Splitting stars – for us and for you!

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

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

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

Note on coordinates used in the blog posts: The coordinates used in our posts come directly from the WDS identification number for the star under discussion.  For example, the WDS number for Porrima is 12417-0127.  If you look at the blog post (here), you’ll see the coordinates listed are RA: 12h 41.7m Dec: -01° 27m.  The WDS number (and consequently the coordinates) are based on the coordinates of the particular star as of 2000 (frequently referred to as J2000).  Also, in the data listed for each star you’ll see a date in parenthesis which appears after the position angle for each pair or pairs.  That number is the date of the most recent measures (both the PA and the separation) in the WDS at the time the post was written (see the four stars in this example).  In a few cases, I’ve gone through and updated the measures and also updated that date.      JN

The Anatomy of a Multiple Star: Krueger 60 (KR 60)

More than once I’ve stumbled across a multiple star with so many components I’ve wondered if all of them will fit in the field of view of a wide angle eyepiece.  Two questions always bounce from one side of my starlit cranial compartment to the other: Why, and How?  As in Why so many components, and How did they come to be added to the few original components (usually two)?

KR 60 — named for Adalbert Krueger (1823-1896), a German astronomer who in 1873 was conducting observations for the Astronomische Gesellschaft Catalog — is one such star.  The multitude of components generates so much data that a spreadsheet is required to contain it all.  Closer scrutiny shows a total of twenty individual components with four different prefixes, and there easily could have been five if credit had been given where credit was due (more on that later).

List of components for KR 60 (from the Stelledoppie web site). Click to enlarge.

Another characteristic that jumps out fairly quickly as you scan through the list of components is all but three of them are fainter than 13th magnitude (or four, if you import the 13.02 magnitude “H” component into the brighter grouping).  Which raises another question of stellar magnitude:  why include all those fourteenth and fifteenth magnitude components?

And buried within all the double star data, multiple identifications, and eye-straining magnitudes is a tale that involves quite a few more observers than the four who are connected to the KR, HEL, HZE, and FYM prefixes.  Those observers include some of the most astronomically famous names of the late nineteenth and early twentieth century: S. W. Burnham, Eric Doolittle, and E.E. Barnard.

Prior to delving into the depths of the details, let’s take a look at an Aladin image of KR 60 with all of the components labeled:

Aladin image with labels added. “K” is buried in the glare of the AB pair, and “S” can barely be seen protruding from the west side of AB. North is up, east is at the left. Click to enlarge.

After your eyes overcome their attraction to the bright triangle created by the AB, C, and I members of this tribe, you begin to notice there are numerous faint stars in the surrounding area that have not been designated as components — or at least not yet, anyway.  And that gets us back to a question implied in the first paragraph above: what was the logic for including some of the faint components and ignoring others?

Before we start down that road, we need to look at two important details that influenced everything which occurred after Krueger’s initial 1873 observation of KR 60.  The first is the distance of the primary, which the most recent Simbad and WDS data places at 13.05 light years.  Normally when a star is that close to our planet, it displays a significant amount of motion relative to the Earth, otherwise known as proper motion.  Not surprisingly, that’s what we see with the binary AB pair of KR 60.  The rate of motion relative to our position in the solar system is almost a full arc second a year, which is fast — not fast enough to propel the AB pair to first place in the speed department among its stellar competitors, but fast enough for its motion to be obvious in relation to the many background stars surrounding it.  The specific proper motion numbers are guaranteed to catch the eye of those who spend time looking at this kind of data.  The WDS numbers are -806 -399 for the A component, which translated into a less arcane form means the A component is moving at the rate of .806 arc seconds per year west and .399 arc seconds a year south.  Visually, those numbers look like this:

Notice that KR 60 AB and “C” have been shifted to the upper left of this image in order to allow room for the entire length of the proper motion vectors of the AB pair to be shown, which are the red arrows pointing to the southwest from AB. The red arrow emanating from the star between the “I” and “G” components is UCAC 739-08128 (also labeled LSPM J2228+5739), which is a high proper motion star that is not part of the KR 60 system. (Aladin image showing Simbad’s proper motion vectors, click to enlarge).

A fact I’ve skipped over up to this point is that “A” and “B” are an orbital pair, with an orbital period of 44.67 years per the data in the WDS (scroll down at this link to see the data and orbital diagram).  Consequently, the proper motion of the “B” component is essentially the same as the parent “A” component, although the WDS data for “B” (-713 -321) shows a slight variation from “A”, which is also visible in the divergence of the two arrows above.  The reason for that is the orbital motion of “B” imparts a slightly different motion to it as it circles the “A” component.

Now that we have the preliminaries pretty well covered, let’s get back to the history of the multiplicity of components.  The best place to start is with the first component discovered, which normally would be the “B” component of the AB pairing — except in this case it’s not.  If you scan down the column labeled “First” in the spreadsheet-like chart below the second paragraph above (“First” refers to the first date of measure, “Last” to the last date of measure), or click on this link to see it in a separate window, you’ll discover the “I” component was the first to be added.  According to the dates listed, “I” was discovered in 1873, which means it preceded “B” (as well as “C”) by seventeen years (1873 versus 1890).  Except it didn’t and it wasn’t — wasn’t discovered in 1873 and didn’t precede “B”.  If you’re dazed and confused at this point, you’re not the first.

It’s amazing what surprises lie dormant in the dust of old records, waiting for some unsuspecting person to trip over them while on the way to somewhere else.  In this case, that person was me, and what I stumbled over was a very odd comment on page 987 of the second volume of S.W. Burnham’s 1906 General Catalog of Double Stars within 121° of the North Pole: “Noted by Krueger in A.G. Hels., ‘dupl. 12″ pr. Com. 9.3‘ in 1873.73.”  I had to dig out my data digging shovel to find out what that reference meant, but eventually I discovered an explanation by Burnham on p. vii of the second volume of the 1906 catalog: “Stars noted as double by Krueger in A.G. Helsingsfors-Gotha.  The first measures of these pairs are found in Publications of Lick Observatory, Vol. II.”

KR 60 is on the top line — note that Burnham used a “K” for Krueger at the top of the left hand column, as opposed to the KR currently used in the WDS. Click to enlarge.

With the aid of Google Books, I tracked down the Lick volume and found a table Burnham had compiled which consisted of stars Kruger had designated as double.  In the excerpt at the right from that table the pair which Burnham labeled as “K 60” is at the top of the list, and in the right hand column Burnham added the notes which Kruger “appended concerning such of the stars as appeared double.” (p. 147 of source of the Lick volume).

That note refers to the magnitude of the secondary (9.3), which is identified by the term “Com.”, an abbreviation for comes, which was a term used in the early to mid-nineteenth century (possibly from Latin, although I can’t pin that down) for the secondary of a double star (it had pretty much fallen out of use when Krueger made his observation in 1873).  Also shown is the separation (12″) and the magnitude of the primary (9.1).

Burnham’s 1890 KR 60 AB and AC measures are at the bottom of this list. Click to enlarge.

On page 150 of the Lick volume, Burnham lists his 1890.79 measures of the AB and AC pairs of KR 60, which are shown at the right (K 60, at the bottom of the excerpted page).  Notice that neither of Burnham’s measures are anywhere near the 12″ separation referred to by  Krueger (the column labeled “D” lists the separations, or distances, measured by him).  And that 12″ separation referred to by Krueger is nowhere near the 195.4″ separation the WDS shows for the 1873 measure of the “I” component.  So what star exactly was Krueger referring to in his 1873 catalog?

The only thing to do at this point was to see if I could track down the publication with Krueger’s 1873 observations.  After a bit of internet excavation, I found what I was looking for in Google Books, adorned with a formidable title: Catalog von 14680 Sternen zwischen 54° 55′ und 65° 10′ Nördlicher Declination 1855 für das Aequinoctium 1875 nach Beobachtungen am Achtfüssigen Reichenbach’schen Passagen-Instrument der Helsingforser Sternwarte auf der Sternwarte der Universität Helsingfors in den Jahren 1869 bis 1876 und auf der Herzoglichen Sternwarte zu Gotha in den Jahren 1877 bis 1880 von A. Krueger.   It’s actually the fourth volume of the 1890 Astronomische Gesellschaft Catalog, which covers the area of sky between 55 and 65 degrees of declination.

The key to unlocking Krueger’s cryptic comments! Click to enlarge.

That publication is a list of individual stars sorted by right ascension — in other words, it’s not a double star catalog.  Each listing includes Krueger’s catalog number, the magnitude of the star (Gr.), and of utmost importance for resolving this puzzle, the Bonner Durchmusterung catalog number (also referred to as DM in the WDS) in the right hand column.  Because this isn’t a double star catalog, there are no columns for separation and position angle.  However, Burnham was thoughtful enough to include Krueger’s catalog number for the “A” component in his listing of KR 60, which is 13170.  And since both KR 60 A and KR 60 I have Bonner Durchmusterung  catalog (BD) numbers assigned to them, it was easy to locate them in the right hand column of Krueger’s catalog and cross-reference them to his catalog numbers in the first column.  The BD number for the “A” component is +56 2783 (Simbad incorrectly assigns the number to the “C” component), which corresponds to Krueger’s catalog number 13170, and the BD number for the “I” component is +56 2784, which corresponds to Krueger’s catalog number 13177.  And in fact if you look closely at Krueger’s entry for 13170, the 9.1 magnitude “A” component is adorned with a superscripted “3”, which refers to a foot note that appears at the bottom of that same page — and that footnote reads “Dupl 12” praec.; Com. 9^m.3”.  Which is the source of Burnham’s cryptic note that started my meandering path through the dusty stellar archives.

The BD number cited here by Burnham refers to what is now cataloged as the “I” component of KR 60. Click to enlarge.

Also included in Kruger’s catalog listing are the coordinates for each star, so having identified which of his catalog numbers are the “A” and “I” components, it was possible to plug the coordinates for the two stars into a spreadsheet and calculate the separation and position angle of the AI pair at the time he recorded his data.  The result was a separation of 195.311″ and a position angle of 151.9°.  The first data listed in the WDS for the AI pair (dated 1873) is 195.35″ and 151.9°.  So now we know where the 1873 WDS data for the AI pair came from.  In fact, those WDS numbers match the measures listed by Burnham on p. 988 of his 1906 catalog, where he also refers to what we know as the “I” component by it’s DM number (shown above at the left).  Burnham didn’t add this star to his catalog, or designate it with a letter, which would indicate the letter designation came after several of the other components were added to the KR 60 system in 1900 and 1912.  At this point, it was puzzling what would prompt the addition of the “I” component to the KR 60 conglomeration given its distance from the primary and the fact that it’s 1.6 magnitudes brighter than the primary.

But what about that 12″ separation referred to by Kruger in his observing notes?  Given the rather high rate of proper motion of the AB pair, the obvious thing to do at this point was to load the Simbad database into Aladin and use the epoch slider tool to see where the AB pair was in 1873 in relation to the surrounding stars.  That bit of pixelated sleight of hand resulted in the AB pair being positioned very close to the the “C” component.  Using Aladin’s measuring tool, I measured the 1873 distance of AB from “C” at 12″ with a position angle of 46°.

There’s a barely visible red dot southwest of the “C” component which is visible at the end of the yellow arrow. That dot marks the location of the AB pair in 1873. Click to enlarge.

Closer look at the conjunction of the AB and “C” components seen at the center of the larger image. Click to enlarge.

As you can see in the image above, there’s a pair of blue circles superimposed on the AB pair, which dates the image to 1992.  When the epoch slider is moved to 1873, it projects the blue circle backward in time, which in this case means AB is projected northeast towards the “C” companion — or in other words, in the reverse direction of the blue proper motion lines radiating to the southwest from AB.  A closer look at the 1873 positions of of AB and “C” is shown above at the right.  In that view you can see a short arrow projecting a very minor amount of proper motion for “C” towards the southeast (the WDS proper motion data for “C” is very minimal, +003 -001, meaning its virtually stationary relative to the AB pair).  A bit of additional research found Eric Doolittle had arrived at similar 1873 measures in a 1900 paper in the Astronomical Journal.  I stumbled across his numbers buried in this footnote to a discussion of his measures of the AC pair: “The motion here derived would give for the position of the companion in 1873.7: 41.0°, 11.76″.”

So after a long and unplanned detour away from what aroused my initial curiosity, it turns out the “I” component was not in fact measured by Kruger in 1873 or even considered as a companion to the primary of KR 60.  Instead, we’ve discovered the original historical secondary of KR 60 was the “C” component, not the “I” component, and certainly not the “B” component, which was discovered and added in 1890 by S.W. Burnham.   From this point, uncovering answers to my original question about the reason for all the other components was rather straight forward.

S.W. Burnham’s plot of the orbit of the AB pair, as well as their proper motion. Click to enlarge

Burnham not only discovered the “B” component of KR 60 in 1890, but also quickly realized that “B” was orbiting “A”.  Shown at the right is his 1906 plot of the orbital motion of the pair based on his and other observers’ measures between 1890 and 1906.  He also was the first person to provide a careful measure of the AC pair that included the position angle as well as the separation (also in 1890). Also shown at the lower left of the diagram is his plot of the proper motion of the AB pair, which he based on its motion relative to “C”.

The rapid proper motion of the AB pair was also noticed by Eric Doolittle, who combined his own 1898 and 1900 measures with those of Burnham to arrive at a rate of proper motion of .093″ per year in the direction of 247.9 degrees (source).  One of the stars he used as a reference point in order to make those determinations was the one now cataloged as the “I” component of KR 60, which he identified with Krueger’s catalog number of 13177.

Doolittle’s work caught the attention of E.E. Barnard, who responded in the Astronomical Journal just two issues after Doolittle’s article with measures of two stars which he labeled as the “D” and “E” components.  He added the two additional components because of the high rate of proper motion of the AB pair, stating “I have therefore made a series of measures with the 40-inch, introducing two other smaller stars to more thoroughly explain the character of the motion.”  Barnard also suggested designating the AB pair as β 1291 since the “B” component was discovered by Burnham, not Krueger.  However by that time, β 1291 had already been used to designate a pair of stars in Andromeda (WDS 00352+3750), so apparently the idea was dropped.  But Barnard was correct — the AB pair should be designated with a BU in order to credit Burnham with the discovery of “B”.

E.E. Barnard’s plot of the orbital motion of the AB pair. Click to enlarge.

In 1903 Barnard published another paper in the Astronomical Journal which introduced measures for an additional star, which he designated as the “F” component.  He explained the addition of the new component as useful in determining the motion of “B” was orbital, as opposed to rectilinear (straight line motion).  He also used the star later designated as the “I” component as a reference point of measure, referring to it by Krueger’s catalog number, 13177.

Still entranced by both the orbital and the proper motion of KR 60 AB, Barnard in 1916 published a lengthy paper in the Monthly Notices of the Royal Astronomical Society in which he introduced his 1912 measures of two more stars, designated by him as the “G” and “H” components of KR 60.  He also published measures for several additional stars in the vicinity of the AB pair, to which he didn’t assign component labels.

So by 1916, with Barnard having added components to KR 60 up to the letter “H”, I had a hunch the so far unlabeled “I” component would show up in the next large double star catalog published, which was R.G. Aitken‘s 1932 New General Catalogue of Double Stars Within 120° of the North Pole.  I found it on pages 1385 and 1386 of the second volume, and discovered Aitken had only listed Burnham’s 1906 and 1910 measures.  No mention was made of the measures Burnham had derived from Krueger’s 1873 coordinates for “A” and “I”.

Continuing down the list of components for KR 60, “J” was added in 2012 in the form of the AJ and BJ components as HEL 4.  The measures were made in 2009 with the 200 inch Hale Telescope on Mt. Palomar and the ten meter Keck II Telescope in Hawaii as part of a speckle binary survey led by K. G. Helminiak, thus the HEL prefix for the two components.  The next component, “K”, was first discovered and measured in 2006, prior to the first measures of the “J” component.  Added as HZE 5 AK, it was found during a survey for exo-planets which was led by A. N. Heinze and five other observers.

The remaining nine components, all in the range of 15th magnitude or slightly brighter, were first measured by Marcel Fay in 2012 and added into the WDS as FYM 118.  The 1999 first dates of measure in the WDS were derived from data in the 2MASS and UCAC4 catalogs, as well as the AAVSO‘s APASS survey.  Curious as to what prompted the addition of the nine faint stars, Fay replied in an email that he was interested in the possibility of shared proper motion between the cluster of stars in and around KR 60.  Fay was replying to an email sent to him by Dr. Wilfried Knapp, who is the co-author of a more detailed study of KR 60 which the two of us did.  That study has been published here in the Journal of Double Star Observers (JDSO).  As to whether shared motion exists between the cluster of stars surrounding KR 60, we concluded “currently existing data does not give any serious hint in this direction — proper motion of most stars is according to UCAC5 very small with rather different PM vector direction and GAIA parallax data is currently not available.”

So as star dust settles over KR 60, we now have answers to why so many components were added to this system.  “B” is the only star in the system which is a genuine binary companion, so it unquestionably belongs here.  Based on statements by the various observers involved, we know the “C” through “I” components were added as reference points for tracking the high rate of proper motion of the AB pair, with the exception of “F”, which Barnard added to track the motion of “B” relative to “A”.  Proper motion doesn’t seem to have played a role in the addition of the “J” and “K” components, but there is the suggestion of an orbital relation in regard to “J”.  Shared common motion was the rationale for adding the “L” through “M” components.  Whether that’s an adequate basis for the addition of a large group of faint stars as KR 60 components is at the very least an open question since at this point there is no clear indication that such motion exists.  The preliminary work by Dr. Knapp and I failed to turn up any conspicuous evidence of shared motion, but what is really needed are distances for all these stars.  Those aren’t available as of the date this is being written.  Hopefully, when all the GAIA data is released in a few years, we’ll have parallaxes for each of these stars, which should provide a much clearer picture of where the FAY components lie in relation to each other in interstellar space.

New Information on Sirius A and B

I just came across an interesting blog post on Sirius.  Among other things, the age of Sirius A is now estimated at 237 to 247 million years and Sirius B (the white dwarf companion) at 228 million years, with an uncertainty of about ten million years for each star.  Surprisingly, Sirius B is estimated to have begun the transition from a normal star to a white dwarf about 130 million years ago, which would mean it was only about a hundred million years old at the time.

This piece is written by Phil Plait, who writes a blog entitled Bad Astronomy.  Here’s the link:

Why so Sirus?

Beyond the Weird and Wonderful World of 8 Andromedae: Σ 2987, OΣΣ 244, and OΣ 493

Our last trip concentrated on 8 Andromedae/BU 717 and the area immediately southeast of it, so this time we’ll wander a bit farther afield. But we’ll have to take care that our first leap into the darkness doesn’t take us so far from 8 Andromedae that we cut ourselves off from its gravitational grasp — we’ll need that gravitational tug to pull us back to our starting point so we can reverse the process and leap in the opposite direction.

To get oriented once more, here’s a wide look at the stellar terrain where we’ll spend the night:

Stellarium screen image with labels added, click to enlarge.

As I mentioned in the last post, when you first look up into the sky in this general area, the first stars your eyes will be drawn to are the trio of Iota (ι), Kappa (κ), and Lambda (λ) Andromedae. Our destination is the dimmer array of stars to their north and a bit closer to Lacerta. A reliable way to locate the 11-8-7-3 Andromedae grouping is to follow the arc formed by Iota-Kappa-Lambda as it curves toward the southern tip of Cepheus, but keep your eyes on the south side of that arc in order to pick out 11-8-7-3 Andromedae, which are about a third of the distance to Cepheus. Also, as I mentioned before, you’ll probably catch sight of the trio of 8, 7, and 3 Andromedae first, mainly because 11 Andromedae is noticeably fainter than the other three stars (11 Andromedae glimmers weakly at a magnitude of 5.44, while 3 Andromedae gleams more noticeably at a magnitude of 4.66 – not a lot of difference, but it can be enough to make it difficult to visually pluck 11 Andromedae from the sky).

Once you have 11-8-7-3 Andromedae located, point your finder at 8 Andromedae and you’ll find yourself looking at a scene somewhat like this:

Stellarium screen image with labels added, click to enlarge.

The distance from 8 Andromedae to 11 Andromedae is only 29’, whereas 7 Andromedae is about twice as far at 56’, and since both of those two stars will guide us to where we want to go, we’ll center our finder on 8 Andromedae to get started.

As luck would have it, 8 Andromedae is almost equidistant from our two destinations stars (the ones with the turquoise labels, Σ 2987 and OΣΣ 244), so I’ll flip a coin to decide which direction to go first . . . . . and the winner is . . . . . .  Σ 2987!  Center 7 Andromedae in your finder, scan 30’ to the southwest, and you’re eyes will land on Σ 2987. You’ll notice there’s a tight pair of eighth magnitude stars wedged between 7 Andromedae and Σ 2987 which can be used to keep you on course (the brighter and southernmost of that pair is 7.65 magnitude HIP 114537).

Σ 2987  (STF 2987)     HIP: 114420   SAO: 52795
RA: 23h 10.4m   Dec: +49° 01’
Magnitudes: 7.42, 10.41
Separation:  4.4”
Position Angle: 150°  (WDS 2007)
Distance: 148 Light Years (GAIA)
Spectral Class: A is G1

This is a tough one, so click on the sketch to enlarge it and look for the secondary at about midway between the seven and the eight o’clock position. East and west are reversed here to match the view in the SCT.

My first trip in search of Σ 2987 was with a five inch refractor and it was spent trying to split a star that wouldn’t split . . . which was because it was the wrong star. Argh! Not everything goes according to plan when you work in the dark.

I came back a second time with the 9.25 inch SCT and a more deliberate plan, and as you can see from the sketch I found the correct star. Thanks to the larger aperture, it didn’t take much magnification to pry the secondary loose from the primary. Whether I could have done that with the five inch refractor is an open question. Theoretically it should be possible on a night of good seeing, but it would require more magnification than the 123x I used with the SCT.

But the ease with which I split what should have been a more difficult pair left me with a suspicion the secondary is slightly brighter than the 10.41 listed for it in the WDS, although I haven’t been able to confirm that by looking at catalog data. Simbad shows a visual magnitude for it of 10.40 (third star in the list, BD+48 3952B), while UCAC4 and URAT1 were no help whatever since neither catalog lists Vmag values for the secondary. The J and K magnitudes shown in UCAC4 for the secondary yield a visual equivalent of 7.625, which is way too bright, probably a result of the primary overpowering the CCD sensors. It’s also possible the separation is greater than the 4.4” listed for the pair in the WDS, but historical data (discussed below) indicates that’s highly unlikely.

However, there is one thing that we can be certain of:  this pair of stars is carving their way through interstellar space in tandem, as this Aladin image with an overlay of Simbad proper motion shows:

Instead of two arrows, we see three of them super-imposed on this image by Simbad. A third object was sensed at 60.07 milli-arcseconds from the primary (note the blue label), but I haven’t found any data identifying that object. More than likely it’s an error of some kind. Click to enlarge.

You can see the proper motion numbers at the bottom of the image, which show almost identical motion for the primary and secondary. I ran my own numbers by computing the motion using 1999 2MASS coordinates and 2015 GAIA coordinates which resulted in almost identical numbers for the primary, +236 +051.5, and a slightly different number for the secondary, +249 +034, which shows it diverging somewhat from the path of the primary.

Click to enlarge.

Looking back at the measures I could find on Σ 2987, it’s apparent there’s been little change over the years, provided the first measure listed in the WDS from 1828 is excluded. That one shows a separation of 2.8” and a position angle of 172 degrees, which stands out as an exception to the eight measures listed at the right. Since F.G.W. Struve is credited with discovering this pair, I looked in the only likely source for that measure (Catalogus novus stellarum duplicium et multiplicium) and found only coordinates and magnitudes. Lewis shows Struve with an 1832 measure of 3.45” and 166.0 degrees in the excerpt at right from his book, so the 1828 data listed in the WDS remains rather elusive.

On the other hand, looking at the change in separation and position angle in the eight measures listed, it appears this pair has widened slightly since Struve’s 1832 measure, which is in agreement with the proper motion data I generated from the 2MASS and GAIA coordinates. That could be a possible indication of a very slow and ponderous orbit, or, more than likely, the two stars are just linked by a common physical origin, which is reflected in their motion.

Now to our next pair, OΣΣ 244 (STTA 244), which we’ll find is also accompanied by a second pair, OΣ 493 (STT 493). To catch both of them in the same field of view, return to 8 Andromedae for reference, then center your finder on 11 Andromedae, slide it over to the the north corner of your eyepiece, and you’ll find OΣΣ 244 and it’s two companions near the center of the field of view.  For reference, here’s our last chart again (the unlabeled star perched between 11 Andromedae and OΣΣ 244 is OΣ 493).

OΣΣ 244  (STTA 244)     HIP: 115171   SAO: 52912
RA: 23h 19.7m   Dec: +48° 23’
Magnitudes   AB: 6.41, 10.15   AC: 6.41, 11.50
Separations  AB: 100.6”           AC: 119.2”
Position Angles   AB: 293° (WDS 2009)   AC: 108° (WDS 2009)
Distance: 389 LY (GAIA)
Spectral Classifications: A is K1, B is K2

OΣ 493  (STT 493)     HIP: 115114   No SAO Number
RA: 23h 19.0m  Dec: +48° 30’
Magnitudes: 7.67, 10.66
Separation:  7.6”
Position Angle: 28°  (WDS 2010)
Distance: 786 LY (GAIA)
Spectral Class: A is A8

The primary of OΣΣ 244 is at the center of this sketch, with the B component just outside the glare between the 10 and 11 o’clock position, and the fainter C component on the other side of the primary at the 4 o’clock position. OΣ 493 is seen northwest of OΣΣ 244, but you’ll have to enlarge the sketch to see the difficult secondary in the OΣ 493 inset at the right. East and west reversed to match the refractor view, click to enlarge the image.

Because it can be seen within the same field as 11 Andromedae, OΣΣ 244 is an easy triple star to find and, thanks to its wide separations and accessible magnitudes, easy to identify. I had to use a bit of averted vision at first to lasso the C component, but once I had it roped into view, I had little problem seeing it in the five inch refractor. It would likely be an averted vision view for the most part in a four inch refractor, and with careful inspection and a dark sky, should be within reach in a three inch or 90mm refractor.

However, OΣ 493 is a bit more difficult because of its tighter separation. I couldn’t pry the secondary out of the primary’s glare with anything less than 148x (an 8mm eyepiece) in the five inch refractor, but with more magnification it should be visible in a four inch instrument. Anything less will be a real challenge, but theoretically, the secondary should be just within grasp of a 3 inch or 90mm refractor with enough magnification and decent seeing conditions.

As the OΣ prefixes indicate, each of these are Otto Struve discoveries. But before we look at the discovery dates, it might help to illuminate the difference between the OΣ and the OΣΣ prefixes. The OΣ prefix applies to the first group of stars in Otto Struve’s 1845 survey Catalogue de 514 Étoiles Doubles et Multiples Découvertes Sur L’Hémisphère Céleste Boréal par La Grand Lunette de L’Observatoire Central de Poulkova. Those stars were limited to separations of 32” or less, except when the secondary was fainter than magnitude 9.5, in which case the separation was limited to 16” – which in fact, is the majority of stars in that section of the catalog. Pairs with larger separations than those just described were placed in the second section of the catalog (frequently referred to as the Appendix) and were assigned prefixes of OΣΣ.

OΣ 493 was discovered in 1847 and initially measured with a position angle of 26 degrees and a separation of 8.1” When compared with the most recent WDS measures (2010), there’s been very little change in the intervening 163 years, which is not at all surprising considering the primary’s distance of 786 light years as measured by GAIA.

Click to enlarge.

The more interesting of the two stars by far is OΣΣ 244, not only because it’s wider and has an additional component, but because the primary has considerable proper motion. The WDS shows the first recorded measure of the AB pair took place in 1875, but it was discovered by Otto Struve prior to that date, probably at the same time he first saw OΣ 493. His listing for OΣΣ 244 in the second half of the 1845 catalog doesn’t contain an observation date or any measures (the catalog page can be seen at the end of this post), which is why the first date cited in the WDS is 1875. S. W. Burnham credits Dembowski with that measure, which can be seen in the except above from Burnham’s 1906 catalog (the Greek symbol Δ is used for Dembowski). The AC pair was first measured in 1903 according to the WDS, but there’s no mention by Burnham of the C component in the catalog entry above, which is an indication the discoverer was someone other than Burnham.

When you compare the first measures of the AB and AC pairs with the most recent WDS data, it’s evident one of the three stars is moving fairly rapidly in comparison to the other two stars:

AB in 1875:  78.9”, 305°         AC in 1903: 137.8”, 104°
AB in 2009: 100.6”, 293°        AC in 2009: 119.2”, 108°

As I mentioned above, the cause of those very noticeable changes in relative positions is the proper motion of the OΣΣ 244 primary, which is illustrated below in an Aladin image with Simbad’s proper motion data overlaid on it:

It’s true – a picture is worth a thousand words! Simbad’s proper motion data is at the bottom of the image in the columns labeled PMRA and PMDEC, and the super-imposed arrows on the individual stars are proportional to that data.  The blue arrows on the B and C components are difficult to see, so click to enlarge the image. (Aladin image with Simbad data and additional labels added).

Again, for those not familiar with the way the proper motion data is presented, each of the numbers in those two columns represents thousandths of an arc second. So the first number in the PMRA column, which reads 206.29 is actually .20629”, and the number next to it in the PMDEC column, 31.3, is actually .0313” (multiply each number by .001). The absence of a plus or a minus sign indicates eastward motion in right ascension (RA) and northward motion in declination (DEC) (sometimes a “+” sign appears in front of the number in those cases, but it’s been left out here). A negative sign in front of the values indicates westward motion in RA and southerly motion in declination.

Frequently you’ll see the proper motion data is rounded to just three places, and the RA and Dec numbers are presented as a pair of three digit numbers.  For example the WDS would list the numbers I mentioned above for the primary as +206 +031, the B component values as -007 -020, and the C component values as +019 +008.

Of course, you don’t need to know all of that to enjoy the celestial sights above, but on the other hand, when you peel back the outer layer of the heavens, you’ll find the secrets of the universe begin to reveal themselves one at a time. It’s always just a bit humbling to realize that vast vault of stars over our heads are constantly in motion relative to each other, even if it’s only at a snail-like pace of one thousandth of an arc second at a time. Change is constant, even when it’s imperceptible – and time is relative to the scale on which it occurs.

Clear Skies and tolerable temperatures! 😎

Page 56 of Otto Wilhelm von Struve’s 1845 Catalog. STTA 244 is the seventh star from the bottom of the page.  The numbers in parentheses in the right hand column are estimated magnitudes.  Click to enlarge.

The Weird and Wonderful World of 8 Andromedae: BU 717, ES 2725, and ARY 3

On one of those crisp September nights when I was lingering in Lacerta over delicately separated double stars and diminutively defined open clusters, I happened to look away from the eyepiece just long enough to catch sight of an arc of three faint stars lined up on the Andromeda side of Lacerta (as opposed to the Cygnus side — see chart below).  Puzzled because I had never noticed them before, I flipped open my dog-eared copy of Sky and Telescope’s Pocket Atlas to Chart 72 and identified the three stars as Iota (ι), Kappa (κ), and Lambda (λ) Andromedae. I noticed the three stars were devoid of double star designations (although Kappa is most definitely a multiple star that goes by the designation HJ 1898), but my wandering eyes were quickly drawn a few degrees north to another concentration of stars curving towards Lacerta, which were labeled as 11, 8, 7, and 3 Andromedae. And that subtle little international double star symbol — a line drawn through the dot of a star on a star chart – that short line that makes the heart of every double star enthusiast skip a few beats and then pulsate as wildly as Sirius when its five degrees above the horizon . . . well, let’s just say that horizontal splash of line split more than a few dots of stars.

In other words, a veritable double star feast before my very eyes.

But before we dine on double stars, first we need to take a careful look at this area, because it’s very easy to mistake the Iota (ι), Kappa (κ), and Lambda (λ) trio for our destination, which instead is the threesome of 11, 8, and 7 Andromedae.

Stellarium screen image with labels added, click to enlarge.

When you first cast skyward eyes on the general area at the center of this chart, Iota (ι), Kappa (κ), and Lambda (λ) Andromedae catch your gaze first because they’re brighter than 11, 8, and 7 Andromedae. The first three stars have magnitudes of 3.82, 4.14, and 4.29, respectively, whereas the last three are notably fainter at magnitudes of 5.44, 4.86, and 4.53, again, respectively. But if you follow the arc formed by Iota (ι), Kappa (κ), and Lambda (λ) as it curves toward the southern edge of Cepheus, you’ll find it takes you right over the top of 11, 8, 7, and 3 Andromedae.

Again, you have to be careful here because your eyes are likely to miss the first of that group, 5.44 magnitude 11 Andromedae, and instead will be drawn to 8, 7, and 3 Andromedae, that last one’s 4.66 magnitude being distinctively brighter than 11 Andromedae. But once you point a finder at 8 Andromedae, the middle star of the trio we’re concentrating on, you’ll find 11 and 7 Andromedae become distinct — as the chart below shows:

Stellarium screen image with labels added, click to enlarge.

We’re going to take a look at a total of six double and/or multiple stars in this area, so to keep the length of this thing from getting out of control, I’ll divide our excursion into two parts. This first part will look at 8 And, ES 2725, and ARY 3.

8 Andromedae also goes by the double star designation BU 717, and that’s where we’re going to start – and also where we’re going to find a mysterious surprise.

BU 717  (8 Andromedae)  HIP: 115022  SAO: 52871
RA: 23h 17.7m   Dec: +49° 01’

Identifier	Magnitudes	Separation	PA	WDS
BU 717 AB:	5.01, 13.00	7.8”	160°	2015
BU 717 AC:	5.01, 10.83	217.3”	131°	2008
FOX 273 AD:	5.01, 12.46	58.6”	233°	2007
WAL 147 AE:	5.01, 12.34	97.9”	107°	1903
KUI 116 AF:	5.01, 16.00	14.6″	179°	2015
KUI 116 BF:	13.00, 16.00	7.6”	200°	2015

Distance: 563 LY (Simbad)
Spectral Class: A is M2

Once you get past the irresistible orange glow of the primary, the companions to look for are C, D, and E. The secondary, B, is irretrievably buried in primarial glow (thanks to the eight magnitudes of difference between A and B at a distance of 7.8”), and with the F component hampered by a magnitude of 16, it’s well out of reach. (East and west reversed in this sketch to match the SCT view, click for the larger version).

I’ve looked at 8 And/BU 717 with both a five inch refractor and the 9.25 inch SCT used for the sketch, and in each case I had little problem digging C, D, and E out of the rich orange glow of the primary, although I had to call on averted vision to pry D and E out of the sky in the five inch refractor. BUT – despite this apparent cooperative beginning – I was confronted with a perplexing problem when I first peered into an eyepiece and started identifying components.

Where in the world is WAL 147???

On the night I first glued my observing eye to 8 And/BU 717, the AE pair (WAL 147) was listed in the WDS with a distance of 57.1” at a position angle of 89 degrees. For the sake of relative spatial comparison, I had the AD pair (FOX 273) which the WDS showed parked at a distance of 58.6” from the primary. So with both the D and E components having (supposedly) similar separations, and E (supposedly) parked almost right at 90 degrees, I knew exactly where to look – and there wasn’t anything there. That spot was simply empty, unoccupied, vacant – devoid of stellar light, in other words. So where in the astronomical world was WAL 147?

I had also noticed the magnitudes of D and E were very similar, 12.46 for D and 12.34 for E, so I began scanning for a star similar in magnitude to D – and I found one, parked a bit further south of the 90 degree position and at almost double the distance listed in the WDS. But that distance caused skeptical alarm bells to shatter the peace and quiet of the night, so after carefully sketching the position of that star in relation to all the others, I retired to a drier, warmer, and more comfortable spot in front of a computer, pulled up an Aladin image of BU 717 on a computer screen, and went to work.

Aladin allowed me to do two things – check the magnitude of the star I flagged as a possible candidate for the E component, and measure its distance and position angle.

To avoid confusion, I’ve flipped the Aladin image to match my sketch of BU 717 above, so west is at the left and east at the right. Aladin image with data and labels added, click to enlarge.

I’ve labeled the C, D, and E components in the image above, and below the image I’ve added the WDS data which was current at the time I sketched BU 717. Notice the measures for AE are shown as 57.1” and 89 degrees – that spot is labeled in the image with an “X”. You can see a star near that location which is shown with a magnitude of 17 in the URAT1 catalog, which is far too dim to be a candidate for the 12.34 magnitude WDS companion, and of course was well out of the reach of both of my telescopes.

Also shown to the right of the WDS data are the measures I plotted using 2015.0 GAIA coordinates, which in the case of the C and D components differ somewhat from the older WDS data. After I sent my findings to Bill Hartkopf at the USNO/WDS, he established a separation of 97.9” and a PA of 107 degrees for the AE pair, which is both wider and a bit more southerly than what I came up with using GAIA data. However, that data is based on a 1903 measure (probably from a photographic plate), which is now the only observation and measure listed in the WDS for WAL 147. Prior to sending my findings to the WDS, there were observations dated 1944 and 1998, which can be seen in the WDS data beneath the Aladin image above, so it appears there was some kind of error associated with that particular WDS data.

Click to enlarge.

In case you’re wondering about how that difficult B component we couldn’t see was pried out of the primarial glare, S.W. Burnham managed it in 1887 with the 18.5 inch Clark refractor at Dearborn Observatory (shown at right), which at the time was attached to the University of Chicago. Philip Fox added the C component in 1915, also while using that same refractor.

Now we’ll leave the weird world of 8 And/BU 717 and move on to our last two stars, which agreeably can be seen in the same field of view. This isn’t going to be a difficult move since all we’re going to do is nudge 8 And over to the west corner of our field of view until the similarly-hued 11 And appears in the southern corner of the view. That will put ES 2725 close the center of your field of view and ARY 3 will appear in the southeast corner of the eyepiece, just a bit more than 10’ northeast of 11 Andromedae.

ES 2725     HIP: 115128   SAO: 52899
RA: 23h 19.1m   Dec: +48° 55’
Magnitudes   Aa, Ab: 7.35, 11.20    AB: 7.27, 8.62
Separations   Aa, Ab: 0.5”              AB: 54.1”
Position Angles:  Aa, Ab: 170° (WDS 1991)   AB: 235° (WDS 2013)
Distance  A: 417 LY (GAIA)    B: 1173 LY (GAIA)
Spectral Classes:  A is A2, B is G5
Note: Aa, Ab is HDS 3321, AB is ES 2725

ARY 3     No HIP Number    SAO: 52929
RA: 23h 20.7m   Dec: +48° 48’
Magnitudes: 8.96, 9.47
Separation:  118.1”
Position Angle: 210°  (WDS 2010)
Distance  A:  232 LY (GAIA)    B: 421 LY (GAIA)
Spectral Classes:  A is G5, B is F8

ES 2725 is the pair of stars at the very center of this view, tilted at about a forty-five degree angle (and identified in the box at the right). ARY 3 is the fainter and wider pair at the southeast edge of the view (18’ southeast of ES 2725 and on a line with BU 717 and ES 2725), tilted more noticeably to the north than the ES 2725 pair. (East and west reversed to match the refractor view, click on the sketch to bring it to life).

Now I know these aren’t the most stunning double stars ever to grace an eyepiece, but since we didn’t have to wander far to find them, we may as well pay them the courtesy of a visit. And with a minimal investment of time, we can even mine a few morsels of information from them. For example, according to GAIA’s data, the A and B components of ES 2725 have 756 light years of distance between them. And the ARY 3 pair are considerably less distant from each other with 189 light years of interstellar space wedged between them. That would make each of them an optical pair, although that doesn’t necessarily apply to the Aa Ab pair of ES 2725, since there’s no data on the distance of that 11.20 magnitude companion sitting half an arc second from the primary.

Not surprisingly, if we look at how they’re moving through interstellar space, we’ll also find there’s no shared motion between each of the pairs.

Aladin images with labels added, PM vectors plotted by Aladin. Click to get a much better view of the directional arrows.

In case the PM numbers at the bottom of the image mystify you, the first of each three digit pair of numbers is the motion in right ascension (east or west) and the second is the motion in declination (north or south). The numbers represent thousandths of an arc second, and the plus sign denotes northerly or easterly motion, whereas the negative sign signifies westerly or southerly motion.

So in the case of ES 2725, the A component is moving east in right ascension at the rate of .078” per year and north in declination at the rate of .008” per year, and the B component is moving east at the rate of .022” per year and north at the rate of .011” per year.  Notice the rate of motion of the primary is greater than that of the secondary, which is not a surprise when you look at the individual distances in the data line above and find the secondary is farther away from us (1173 light years for the secondary, 417 light years for the primary).

The primary of ARY 3 is also moving east and north, but its secondary is moving in the opposite direction at the rate of .042” per year west and .068” per year south. In each case, the arrows correctly indicate the combined direction (right ascension and declination) and the combined rate of motion for each of the components.  Also notice the rate of motion of each of these stars matches well with their distance when compared with the ES 2725 pair.

So there you have it – just enough data about ES 2725 and ARY 3 to tell you more than you knew before you got to this point! You can even pass it on to your friends and neighbors. They’ll either be totally amazed or they won’t speak to you again in public.

Either way, don’t despair, because we’re going to stay in this immediate vicinity for our next trip. We’ll look at three more double and/or multiple stars . . . and who knows what arcane details of stellar motion we’ll uncover next.

Clear Skies! 😎

STT Pairs in Cepheus: OΣ 32, OΣ 436, OΣ 458, and OΣ 461

Now that we have the STT pairs in Lacerta wrapped up (here and here), we’ll finish this series by looking at four rather challenging STT objects in Cepheus. For the most part, these are going to require apertures of at least six inches in order to have a fighting chance to pry faint companions from obnoxious primarial glares, although OΣ 461 has a little something for everyone, regardless of aperture.

Let’s look at a wide view of where we’re going to spend this observing session and at the same time we’ll get our directions established since they can be confusing this close to Polaris.

Stellarium screen image with labels added, click to enlarge.

Notice Cepheus is parked to the right of Ursa Minor and Polaris in this view. Since Polaris marks celestial north, that means regardless of where you are in Cepheus, north points directly at Polaris — which also means south points in the opposite direction. If you were to look at Cepheus two or three hours after it was in the position shown here, you would notice it was rotating in a direction that takes it up and over Polaris. In the world of celestial directions, the direction the stars move is celestial west, which explains why that “W” is at the top of the directional indicator situated between Cepheus and Polaris. So what that means is the directional indicator has to keep pace with the rotation of the stars . . . and that means it essentially rotates in a counter-clockwise direction to match the rotation of Cepheus.

Also, just to remind us what’s really taking place here, the stars actually aren’t moving at all. We are, and that’s because we have our feet planted firmly on Earth, the rotation of which is the real cause of this long explanation. If you want to delve deeper into celestial directions, see Greg’s post here which goes into the subject in greater detail.

Now let’s put our directional knowledge to good use and go find our first object, OΣ 32 (STT 32), which is north (celestially speaking) of Cepheus. In fact, as the chart below shows, it’s much closer to Polaris than it is to Cepheus, so we’re going to start star hopping from second magnitude Polaris.

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

Our first stepping stone will be 4.26 magnitude 2 Umi (also known as HIP 5372), which is three degrees southeast of Polaris. From there, it’s just a short hop to the east of 1° 18’ to OΣ 32.

OΣ 32  (STT 32)       HIP: 8520     SAO: 282
RA: 01h 49.9m   Dec: +85° 13’
Magnitudes:  8.18, 12.5
Separation:    5.3”
Position Angle: 156° (WDS 2000)
Distance: 709 LY (GAIA)
Spectral Class:  A is A5

You’ll have to look at the 408x inset at the right to see the elusive secondary of OΣ 32, which is parked at about the seven o’clock position.  North and south are reversed in this SCT view, click to enlarge and make it easier to see the secondary.

My first look at the field that contains OΣ 32 was with an 18m Radian (136x) in a 9.25 inch SCT, which doesn’t exactly provide the widest field of view in the universe.  Because the secondary couldn’t be seen at that magnification, it was a bit difficult to establish which star was OΣ 32, and it didn’t help that I was looking at a confusing field of stars of similar magnitudes. I finally pinned it down with the help of the three 8.5 to 9th magnitude stars running along a northeast-southwest line across the lower part of the field of view in the sketch and then moving due north from the middle of the three to OΣ 32.

Then began the difficult work of prying the secondary loose from the primary. My first glimpse was a brief averted vision glimpse with a 10mm Radian (240x). The secondary became more distinct at 408x, although it was on the fuzzy side. Because of the interfering 408x primarial glare, it was impossible to compare the magnitude of the secondary with other stars, but given the difficulty it’s possible the secondary is as much as five magnitudes fainter than the primary. The only photometric data I could find on the secondary was a NOMAD1 Vmag of 15.030, which certainly is too faint because that magnitude is well beyond the reach of the 9.25 inch SCT I was using.

It’s interesting to look at the relative motion of the primary and secondary. As the data on the right side of the chart below shows the separation is clearly becoming tighter while at the same time the position angle is edging toward the south, which would indicate the secondary is slowly moving north and west (more west than north) relative to the primary.

Click to enlarge.

And a look at the proper motion data for both stars not only shows that to be the case, but it also shows the primary is moving northeast at the same time – basically in the opposite direction – which has the effect of amplifying the gradual change in position angle and separation. Using the latest GAIA coordinates, dated 2015.0, and comparing them with 2MASS coordinates dated 1999.899, the resulting proper motion data is +013 +014 for the primary (.013” east/yr, .014” north/yr) and -.013” +009” for the secondary (.013” west/yr, .009” north/yr), which confirms the motion necessary to produce the changes in separation and position angle we see.

It’s almost tempting to think of the secondary as being in a very long period orbit around the primary, but the opposing motion of the two stars argues against that.  A parallax for the secondary would provide some valuable insight here, but unfortunately that data isn’t available yet from GAIA. So with the information we have now, it appears OΣ 32 is an optical pair.  It also appears the two stars are at or near their closest separation now and before long, that separation will begin to increase.

We’ll move back to Cepheus now and start the search for our next star, OΣ 436 (STT 436), from 3.2 magnitude Beta (β) Cephei (here’s our last chart once more). With that star centered in our finder, the first reasonably bright star we see to the northwest is 7.1 magnitude HIP 105490, located 1.5 degrees away. Continuing in the same direction for a distance of 3° 17’, with a very slight northerly tilt, we reach 6.9 magnitude HIP 104458. From there we’ll bend our direction of travel directly to the north a distance of one degree to reach seventh magnitude OΣ 436, which sits halfway between HIP 104458 and 5.9 magnitude HIP 104968.

OΣ 436  (STT 436)      HIP: 104667   SAO: 9990
RA: 21h 12.1m   Dec: +76° 19’
Magnitudes: 7.09, 11.0
Separation: 11.9”
Position Angle: 227°  (WDS 2003)
Distance: 574 LY (Simbad)
Spectral Class:  A is B9

You’ll probably have to enlarge this sketch in order to see the faint secondary parked at the eleven o’clock position right next to the primary. There’s a 13th magnitude star a bit farther away at the edge of the primary’s glare, also at the eleven o’clock position, which is not cataloged as part of OΣ 436 . North and south reversed once more to match the SCT view.

Considering the WDS magnitude difference and separation for this pair, I found prying the secondary out of the primarial glare to be a bit more difficult than I expected. Looking around for something to compare with the secondary, my eyes were drawn to UCAC4 832-019368, which appeared to be similar in brightness, and possibly slightly fainter, than the secondary. The UCAC4 catalog lists that star with a Vmag of 11.505, so it’s quite possible the WDS magnitude of 11.0 for the secondary may be a half magnitude too bright, which would account for the unexpected difficulty I had in seeing it. But given the glare from the primary, the difficulty of visually estimating within a half magnitude makes it rather hard to come to a firm conclusion.

Otto Struve discovered this pair in 1848, taking three measures of it, which averaged out to a separation of 11.61” and a position angle of 230.3°. Baron Dembowski measured it in 1868 at 11.66” and 230.0°, followed by W. J. Hussey in 1898 with 11.91” and 229.2° (those numbers come from p. 177 of Hussey’s book on Otto Struve’s double stars). So when compared with the 2003 data of 11.9” and 227°, which is the most recent listed in the WDS catalog, this pair is remarkably stable.

Now we’ll head into the southeastern corner of Cepheus, which is more densely populated with stars thanks to it’s location at the edge of the Milky Way.

Stellarium screen image with labels added, click to enlarge.

We’ll start with 3.5 magnitude Zeta (ζ) Cephei, hop northward 1 degree to 5.05 magnitude Lambda (λ) Cephei, and then make a right angle turn to the west and hop another full degree to reach OΣ 461 (STT 461).

OΣ 461  (STT 461)  (15 Cep)     HIP: 108925   SAO: 34016
RA: 22h 03.9m   Dec: +59° 49’
Identifier          Magnitudes        Separation             PA         WDS Data

AB:	6.66	11.40	11.00”	297°	2011
AC:	6.66	10.03	89.90”	40°	2011
AD:	6.66	7.84	184.30”	72°	2011
AE:	6.66	6.96	237.40”	37°	2011
AG:	6.66	14.30	17.50”	335°	2007
EF	6.96	8.14	192.60”	33°	2011

Distance: 1469 LY (Simbad)
Spectral Classes: A is B1, D is A, E is A0

I’ve written about OΣ 461 before (here), so I’ll mainly concentrate on the B and G components here, which were the main focus for this project.

The B component is rather obvious at the one o’clock position in this sketch, but you’ll have to look closer to pick out the much fainter G component, both of which are labeled in the box on the right side of the sketch. There’s plenty of competition for your eye in this view with lots of scattered light radiating from the D and E companions. North and south reversed again to match the SCT view, click to enlarge.

I had no problem picking B out of the 6.66 magnitude glare of the primary – it was easy with averted vision at 204x and 240x, and it popped into direct vision view at 408x. I noticed UCAC4 749-071975, shown below and to the left of the primary in the sketch, was similar in brightness to B. The UCAC4 catalog lists a Vmag of 12.114 for the comparison star, an f.mag of 11.784, and its J and K magnitudes compute to a visual magnitude of 11.906.  All of those values tend to suggest the B component is slightly fainter than the 11.40 value assigned to it in the WDS.

Based on the 14.3 magnitude assigned to it in the WDS, I really didn’t expect to see the G component, so I wasn’t surprised to find it was invisible when I first looked for it at 240x. After I increased the magnification to 408x, my prying eyes latched on to it with averted vision, and when I went back to 240x, I was able to catch it again with averted vision. If it was really a 14.3 magnitude star, G would have been beyond the reach of the 9.25” SCT, especially given the glare of the primary. The UCAC4 catalog lists an f.mag of 13.321 for it, and URAT1 lists a more optimistic f.mag of 12.97. Neither catalog shows a Vmag for the star, but both have the same J and K magnitude values for it, which works out to a visual magnitude of 13.237. Even that would have been tough to see in the glare of the primary, so I suspect the actual visual magnitude is in the 13.0 range.

Regardless of whether you succeed in picking out the G component with whatever scope you’re using, it’s worth ratcheting up the magnification to the 400x range just to enjoy the magnified spectacle of white light pouring out of the primary and its D and E companions.  Don’t pass up that chance — OΣ 461 is really a spectacular grouping of stars.

Our last Otto Struve discovery on this tour is OΣ 458 (STT 458), which is a short one degree hop due west from OΣ 461 (here’s our last chart again). You can use 7.85 magnitude SAO 33939 as a reference point to keep you on course.

OΣ 458  (STT 458)     HIP: 108301   SAO: 33894
RA: 21h 56.5m   Dec: +59° 48’
Magnitudes   AB: 7.20, 8.41   AC: 7.20, 12.60
Separations   AB: 1.00”          AC: 21.60”
Position Angle  AB: 348° (WDS 2014)   AC: 24° (WDS 2003)
Distance: 1469 LY (Simbad)
Spectral Class:  A is A0

The goal here was the C companion, which wasn’t all that difficult given it’s distance and cooperative magnitude.  But splitting the tight AB pair was a real bonus and not as difficult as I expected it to be. North and south reversed once again, click to improve the view.

UCAC4 749-070690 caught my eye when I was looking for a comparison star for the C component of OΣ 458. The UCAC4 labeled star has a Vmag of 12.119, an f.mag of 12.011, and its J and K magnitudes work out to a visual magnitude of 11.620. The C component looked a bit fainter than the UCAC4 star, so it appears likely the WDS magnitude of 12.60 for it is about right.

Click to enlarge.

What is now labeled as the AB pair of OΣ 458 was first measured in 1845 by Johann Heinrich Mädler with an erroneous position angle of 44.6 degrees, which also included a remark by Mädler that he was uncertain if the star he measured was elongated. The WDS shows the first recorded measure of the pair was in 1846 (350° and .7”). Hussey shows Otto Struve measuring the pair in 1851, but as you can see in the excerpt at the right from Hussey’s book, the 1851 measures appear to be in error in comparison to the measures made in 1870, 1878, 1889, and 1898. Also shown in the excerpt from Hussey’s book is S.W. Burnham’s initial 1878 measure of what is now the C component at 32.9° and 22.71”.

Looking at the apparent widening separation of the AB pair, it appears there’s some relative motion of the two stars taking place. URAT1 shows the primary with proper motion of +053 +017 (.053”/yr east, .017”/yr north), but neither it or GAIA shows any proper motion data for B, nor do they include coordinates for it. There’s also relative motion taking place with respect to the A and C components, and judging by the PM data listed in URAT1 for C, +005 +011 (.005”/yr east, .011”/yr north), the primary is outrunning the C companion in a northeasterly direction – not by a lot, but enough to result in a gradual widening of the separation.

Speaking of outrunning, we’re running out of space (and time), so it’s time to wrap up this three part look at STT pairs in Lacerta and Cepheus and move on to less difficult targets which are in the range of smaller scopes. Next trip we’ll wander over to a neglected area of Andromeda and round up a wide variety of double and multiple stars, so stay tuned.

Meanwhile, clear skies and cooperative seeing! 😎

STT Objects in Lacerta, Part 2: OΣ 459, OΣ 465, and OΣ 472

On to the second part of a look at some STT objects in Lacerta. In case you missed the first part, you can get to it by clicking on this link.

We’ll get started with OΣ 459 (STT 459), which is located in the southern sector of the Lacertan lizard.

Stellarium screen image with labels added, click to enlarge.

We’re going to start at 4.15 magnitude 1 Lacertae, which is located at the south tip of the constellation, and then follow the constellation diagram line that leads toward the north.  That line comes to a halt at another similarly bright star with a magnitude of 4.50 which surprisingly has no commonly used identification other than h 1746 (HJ 1746), a pleasing double star I covered a few years ago in this post. But at the moment we’re going to use it as a jumping off point to reach OΣ 459. Here’s our chart:

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

Starting at h 1746, move west 30’ to 7.25 magnitude HIP 109543 and then continue west a full degree to reach 7.67 magnitude HIP 109014, which is paired with 7.73 magnitude HIP 109031 to the north. From that last star, a 25’ hop due west will land you on OΣ 459, which is shadowed to its south by 8.43 magnitude HIP 108833. For reference, there’s another dim pair of stars another 25’ further west, 7.65 magnitude HIP 108867 and 7.11 magnitude HIP 108695.

OΣ 459 (STT 459)      HIP: 108841   SAO: 71981
RA: 22h 02.9m   Dec: +39° 34’
Magnitudes: 8.2, 10.8
Separation:  10.6”
Position Angle: 196°  (WDS 2010)
Distance: 1884 Light Years (GAIA)
Spectral Classification:  A is A0

The white glow of OΣ 459 and its companion is at the center of this sketch, with one of our navigational stars, HIP 108833 parked at the south edge of the field of view (left in this sketch). North and south are reversed in this refractor view, click to get a better look.

With a difference of 2.6 magnitudes and a decently wide separation of 10.7”, this is not a difficult pair to split. I spied the secondary quickly with an 18mm Radian (84x) in my six inch refractor, but increased the magnification to 152x with a 10mm Radian in order to provide a more pleasing frame for the image. My search for a star of similar brightness to the OΣ 459 secondary eventually landed on UCAC4 649-106803, which has a UCAC4 Vmag (visual magnitude) of 11.150, so it appears the WDS value of 10.8 for the secondary is about right.

This pair was discovered by Otto Struve in 1845. He took two measures at that time, coming up with separations of 10.51” and 10.80”, and position angles of 197.8 and 196.5 degrees (p. 182 of this source). Compared with the most recent WDS measure of 2010, there’s been virtually no change in this pair, which is not surprising given its distance of 1884 light years.

Our next move is to a considerably more complicated star, OΣ 465.  To get there we first need to head north to 4.44 magnitude Beta (β) Lacertae, which is located at the north tip of the Lacertan diamond (here’s the wide view again to get you headed in the right direction).

Stellarium screen image with labels added, click to enlarge.

From Beta (β) Lacertae, which is located at the lower left center of the chart, it’s a two degree southwest leap (2° 9’ to be precise) to OΣ 465 (STT 465). You’ll find it 38’ south and slightly east of 5.38 magnitude HIP 109521, which is the first star you’ll come to on the southwest leap that’s similar in brightness to Beta (β) Lacertae. HIP 109521 is also known as h 1741 (HJ 1741), which is another double star we’ve looked previously and is in the same post referred to in the second paragraph above. As you scan the OΣ 465 chart, notice that 4.58 magnitude 4 Lacertae and 4.44 magnitude Beta (β) Lacertae from a triangle with STT 465 at the western tip, which should help to make sure you’re in the right place.

OΣ  (STT 465)     HIP: 109586   SAO: 51749
RA: 22h 12.0m   Dec: +50° 12’
Magnitudes  AB: 7.30, 10.55   AC: 7.30, 13.30
Separation   AB: 12.80”           AC: 17.80”
Position Angle   AB: 317°  (WDS 2010)   AC: 233°  (WDS 2003)
Distance: 2118 Light Years (Simbad), 4025 Light Years (GAIA)
Spectral Classification:  A is F0

You’ll need to enlarge this sketch by clicking on it in order to catch glimpses of the B and C components. This is a rather close approximation of the visual difficulty I experienced while trying to pry the two faint companions loose from the primarial glare. We’re dealing with a wider range of magnitudes here than we did on the previous star, so be prepared to strain your visual receptors just a bit.   (North and south reversed again to match the refractor view).

I’ve paid three visits to this triple star and each time was able to catch B pretty quickly in my six inch refractor with averted vision, hovering at the edge of the glare from the primary, but I needed 152x to do it. With a bit more concentration I even managed to capture it visually with direct vision for short periods.

My search for comparison stars landed on the two UCAC4 stars identified in the sketch to the west of the primary (above it in the sketch). Trying to keep B in view, whether with direct vision, or especially with averted vision, while comparing it to a similarly faint star is just a bit challenging to say the least, and can be a dubious process, as you’re about to see.  I finally decided B is about midway between the two UCAC4 stars in brightness.

UCAC4 701-104020 has a UCAC4 Vmag of 11.518 and UCAC4 702-100946 a Vmag of 12.589, which would make B about 12^th magnitude, or 1.5 magnitudes fainter than the WDS value, which really seems unlikely because B didn’t impress me as being a full magnitude fainter than UCAC4 701-104020.  So it looks as though the 12.589 Vmag value for UCAC4 702-100946 may be an error. Adding to my doubts that B is 1.5 magnitudes fainter that the WDS value is the 10.546 UCAC4 Vmag for B. We never got around to measuring the magnitude of B, so I’m tempted to say the WDS value for B is probably about right, especially considering the experience I’m about to describe with the C companion.

That one was a real chore, but I managed to latch onto it a couple of times. If the 13.30 WDS magnitude is correct, there’s no way I would have seen it in my six inch refractor. More than likely it’s in the 12.7 to 12.8 range, which would be about at the limit of what I can glimpse in that scope while trying to see around the edges of the seventh magnitude glow of the primary. UCAC4 702-100946, with it’s supposed Vmag of 12.589, was nowhere as difficult to see, which is another reason I have doubts about the accuracy of that magnitude.

At any rate, comparing stars as faint as these, especially when some of them are imbedded in the glare of a primary, in order to arrive at a magnitude estimate can sometimes produce more questions than answers.  It’s no wonder I found myself muttering in the damp darkness about the fickleness of faint stellar magnitudes while fighting off visions of a comfortable seat beside a warm fire with a good book and a hot cup of tea.

I don’t know how damp the darkness was when Otto Struve measured the B component in 1848, but according to Hussey’s account (p.191) he came up with separations of 15.26” and 15.38” and position angles of 324.1 and 324.6 degrees, which is notably different from the 2010 WDS numbers of 12.8” and 317 degrees.

Click to enlarge.

There seems to be something fickle here, too, so let’s begin by looking at the two distances I’ve listed on the last line of the data above for OΣ 465.  You’ll notice there’s a huge difference between the Simbad and the GAIA distances, but even if you go with the closest distance of the two, the primary of OΣ 465 is too far away to display any significant proper motion in the 162 years between Otto Struve’s 1848 measure and the 2010 WDS measure. I looked at some archived copies of the WDS and found there’s a consistent change in the separation and position angle of the AB pair, which is shown just above at the right.  That list shows the average of Otto Struve’s two 1848 measures, as well as 1867 and 1898 measures by Dembowski and Hussey, respectively, which come from p. 191 of Hussey’s book. It’s quite possible B is a foreground star and is slowly moving in front of the primary, which would make this an optical pair and account for the steady change in separation and position angle. GAIA doesn’t have any parallax data yet on B, so without that crucial piece of information, there’s no way to be certain at this point where it lies in relation to the primary.

As for who added C, it took some digging, but persistence paid off. The WDS shows the first measure of the AC pair was made in 1908, which is a strong hint that S.W. Burnham was involved. However, I had no luck in finding it in his 1913 Proper Motion Catalog, which is the only catalog he published after 1908. So I turned to R.G. Aitken’s 1932 New General Catalogue of Double Stars Within 120° of the North Pole and tracked down OΣ 465 on page 1364 of the second volume. And sure enough, the catalog entry identified Burnham as the source of the first measure, including the actual numbers, which match the WDS data. And unlike the AB pair, those numbers are pretty close to the 2003 measures in the WDS, which again points to B as the half of the AB pair responsible for their gradual change.

On to our last STT object in this trip through Lacerta. You’ll find OΣ 472 one degree almost due east of Beta (β) Lacertae, and you’ll skirt past the very small open cluster NGC 7296 on the way. Here’s our previous chart once again.

OΣ 472 (STT 472)     HIP: 111058   SAO: 34519
RA: 22h 29.9m   Dec: +52° 25’
Magnitudes  AB: 6.63, 11.50    AC: 6.63, 12.60
Separation   AB: 12.90”            AC: 12.50”
Position Angle  AB: 300° (WDS 2013)    AC: 356°  (WDS 2013)
Distance: 404 Light Years (Simbad, no data in GAIA).
Spectral Classification:  A is G8
Note:  AB is LEO 53, AC is STT 472

Again, you’ll have to enlarge this sketch by clicking on it and then looking closely at the one o’clock position to see a small speck of light. That’s the C component, the one discovered by Otto Struve. North and south reversed once more to match the refractor image.

I’ve looked at this triple star twice, about a year apart, and had no luck whatever at spying the B component. C wasn’t easy either, but with persistent averted vision and parallax-induced patience I managed to to pry it out of the primarial glare both times. I found it was very similar in magnitude to UCAC4 713-102498, which has a UCAC4 Vmag of 12.288. So it’s possible the C component is slightly brighter than the WDS value of 12.50.

On the other hand, the B component, located at virtually the same distance as C, is pretty clearly considerably fainter than the WDS value of 11.50. The only photometric data available on B is a UCAC4 f.mag of 13.924, which is a definite hint that B is somewhere in the 13.5 magnitude range.

Click to enlarge.

The AC pair first appeared in Otto Struve’s 1845 catalog with an estimated separation of 15” and no position angle (see excerpt at right).  The first published measure of the pair was made by Baron Dembowski in 1867, 15.80” and 365.8 degrees (p.192 of Hussey). OΣ 472 was later rejected in the second edition of the Pulkovo catalog because it was decided the separation of the pair exceeded the catalog limit of 16”, so apparently there was a measure made between 1843 and 1867.

As for the ear-catching LEO 53 (no association with Leo the Lion of constellation fame), it was pried out of the primary’s radiant glare in 1928 by Frederick C. Leonard, using the 60-inch reflector on Mt. Wilson. However, at Leonard’s request the actual measures were made by Aitken using the 36 inch Lick refractor. Leonard made a total of 56 double stars discoveries between 1917 and 1943. Because his published record of LEO 53 goes into more detail than is usual for a new double star measure, I thought it would be worth while to include it below in its entirety (source).  Notice that Leonard estimated the magnitude of B to be ±13.5 at the time of discovery.

That wraps up Lacerta for now, but we’re not yet done with Otto Struve who will be back shortly to take us on a tour of four of his discoveries in Cepheus.

Clear skies and tolerable temperature! 😎

STT Objects in Lacerta, Part 1: OΣ 475, OΣ 477, and OΣ 479

It’s rather ironic that I find myself back in Lacerta once again, which is the scene of the last post I wrote here several months ago. But this is an intriguing little constellation, dim though it is, and is well worth spending some time here. This time we’ll concentrate on six of Otto Wilhem von Struve’s more challenging discoveries. The challenge here isn’t feeble starlight (with one exception) as much as the more dreaded difference in magnitudes. Fortunately the stingiest separation is 10.7”, so we have a fighting chance to separate these pairs. You’ll need a minimum of six inches of unobstructed aperture to resolve these stars, although given very dark skies, great transparency, and stable seeing (in other words, rather rare atmospheric cooperation), you might get by with five inches.

As historical background, Otto Struve published the first catalog of his discoveries in 1843 with a lengthy title which was typical of the era, Catalogue de 514 Étoiles Doubles et Multiples Découvertes Sur L’Hémisphère Céleste Boréal par La Grand Lunette de L’Observatoire Central de Poulkova. Fortunately, the title which has come into common usage is The Pulkova (or Pulkovo) Catalog. This particular survey of double stars was actually started on August 26^th, 1841, by Otto’s father, Friedrich Wilhelm Struve, who turned it over to his son within a month. There were several additions and modifications to this catalog over the next decades, which resulted in the printing of subsequent editions, including a supplement of much wider pairs. Also lending a hand and providing many of the measures of these pairs was Johann Heinrich Mädler.

Let’s start by getting situated in Lacerta, which lies in the dim region between Cepheus and Cygnus. Even though the area is sparse in regard to eye-catching magnitudes, the north end of Lacerta lies in a star strewn stream of the Milky Way as it meanders through Cygnus, Cepheus, and Cassiopeia.

Stellarium screen image with labels added, click to enlarge.

Note the directions indicated in the top left hand corner of this chart. Astronomical west is always the direction in which the constellations are rotating, which explains why it’s pointing in the direction shown. This is a depiction of the scene in late August or early September, when the constellations are slowly rotating toward the top of the chart.

Stellarium screen image with labels added, click to enlarge.

If you’re having trouble pinning down the Lacertan Lizard, notice that a line drawn from Beta Cephei through Delta Cephei will take you right through the center of the distinctive Lacertan parallelogram. Also, a line drawn from Delta Cygni (out of view at the upper right hand corner) through Deneb will take you to the southern tip of Lacerata.

Our first stop is OΣ 477, which lies a couple of degrees north of 11 Lacertae:

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

If you look closely at the chart above, 4.46 magnitude 11 Lacertae forms a triangle with 6.38 magnitude HIP 111753 and 6.55 magnitude HIP 111428. OΣ 477 stands out distinctively just half a degree west of HIP 111428.

OΣ 477 (STT 477)     No HIP Number    SAO: 52303
RA: 22h 43.5m   Dec: 46° 02’
Magnitudes  AB: 7.43, 12.20   AC: 7.43, 11.24   CD: 11.24, 12.70
Separation   AB: 22.50”          AC: 182.70”         CD: 10.40”
Position Angle  AB: 262° (WDS 2015)  AC: 344° (WDS 2002)  CD: 127° (WDS 2015)
Distance: 256 Light Years (GAIA)
Spectral Classification:  A is F6

As I mentioned above, you need six inches of unobstructed aperture to spy the dim companions featured in this series. So you have to look closely to see the twelfth magnitude B companion, as well as distinguishing the difficult CD pair. Clicking on the sketch will enlarge it and make things much easier. (North and south reversed to match the refractor image).

This was my third visit to this multiple star, and each time was an improvement over the time before. My first visit was on 8-21-2015, during which eleventh magnitude C was the only component I could catch. I came back a couple of weeks later (9-7-2015) and that time, with a determined application of averted vision, I pried 12.2 magnitude B out of the primarial glare, but still couldn’t distinguish 12.7 magnitude D clinging to C. My most recent visit, almost exactly a year after the second, was under much improved seeing conditions. Not only was B much easier to see, but D was also obvious when I looked closely. In fact all three components were such a breeze that I was surprised to see how difficult they had been when I looked at my notes from the prior visits.

Not only were the three components more cooperative, but I also picked out the faint star which is shown just to the left of B in the sketch, which was totally absent during the earlier encounters with OΣ 477. That star is identified in Aladin as UCAC4 681-126049 with a visual magnitude of 13.073. Combining the J and K magnitudes for it results in a similar magnitude of 13.021, so it’s safe to call it a 13.0 magnitude star. Again, it’s amazing the difference a cooperative atmosphere can make – sort of what you might call the difference between night and day.

By the way, a comparison of various UCAC4 and NOMAD-1 magnitudes for B, C, and D all resulted in remarkable consistency, each coming in within a few tenths of a magnitude of the WDS values, so all of the magnitudes shown in the data line above are very reliable.

Getting back to 13.0 magnitude UCAC4 681-126049, you might wonder why Otto Struve ignored that one at the time he observed B. There’s an easy answer to that question. When his father, F.G.W. Struve, started this survey of double stars, he established specific criteria, among which was a separation limit of 16” for companions fainter than ninth magnitude (p.16 of this source). Aladin shows a separation of 36.28” between UCAC4 681-126049 and the OΣ 477 primary, so that explains that. Otto Struve later added a supplement to the Pulkovo Catalog for wider pairs, but he apparently didn’t come back to this one. (The stars in that supplement were assigned a prefix of OΣΣ, which in WDS jargon has been transformed to STTA).

Of course that raises questions immediately with regard to the B and CD components since they’re well outside the 16” limit. With regard to the CD pair, the answer is pretty straight-forward: it was added in 1880, most likely by S.W. Burnham, although I haven’t been able to pin that down definitively. As for B, the answer is A – which is a cryptic way of saying that A has a lot of proper motion. In fact, that can be illustrated by the separation of the AB pair at the time of discovery in 1846, when it was a much tighter 9.6” (with a considerably different PA of 123 degrees). The most recent data, which comes from the GAIA catalog, shows the A component with a proper motion of +185 -009 (.185”/yr east and .009”/yr south), which means it’s moving eastward at a pretty good pace. The effect of that motion is easy to illustrate by using the Epoch tool slider in Aladin to compare and contrast the relative positions of the AB pair in 1846 and 2016:

Aladin image with labels added, click to enlarge.

Notice the red circles represent the positions of the two stars at the two dates shown. More proof that the heavens change just like everything else, albeit at a snail’s pace. Also, the separation between A and UCAC4 681-126049 in 1846 was 43”, which again illustrates why it wasn’t included in 1846 when Otto Struve measured the AB pair.

Now that we have that covered, we’ll move on to OΣ 479, also known as STT 479, AKA HN 42, AKA 13 Lacertae. Starting again at 11 Lacertae, you’ll find OΣ 479 is located 2 ½ degrees to the southeast. It and 11 Lacertae form a triangle with 4.95 magnitude 15 Lacertae. (Here’s our previous chart again).

OΣ 479 (STT 479) (HN 42) (13 Lacertae)
HIP: 112242    SAO: 52317
RA: 22h 44.1m   Dec: 41° 49’
Magnitudes: 5.21, 10.9
Separation:  14.4”
Position Angle: 130°
Distance: 256.5 Light Years (Simbad)
Spectral Classification:  A is G8 (WDS)

Again, you have to look closely to see the secondary, which is a bit more difficult than the secondary in the previous sketch. (North and south reversed to match the refractor image, click for a better view).

I had very little difficulty with this pair on the night I made the sketch above at 201x, which wasn’t the case a year earlier when I looked at it. On that night the secondary was immediately visible at 84x, but it decided to become difficult when I increased the magnification. At 152x, it vanished into the primarial glare, and then reappeared sporadically when I dropped back to 127x. It was more cooperative at 109x, but still a bit elusive, so I went back to 84x and was able to see it most of the time with direct vision, at other times only with averted vision.

There’s a huge difference in magnitude between the two stars, somewhat comparable to seeing the secondary of Polaris in a 50mm refractor. That pair has a Delta_M of 7.06 (magnitudes of 2.04 and 9.1) vs. 5.69 for this pair, which is fainter, so the comparison is not quite exact, but it will give you an idea of what to expect. However, I estimated the secondary to be at least a full magnitude fainter based on comparison with two nearby stars, which sheds some light on the comparison with Polaris. B appeared to me to be slightly fainter than UCAC4 659-108762 (which has a UCAC4 Vmag of 11.640) and slightly brighter than UCAC4 660-110091 (with a Vmag of 12.818), so the actual magnitude most likely lies somewhere in between.

William Herschel appears to have been the first to come across this pair of stars, having looked at them on October 17th, 1786. However he didn’t publish that observation until 1822, assigning a catalog number of H N 42 to it. His remarks on the pair were rather brief: “13 Lacertae has an extremely small star following, 3d class.” (p.171 of 1822 catalog). John Herschel also looked at 13 Lacertae in 1828, providing an estimated separation of 12” with a PA of 132.9 degrees. The first actual measure of the pair was made by Otto Struve in 1849. He recorded a separation of 14.57” and a position angle of 129.2 degrees. John Herschel recorded another measure of the pair that same year, turning in a separation of 14.70” and 129.1 degrees. Comparing those 1849 measures to the most recent 2012 WDS data shows very little change over the past 167 years.

On to our last star now. We’ll head south from OΣ 479 (with a bit of a tilt to the west) for a distance of 1° 40’ to 5.82 magnitude 12 Lacertae, then continue in the same direction another 1° 15’ to 4.89 magnitude 10 Lacertae, and then angle southeast for a distance of 1° 28’ to 6.03 magnitude HIP 111869. You’ll see OΣ 475 at the western corner of a triangle it forms with HIP 111869 and 6.65 magnitude HIP 111864. (The previous chart once more).

OΣ 475 (STT 475)     HIP: 111828   SAO: 72569
RA: 22h 39.1m   Dec: 37° 23’
Magnitudes  Aa, Ab: 6.83, 10.52   AB: 6.84, 10.80
Separation   Aa, Ab: 0.60”            AB: 16.10”
Position Angle  Aa, Ab: 50° (WDS 2009)    AB: 73°  (WDS 2008)
Distance: Unknown  (negative parallax)
Spectral Classification:   A is B2
Note: Aa, Ab is HDS 3216, AB is STT 475

And again you have to look closely to see the B component of this pair (it’s hiding in the glow of the primary between the four and five o’clock position). Notice both HIP 111869 and HIP 111864, which we used to locate OΣ 475, are in the field of view with it. (North and south reversed once again, click for a much better view).

I had little problem with the secondary during my two year-apart-observations since it popped into view immediately at 84x both times. I estimated it to be very similar in magnitude to UCAC4 638-120691 (located 9’ northwest), which has a Vmag of 11.008, so it appears the WDS magnitude of 10.8 is about right. Otto Struve first measured this pair in 1847 at 15.53” with a position angle of 72.8 degrees. John Herschel showed up here as well that same year, turning in a separation of 15.66” and a PA of 73.6”.

As for the Aa, Ab pair, good luck. A separation of .60” wouldn’t be out of reach for a large aperture dobsonian –- except for that annoying 3.69 magnitude difference between the two components. The HDS prefix refers to the Hipparcos Double Star survey, which first detected it in 1991. With a total of four observations recorded in the WDS, you can at least rest assured the secondary is really there if you launch a search for it.

Also hovering in the southwest quadrant of the field of view is an evenly illuminated pair, AG 284 (WDS 22387+3718), which has magnitudes of 9.86 and 9.94, separated by 26.3” with a PA of 230 degrees (WDS 2008 data). Your double-starred vision should have no problem latching onto those two.

That’s it for the first half of this tour – click here to continue to the second half.

Clear Skies! 😎

Difficult Double Stars of the STT Variety

Back in the golden era of the late nineteenth and early twentieth centuries, when astronomy began to grow rapidly in the United States and Europe, communication with other astronomers was a slow process — especially when it took place between continents. For example, S.W. Burnham (1838-1921) sent many of his first double star discoveries of the early 1870’s to Milan, Italy, where Baron Ercole Dembowski (1812-1881) then made the first measures of those stars and mailed them back to Burnham in Chicago — a cycle which frequently took most of a year and sometimes longer. Burnham also actively published in European journals, primarily Germany’s Astronomische Nachrichten and England’s MNRAS (Monthly Notices of the Royal Astronomical Society), as did other American astronomers. Many a list of observations or manuscripts were dropped into the mail accompanied by doubt as to when, or if, it would reach its destination. Patience and confidence were virtues that came with experience, some of it no doubt learned with difficulty.

Communication between continents in this day and age is of course much faster, although publication cycles haven’t changed all that much – a paper or article sent to a publication frequently takes six months or longer to see the light of day. But the era of the internet and email creates possibilities that astronomers of Burnham and Dembowski’s day never would have dared to contemplate.

I’ve spent most of the last year putting those tools to good use, which has resulted in numerous publications in the Journal of Double Star Observers (JDSO), the vast majority of which have been in collaboration with Dr. Wilfried Knapp of Vienna, Austria. Most of those publications concern the more challenging of the double stars discovered by Otto Wilhelm Struve, which is why the articles are all titled “STT Double Stars with Large Delta_M.”

Now it’s a basic fact of life that when you push yourself beyond your comfort zone, you learn and grow in ways you never anticipated. Put more concisely, if you don’t try, you’ll never know. That applies to observational astronomy as well – in fact, especially to observational astronomy. When I first cast eyes on the list of double stars to be examined for the STT project, my initial thought was most of the faint secondaries on the list were too difficult to separate from their much brighter primaries. The astronomical term which describes that challenging difference in magnitudes between the two stars is “delta_M (or Δ_M)”, and thus the title of the papers.

Reams of material has been published about the relation between magnitude differentials (delta_M) and aperture, and numerous attempts have been made to pin down more precisely what can be detected and what can’t with specific apertures and magnitude differences. Although they’re certainly well intended, I’ve never been a big fan of those efforts, primarily because there are so many variables involved. The ability and experience of the observer, the quality of the optics, the telescope type, atmospheric conditions, altitude – all of those factors play a role that can’t be easily converted to numbers. But there’s one variable which is frequently overlooked: the accuracy of the published magnitudes.

I suspect that last one may catch many observers by surprise. But the reality is that magnitudes don’t get near the attention in double star catalogs as do separations and position angles. In fact, it’s not at all unusual in the case of the older double star discoveries, such as those of Otto Struve, for the current published magnitudes of secondaries to be in error, chiefly because they’ve been carried over from older observations, if not the original observation.

That factor was at the heart of the STT double star project. Of the approximately one hundred STT double stars we observed and measured, roughly half of the secondaries had noticeable magnitude errors, some of which were quite significant. We took two approaches to this.  One was an effort to estimate the magnitudes of the secondaries visually, using comparison stars where possible in order to arrive at our estimates.  The results of those comparisons were inconsistent, primarily because the glare from the primaries over-powered the secondaries, which for the most part were visible only with averted vision.  Attempting to hold an elusive and dim star in view with averted vision while at the same time latching onto a comparison star with the same eye is not an approach calculated to succeed every time.  The other was a photographic approach in which Wilfried utilized the facilities of a remote telescope site to determine magnitudes, as well as to produce precise measures of separation and position angle.  That approach proved to be quite accurate and dependable. 

We produced a total of eight papers for the STT series, and as each is published our results are finding their way into the WDS, resulting in a very satisfying and rewarding project.  I’ve listed the eight papers below, five of which have been published so far in the JDSO.  I’ll add links to the remaining three as they’re published. There’s a lot of detail in each of these papers, but the heart of them lies in the two tables near the end, one of which summarize the magnitude findings, and the other which summarizes the separation and position angle measures.

In addition to the STT pairs covered in the JDSO papers, there were another fourteen that didn’t find their way into publication because of other projects, so I’ve decided to cover my observations of that group in the next few Star Splitter posts. Those stars are located in Cepheus, Lacerta, and Lynx. Each of the pieces will be oriented more toward observation than the papers are, so stay tuned for a few star-hopping adventures that will provide you with a chance to test your observational talent and hopefully raise your averted vision skills a parsec or two.

JDSO Articles :

STT Doubles with Large Δ M – Part I: Gem  (with Steve Smith)
STT Doubles with Large Δ M – Part II: Leo and UMa (with Steve Smith)
STT Doubles with Large Δ M – Part III: Vir, Ser, Com, CrB, and Boo
STT Doubles with Large Δ M – Part IV: Ophiuchus and Hercules
STT Doubles with Large Δ M – Part V: Aquila, Delphinus, Cygnus, Aquarius
STT Doubles with Large Δ M – Part VI: Cyg Multiples
STT Doubles with Large Δ M – Part VII: And, Psc, Aur
STT Doubles with Large Δ M – Part VIII: Tau, Per, Ori, Cam, Mon, Cnc, Peg

Problems of a Different Magnitude in Lacerta: 8 Lacertae (STF 2922/A1459) and ROE 47

It had been a long while since I last took a stroll through Lacerta, so I had to grab my well-worn copy of Sky and Telescope’s Pocket Sky Atlas and relocate the constellation’s dim outline between Cygnus and Cepheus.   Lacerta is not one of those constellations that draws attention, which is unfortunate since the Milky Way runs through about 90% of its stellar real estate – meaning it has more than its share of double stars and open clusters. I was back to check on the Lacertan lizard once again because of a question about the magnitude of one of the components of 8 Lacertae, which in keeping with Lacerta’s rich stellar tradition, also has more than its share of stellar companions.   And as long as I was there, I decided to poke around and see what else I could see, which led to a magnitude of additional questions.

Even though it’s the first part of December as I write this, from my forty-five degree latitude Lacerta is almost directly overhead at 7 PM, parked in a holding position between Cygnus, Andromeda, and Pegasus, and Cepheus.

Stellarium screen image with labels added, click to enlarge.

A line drawn from Beta (β) Cephei through Zeta (ζ) Cephei will actually lead you directly to 8 Lacertae:

You can also draw a line from Delta (δ) Cygni (just out of sight at the upper right of the chart) through Deneb, which will just miss the southern edge of 8 Lacerate. (Stellarium screen image with labels added, click to enlarge).

But because Lacerta is a dim constellation . . . . . .

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

. . . . . . you might find it easier to aim an 8×50 or 9×50 finder at 4.5 magnitude 6 Lacertae, move northeast a few degrees to 4.5 magnitude 11 Lacertae, and then drop southeast to 5.1 magnitude 13 Lacerate, using 5.0 magnitude 15 Lacertae as a reference point, and then move south to 5.3 magnitude 12 and 4.9 magnitude 10 Lacertae, which form a triangle with sixth magnitude 8 Lacertae parked in the west corner.   That way you’ll be sure to land on the right star at least.   There should be little chance of confusing 8 Lac with another star since “A”, “B”, and “E” are bright and very obvious:

8 Lacertae  (AB is H IV 86)      HIP: 111546   SAO: 72509
RA: 22h 35.9m   Dec: +39° 38

Identifier	Magnitudes	Separation	PA	WDS
STF 2922 AB:	5.66,  6.29	22.40″	185°	2014
A 1469 AC:	5.66, 10.38	48.90″	168°	2014
A 1469 AD:	5.66,   9.09	81.60″	144°	2014
A 1469 AE:	5.66,   7.25	337.80″	239°	2011
DAL 28 AG:	5.66, 14.08	78.60″	194°	2012
COM 8 BF:	6.29, 10.97	127.60″	175°	2012
A 1469 CH:	10.38, 14.60	1.40″	254°	1932
A 1469 DI:	9.08, 13.30	10.10″	227°	2012
DAL 28 GJ:	14.08, 12.99	6.10″	78°	2009

Distance:  “A” is 2160 Light Years; “E” is 428 LY (Simbad)
Spectral Classifications:  “A” and “B” are B2, “D” is A0, “E” is F0
Notes: Mag of I changed from 11.0 to 13.3 as of 10-29-2015
Magnitudes of GJ are reversed in WDS, should be 12.99 and 14.08

In a mid-October email from Mike Hyrczyk via Chris Thuemen, Mike mentioned he had looked at 8 Lacertae and found the “I” component wasn’t visible in his six inch refractor. At the time, it was listed in the WDS at a magnitude of 11.0, normally well within reach of a six inch scope. That evening, I pointed my six inch f/10 refractor at the complex star and, at 152x, confirmed Mike’s observation. I tried higher magnifications – 253x, 365x, and 380x – and may have had a brief glimpse of the fickle star, but there was no doubt it was fainter than the WDS’s 11.0 magnitude. Chris used a 9.25 inch SCT the following night and basically had the same experience, although he may have detected an elongation in the DI pair. Chris also noticed the magnitudes of the GJ pair were reversed in the WDS, which hasn’t been corrected as of this writing.

Given the 10.10” separation listed for the DI pair, experience told me that a magnitude of 13.0 was about the brightest “I” could be, if in fact I had actually seen it with my six inch refractor in the combined AB glare. A check of photometry records in the UCAC4 catalog showed magnitudes of 13.828 (f.mag) and 13.598 (J and K converted to visual), which were too faint for me to have had a glimpse of the star. I sent what information I had to Bill Hartkopf at the USNO/WDS, who consulted additional photometry records, arriving at a magnitude of 13.30 for “I”.

So — after that long introduction, it’s about time we took a look:

“A”, “B”, and “E” are the stars that catch your eye on first view, all of which are white, followed by “C” and “D”. You have to look a bit closer to get your first glimpse of “F”. The missing “I” component is both too faint and too close to “D” to be seen here. There are two more faint pairs to the south of 8 Lac, neither of which are cataloged in the WDS as double stars. (East & west reversed, click on the sketch for a better view).

There’s also an excellent photo and discussion of the 8 Lacertae complex on page 52 of the November issue of Sky and Telescope. Sue French was unable to see “I” with a 10 inch reflector, but found a fifteen inch scope brought it into view, which supports the WDS magnitude change to 13.30.   Sue also noticed the error in the WDS listing for the GJ pair.

8 Lacertae has an interesting history. Sir William Herschel was the first to record it for posterity, cataloging the AB pair as H IV 86 in 1782 (source, sixth title from the top):

His 84° 30’ south preceding works out to a present day figure of 185° 30’, which is a good match with the current WDS figure, but his separation of 17” 14’” puts the AB pair five arc seconds closer than the WDS data. He describes six stars, which probably correspond to the A through F pairs, although his description of their relative magnitudes is difficult to follow. The Latin phrase at the top of his catalog entry translates as “In the middle of the tail”, which seems to indicate a slightly different configuration for Lacerta than what I show above in the first chart.

Click to enlarge the image.

Sirs John Herschel and James South made two observations of 8 Lacertae in September of 1823, which are shown at the right (source, last title on page).  Their measures of AB, which are summarized near the bottom of the page, are in line with the current WDS data, as are their measures of the AD pair (145° 15’, 82.52”, which they refer to as AC).   They seem to have entirely missed the closer 10.38 magnitude star now referred to as “C”.

At the bottom of that same page, they refer to an erroneous measure of the AB pair made by Piazzi in 1800 (212° 58’ and 19.072”). Admiral W.H. Smyth also refers to that error on pp. 519-520 of his Bedford Catalog, as well as William Herschel’s 1782 PA error. Relying on his distinctive pre-Victorian vocabulary to make the point, he wrote: “Here the anomalies are palpably owing to error, and the fixity of the objects appears unquestionable.”

The Admiral was irrefutably correct in regard to the “unquestionable fixity” of the objects.   Given the 2160 light year distance of “A”, little proper motion is exactly what would be expected.   Simbad doesn’t provide a distance for “B”, but it does show “E” to be at 428 light years, which is also far enough away that minimal proper motion would be the norm. I checked the most recent PM data available, which comes from the USNO’s URAT1 catalog, and it confirms the minimal motion for each of the stars:

Aladin image with labels and data added, click to make the text more legible.

“E” shows the most motion, which again is to be expected since it’s four times closer to us than “A”.   There are no parallaxes available in Simbad on the other components of the system, but judging by their slight motion, they may well be about the same distance as “A”. And at those distance, it’s impossible to come to any conclusion on shared physical motion based on the PM numbers.

Before heading out into the night air to look at 8 Lacertae, I used Sky Tools 3 to take a quick look around the neighborhood for other interesting stars, and quickly found an intriguing multiple star, ROE 47, located just 41’ to the west (here’s our third chart again).   So give your scope a careful nudge in that direction and you’ll be greeted by a sixth magnitude star with several faint companions.

ROE 47        HIP: 111259   SAO: 72446
RA: 22h 32.4m   Dec: +39° 47’

Identifier	Magnitudes	Separation	PA	WDS
ROE 47 AB:	5.90, 11.46	42.90″	155°	2012
ROE 47 AC:	5.90, 12.40	33.50″	341°	2012
ROE 47 AD:	5.90, 12.20	103.70″	216°	2010
FYM 109 AF:	5.90, 14.11	22.00″	106°	2012
ROE 47 DE:	12.20, 12.30	6.60″	175°	2012

Distance: 684 Light Years
Spectral Classification:  “A” is A6
Notes: Mag of C changed from 10.2 to 12.4 as of 10-29-2015
Mag of D changed from 11.36 to 12.2 as of 10-29-2015
Mag of E changed from 9.90 to 12.3 as of 10-29-2015

This one had what you might call a magnitude of problems, but before wrestling with that issue, let’s take a look:

“A” was very white; “C” was very faint and mainly an averted vision apparition; “B” was distinct; and “D”, which was just a bit easier to see than “C”, was marginally duplicitous at 152x, but it cooperatively separated at 253x with a 6mm Astro-Tech/Sterling Plössl, as shown in the insert below the insert at the right. (East and west reversed once more, click on the sketch to improve the view considerably).

It didn’t take but a few seconds to realize that some of the fainter components I was looking at were fainter than the WDS data said they were. As the “C” component flickered in and out of view, I could see it was clearly fainter than the 10.2 magnitude then listed for it in the WDS. There was also something clearly amiss with “D”, which wavered between direct vision and averted vision, meaning it was also fainter than the WDS’s 11.36. And “E”, which was listed at a magnitude of 9.9, was not the conspicuous speck of light it should have been – in fact, it should have been over-powering “D”.   After I separated the DE pair at 253x, it was clear they were both about the same magnitude – so 9.90 was nowhere close to being correct. Chris Thuemen also looked at ROE 47 and basically came to similar conclusions.

There’s a huge amount of photometric data available in both the NOMAD-1 and the UCAC4 catalogs, so I turned to both of those to see what I could find.   Looking at “C”, I found data pointing to a magnitude of 12.3. In the case of the DE pair, the UCAC4 Vmags, which are normally very dependable in this range, showed 11.358 for both stars, which seemed too bright to me.   The UCAC4 f.mag and the J & K visual approximations pointed toward a magnitude of 11.9 to 12.0, which struck me as being closer to what I had seen.

Click to enlarge and make the data more legible.

I sent off what I had to Bill Hartkopf at the USNO/WDS, who used additional data to make the changes I’ve listed at the bottom of the ROE 47 data above. Incidentally, Bill is always quick to say he appreciates these observations very much. With the WDS data base approaching something like 130,000 stars, the only way these kinds of errors get corrected is when visual observers note the discrepancies and report them to the WDS.

Click to enlarge the image.

Digging into the history of ROE 47, it appears the AB and AD pairs were discovered in 1895 by E.D. Roe, Jr., a British amateur astronomer, who used a six inch refractor. He added the “C” and “E” components in 1910, as shown in the excerpt at the right from a 1911 issue of the Astronomische Nachrichten.

I couldn’t find any biographical material on E.D. Roe, but it appears he must have had an astronomically dry sense of humor.   If you look at the top left hand corner of the image above, you’ll see he used the Greek symbol “ρ” as an identifier, which in Greek is pronounced rho, as in Roe.  Obviously he liked a good laugh.

Next trip – who knows. The winter rains are here and the few clear skies I’ve seen have had more dancing and twinkling stars than an out of control strobe light at an all-night dance party, meaning atrocious seeing, which is not usual for this time of the year. As soon as the weather cooperates (raining hard now with 60mph gusts of wind), I’ll see what I can find to grace the pages of this blog.

Until then, Clear and Cooperative Skies!   😎

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

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

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

Stellarium screen image with labels added, click to enlarge.

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

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

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

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

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

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

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

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

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

(Click to enlarge)

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

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

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

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

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

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

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

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

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

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

Click for another view.

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

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

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

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

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

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

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

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

Click to enlarge.

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

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

Until then, Clear and Stable Skies!   😎