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Splitting stars – for us and for you!

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

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

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

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

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

Stellarium screen image with labels added, click to enlarge.

Stellarium screen image with labels added, click to enlarge.

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

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

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

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

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

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

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

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

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

Wm. Herschel on Beta Lyrae

Click to enlarge.

Click to enlarge.

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

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

Click to enlarge.

Click to enlarge.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Click to enlarge.

Click to enlarge.

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

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

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

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

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

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

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

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

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

Wm. Herschel on Zeta Lyrae

Click to enlarge.

Click to enlarge.

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

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

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

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

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

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

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

Our next trip will either take us back to Eta (η) Lyrae and a few friends, or to a new mystery in Hercules, depending on how cooperative the seeing is.

Until then, Clear Skies.   :cool:

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

This is an erect image view — click to enlarge!

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

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

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

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

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

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

Click to enlarge!

Click to enlarge!

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

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

Click to enlarge the image.

Click to enlarge the image.

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

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

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

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

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

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

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

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

Click to enlarge!

Click to enlarge!

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

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

Here’s why:

Click to enlarge.

Click to enlarge.

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

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

Click for the larger view.

Click for the larger view.

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

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

Click to enlarge.

Click to enlarge.

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

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

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

Click to enlarge and make the data more legible.

Click to enlarge and make the data more legible.

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

Until then, Clear Skies!   :cool:

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

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

Stellarium screen image with labels added, click to enlarge.

Stellarium screen image with labels added, click to enlarge.

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

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

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

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

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

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

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

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

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

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

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

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

Click to enlarge!

Click to enlarge!

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

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

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

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

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

Stellarium screen image, click to enlarge.

Stellarium screen image, click to enlarge.

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

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

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

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

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

Click to enlarge.

Click to enlarge.

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

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

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

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

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

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

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

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

Wm. Herschel on STF 1333

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

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

Click to enlarge the image.

Click to enlarge the image.

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

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

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

Click to enlarge.

Click to enlarge.

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

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

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

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

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

Clear Skies!   :cool:

A Book! Tales from the Golden Age of Astronomy

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

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

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

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

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

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

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

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

Cheers, Prost, and Clear Skies!

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

9.6 Inch Dorpat Refractor

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Click to enlarge

Click to enlarge

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

1997: 258°, 2.3”
2005:   77°, 2.1”

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

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

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

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

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

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

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

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

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

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

Click to enlarge.

Click to enlarge and improve the clarity.

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

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

Click to enlarge.

Click to enlarge.

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

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

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

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

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

Click on the excerpts to enlarge them.

Click on the excerpts to enlarge them.

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

Click for a larger view.

Click for a larger view.

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

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

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

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

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

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

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

Clear Skies until then!   :cool:

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

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

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

 Stellarium screen image with labels added, click to enlarge.

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

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

Stellarium screen image with labels added, click to enlarge.

Stellarium screen image with labels added, click to enlarge.

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

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

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

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

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

Aladin image with UCAC4 data, click to enlarge.

Aladin image with UCAC4 data, click to enlarge.

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

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

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

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

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

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

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

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

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

Click on the image to make the data more legible.

Click on the image to make the data more legible.

Click to enlarge.

Click to enlarge.

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

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

Click to enlarge.

Click for a much better view.

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

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

Click to enlarge.

Click to enlarge.

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

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

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

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

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

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

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

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

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

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

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

Burnham on 7 LMi

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

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

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

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

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

Clear Skies until then! :cool:

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

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

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

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

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

 Stellarium screen image with labels added, click to enlarge.

Stellarium screen image with labels added, click to enlarge.

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

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

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

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

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

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

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

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

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

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

Frost prevention in the days before dew heaters and electrical power!

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

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

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

Burnhan on 42 LMi

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

South-Leiden-Burnham chart

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

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

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

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

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

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

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

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

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

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

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

Lewis on STF 1432

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

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

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

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

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

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

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

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

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

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

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

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

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

In the meantime, Clear Skies!   :cool:

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