Southern Doubles, Stars and Variables
10 Mar 2009
RA : 00h
Dec : -30° to -90°
Constellations : Phe, Hyi, Hor, Oct.
Best Observed : Aug - Jan (Text Ordered by RA)
RA : 00h
Dec : -30° to -90°
DS 00h 01h 02h 03h 04h 05h 06h 07h 08h 09h 10h 11h
NEW 12h 13h 14h 15h 16h 17h 18h 19h 20h 21h 22h 23h

Δ1 / β1,2 Tuc
LCL 119 AC Tuc
B 7 AB / Aa Tuc
I 260 CD Tuc
B8 / β3 Tuc
LDS 6092 Tuc
RST 10 Tuc
COO 03 Tuc
Δ2 / λ1 Tuc

None Listed
None Listed

None Listed

Positions given as;
I.e. (13583-6018), are;
13h 58.3m
-60° 15′
This follows the current
WDS Conventions.

or arcsec
In arc seconds or
or arcmin
In arc minutes or
mas - milli arc seconds

( ° ) Angle in degrees.
Measured from
North through East

v - visual (naked-eye)
p - photographic
V - Photometric Visual
B - Photometric Blue
MV - Absolute @ 10pc.

pc. - parsecs
ly. - light-years
AU - Astronomical Unit


T: Periastron (yr.)
P: Period (yr.)
a: Semi-Major Axis (arc sec.)
e: Eccentricity
i: Inclination
Ω: Orbital Node (°)
ω: Angle True Orbit (°)

R.A. 00 Hours

Δ1 / β1, β2 Tuc / LCL 119 (00315-6258) was first recognised as a wide optical double star by N. de Lacaillé in 1752. The pair was then rediscovered, or more precisely re-catalogued, by James Dunlop in 1826. β1, β2 Tuc features as the first double star in Dunlop’s 253 double stars catalogue, which was ordered by number in increasing right ascension. He also found a third star being the whitish β3 Tucanae placed some 9.1′SW from the main pair. All three of these stars remain easily visible in binoculars. Closer inspection finds that all these components are again double — all having similar proper motions. It is very likely we are looking at a real complex multiple star system with at least six or seven components.

β1 and β2 Tucanae

LCL 119 AC (00315-6258) was first measured by Dunlop using a homemade micrometer finding both stars separated by 24.86 arcsec along PA 84° 05′ np corresponding to the PA of 354.1°. Dunlop has confused β1 and β2 Tuc here suggesting β2 is the brighter component. The stars are the reverse of this, so Dunlop’s PA should actually read 174.1° for 1826. John Herschel measures are taken in the WDS01 as the first value, finding the PA in 1835 as 172°. The AC main pair is significantly wide — though the true aspects of the all the stars in the system were not recognised by Lacaillé, Dunlop or John Herschel. In the WDS01 this is given as the wide 4.53v magnitude ‘C’ companion making the visual pair LCL 119 AC that lies presently some 27.0 arcsec away at PA 168° — with the PA continuing to slowly diminish.
The primary ‘A’ is a blue B9 V star of 4.36v with the ‘C’ companion being 4.53v magnitude. Both these stars seem to be associated as they have similar proper motions. If we assume the mean parallax as 21.45±1.75mas, then the system lies 46.62±3.82pc or 152.1±12.5 ly. away. Based on the observed separation in the sky, both stars are separated by some 1 260AU.
Respective colours were observed as bluish-white and white — matching well with the given main-sequence spectral types of B9V and A2V with absolute magnitudes of (MV) of +1.09 and +1.19.

β1 Tucanae

B 7 AB / Aa (00315-6258) is the main β1 AB system was found by van den Bos in 1926. The primary ‘A’ is 4.4 magnitude with the difficult to see ‘B’ companion being the faint 13.5 magnitude star separated by 2.6 arcsec along PA 153°, which seems to remained relatively fixed. ‘A’ itself is also a spectroscopic binary ‘Aa’ listed as TOK7, but it does not appear in Batten’s “8th Spectroscopic Orbital Catalogue” (1992) because of the lack of suitable observations. Hipparcos find the parallax of β1 Tucanae as 23.35±0.52mas, suggesting the distance is 42.82±0.95pc or 139.7±3.11 ly. If these stars are attached, then the true separation between the two stars is 105AU. This is a tough pair to split and I have only read one amateur description that splits the duo — and that was in 40cm. I suspect 30cm could see it if the observing conditions were just right.

β2 Tucanae

I 260 CD / HIP 2487 / HD 2885 (00316-6258) is the visual binary with the short period of 44.66 years. Discovered by R.T.A. Innes in 1895, this duo’s 4.8v and 6.0v magnitude makes it a very tough pair for amateur apertures. It is likely only to be seen when the stars are at their maximum distance apart which is in the order of about 0.58 arcsec along the PA around 280°. Presently (2002), the retrograde orbit is diminishing and has become impossible to see for amateur eyes until about 2030 A.D, with the next periastron occurring in May 2012 (2012.36). (Last being December 1967 (1967.93)). Several orbits have been produced for this star with one being for the first of two possible orbital solutions as determined by Eggen in 1965. Since this time another orbit has appeared that was published in the Information Circulars of the U.S.N.O. This was produced by B.D. Mason and W.I Hartkopf (2001) that upgrades the orbit to Grade 3 and finds only slight but more precise changes to Eggen’s calculated orbit. The Tables below give the orbits are the calculated Ephemerides for both Eggen and Mason & Hartkopt. The main sequence spectral types re given as A2 and A7 corresponding to the respective temperatures of 8 870K and 7 810K. Innes described the ‘D’ star as “...decidedly yellow, although the spectrum is A”.

I 260 CD Orbital Elements and Ephemerides

T P a e i Ω ω Source Grade
1923.50 44.43 0.385 0.800 142.0 40.3 282.1 Eggen (2) (1965) 4
2012.84 44.66 0.404 0.740 146.9 63.3 303.7 Mason & Hartkopt (2001c) 3

Year PA1 Sep1 PA2 Sep2
2002 271 0.47 271.5 0.452
2003 268 0.45 268.8 0.520
2004 267 0.44 265.9 0.495
2005 265 0.43 262.7 0.43
2006 264 0.41 259.1 0.435

NOTE: PA1, Sep1 are Eggen’s Elements; PA2, Sep2 are Mason & Hartkoft’s Elements.

β3 Tucanae

B 8 / β3 Tucanae (00327-6302) is another whitish 5.14v magnitude star is β3 Tucanae, lies some 9.1′SW at PA 118°. It also shares similar proper motion with the main and wide ‘AC’ pair. Known as B 8, its duplicity was found by van den Bos in 1926. It remains ‘unsplitable’ in all amateur telescopes as the separation is merely 0.1 arcsec, which has remained the almost the same despite some twenty-four observations being made since 1964. Some evidence exists that the PA has reduced from 173° to 171° but this is likely reflects more random errors than any real motion for such a close system. Few observations since this date have been achieved but there is no doubt this is a binary system. Spectral class is given as A0V.

Summary of the Beta Tucanae System

Component A Aa B C D A B β1,2 - β3
Related Component β1/ B7 β1 β1 β2 β2 β3/ B8 β3 β1
Magnitude 4.36 --- 13.5 4.53 6 5.8 6 5.07
Spectral Class B9V --- G? A2V A7 A0 A5? A0V
Separation (arcsec) --- --- 2.6 27 0.58 --- 0.1 546
Postion Angle (deg) --- --- 151 169 280 --- 171 117
Parallax (mas) 23.35 --- --- 20.20 --- 21.52 --- ---
Distance (pc) 42.82 --- --- 49.51 --- 46.46 --- ---
True Sep (AU) --- --- 150 --- 1260 --- 4.7 25400
Mv 1.09 --- 10.3 --- 1.19 2.5 2.7 ---

[Version 2 : 19.04.04]

LDS 6092 (00323-6302) is a very faint pair that was discovered by Luyten as recently as 1985 and appears in his proper motion catalogue. Much interest has been with this pair as the proximity to Beta Tucanae suggested association. The parallax of 38.85±1.1mas gives the distance of 25.74±0.73pc or about 84ly. Furthermore, the proper motion is 562.3 arcsec (or 9′ 22.8″) per millennia and is presently moving towards the northeastern PA of 101°
Separation is 1.1 arcsec along PA 131°, but the 11.2v and 14.5v magnitude companion makes it a faint pair possibly seen in 20cm to 25cm. Based on this data, the projected separation is 28 AU., roughly the distance between the Sun and Neptune. It is likely, if the two are associated, that the period of this pair is around 100-odd years Observation is the first half of this century may prove this prediction true.
I haven’t observed this pair because of its relative ‘newness’ and my lack of aperture, but I estimate it is a perhaps a little easier to see. Else, little is known of the pair but the future interest in this pair will be drawn by the proximity.


LDS 6029

DESIG: (00323-6304)
Sep. : 1.1 arcsec
P.A. : 131°
YEAR : 1985
Mag.A: 11.2 B : 14.5
Sp. A: ? B : ?
π : 38.85±1.1mas
Dist.: 25.74±0.73 pc.
pmRA.: 565.80±35.2
pmDec: -160.90±20.0
Source: WDS04, Tycho

RST 10 (00310-6237) is another faint pair some 16'N of β Tucanae itself. Since measured in 1928 the PA shows indications of minor changes in the position angle, which is only +2°. At present the separation is 1.6 arcsec aligned along PA 97°. The magnitude of the component is a faint 11.3 and 11.4. RST 10 can be separated in 20cm, though I have no really suggestion of what aperture could separate this faint pair. Those with 10.5cm in good skies might like to try this pair for themselves. Little is known about this pair.

COO 3 (00445-6230), in Tucana, was discovered at the Cordoba Observatory in 1894. Surprisingly missed, especially or such a bright star, by Herschel, Dunlop and Russell, COO 3 is placed some 1.6°ENE of β Tucanae with the yellowish and yellow pair having its companion 2.3 arcsec away at PA 66°. The magnitudes are 6.31 and 8.01, but the three recent photometric observations give the Δm as 1.78. Since 1894 the PA has change by some 24° while the separation has decreased by 1.3 arcsec. The combined spectra is F5III-IV and it is likely the two are connected. Distance from the 11.89±0.67 parallax is 84.31±4.80pc.

COO 3 has a significant proper motion of 103.35 arcsec 100yr-1, and is moving almost eastward (PA 86.5°) from its current position. However, it is only about a quarter that of LDS 6092. A 10.5cm will clearly separate the two with a reasonable seeing night. Overall, an uncommonly beautiful pair.

Δ2 / Lambda (λ1) Tucanae (00524-6930) lies in southern Tucana some 3°N of the Small Magellanic Cloud, and is placed some 1.6°NNW of the globular cluster NGC 362. The general field contains three stars, λ1 A and λ1 B (Δ2) and λ2. All three stars appear yellow, with λ2 perhaps being deeper in colour. Not recognised as a pair, both λ1 and λ2 Tuc are separated by 13.5′E (PA 96°). λ1 is about 1.2 magnitudes brighter than the Δ2 pair. It seems that all three stars maybe associated as the c.p.m. is about the same order an in similar directions.

Δ2 itself is a moderately wide 6.67 and 7.56 magnitude yellow pair separated by some 20.4 arcsec along PA 82°, which should not be confused by the observer with the wider λ1, λ2 Tuc. Since discovery by Dunlop in 1826 but first measure by Herschel in 1834, the PA has increased by some 5° while the separation has reduced by some 2.1 arcsec. The primary is a gorgeous deep yellow which reminded me very much of the companion to p Eridani. It is odd that Dunlop describes by micrometric measurements for the separation as 6.62 arcsec., but the distance is certainly three times this value. This field contains few other stars but the pair does look magnificent in binoculars or small telescopes. A wonderful visual treat.

Southern Astronomical Delights”
© (2012)
10 Mar 2009