Another Way to Polar Align

If you’ve been reading this blog for a while, you probably realize I thread my way through the night sky by star hopping.   There was a time when, like many other people, I used a Go-To mount and let it figure out how to get me to where I wanted to go.   But I soon realized I really wasn’t learning my way around the sky, which felt distinctly unsatisfying – kind of like relying on a GPS device to get you from point A to point B repeatedly without taking the time to learn the road and street signs you pass every day.   Given the fact that the skies above me are pretty darn close to magnitude six on a decent night, I decided there was no excuse for being lost most of the time when I looked up. It took a while, but I now know the constellations as well as I know my eyepieces, and there are parts of some constellations that are permanently etched into the corner of my mind reserved for maps.

But to be honest, if I was laboring under the typical light polluted urban sky, I would most likely have felt differently about the whole matter. My experience with light pollution and telescopes is limited to natural pollution, otherwise known as the full moon. It’s certainly possible to star-hop under light blasted skies, but I’ve found the typical 8×50 finder is limited to stars of about 6.0 to 6.5 magnitude when a full moon is hard at work refracting its rays all over a moisture laden sky. Under dark skies I can see stars as faint as 8.5 to 9.0 magnitude in an 8×50 finder, which makes finding my way around much less of a battle than it is when the moon is in charge of things.

If you use an equatorial mount, you quickly learned it needs to be aligned with the north or south pole in order to track an object in right ascension. If, like me, you have a motorized (tracking) EQ mount without GoTo capability, pointing it at Polaris will provide reasonably accurate tracking for most purposes.   But if you stay fixed on an object long enough, you’ll find it drifts from the center of the field of view, which requires you to use the mount’s declination controls to re-center the object.   For low-powered viewing, that’s not much of a problem.

But if the object of your attention requires high magnification, you’ll find yourself constantly re-centering it.   And if you’re trying to sketch the field of view, that perpetual wandering away from the center can make it difficult to accurately represent the stars in the field relative to each other. Which raises two questions: Why does it happen, and What do you do about it?

The answer to the first question is .75 of a degree, which is how far Polaris is from true celestial north. Which is another way of saying Polaris is really not quite the north star you thought it was. At low magnification, that .75 degree difference is minor, but with each increase in magnification, the quicker the object becomes unlatched from the center of the field. The more magnification you add, the sooner it starts to roam — somewhere around 200x you’ll see the object begin to take off almost immediately.   And if you’re a double star observer who finds 300x and 400x to be rather useful on occasion, you’ll find yourself constantly re-centering the object.

The answer to the second question – What do you do about it? – can be summed up in four words: find another north star. Or at least one closer to the actual celestial pole. As it happens, there’s a 9.65 magnitude star located a mere 13.5’ from true celestial north, which goes by several names: BD +89 38, GSC 04661-00002, SAO 3788, and TYC 4661-2-1. We’ll call it SAO 3788 since that’s the name most likely to be used to designate it.

If you’re beginning to feel a bit lost or puzzled, let’s take a look at Polaris in relation to the north celestial pole:

Stellarium screen shot with labels added, click to enlarge.

As you can see, Polaris is a bit shy of occupying the actual north celestial pole, which is the point at which all the lines converge.   But as you can also see, there are several stars which lie closer to the actual pole, one of which is the previously mentioned SAO 3788.

So now for the main question: how do you get to it?   You star hop to it, of course! Fortunately, we don’t have far to go, so if the idea of star hopping has you on the edge of your seat, despair not. You can do this quite easily from within the field of view of a wide angle eyepiece.

But before we get to the eyepiece view, there are a couple of things we need to pin down, the most important being the positon angle of the ninth magnitude companion of Polaris, which also serves as an important navigational tool.   In fact, we might just as well take a quick look at all the pertinent data on Polaris:

Polaris (Σ 93)  (H IV 1) (Alpha [α] Ursa Minoris)
HIP: 11767   SAO: 308
RA: 02h 31.8m  Dec: +89° 16′
Magnitudes: 2.04, 9.10
Separation: 18.10″
Position Angle: 233° (WDS 2013)
Dist: 432 Light Years
Spectral Type: “A” is F8, “B” is F3

Note the declination of +89° 16′ — further confirmation that Polaris is three-fourths of a degree short of celestial north, in case you still had doubts.

But the key number is the position angle, 233°. We’re going to use that as a reference point for determining which direction to move in order to aim ourselves towards the north celestial pole (which is at 360°). Determining celestial directions in the vicinity of the celestial pole is a very tricky business, even for the experienced observer, and it can be downright confusing when you’re gazing into an eyepiece.  The old trick of turning off your drive motor and letting a star drift across the field of view to determine which direction is west doesn’t work this close to the pole, so a navigational aid is a necessity.

Let’s start by imagining that the the line running from Polaris A through Polaris B stops at the edge of your eyepiece.   We’ll label that point 233°. When we subtract 233° from 360°, we get 127°, which is how far we need to move around the outer perimeter of the eyepiece in order to point ourselves towards celestial north.

Now we’re faced with the big question: which direction do we go? Clockwise or counterclockwise? The answer is that it depends on the kind of telescope you’re using, so pay close attention — it means the difference between success and frustration.  Assuming the use of a conventional inverting star diagonal (NOT an erect image diagonal), if you’re using a refractor or an SCT, north is clockwise from the 233° mark. If you’re using a reflecting telescope (Dobsonian, Newtonian), north is counter-clockwise from 233°. If moving by degrees around the outer perimeter of the eyepiece field is confusing, you can draw a line perpendicular (90°) to the line running between Polaris A and B and then add another 45° to that to point you toward north.

Here’s a diagram which should make all that more clear:

This may look simple when north and south are straight up and down, but that will seldom be the case when you peer into the eyepiece! Click to make the image easier to read.

And here’s how that move looks when superimposed on our previous chart:

Stellarium screen shot with labels added, click to enlarge.

Now that we’re directionally oriented in the eyepiece, there’s one more thing we need to discuss before going any further, which is how to move to where we want to be. If you’re new to this, it may come as a surprise, but it’s the mount that needs to move, NOT the telescope.

When you bought your mount, the instructions for it should have covered the procedures for lining up on Polaris. The first thing you would have done is set up your mount so that the declination axis was pointing toward Polaris, and then you would have used the altitude control to move the tilt of the declination axis so that it matched your latitude – in my case, that just happens to be 45 degrees. Then you would have centered Polaris in your finder by using both the declination and azimuth (horizontal) controls on the mount, and then fine-tuned that further by making final adjustments to center Polaris in your eyepiece. During that entire procedure, you would have left the telescope untouched.

So that’s what we’re going to do here.

With the counterweight shaft pointing straight up and down, and the declination circle lined up with the ninety degree mark, lock the declination and right ascension clutches on the mount and then use the altitude and azimuth controls to center Polaris, first in your finder, and then in your eyepiece (if your mount has locks for the altitude and azimuth controls, make sure to unlock them now – and don’t forget to lock them when we’re done!). Here are photos of two frequently used equatorial mounts, which will give you an idea of what to look for in the way of altitude and azimuth controls:

This is a Celestron CG4 mount. The altitude and azimuth controls are unlocked when one of the pairs of control devices is loosened, and locked when the two opposing devices are turned so they’re pressed tightly against one another. Other mounts, such as the CG5, have similar controls. Click for a larger view.

 

To unlock the azimuth and altitude controls on the Losmandy G11, just loosen the wing nuts shown in the photo — note there are two, one each on opposite sides of the mount. The Losmandy G8 uses the same setup. Click for a larger view!

All the movements we’re going to make from this point forward will be made using the altitude and azimuth controls on the mount.

Now if you look carefully at the chart above (here it is again), you’ll see there’s actually an easy way to star hop to SAO 3788. Notice that the Polaris A-B line points almost directly at 6.45 magnitude HIP 7283, which is distinctive because it’s bright and because of the ninth magnitude star located next to it (that star has a name by the way, SAO 223).   And if you move towards true celestial north from HIP 7283, you’ll see it leads you past 8.10 magnitude HIP 3128. And if you extend that line an equal distance, it just happens to lead you to our goal, 9.65 magnitude SAO 3788.

And here’s how that looks when diagrammed, minus the celestial grid in our previous chart:

Stellarium screen image with labels added. (Both this and the previous image portray the scene as it would be seen in a refractor or SCT, meaning east and west have been swapped).

Here are those moves once more, but this time plotted on our earlier grid:

Stellarium screen image again, click to enlarge.

So how does all that look in the eyepiece?

Click to enlarge – note, east and west are reversed here to match a refractor or SCT view.

This is the view with a 40mm Celestron Plössl in a 9.25 inch SCT. I’ve moved Polaris to the eastern corner of the field in order to pull HIP 7283 and HIP 3128 into the field of view.

If you now move toward the north until HIP 3128 is in the same position in the eyepiece as HIP 7283 was, you’ll see our goal, SAO 3788, come into view at the opposite (north) corner of the field of view:

Click to enlarge!

Center SAO 3788 in your eyepiece and you’re now a mere 13.5’ from true celestial north.   Once you’ve done this a few times, you’ll find it’s quick and easy to do.

I’ve found parking SAO 3788 in the center of my eyepiece is more than sufficient for a 400x view — I can barely detect any motion unless I stay on the object for ten minutes or so. Remember, we’ve gone from being 44’ off center from celestial north to 13.5’, which is a huge improvement.

Lock up your altitude and azimuth controls, unlock the declination and right ascension clutches, grab a 4mm eyepiece, and go split that pair of sub-arcsecond stars that’s been on your list for the past year without having to chase it across the field of view!

Happy star hopping and clear skies!

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.

Eta (η) Lyrae was a popular item with the early double-star detectives of the late 18^th and early 19^th 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 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 29^th, 1779, and recorded this observation in his 1782 catalog (twelfth title from the top):

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 16^th, 1823 (source for their 1824 catalog, last title on the page):

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.

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.

The brightest of the threesome of doubles surrounding Eta (η) Lyrae, SHJ 289, was cataloged by John Herschel and James South on June 16^th, 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)

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

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 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!  😎

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.

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.

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 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.

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).

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 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!

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.

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).

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.

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).

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

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.

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.

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.

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!   😎

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.

“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).

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

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 13^th 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 14^th 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.

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

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.

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.

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).

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):

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 5^th, 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”.  “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.   😎

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.

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

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 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 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.

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!

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 “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!

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.

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).

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!

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.

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.

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.

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.

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!   😎

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.

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).

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).

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 41^st 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!

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.

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

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 (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.

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.

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 another William Herschel discovery, dating to March 5^th, 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).

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.

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.

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!   😎

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.

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).

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 (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

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 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).

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 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.

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).

Click to enlarge!

Update 4/22/2017:  Mark McPhee took the image of OΣ 216 (STT 216) which is shown at the right which shows the secondary very clearly.  Note east is at the left in this image, north at the top.  This is a much closer view of the two stars than my sketch!

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.

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.

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).

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!   😎

Leo in a Minor Key, Part Two: 7 LMi, 11 LMi, and Σ 1374

This excursion in Leo Minor will take us along the western edge of the constellation, close to its border with Lynx. (If you missed it, the first part of this tour is here).  All three of the stars we’re going to look at this time are aligned along a north-south line, so the chances of getting lost and disappearing into the starless black void typical of this area are pretty slim.

First, here’s an overview of where we’re headed (if you find Leo Minor difficult to track down because it’s frustratingly faint, the paragraphs above and below the first chart in part one describe how to locate it and trace its outline):

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

Here’s a closer look, which includes the three destinations for this tour, all of which are north or south of 10 LMi, and all of which are labeled in tantalizing turquoise:

Stellarium screen image with labels added, click to enlarge.

Since 10 LMi is situated in the middle of our target area, we’ll start there and begin by moving north to Σ 1374, which is located three degrees north and slightly east of 10 LMi.   There’s a triangle of fifth magnitude stars (42 and 43 Lyn, and HIP 47029) just north of Σ 1374, which makes it easy to locate.

Σ 1374  (AC is ABT 7)      HIP: 47527   SAO: 61629
RA: 09h 41.4m   Dec: +38° 57’
Magnitudes   AB: 7.28, 8.65    AC: 7.28, 13.13
Separations  AB: 2.80”            AC: 307.60”
Position Angles   AB: 313° (WDS 2013)   AC: 10° (WDS 2002)
Distance:  167 Light Years (Simbad)
Spectral Classifications:  “A” is G3

This is what you might call a spatially diverse triple star. The secondary is close enough to hide in the primary’s glow, aided by the 1.37 magnitudes of difference between the two stars. At 152x the two stars were barely separated, but as the inset at the right shows, the view improved considerably at 253x. Both of those stars appeared white to my eyes, with no trace of the yellow hinted at by the G3 spectral classification of the primary. The “C” component is both very faint and very distant, and requires adequate aperture and a discerning eye to locate it. (East & west reversed to match the refractor view, click on the sketch to improve the view of one heck of a lot).

If you look closely (you’ll have to enlarge the sketch), you’ll see three very faint stars at the southwest (left) edge of the field.   By overlaying the WDS catalog on the Aladin image below, I was able to determine those three stars are not cataloged in the WDS.  I used the UCAC4 catalog to identify the three, which shows they’re all in the twelfth and thirteenth magnitude range.

Aladin image with UCAC4 data, click to enlarge.

The proper motions are also listed in the data at the bottom of the image and show some similarity in motion for the stars numbered “1” and “2”.  Considering how slight that motion is, the chances are the two stars are located quite a distance from us, which makes it difficult to come to any conclusion as to whether the pair is physically related.  Interestingly enough, the pair that are closest together visually, “2” and “3”, are moving away from each other.

But to get back to our main interest, the “A” and “B” components of Σ 1374 are a genuine orbital pair with a period of 1377 years (the orbit and data can be seen here).  The pair are in a phase of their orbit where they’re moving closer together, although at a very slow rate.  The WDS Ephemerides shows them with a separation and position angle of 2.778” and 314.2 degrees in 2030, so there’s no need to feel anxious about catching them before they get too close together to be caught.

As for “C”, why it was added to the Σ 1374 pair is something of a mystery (the ABT initials of ABT 7 refer to Giorgio Abetti).   At the bottom of the image above, I included the UCAC4 data on the three components of Σ 1374, which also include the proper motions of each of the stars.  It’s obvious “C” has no relation whatever to the AB pair of Σ 1374, and given that it’s over five arc minutes away from that pair, it’s hard to say what prompted Abetti’s inclusion of it in 1921 — possibly its position angle and separation were measured as a reference point for the proper motion of the AB pair.

Sometimes when you dig deep, the stellar puzzles seem to multiply at an astronomical rate.

Let’s go back south to 10 LMi now and take a look at a more difficult pair, 11 LMi, also known as HU 1128.   It’s easy to find since it’s parked just 39’ south and slightly east of 10 LMi (here’s our chart again).

11 LMi  (HU 1128)     HIP: 47080   SAO: 61586
RA: 09h 35.7m   Dec: +35° 49’
Magnitudes: 4.8, 12.5
Separation:  6.41”
Position Angle: 49.9° (WDS 2015 Ephemerides)
Distance: 37 Light Years (Simbad)
Spectral Classifications:  “A” is G8, “B” is M5

With just under eight magnitudes of difference between the primary and secondary, this is a very tough pair. I barely caught a glimpse of it at 152x in the glare of the yellow-white primary, and did a bit better at 253x. (East & west reversed once again, click on the sketch to get a better view of the secondary).

Located 4.8′ north and slightly east of 11 LMi is ALI 357, with magnitudes of 12.5 and 12.6, separated by 7.60” at a PA of 96° (WDS 2002).  I didn’t notice them, probably because they were more closely spaced than the fainter pair of stars seen about 1.6’ southwest (left in the sketch) of the primary of 11 LMi.  That’s another pair which is not cataloged in the WDS, and as the data at the bottom of the image below shows, the two stars don’t appear to be linked by proper motion. The UCAC4 catalog data shows the northernmost of the pair with a magnitude of 13.5 and the southernmost at a magnitude of 12.98 — the separation is about 19″.

Click on the image to make the data more legible.

Click to enlarge.

11 LMi, aka HU 1128, is also an orbital pair (here’s the orbit and data), with a relatively short period of 201 years.   The last date of observation in the WDS is 2006, but because the position of the two stars is changing significantly, I used the 2015 WDS Ephemerides for the data above, which is included in the chart at the right.  Notice it shows the stars will continue to widen over the next fifteen years.

The 11 LMi pair have a rather high rate of proper motion, which isn’t surprising considering they’re a short 37 light years from us:

Click for a much better view.

Rounded off to three decimal figures, the column labeled PMRA shows motion of .729”/year west in right ascension and .260”/year south in declination, which means this pair are strolling across the sky at a rate of almost one arc second per year. There are two more stars in the photo above with significant proper motion (the data there is from Simbad also), neither of which are associated with 11 LMi.

The HU in HU 1128 refers to William Joseph Hussey, a prolific observer who spent much of his career at Lick Observatory in northern California.  When he first caught sight of this pair of stars in 1904, they were at a different point in their orbital waltz (source):

Click to enlarge.

Let’s drop south and slightly west now for a distance of about two and half degrees to 7 LMi (here’s our chart once more).  You can use 5.39 magnitude 8 LMi as a reference point, which sits almost midway between the two stars and about 20’ west of the line which connects them.

7 LMI  (H V 69)  (HJ 1166)  (STTA 100)     HIP: 46652   SAO: 61529
RA: 09h 30.7m   Dec: +33° 39’
Magnitudes   AB: 5.97, 9.66    AC: 5.97, 11.58
Separations  AB: 61.30”          AC: 95.90”
Position Angles   AB:  125° (WDS 2011)   AC: 217° (WDS 2001)
Distance:  502 Light Years (Simbad)
Spectral Classifications:   “A” is G8, “B” is K0

We haven’t heard from the admirable Admiral William Smyth for a while, so let’s see what he has to say about 7 Leonis Minoris:

A wide double star, immediately under the animal’s right fore-paw. A 6, bluish white; B 11, livid. This object was registered 69 H V, in 1782, with a distance of 58.30”, but no angle of position; and it is No. 1116 of H.’s twenty-foot Sweeps. The companion is one of those minute and dusky objects which are best seen by averting the eye to the verge of the field; but there are many of much smaller magnitude, which shine quite sharply, and emit a strong blue ray. It may be found by carrying a line from Regulus close to the eastward of ε Leonis, and passing it exactly as far again into the north-north-west region.”   (The Bedford Catalogue, p. 217)

I’m not quite sure what the good Admiral meant with his description of “B” as livid, but I saw a hint of orange in it, and I saw yellow-orange in the primary instead of the Admiral’s bluish white. “C”, which was added in 1912, was colorless, but no problem to see. The field of view is rather sparse, which has been typical of the stars we’ve looked at in this area. (East & west reversed once more, click on the sketch to improve the view).

7 Leonis Minoris has had a lot of visitors, as is evident from the first line of data above.  William Herschel (H V 69), John Herschel (HJ 1166), and Otto Struve (STTA 100) — and of course, Admiral Smyth — all stopped here for a visit.  The father-son observations of the two Herschel’s are shown below (source for Wm. Herschel [six titles down), source for John Herschel):

Sir William’s work is at the top, Sir John’s is at the bottom. Click to enlarge.

As Admiral Smyth mentioned, William Herschel didn’t include a position angle in his notes, and in case you’re wondering, his Latin translates roughly as “in the extreme of the front foot.”  John Herschel’s 45° sf (south following) translates to 135°, which misses the 2001 WDS number by ten degrees, but since Sir John’s number was an estimate, we can call it in the ball park.  Their separations are considerably less than the 2001 WDS figure of 61.30”, and as was the case with Admiral Smyth’s magnitude estimates, their numbers are different from the 5.97 and 9.66 values shown in the WDS.

S.W. Burnham included another three measures in his 1906 catalog (the first is William Herschel’s original observation), which show gradual changes in both the position angle and separation:

Those numbers suggest the proper motions of the primary and secondary should show the two stars are gradually moving away from each other, and in fact that’s exactly what we see:

Simbad’s data is shown in the top panel, UCAC4 is shown in the bottom one.  Click to make the date more legible!

“A” is moving west at a rate of .023”/year and south at .048”/year, while “B” is moving west at .002”/year and south at a rate of .029”/year. Simbad doesn’t show any data on “C”, but the UCAC 4 catalog shows it moving due west at the rate of .051”/year with a very slight southern tendency of .0004”/year – so it’s moving away from the other two stars as well.  Notice the Simbad and UCAC4 proper motions for “A” and “B” are slightly different.

And that should cover Leo Minor for a good while. Our next tour will take us down into the larger Leo for a look at some rather difficult stars, so order up some good seeing and break out the five and six inch scopes.

Clear Skies until then! 😎

Leo in a Minor Key, Part One: 42 LMi, Σ 1432, and OΣΣ 104

It’s not distinctive, but it’s there if you look closely – Leo Minor, that is.

During the many hours I’ve spent in the larger Leo, perusing double stars and galaxies, I’ve always been aware of the smaller Leo to the north. Most atlases portray Leo Minor in a skewed diamond-shaped configuration, but the few times I’ve glanced up that way in a semi-serious search for it, I’ve never found anything but a wide scattering of faint and un-spectacular stars. Sooner or later I knew I would have to grab my Sky &Telescope Pocket Atlas, hold it up to the sky, and pin little Leo into place.

Sooner came later than I had planned, but at least it arrived.

Leo Minor is sandwiched between several somewhat dim, but discernible, reference points in a fairly faint part of the sky: Allula Australis, Allula Borealis, Tania Australis, Tania Borealis (all in Ursa Major), and Alpha (α) Lynicis, the brightest star in another faint constellation known for being spectacularly faint.

Stellarium screen image with labels added, click to enlarge.

The easiest way to pin down Leo Minor is to begin by locating one of the Great Bear’s (Ursa Major’s) three distinctive feet. We’ll start at third magnitude Delta (δ) Leonis, also known as Zosma, which marks the rear of Leo the Lion’s back. Fourth magnitude Allula Australis, located at the south tip of the Great Bear’s rear leg, is eleven degrees due north of Zosma, where it sits linked to its slightly fainter neighbor, Allula Borealis, one and half degrees further north. From Allula Borealis, a five degree leap due west with a very slight tilt to the north will get you to 3.83 magnitude 46 Leonis Minoris.  From there, it’s a matter of branching out both northwest and southwest about five and half degrees to reach 4.21 magnitude Beta (β) LMi and 4.74 magnitude 30 LMi.  And from there, continue west and slightly north to pick out 4.49 magnitude 21 LMi and 4.56 10 LMi.

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

We’re going to start with fifth magnitude 42 Leonis Minoris, also known as S 612, which is four degrees south and slightly west of 46 LMi.   On the chart, you can see it’s the southernmost of a line of three stars formed with 4.74 magnitude 30 LMi and 4.72 magnitude 37 LMi.

42 LMi (S 612)        HIP: 52638   SAO: 62236
RA: 10h 45.9m   Dec: +30° 41’

Identifier		Magnitudes	Separation	PA	WDS
S 612	AB:	5.34, 7.78	196.50″	174°	2012
ARN 3	AC:	5.34, 8.31	424.60″	94°	2012

Distances   A: 382 Light Years     B: 661 LY     C: 373 LY  (Simbad)
Spectral Classifications   “A” is A1, “B” is K2, “C” is F0

A wide triple star that comes darn close to forming a perfect right angle triangle. “A” and “C” appeared white, and a careful look at “B” turned up a slight hint of orange, which dims it just enough to make it look about the same magnitude as “C”. (East & west reversed to match the refractor view, click on the sketch for a better version).

The AB pair was discovered by Sir James South on a frosty March night in 1825, which he describes rather well in this page from his 1826 catalog:

Frost prevention in the days before dew heaters!  Click to enlarge.

Sir South’s final position angle of 82° 36’ sf (south following) works out to a present day PA of 172° 36’ and when converted to arc seconds, his separation is 200.304”.

A look at S.W. Burnham’s 1906 double star catalog turns up two more observations of 42 LMi  . . . . . . .

. . . . . . . and when the three measures are listed together, they show a gradual decrease in separation as well as a gradual change in PA toward the south, both of which are confirmed by the 2012 WDS measures which continue that trend:

A look at an Aladin photo of 42 LMi with Simbad’s proper motion data super-imposed on it clarifies why those changes are taking place:

The motion here is south and west in this erect image version of 42 LMi (east and west are reversed in the mirror-image refractor sketch above). Decoded, the proper motion data for “A” means motion in arc seconds of .026”/year west and .037”/year south. The negative signs indicate westward motion in right ascension and southerly in declination.

The southerly motion of “A” towards “B” is obvious here, and given enough time, the two stars will probably appear to intersect. However, as the distances of “A” (382 LY) and “B” (661 LY) listed in the data lines above for 42 LMi indicate, there are 279 light years between the two star, so a stellar scale impact isn’t looming in the very distant future.

The “C” component (ARN 3), at 373 LY, is much closer to “A”, and is moving pretty close to parallel with it. But there’s enough difference in direction and rate of motion to cast doubt on a physical connection between the two stars, as well as the nine light years of distance between them.  ARN 3 refers to Dave Arnold, who added the “C” component sometime around 2000 or 2001, as near as I can tell.   At that time, he published his results in the Double Star Observer, which was succeeded in 2005 by the Journal for Double Star Observers, better known as the JDSO. I’ve had no luck with numerous internet searches for back issues of the Double Star Observer, so if anyone is aware of their existence, please leave a comment and I’ll follow up on it.

Next on our list is Σ 1432, a faint double located in a lonely part of the sky southwest of 42 LMi.  To get there, we’ll need to negotiate  a distance of almost four degrees (3° 45’) west and slightly south through relatively featureless terrain until we reach 6.61 magnitude HIP 51325 (here’s our last chart again).  Σ 1432 is a faint dot of eighth magnitude light wedged between HIP 51325 on the east and 6.36 magnitude HIP 50904 on the west.

Σ 1432     HIP: 51158   SAO: 81347
RA: 10h 27.0m   Dec: +29° 41’
Magnitudes: 7.84, 10.28
Separation:  28.5”
Position Angle: 121° (WDS 2012)
Distances   A: 327 Light Years   B: 399 LY (Simbad)
Spectral Classification:  “A” is F2

The field of view surrounding Σ 1432 is about as bleak and featureless as the terrain we navigated to get here. Apart from the ash white glow of the primary, the only other notable object is TDS 7264, a faint pair with magnitudes of 11.1 and 11.39 separated by 0.7” at a position angle of 134° as of 1991 – and well below the threshold of my detection. (East & west reversed once more, click on the sketch to enlarge it).

This is one of F.G.W. Struve’s more challenging pairs, with a 2.44 magnitude difference between the primary and secondary. It’s not particularly difficult, but you have to look closely to catch the much fainter secondary’s diminutive dot of light.

There’s been a slight narrowing of the separation and a minor change in direction in the position angle since Struve’s first measures, which can be seen in the following fifty years of observations taken from Thomas Lewis’s book on Struve’s double star catalog:

That narrowing of separation and the slight PA change can be seen taking place in this Aladin photo, which shows the direction and rate of motion of both stars:

The motion shown here in this erect image is west and south, and the explanation of the numbers included in the Aladin-Simbad photo above of 42 LMi applies here as well. Click for an improved version!

We can get a three-dimensional feel for what’s actually taking place here if we mentally super-impose the distances of “A” (327 light years) and “B” (399 light years) on the photo.  Since it’s obvious in the photo that “A” is the brighter of the pair, it’s not difficult to perceive it as being in the foreground of the image.  If you can pull it off, you’ll have an inkling of what a difference of 72 light years looks like!

Now we’ll move on to a pair that is wider, more colorful, and almost evenly matched in magnitude, OΣΣ 104.  From Σ 1432, we’re going to move four degrees due north to 4.74 magnitude 30 LMi (our second chart once more).  Once you have that star centered in your finder, you’ll see the twin glow of OΣΣ 104 a short 31’ to the northwest.

OΣΣ 104     HIP: 50951   SAO: 62021
RA: 10h 24.4m   Dec: +34° 11’
Magnitudes: 7.21, 7.27
Separation:  209.4”
Position Angle: 287°  (WDS 2012)
Distances    A: 1028 Light Years   B: 953 LY  (Simbad)
Spectral Classifications:  “A” is M4, “B” is K0

The appearance of a pair of weakly tinted yellow-orange stars in the center of my eyepiece was a welcome change after the persistent white of our two previous objects. These two stars point almost due west on first glance, and the scene is improved by the intriguing parallelogram of three twelfth magnitude stars and one tenth magnitude star on the south side of the OΣΣ 104 pair. (East & west reversed once more, click to enlarge).

There’s a distance of 75 light years between the two stars of OΣΣ 104 according to Simbad’s data, so they’re purely a line of sight pair. They’re also moving away from each other as seen below:

“A” is moving east at .006”/yr (east is indicated by the plus sign) and south at the rate of .021”/year, while “B” is moving west at .005”/yr and south .014”/year.  Notice the NOMAD-1 PM is slightly different.  Click to make the data more legible.

The UCAC4 and NOMAD-1 data is included at the bottom of the photo above because I found a magnitude conflict with the AAVSO data.  I stumbled on that discrepancy after discovering the primary of OΣΣ 104 is a variable star (Simbad labels it a semi-regular pulsating star). The AAVSO identifies the primary as UU LMi, with a magnitude range of 6.89 to 7.03. Since that magnitude range conflicts with the 7.21 magnitude assigned to the primary in the WDS, I checked the UCAC4 and NOMAD-1 catalogs and found visual magnitudes of 7.202 (UCAC4) and 7.048 (NOMAD-1) for the primary. So it’s possible the WDS magnitude for “A” is off slightly (although the similar UCAC4 Vmag value was probably generated by the AAVSO’s APASS data), but certainly not enough to be detectable visually unless you happen to have photometric cells in your eyes.

We’re not done with Leo Minor quite yet.  On our next trip, we’ll wander to the west edge of little Leo for a look at three more stars.

In the meantime, Clear Skies!   😎

Double and Triple Stardom in Taurus: 37 and 39 Tau, Σ 479, and Σ 494

Floating in the sky northwest of the V-shaped asterism in Taurus which is home to the Hyades is a pair of stars that would probably be better known if fate hadn’t decreed they should occupy a stellar address within a few degrees of the Pleiades. Over-shadowed by the brilliant blue-white light and glowing nebulosity of the most dazzling naked eye open cluster in the heavens, 37 and 39 Tauri are ignored night after night by double star sleuthers.

But . . . . . . . not tonight!

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

There are a couple of different paths to 37 and 39 Tauri, both starting from well-known objects.  First, you can start at first magnitude Aldebaran and scoot across the northeast edge of the Hyades to 3.5 magnitude Epsilon (ε) Tauri (also known as Ain), a distance of about three degrees. From there, adjust your direction of travel very slightly to the south and leap another three degrees to fifth magnitude Omega (ω) Tauri, which sits just south of a trio of stars known as 56, 51, and 53 Tauri.  Continue along the same line of travel another three and a half degrees and you’ll find yourself looking at 37 and 39 Tauri.

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

A shorter approach is to start from the Pleiades and move southeast a distance of 2.75 degrees to 5.6 magnitude 32 Tauri, and then correct your direction slightly to the north and hop another two degrees to reach 37 and 39 Tauri. That route is shorter, although you may find yourself mesmerized by the Pleiadic glow and forget what you came for.

Depending on how much aperture you’re wresting with, you’ll find yourself looking at either a double-double or a triple-triple:

37 Tau glows orangely on the left side of this mirror-image view, and 39 Tau gleams whitely on the right, but if you look carefully you can see a weak shade of orange in its secondary. The distance separating the two primaries is about 10’. The secondaries of both stars are obvious even in a 60mm refractor. However, to pry the 12.6 magnitude “C” components out of interstellar space you’ll need five to six inches of aperture. (East & west reversed to match the refractor image, click on the sketch for a better view).

Also shown to the south of 37 Tauri is SCA 30, with magnitudes of 9.54 and 12.92, separated by 42.6” at 345° (WDS 2000), which I was unaware of at the time I made the sketch. With some careful attention and averted vision, it should be possible to separate that pair with a six inch refractor.

37 Tau (OΣΣ 558)        HIP: 19038   SAO: 76430
RA: 04h 04.7m   Dec: +22° 05’

Identifier		Magnitudes	Separation	PA	WDS
STT 558	AB:	4.46, 10.01	134.30″	193°	2003
STG 4	AC:	4.46, 12.62	235.80″	215°	2000

Distance: 187 Light Years (Simbad)
Spectral Classifications: “A” is K0, “B” is G0

37 Tauri captured my attention first because of its attractive orange tint. The tenth magnitude secondary shines south of it, and a careful perusal south and west of the secondary turned up the much weaker “C” companion, which is designated as STG 4. That three letter designation refers to Georg Hermann Struve, one of the lesser known members of the famous Struve family – more information on him can be found here.

39 Tau (OΣΣ 559)         HIP: 19076   SAO: 76438
RA: 04h 05.3m   Dec: +22° 01’

Identifier		Magnitudes	Separation	PA	WDS
CHR 158	Aa, Ab:	None listed	0.40″	252°	2003
STT 559	AB:	5.97,   8.09	176.80″	359°	2003
STT 559	AC:	5.97, 12.60	148.80″	16°	2000
STT 559	BC:	8.09, 11.50	58.30″	124°	2000

Distance: 55 Light Years (Simbad);  also Simbad shows “B” at 797 LY
Spectral Classifications: “A” is G5, “B is K0

When you first look at the data on 37 and 39 Tauri, they seem to resemble each other because their three main components are all widely separated. But 39 Tauri includes an additional component, an elusive star of undetermined magnitude, CHR 158 (the CHR stands for Center for High Angular Resolution Astronomy). According to the WDS notes file, there were numerous attempt to resolve that companion between 1985 and 1998 that resulted in an “uncertain” resolution at a distance of 0.22”, followed by a successful attempt at resolution in 2003 at a distance of .41”.

Click to enlarge.

Both 37 and 39 Tauri have significantly high rates of proper motion, which are shown below in this Aladin photo with Simbad’s proper motion rates added as an overlay:

This is an erect image, so east and west are opposite of what’s shown in the sketch above. Click to enlarge the image. (All motions are east (“+”) and south (“-“); for example in the case of 39 Tau A, +172 -131 means motion of .172”/yr east and .131”/yr south).

At first glance, it appears there may be some relation between the primaries of 37 and 39 Tauri, but a look at their distances shows they’re much too far apart. Simbad has 37 Tau “A” at a distance of 187 light years and shows 39 Tau “A” quite a bit closer at 55 light years.  None of the other components shown appear to have any relation to their primarial parents, and in fact, Simbad includes a distance for 39 Tau “B” of 797 light years, placing it much further away than its primary.

Our next star on this tour, Σ 479, is located about one and half degrees (1° 25’) northwest of 39 Tauri.   (Here’s our last chart again). You can use 7.8 magnitude HIP 18833 as a stepping stone, which is a 40’ hop northwest of 37 Tau. Another short jump of 50’ more north than west will land you on Σ 479.  HIP 18833 is also a double star, by the way, sporting an identification of LDS 5477 (magnitudes of 7.88 and 12.93, separated by 58.8” at a PA of 356° as of 2000).

Σ 479  (H N 93)  (S 442)        HIP: 18748   SAO: 76388
RA: 04h 00.9m   Dec: +23° 12’
Magnitudes   AB: 6.92, 7.76     AC: 6.92, 9.45
Separations  AB: 7.20”            AC: 57.40”
Position Angles  AB: 127° (WDS 2013)    AC: 242° (WDS 2012)
Distance: 1072 Light Years (Simbad)
Spectral Classifications: “A” is B9, “B” is A3, “C” is A5

This Struvian selection is a compact triple star with a yellow-white primary and a similarly colored secondary in which the hues are a bit less pronounced. Eleventh magnitude TYC 1813-981-1 sits a bit more than 2.5’ northwest of the AB pair of Σ 479. (East and west reversed once more, click on the sketch for a larger view).

William Herschel was the first person to come across what later became Σ 479.  He found it on January 4^th, 1793, and cataloged it as a double star, but seems to have made several errors in describing its location (source):

His “north preceding 36 (A.) Tauri 1 1/2°” is an error, since Σ 479 is located just over a degree southwest of 36 Tauri, not north (our chart again) – but it does precede 36 Tau. The distance separating the two stars is 1° 12’, so he’s sort of in the ballpark with his  measure of 1 1/2°.

Click to enlarge.

Herschel also refers to Σ 479 and 36 Tauri as being “parallel to 54 (ν) and Pleiades.”   54 Tauri is Gamma (γ) Tauri, which is located at the point of the “V” at the southwest tip of Taurus (here’s our first chart, which has a wider view). Nu (ν) Tauri (also designated 38 Tauri) on the other hand, is located ten and half degrees southwest of Gamma (γ) Tauri and eighteen and a half degrees almost due south of the Pleiades. But if you look closely at the chart just mentioned, you’ll see Σ 494 and 36 Tauri are parallel with a line drawn from 54 Tauri (γ Tauri) to the Pleiades. So it appears Sir William confused Σ 494 and Σ 479.   Must have been a bad night at the scope, and we’ve all had that happen.

In his book on F.G.W. Struve’s double stars, Thomas Lewis includes measures of both the AB pair and the BC pair (shown at right).   James South seems to have been the first person to measure the AB pair in 1823, which would normally mean the star should carry his catalog number, S 442. Struve didn’t get to it until 1831, followed by Admiral William H. Smyth in 1835.

For the most part, all of the measures listed by Lewis for both the AB and BC pairs are remarkably consistent, with the exception of an 1861 measure of AB by Mädler.   A look at the Aladin image below provides a visual clue as to why:

Click to make the data more legible — see the previous Aladin image of 37 and 39 Tau for an explanation of how to read the proper motion data. (Erect image once again).

It’s obvious all three components of Σ 479 are moving in the same direction, as well as at pretty close to the same speed, although “B” is lagging behind a bit. Unfortunately the only star we have a distance for is the primary, “A”, which Simbad shows at 1072 light years.   Simbad lists radial velocities of +13.80 km/sec for the primary and +10 km/sec for secondary, but doesn’t list a number for “C”.   So even though the stars appear to be physically related, there’s not enough data yet to be sure.

Our last star, Σ 494, is waiting patiently for us about two degrees (1° 50’) due east of our present location (here’s our second chart again). 8.3 magnitude HIP 19078 lies midway between the two, so it’s an ideal place to pause. That stars has a spectral classification of K0, so it’s worth taking a close look to see if you can detect any hint of orange in it. Simbad, by the way, shows a distance for it of 1468.5 light years.

 Σ 494  (H N 17)  (S 444)        HIP: 19363   SAO: 76476
RA: 04h 08.9m   Dec: +23° 06’
Magnitudes:  7.53, 7.65
Separation:   5.3”
Position Angle: 188° (WDS 2013)
Distance: 343 Light Years (Simbad)
Spectral Classifications:  Both stars are A8

Nothing like an old fashioned pair of closely spaced stars similar in magnitude! Both stars were unmistakably white. Barely seen in the southwest corner of the view is Cou 152, with matched magnitudes of 10.70 for both the primary and secondary, spaced a claustrophic 0.30” apart at a PA of 40° (WDS 2008). Cou 152 also includes a 16th magnitude third component at a distance of 3.40” and a PA of 204° (WDS 1970) – all well out of my reach, unfortunately. The inset at the right shows another double star, GRV 206, which we’ll come back to shortly. (East and west reversed once more, click on the sketch to improve the view).

William Herschel was first on the scene of this pair of stars also, discovering it on November 16^th, 1784 (source):

Click to enlarge.

Once again, Sir William’s directions are confusing.   He seems to be saying 65 Tauri is preceding Σ 494 at a distance of 16’35” as well as being located north of 65 Tau at a distance of 0° 45’.   I checked those measures against Sky Tools 3 and found the 0° 45’ measure is very close, but the other measure should be in the vicinity of 3.75°. (You can see 65 Tauri at the left middle edge of this chart). At any rate, his right ascension and polar distance (P.D.) numbers are correct.

Thomas Lewis’s entry (shown at right) on Σ 494 includes a long list of measurements, starting with that of James South in 1825, and including measures by Struve in 1828 and 1832, John Herschel (h) in 1829, and the Reverend W.R. Dawes in 1842 and 1860.

Starting with Mädler’s measures in 1844, the separation and position angle begin to be remarkably consistent (source).

And again, when we look at the proper motion numbers for the primary and secondary of Σ 494, that makes sense:

Erect image once again, click to see all the data more clearly.  PMRA stands for proper motion right ascension and PMDEC is proper motion in declination.

Whoops – we got more than we bargained for here! Not only did we turn up a restless collection of stars, but we also uncovered another double I was unaware of at the time I did the sketch. GRV 206 (WDS ID 04086+2301) is a pair of stars with magnitudes of 12.56 and 13.39, separated by 41.2” at a PA of 44° (WDS 2013). I went back and looked at my sketch and found I captured the primary, but not the secondary, although it may have been there with some judicious use of averted vision.

The object with the 2MASS label is a star with a visual magnitude of 16.3 (determined by combining the J (14.033) and K (13.204) values).   There’s no distance shown in Simbad for that star, but chances are that with the rate of proper motion it displays, it’s relatively close to us.

If you look closely at the overlay, you’ll see three circles super-imposed on the STF 494 pair. One of those circles belongs to HD 26128, which is an identification assigned to both stars. There are proper motion numbers for that designation, as well as for the identifications assigned to both “A” and “B”, which is confusing, to say the least. Simbad shows the data for HD 26128 is from 2007 (the shorter of three arrows), the data for “A” is from 2012 (the longest of the arrows), and the data for “B” is from 2000.   At any rate, it appears STF 494 “A” and “B” may be physically related, although the only distance we have is for “A”, so more definitive information would be helpful.

That’s it for Taurus this year.   Next time we’ll head east and see what there is to see in Leo Minor, a constellation known for being small, faint, and populated with about as many galaxies as double stars.

Clear Skies! 😎