a few years before the first telescopic devices were being invented.

The first telescopes were inevitably crude devices, but that did not deter their enthusiastic use and their potential to revolutionize mankind’s visual reach ever further into the heavens.  As optical improvements began to take place, they created an insatiable desire for further improvements.  And as the telescope improved, so too did the skills and talents of the first people to utilize them.

Who these men and women were, the difficult conditions in which they frequently labored, and the many surprising – indeed, given the nature of their equipment, often amazing – discoveries they made, is the subject matter of this book.  It’s a fascinating allegory of dedication, insight, intuition, and perseverance, all of which were fueled by an unquenchable thirst to understand both the logic and the cycles of the heavens.  Well-known figures such as Galileo and William Herschel will receive the attention they so richly deserve, but the book also presents a large supporting cast of lesser known men and women.  Each of them played important roles in constructing the foundation of the noble science of astronomy as we recognize it today – and all of them employed the tools of visual astronomy to achieve their goals.

Cheers, Prost, and Clear Skies!

P.S — A little something to whet the appetite:

9.6 Inch Dorpat Refractor

Crowded Starlight in Leo: OΣ 215, OΣ 216, Σ 1417

For as large as Leo is, it’s a little light on double stars.  That’s not surprising since it lies north of the plane of the Milky Way, but it also explains why it’s a rich hunting ground for galaxies.  In fact, the eastern half of the constellation is something of a gateway leading to the large numbers of galaxies in Virgo, Coma Bernices, Canes Venatici, and Ursa Major.

Despite its relatively sparse allocation of multiple starlight, Leo at least can boast of being the home of one of the most dazzling double stars in the heavens, Algieba, aka Gamma (γ) Leonis. Less dazzling but at least as alluring is 54 Leonis, and then there’s the diabolically difficult Iota (ι) Leonis, which demands a night of good seeing in order to be seen.

And speaking of Leonine difficulties, I came across a pair of Otto Wilhelm von Struve’s pairs a couple of years ago, which managed to elude my numerous attempts to pry them apart.  In fact, I had so little luck I was never even sure I had located them. But in this line of endeavor persistence is a prerequisite, so I persisted, and finally the sky gods relented and ordered up the missing ingredient: a night of cooperative seeing.  Also eluding me elusively was a pair of stars discovered by the senior Struve (Friedrich George Wilhelm von Struve), which finally parted on that night to reveal a pair of dueling wisps of light.

One word of cautious warning: these three stars are challenging – which is a polite way of saying they can be difficult to the point of exasperation. The reason they’re challenging and difficult is because they’re relatively faint and unequivocally tight. But once you hook onto one of these impertinent pairs, you’re likely to find their subtle beauty absolutely irresistible.  Five to six inches of aperture and seeing equivalent to at least a III (average) on this scale will give you a fighting chance.

Here’s a wide view of where we’re headed:

Stellarium screen image with labels added, click to expand the view.

Stellarium screen image with labels added, click to expand the view.

And now we’ll zoom in to the vicinity of Algieba:

Since Algieba is near the three stars on our itinerary, we’ll start there and use it for a jumping off point to get to Σ 1417. (Stellarium screen image with labels added, click for better view).

Since Algieba is near the three stars on our itinerary, we’ll start there and use it for a jumping off point to get to Σ 1417. (Stellarium screen image with labels added, click for better view).

Located where Leo’s neck joins his back, Algieba is easy to locate – and as long as we’re starting with it, you might as well put it at the center of your eyepiece and enjoy its gleaming gold photons until you’re sublimely satiated. When – or if — you can tear yourself away from it, go back to your finder and move a short 22’ south and slightly west to 4.80 magnitude 40 Leonis and then turn to the southwest and move a bit more than a degree (1° 8’) to reach Σ 1417. Since it’s a weak ninth magnitude, you may have a problem seeing it in your finder, so while you have 40 Leonis centered, nudge your scope southwest just enough to put 40 Leonis about a quarter to a third of the way from the center of the finder’s field of view. That should put Σ 1417 somewhere in the field of view of your eyepiece.

Σ 1417      HIP: 50223   SAO: 99023
RA: 10h 15.1m   Dec: +19° 07’
Magnitudes: 9.24, 9.31
Separation:  2.2”
Position Angle: 77° (WDS 2013)
Distance: 767 Light Years (Simbad)
Spectral Classification: “A” is F2

Obviously these two stars aren’t a pair of Porrima-like dazzling white orbs, but they’re all the more impressive for their sheer delicacy. Notice how sparse the field is, which is a common characteristic of this part of the sky, and which adds immeasurably to the desolate beauty of the ninth magnitude pair. 9.23 magnitude HIP 50207, which is shown on the finder chart we just used, is seen here halfway to the southwest edge of the field of view (left in the sketch). East & west are reversed here to match the refractor view.

Obviously these two stars aren’t a pair of Porrima-like dazzling white orbs, but they’re all the more impressive for their sheer delicacy (you’ll have to enlarge the sketch by clicking on it to see this pair). Notice how sparse the field is, which is a common characteristic of this part of the sky, and which adds immeasurably to the desolate beauty of the ninth magnitude pair. 9.23 magnitude HIP 50207, which is shown on the finder chart we just used, is seen here halfway to the southwest edge of the field of view (left in the sketch). East & west are reversed here to match the refractor view.

This pair of stars was discovered and cataloged by F.G.W. Struve in 1830 when the separation was slightly wider. If you look carefully at the separations shown below (from Thomas Lewis’s book on Struve), you’ll see some significant fluctuations:

Click to enlarge

Click to enlarge

Curious about those numbers, I looked through some old WDS files and found two additional measures of Σ 1417, but I also discovered a dramatic change in position angles had taken place in 2005:

1997: 258°, 2.3”
2005:   77°, 2.1”

Because I had been looking at Lewis’s data and was seeing position angles ranging from 258° to 261°, it looked like an error had been made in 2005. But on a hunch, I subtracted 180° from the 1997 position angle of 258°, resulting in a figure of 78°. What has happened is the designations for “A” and “B” have been reversed once photometric data was able to identify which of the two stars is the brightest.

This pair of stars isn’t identified as an orbital pair, but in looking at Simbad’s proper motion data, it looks like there’s a pretty good possibility there’s some kind of bond between the two stars:

The proper motion numbers for Σ 1417 show the primary moving west in right ascension at the rate of .031” per year and south in declination at .005” per year, while the secondary is keeping pace at .034” per year west and .004” per year south. Click for a larger view.

The proper motion numbers for Σ 1417 show the primary moving west in right ascension at the rate of .031” per year and south in declination at .005” per year, while the secondary is keeping pace at .034” per year west and .004” per year south. Click for a larger view.

The proper motion for HIP 50207 is also shown above, illustrating once again the random and unpredictable nature of stellar motion which is frequently seen in our galaxy.

To get to our next star, OΣ 215, we’ll go back to Algieba and move south and very slightly west two degrees, using 40 Leonis as a pointer (here’s our last chart again). That move will put you midway between two stars: the one to the east is 6.85 magnitude HIP 50508 and the one to the west is our goal.

OΣ 215      HIP: 50305   SAO: 99032
RA: 10h 16.3   Dec: +17° 44’
Magnitudes:  7.25, 7.46
Separation:   1.558”
Position Angle: 178.4°  (WDS Ephemerides for 2015)
Distance: 373 Light Years (Simbad)
Spectral Classification:  “A” is A9

If this looks like déjà vu all over again, that’s because it almost is (you’ll have to click on the sketch to see the full-sized version).   Except that in this case the stars have a faint tint of orange in them – which is contrary to the white suggested by the primary’s A9 spectral classification – and, they’re significantly closer at 1.558”. The few background stars that were visible were very faint, almost to the point of being averted vision objects only.   The moon didn’t help, since it was about forty degrees to the west, waxing to about 30% of its full illumination.   (East & west reversed once more).

If this looks like déjà vu all over again, that’s because it almost is (you’ll have to click on the sketch to see the full-sized version). Except that in this case the stars have a faint tint of orange in them – which is contrary to the white suggested by the primary’s A9 spectral classification – and, they’re significantly closer at 1.558”. The few background stars that were visible were very faint, almost to the point of being averted vision objects only. The moon didn’t help, since it was about forty degrees to the west, waxing to about 30% of its full illumination. (East & west reversed once more).

This is a genuine orbital pair, but it didn’t quite start out that way.  The first series of measures over a span of sixty years was impeccably inconclusive, suggesting both orbital motion and straight line motion (the term used in the study of stellar motion is rectilinear). Just a glance at the two orbital diagrams below (from S.W. Burnham’s 1906 catalog and W.J. Hussey’s survey of Otto Struve stars) shows why it was hard to come to a conclusive decision.

Click to enlarge.

Click to enlarge and improve the clarity.

Burnham considered orbital motion to be a possibility, but leaned more towards rectilinear motion, while Hussey seems to have been inclined toward orbital motion, although it’s difficult to detect that in the spaghetti-like plot excerpted from his book.  A look at the measures shown beneath Burnham’s diagram shows the cause of the erratic motion of the secondary in the plots is an irregularity in the changes in position angle, which contrasts with fairly smooth changes in separation.

The initial guess as to orbital period was 107.94 years, which is mentioned at the top of Hussey’s diagram.  Further observation in the last one hundred plus years puts the orbital period at 620.27 years, but the WDS data grades that orbit as a 4, which is about halfway between definitive and indeterminate.  Not surprisingly, as the green lines in the most recent WDS orbital diagram (also available here) show, there is still some irregularity in the measures of this pair:

Click to enlarge.

Click to enlarge.

Our last star, OΣ 216, is a close relative, both numerically and spatially, since it’s located a short three degrees to the southeast of our present position. A quick glance at our second chart shows it’s easy to spot, shining a short 25’ north and slightly east of 6.16 magnitude 42 Leonis.

 OΣ 216      HIP: 50829   SAO: 99091
RA: 10h 22.7m   Dec: +15° 21’
Magnitudes: 7.38, 10.28
Separation:  2.230”
Position Angle: 231.2°  (WDS Ephemerides 2015)
Distance: 94 Light Years (Simbad)
Spectral Classification:  “A” is G5

Déjà all over again times two! Although this is the widest of the three stars we’ve looked at, it’s also the most difficult because of the 2.90 magnitudes of difference between the primary and secondary.   Again, you’ll have to click on the sketch to see the full-sized version.   The secondary was very elusive at 152x, but patient scrutiny at 304x was more successful. As is frequently the case, once I had confirmed the secondary at the higher magnification, it was easier to see at the lower magnification. (East & west reversed once more).

Déjà all over again times two! Although this is the widest of the three stars we’ve looked at, it’s also the most difficult because of the 2.90 magnitudes of difference between the primary and secondary. Again, you’ll have to click on the sketch to see the full-sized version. The secondary was very elusive at 152x, but patient scrutiny at 304x was more successful. As is frequently the case, once I had confirmed the secondary at the higher magnification, it was easier to see at the lower magnification. (East & west reversed once more).

This is another orbital pair, and just like its sibling, OΣ 215, the first sixty years of data was inconclusive and un-illuminating.   I went back to Burnham and Hussey again to get the first attempts at diagramming the motion of the two stars in relation to each other, and to quote Burnham, “The best of the measures have too much error to make it possible to decide as to the character of the motion.”

Click on the excerpts to enlarge them.

Click on the excerpts to enlarge them.

There was no attempt by either Burnham or Hussey to estimate an orbital period, but current WDS data puts that figure at 314.93 years and assigns it a grade of 4, which is the same as was assigned to OΣ 215. Here’s a look at the WDS orbital diagram, which can also be seen here.  Note the irregularities in motion shown by the green lines extending from the ellipse of the orbit:

Click for a larger view.

Click for a larger view.

Burnham describes the brighter of the two stars as having “considerable” proper motion, which is obvious in this plot based on Simbad’s data:

Click to enlarge the image (the circles at the lower right are a group of galaxies).

Click to enlarge the image (the circles at the lower right are a group of galaxies).

Simbad shows the proper motion of only one of the two stars, while the WDS lists proper motions for both stars.  A closer looks reveals the WDS data for the secondary is very similar to the Simbad data, which presumably refers to the primary:

Simbad proper motion data:       -261 -087   (.261”/year west, .087”/year south)
WDS proper motion data:   A =  -251 -101   B =  -262 -086

Regardless of which star the data refers to, what stands out is the relatively speedy motion of this pair through the galaxy.  Given their neighborly distance of 94 light years, that’s not too surprising.

And that’s it for the two Leos this season.   Our next tour will take us up to Leo Minor’s western relative, Lynx, where we’ll thread our way carefully through another barren and dim section of the sky.

Clear Skies until then!   :cool:

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