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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

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

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

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

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

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

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

Click to enlarge.

Click to enlarge.

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

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

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

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

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

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

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

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

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

Wm. Herschel on Zeta Lyrae

Click to enlarge.

Click to enlarge.

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

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

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

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

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

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

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

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

Until then, Clear Skies.   😎

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