Southern Doubles, Stars and Variables
10 Mar 2009
RA : 05h
Dec : -30° to -90°
Constellations : Cae, Col, Pic, Dor, Men, Oct.
Best Observed : Nov - Mar (Text Ordered by RA)
RA : 05h
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

η1 Pic / RST 120 Pic
η2 Pic
η Pic Pair "2"
RST 125 Pic
β Ori / Rigel / 19 Ori
Σ668 / STF 668 Ori

κ Col / Δ19? Col
η Ori / 28 Ori / DA5AB
η Ori / MCA 18 Aa
η Ori / H 67 Aa-C
θ Pic / Δ20 / I 345 BC Pic
Δ21 AD / HJ 3767 A-BC
/ RST 136 BC Pic
I 62 Pic
Δ22 Col
S Pic
T Pic
T Col
TZ Men

β Ori / Rigel
α Aur / Capella
η Ori / 28 Ori
β Pic / Beta Pictoris


None Listed
NGC 1803 Pic
ESO 203-19 / Fair 302 Pic
ESO 253-9 Gal Pic
ESO 306-4 Col
ESO 306-9 Col
MAC 0539-4209 Col
MAC 0531-4206 Col

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. 05 Hours

Eta (η1) Pic / RST 120 (05028-4909) is a bright yellow star some 33'NW (PA 320°) from η2 Pic (05050-4934). This star has a faint component of 5.1 and 13.0 magnitude that is separated by 10.6 arcsec along PA 198°. Since discovery in 1928 the PA has reduced by some 8° and the separation has slowly broadened. This is a difficult pair in small apertures because the brighter component literally swamps the light of its companion. The companion is visible in 30cm using the hexagonal diaphragm though it still requires good seeing. As time passes the pair is getting easier to see. Another star is found some 2.6'NE (PA 303°) and appears as a 10.6 magnitude yellow or yellowish star. This, however, should not be confused with RST 120. Few measures have been made of these two stars and their association is still uncertain. Using the Hipparcos data, the parallax is 38.19±0.51mas giving the distance as 26.18±0.35pc or 85.42±1.14 ly (±1.3%). Proper motions are pmRA -43.96±.49 arcsec per century and pmDec +27.18±0.52 arcsec per century. Spectral class is F2V- hotter than the Sun but still a run-of-the-mill main sequence star.

Eta (η2) Pic (05050-4934) is one of my own pair that missed the Dunlops wide-pair catch net. The field here is just wonderful which becomes even more appealing, as the galaxy NGC 1803 (05054-4934) is just 4.5'E (PA 85°) of the main star. The primary is HIP 23649 / SAO 217164 / PPM 309337, and appears as a rich orange K5 star, and seems coloured much more strongly than nearby η1 Pic. The B-V is 1.484, and the later catalogues than the PPM gives the spectral class of M2 III. It is also is the suspected variable NSV1827 / HR 1663, whose variations are 5.0V to 5.1V magnitude in an unknown period. Hipparcos gives the parallax as 6.88±0.50mas, giving the distance of 145±11pc or 474±35ly. Proper motion is 68.74 arcsec per century in RA and -3.03 arcsec per century.

A 8.4 magnitude white A5 companion star is 5.7' away (WSW - PA 256°) making a startling contrast. This is SAO 217159 / PPM 309230. A third 9.8 magnitude yellow star lies another 3.5'S. This is PPM 309319. Another faint 13th magnitude "D" star appears between "B" and "C", roughly 1.5'S (90 arcsec) of "B". It seems that the "A" star is not associated with the "B" and "C" stars. "B" and "C" show similar motions through space.

NGC 1803 (05054-4934) is the 13.4B magnitude barred spiral galaxy appears as a small and slightly elongated 0.5' smudge. It is catalogued in the RC3 as 1.2'x0.7' of class .SBS4* inclined at PA 62°. The radial velocity is +4 127kms-1, giving the distance as about 63.5Mpc. Another 2.2'SE is the 14.0p magnitude companion galaxy, which is likely associated with NGC 1803, has the radial velocity is +4 389kms-1, giving the distance as 67.5Mpc. This is ESO 203-19 / Fair 302 (05056-4936) being visible in 20cm or 25cm under dark skies. This is a bit more difficult to see because of the nearby 5th magnitude η2 Pic. Using the occultation bar in the 20cm improves its appearance. ESO 203-19 is classed as an LXR+ type galaxy in the RC3.

Eta Pictoris Pair 2 / PPM309302 and T8081:1425:1 (05033-4930) lies 17.4'W (PA 268.6°) is another orange and yellowish wide pair some 1.4' apart at PA 210°. Magnitudes are 7.2 and 10.7, and this pair forms a flat triangle, equidistant from η1 and η2 Pic. This pair forms the top of a gaggle of ten 8th to 12th magnitude stars some 13' long in a north-south direction. Some 3.3'NE is a tiny near edge-on galaxy that can be seen in 25cm with care. At 15.0 magnitude is the spiral galaxy is ESO 203-17 which is catalogued as 0.9′;×0.3′, that I estimated was more like 0.5'×0.1' or 30×6 arcsec.

NOTE: To see all these objects around the Eta Pictoris stars field use the centre coordinates as (05039-4923) in an 0.65° eyepiece field.

RST 125 (05107-4827) is some 3.6′NW (PA 320°) of S Pic. This white pair whose 7.7 and 11.7 magnitude components are separated by 2.6 arcsec along PA 193°. Little has changed except for the separation increase by 0.3 arcsec since Rossiter discovery the duo in 1928. Spectrum of the primary is A4m.

S Pic (05110-4830) is a Mira variable that is placed some 1.5°ENE (PA 65°) of 5.4 magnitude η1 Pic / Eta (1) Pictoris. This variable has a period of 428.0 days and fluctuates between 6.5 and 14.0 magnitude. The shape of the light-curve find that the rise in brightness occurs in 36% of the period calculating the rise in brightness is over about 154 days. Spectra class for this deep red star is M6.5e-M8III-II.e. The RASNZ Variable Chart number is 345 and S Pic is designated in the variable star scheme as S Pic 0508-48.

Beta (β) Orionis / Rigel / SAO 131907 / 19 Orionis / Σ668AB / STF668AB / ADS3823 (05145-0812) appears opposite to the Orions red giant Betelgeuse in the sky and whose name is translated from the Arabic as literally Orions Left Foot. Its vivid blue, with the B-V =-0.03 a B8 Iae: spectral class, suggests a blue supergiant with the surface temperature around 10 700K and the diameter of some 116 million kilometres. From evolution theory rather than using the stellar parallax, distance has been estimated to be about 250pc. or 860ly. Hipparcos found the parallax of 4.22±0.81mas equal to 237±40pc or 773±130ly., giving just marginal improvements to this value. The determined absolute magnitude (Mv) is around -7.0±0.2 — some sixty thousand times more luminous than the Sun. If Rigel were placed at 32.6 light years from us, its brightness would easily rival either the four or five-day old Moon at (-7 magnitude), but would still appear as just a tiny stellar point. In the overall ranking, this puts Rigel near the top of all the stars in our Galaxy.

F.G.W. Struve discovered in 1822 as a visual double. The brightness is +0.12 and 10.4 magnitude companion whose present separation is 9.5 arcsec along PA 204° (2002). The separation has not really changed in the years that have followed, however, the PA has increase marginally by some 5°.

In the 1880's using the 36-inch Refractor at Lick Observatory, both Burnham and Sadler suspected that the companion sometimes appeared elongated, stating that; …perhaps a very rapid binary, that is never wider than 0.2 arcsec (This shows the amazing visual acuity of these 19th Century observers, as 0.2 arcsec is far below the resolution limit due to atmospheric seeing.)

Later in 1908, J.S. Plaskett (AJ., 28, 266 (1909)) found the companion (Bb) to be a spectroscopic binary, making Rigel a triple star. Yet the data was so poor that details of the orbital data were rejected for some time because no one could verify its spectroscopic nature - likely because the secondary's light was swamped by the intense brightness of Rigel itself. (Refer Burnhams Celestial Handbook Vol.2 pg.1300) In late-1939, using more detailed observations of the fluctuating spectral lines, the period was finally tied down to 9.86 days during the beginning of 1940. The separation between the pair varies between 3.4 million and 4.3 million kilometres in its orbit, though the minimum masses of 0.11 and 0.08 seem far too small for their spectral type, unless there has been significant mass loss from the system in the past. By mass the star weighs about 8.4% of its primary. If Rigel B is about 1.5M⊚ then the companion is a tiny 0.13M⊚

Rigel A is also thought to be the new suspected variable - NSV 1882 or ZI 362, changing between 0.03 and 0.30 magnitude over an unknown period. The type of variable is also unknown.

T Pic (05151-4655) is another Mira variable located 2.6°W (PA 272°) from Δ21 or 3.0°NE from 5.4 magnitude η Pic / Eta (1) Pictoris. Variation is brightness of 7.9 to 14.4 over the average period of 200.58 days. The cycle fluctuated rough equally on the rise and fall in brightness with the various maximum and minima have differing magnitudes. Spectrum displayed is M6III.e. Appearing in the RASNZ Variable Chart number is 344. T Pic is designated in the variable star scheme as T Pic 0612-47.

Alpha (α) Aurigae / Capella / 13 Aur / ST 3 (05167+4600) is the sign of the beginning of the southern summer and the Christian festive season of Christmas, which is marked by the early-evening appearance of the bright first-magnitude deep yellow star Capella. This is the brightest star of the northern constellation of Auriga the Charioteer, whose name is though to be Assyrian in origin. Some consider have considered it is was likely known as this from even earlier times. One of the ancient Greeks myths say Auriga is the mythological son of Vulcan, Erechthonis. Legend holds that Erechthonis was born with physical deformities, and because of the likely disapproval of the Gods, his mother Athene hid the boy away from their eyes. Eventually he was adopted and raised by Amalthea. (A name usually associated with the fifth moon of Jupiter.) Although disabled, his mind proved to be both inventive and clever, a trait he inherited from his famous father. On his coming of age, and cured from his affliction by a drop of blood from the dreadful Medusa, he became the King of all Attica whose throne was held in Athens. One of his main inventions was creating the four horse chariot and showing the inhabitants how to forge and use metallic silver. Zeus was so impressed with this practical invention, he placed Erechthonis among the stars. [This story comes from the poem written in Hyginus Poetic Astronomy (ii.13.)] Capellas name is thought to come from Roman times, meaning The Little She-Goat - literally the Nanny Goat. Throughout many cultures this star has held several dozen names - but has always been related to goats or chariots.

Capella is the most northern of the first magnitude stars (0.09 mag.) whose rank among the distant stars is sixth brightest. Observers from Southern and Central New South Wales see this star culminating at midnight on the 8th December, and at 9pm on the 23rd January. From Sydneys latitude, the star rises a mere 20°, on any given night will remain 3 hours and 9 minutes above the horizon and this assumes a perfectly flat site! As Capella remains close to the horizon for southern observers, it is liable to be more prone to suffer from the effects of seeing. More often than not, the resultant very poor conditions, can make the star seem to spectrally dance in a rapidly changing multitude of colours. From Tasmania or Southern New Zealand, Capella will rise merely 5° from the horizon.

The true distance of the star is estimated to be 45 ly. away from us, thought the latest Hipparcos data suggest it is a bit closer at 42.2ly. Capella is known to be moving away from us at about 30kms-1 - equivalent to 946 million kilometres each year.

Investigations have shown this is a yellow spectral G6 type star is a spectroscopic binary. Binaries of this type are only different from the so-called telescopic visual binaries, in that they generally cannot be resolved by naked eye - and only revealed by the duplication of their spectral lines. Almost exactly ninety nine years ago, W.W. Campbell and H.F. Newall in October and November 1899, independently discovered the duplicity. Examining the spectral lines quickly found the periods of the two stars was 104 days 29 minutes, which is inclined to the line of sight at 27° to the equatorial plane. In terms of velocity, both stars change their speeds by about ±26kms-1, close to the observed orbital velocity of the planet Venus around the Sun. Capella A and B were the first stars resolved by the observational technique known as interferometry by J. Anderson in 1920, who found near perfect circular orbits. Combining these results from the orbital elements obtained by spectroscopy, allowed astronomers to determine the physical natures of the component stars. Both stars are giants, having masses of 4.2 M⊚ and 3.3 M⊚ suns, respectively, and are separate in real terms by some 126 million kilometres - and in Solar System terms, about half way between the orbits of Earth and Venus. The apparent magnitude of the components is c.0.7 and 1.2, combining to the 0.06 magnitude as stated earlier. In solar diameters, both are about three times bigger than our own Sun.

Orbiting the bright Capella is the faint red dwarf pair ST 3 (0517.7+4551), which was discovered in 1935 by C. Stearns. This 10.5 and 13.0 magnitude pair is located some 13.5'SE of Capella, and since discovery, the separation has increased from 1.8 to about 4.1 arcsec, and the current motion is prograde, with a current PA of c.172°. In real terms, these stars are 0.02 ly (1 100 AU or 165 billion kilometres) from Capella AB. This double is difficult because of the overwhelming brightness of Capella. The pair is best made using an occultation bar to block out Capella, but 20cm or 25cm is required to see them.

Δ19 / κ Col / Kappa Columbae (05178-3326) is not listed as a pair in most double star catalogues. Dunlop gives the positions as RA (1827): 05h 10m 17s DEC: -33° 44', which precesses to 05h 16m 38s -33° 33'. The only details we are give is that this pairs angular alignment is 48° 12' sp - equivalent to PA 270 - 40.2 or 229.8°, and that the duo is 7,7. Unfortunately, Kappa Col appears at position (06165-3508) and is significantly different from Dunlop's position. If we assume Dunlop got the coordinate as 06h 10m 17s -33° 44', we get the precessed coordinates as (06165-3347) for Kappa Columba - still 1.5° too far north. Secondly the 7th and 7th magnitudes do not match the total 4.4 magnitude for Kappa Columba.

I think Dunlop used Kappa Col to find the position of his pair and has wrongly given the name of the pair as Kappa Col - and for us he disappointingly gives us no further clues. Nearest to the coordinates is yellow 6.95 magnitude HIP 24577 / PPM195705 / SAO195705 (05164-3332), which is some 3.0'W of this position. No other star of this brightness is near here, but there is a wide pair some 20.5'ENE (PA 73°) from this place. These are Δ19? / PPM 281284 and PPM 281292 (05178-3326) - separated by 4.6' at PA 277° and listed as 8.1v and 8.6v (PPM) - 7.87V and 8.61V magnitude (Tycho). Both these stars I saw as blue and white with about 0.5 magnitude difference.

Which stars are now the double remains uncertain, though there is an outside chance that the wide pair mentioned above might be the culprit as there are no other possibilities with 2°. However, if they are attached, the separation of the two, assuming the Tychos catalogue parallax is 6.61±5.5mas, giving the distance as 158pc or 517ly, then the rough true separation is 0.2pc., 0.7l.y or 44 000 A.U. Chandrasekar, S. (AJ, 99, 54, (1944)) calculated that the gravitational stable limit of pairs to be less than about 40 000AU, so these two stars are near the very limits of any possible binary star. If we examine the catalogue limits where the maximum separation is A and is the mean visual magnitude (mv). Then the largest acceptable distance apart is;

A = 10 ( 2.8 - 0.2 ⊚ mv)

In this case, the limit of interest for the pair stops at separations larger than about 14.5 arcsec. Consequently these stars remain astronomically uninteresting. Overall, this is a mysteriously missing pair that is certainly not the claimed κ Columbae!

T Col / HIP 24824 (05193-3342) is a variable star 1.2°N of 4.8 magnitude Omicron (ο) Columbae or alternatively 35'ESE of my suspected pair for Δ19? / PPM 281284 and PPM 281292 (05178-3326) T Col is a red variable that Dunlop also does not note in his observations of Δ19, although it makes a good marker as an identifier for this pair. T Col itself has a magnitude range of 6.6p to 12.7p magnitude over the period of 225.84 days. The shape of the light-curve is almost sinusoidal and is positively a Mira-type variable. The spectrum has been also observed to change between M3e and M6e - the latter being at the time of minima. Hipparcos gives the parallax as 0.52 mas suggesting the distance is too uncertain to predict. This is a common fault with all red variables double enhanced with uncertain luminosities. To me, T Col seems orange-red than the familiar red to deep red colour.

ARTICLE : The Multiple System of Eta Orionis

Eta (η) Ori / 28 Ori / DA5 AaB - MCA 18 Aa - H 67 AaC / HIP 25281 (05245-0224) is the main visual "AaB" pair that was discovered by W.R.Dawes in 1848. Now labelled as DA 5, this pair is one of my favourite double stars, the AB pair can be easily found as it lies on the lip of the popular southern asterism known as the Saucepan, appearing to opposite to Orions sword. Rev T.W.Webb in the classic book Celestial Objects for Common Telescopes said this was an Excellent test for 14 cm refractor he was using when the seapation was 1.2 arcsec. This 3.56 and 4.87 magnitude pair today is visible under high power (and good seeing) in 10.5cm but is much easier in 20cm. Since the first measures were made, the separation has slowly increased from 0.9 to 1.7 arcsec, while the PA has decreased by some 10° (87° to 78°)(2002). I saw the colours as bluish and bluish on 30th December 1979 and then bluish and bluish-grey on the 7th February 1983 - reflect nicely the B1V+B2e spectral type.

Four stars, possibly five, are associated with this system, making a good classical archetypal example of a hierarchical multiple. Eta Orionis stands out from others multiples, because each component makes a visual binary, a spectroscopic binary and one eclipsing binary. All the stars and have very similar in spectral class, ranging between B1 and B3, and masses between 1.0⊚ and 1.3 M⊚.

Some eighty multiple systems are known to contain eclipsing binaries, but only a handful has this type of hierarchical configuration. With multiples, the property of the hierarchy is based on the orbital arrangements of the individual gravitational pairs. First theorised by Evans in 1968, these arrangements can be likened to a childs mobile, where each of the varying masses throughout the entire system can be balanced. Each level of an existing pair is measured downwards, so the widest binary is Level 1, a second sub-binary is Level 2, etc.

Eta Ori hierarchical

Figure 1 - Mobile Diagram of Eta Orionis; shows the configuration of likely Eta Orionis - so this system is classed as a Level 3 multiple. To paint the mental picture of the separation within each levels; if the eclipsing binary on Level 3 was 1cm apart, then the spectroscopic component on Level 2 would orbit 42cm from the combined masses. Moving up to the visual pair on Level 1, the three sub-components would be separated by about 100cm.

η Ori AB

Telescopically, and using the meagre data available, the AB pairs period is about 1470 years, though the more recent analysis by Chambliss (PASP, 184, 663-677 (1992)) gives 2300 years. A rough computation, using the combined masses of the trio A component, finds 23.05 M⊚, with the inaccurate B mass of 9 M⊚, computed by the magnitude difference. Photometric observation shows variations between 3.14 and 3.35 magnitudes, which is likely caused by the fluctuating light of the eclipsing binary. According to this data, the AB system has a separation axis of 1.65 arcsec, suggesting that the pair is near its greatest true separation - its apastron. Calculations suggest the mean true separation of about 410 A.U. or 61.5 billion km. Hipparcos has produced the parallax for both these stars of 3.62±0.88 arcsec, giving the distance of c.276±54 pc. or 890±165 ly. This value is give further credence from the derived dynamical parallax of 4.0 mas discovered in 1952.

η Ori Aa

Unlike most systems, the A is again another single line spectroscopic binary with an estimated period of 9.22 years, while the WDS01 states in 9.51 years. In 1981, speckle interferometry first resolved these stars, finding separations ranging between c.0.16 and 0.05 arcsec. From the orbital data, deduced by McAlister (1976), the total mass subdivides into 21.8 solar masses for Ab and a minimum mass of 1.25 M⊚ for the "Ac" components. This apparent orbit is highly elliptical, with a mean orbital velocity of 19.5kms-1. Speckle interferometry observations in November 1985 revealed the true orientation of the orbits, but unlike most spectroscopic binaries, here the orbital data is deemed fairly accurate. Mean separation of this binary pair is 1.88 billion kilometres, but due to the eccentricity of the orbit, this may vary between 2.7 and 1.0 billion kilometres - roughly the size of Uranuss orbit down too just a tad larger of Jupiters one.

η Ori Aab

Another level down shows the A component splitting again into another eclipsing / spectroscopic binary that is listed as the Aab system. Details of the comparatively minuscular orbit were first obtained by Adams and Stanford in 1903, but later revised by the same team in 1928. This eclipsing binary during the primary eclipse is 3.31 and 3.60. From the orbital elements, the period is 7 days 23h 44.5m (7.989268 days) (11th Jan 1902), though later data suggest the period is 7 minutes less (7.9841 days). Using the orbital data from the 8th Catalogue of Spectroscopic Binaries. (A.H.Batten et al. (1989)), the component's masses are 11.2 M⊚ and 10.6 M⊚, respectively. Throughout the near circular orbit, the true separation is about 0.218 AU or 32.7±2.0 million kilometres, though earlier values gave a separation of 28 million kilometres or 49.1 R⊚. Both stars move with an orbital velocity of 34.6kms-1. (See Eta Ori : Figure 2.)

Figure 2 - The Eclipsing Binary η Ori Aab
Later observations place the upper limit of the combined mass (ΣM⊚) of 24.89 M⊚, giving the upper individual masses of 12.76 M⊚ and 12.13 M⊚. Kaukarkin (1974) was first to state that this is a detached Beta Lyrae type eclipsing binary.

Eta Ori AaB Fig 1

Compared to another nearby eclipsing binary, Delta (δ) Orionis, both stars are intermediately massive and luminous, with the respective diameters of the two stars being 15.68 R⊚ and 20.52 R⊚, respectively. Both throughout the orbit range between 20.6 and 27.1 million kilometres, while the measured relative solar luminosities are 6853 L⊚ and 5826 L⊚ (Roche Lobes are presently filled to 42% and 52%.) Temperatures are 18 870K and 15 860K, reflected by the given B0.5VEA+B3V spectral types. The stellar sizes and the light curve is shown in Eta Ori Aab : Figure 2. Glancing at the properties of this system, you might notice that the most massive star happens to be the smallest, seemingly thumbing its nose in complete defiance of modern stellar evolution theory. Algols Paradox seems to be needed to be apply here, suggesting that some mass transfer has occurred in the past between the eclipsing binary's components - but additional observations are required to confirm this. However if this were so, then how these stars now appear in this configuration is a bit of a mystery! The secondary ("Ab") of the eclipsing binary also shows evidence of being a Beta Cephei variable of an uncertain period - as found by examining the eclipsing binary's secondary light curve. (Beta Centauri and Beta Orionis are other examples of Beta Cepheids - all brighter, incidentally, than its namesake Beta Cepheid!) Waelkens and Lampens (1988) suspect that this data is in error, and that the more distant Eta Ori B is the star producing the slight variations.

η Ori AB-C

A remote fifth component star, component C was discovered by William Herschel who catalogue the AC pair H VI 67, but it was not properly measured until 1904. The physical association of this star to η Ori was first suspected by the double star observer Robert Aitken in the 1928. Known as BD-02135C, this 9.4 magnitude star lies 116.8 arcsec NE of Eta Ori AB itself at PA of 53°. (At the exact position RA 05h 34m 34.4s -02° 22′ 34″) and I thought the brightness of this star to be about one magnitude fainter than this. Little is known about this star because of its proximity to the brighter pair. It can easily be seen in 7.5cm., but if you want see C in a star atlas, it doesnt appear on any of them, including Uranometria 2000.0, the Millennium Star Atlas, or even Megastar 4.0. Both the modern Hipparcos and Tycho catalogues dont list it, nor does it appear in the PPM Catalogue. Looking at the near nonexistent proper motion data of this star, it is likely just a optical foreground or background star.

Note : A main description of Eta Orionis also appears in Burnhams Celestial Handbook Vol.2, p.1306) — but this description is so out of data, that most of the information can now be veiwed as historical.

Δ20 / I 345 AB-C / θ Pic / Theta Pictoris (05248-5219) is a triple with in a fairly poor star field that can be found some 9.9°W of Canopus. This wide bright yellowish visual pair was discovered and first measured by Dunlop in 1826.

θ Pictoris.

AR 5h 20m; Decl. 55° 28′S
5.6 and 6.7m : L. yellow; S bluish white
Pos.14° 14′ np.; 4 obs; Diff.= 4°,96
AR = 04S,19; 5 obs; Diff.= 0S,25
Decl.= 09″,055; 11 obs; Diff.= 1″,50
Dist.= 38″,516; 5 obs; Diff.= 0″,95

Early History of Δ20

Dunlop found the separation as 38.52 arcsec along position angle 14° 04'np, equivalent to the PA of 284.1°. His individual observations were presented in the Mem. Astr. Soc. London; 3, p.257-275 (1829) p.265 were as follows;

Dunlops position translates this as to 38.516 arcsec along PA 360-14.23° or 345.77° (345.8°) John Herschel some ten years later also found similar results.

Recent History of Δ20

Listed today as 20 AC, and lovely in the smallest of telescopes, this near equal 6.9v and 7.2v ("AB" 6.26 and "C" 6.90V) magnitude pair is worth searching in your observation program. Giving the present relative positions as 288° and 38.1 arcsec, little has changed except fora small +4° increase in PA and the reduction of separation by about 0.4 arcsec. Spectral types are A0V and A2V, but like β² Tucs companion, both stars visually appear more yellow than their given types suggest.

Similar proper motions of A: pmRA -6 and pmDec. -30 and B: pmRA: -007 and pmDec. -29 (in mas.yr.-1) suggest these two are very likely associated. Based on the Hipparcos distance of 155±13.2pc. or 507.2±42.9 ly. from the mean parallax of 6.43±0.54 mas gives the true separation as c.5 400 A.U. Absolute magnitudes (Mv) are 0.94 and 1.24, respectively, calculating a sum mass (ΣM⊚) of 5.0 and individual masses of AB of 2.6 M⊚ and C of 2.4 M⊚.

I 345 AB-C is the very close inner AB pair which was discovered by Innes in 1900. This is a difficult pair to split and no doubt part of this entire system. Of AB=6.3v (A=6.9v / B=7.2v) and C=6.8v magnitude, the two stars are presently separated by 0.1 arcsec along PA c.30° (2002) and remains presently invisible to all amateur telescopes. Motion of I 345 is retrograde with the position angle decreasing from 197° to 24° (PA of -173°) (WDS03) in the last hundred-odd years (2004).

Hartung says he saw the duo in 1960 with 30cm suggesting the companion was south preceding (sp) -180°-270°, but surely if the orbit is truly retrograde, this should have been south-following (sf). In AOST1, Hartung says the two stars had widening, but in the latter half of the last century, the stars have significantly reduced. Using the data in the IDS (1976) the 1960 measure was 0.2 arcsec and 152°. Based on this, David Frew in AOST2 says ;

...but the separation was only 0.2″ at the time, so Hartung could not have resolved them with his telescope.

Based on this evidence it is hard to understand what Hartung is saying. Could it be possible he is observing the wrong star? This error is very unusual for E.J. Hartung because the accuracy of his descriptions is almost unquestionable - hence the extraordinary value of the Astronomical Objects for Southern Telescopes Handbook for observers.

AOST2 described the observations made in 1989.9 of 0.13 arcsec at PA 56°, and the position angle today is certainly smaller than this. Extrapolating the available data (2003), the PA might even now be in the 4th quadrant (>360°) and about the same separation as in 1990.

Spectral class of the companion is likely early-A. Using the mean distance calculated for 20 for I 34AB, the minimum period from Innes 0.5 arcsec is about 309 years from a true separation of 77AU. Individual masses for AB of 2.6 M⊚ breakdown to 1.4⊚ and 1.2 M⊚, which incidentally acts as a point source to the far more distant C component.

No doubt this entire system will be an interesting system to watch in the coming decades. This is a truly classical triple. [Version 2 : 21/10/03]

Δ21 AD / HJ 3767 A-BC / RST 136 BC (05302-4705) is an extremely wide pair in a multiple system in a faint but charming field in mid-northern Pictor, and the system can be found 4.8°NW (PA 320°) from 3.9 magnitude Beta (β) Pictoris. Dunlop lists this star as 25 Pictoris. Δ21 AD is easily visible and divided in binoculars, whose 5.5 and 6.6 magnitude components are separated by 197.2 arcsec (3.5') along an east-west PA of 271°. These yellow and light-yellow stars really fall outside the criteria of a visual double star and would normally be dropped from any double star catalogue. Δ21 is certainly an optical pair as the proper motion in declination is seventeen (17) times larger.

HJ 3767 A-BC : This pair was somehow completely missed by Dunlop. Herschel discovered this 11.0 magnitude fainter and moderately wide component separated by 26.4 arcsec in 1835. Today little has changed in separation of 25.9 arcsec though the position angle has changed from 223° to 256° as measured in 1933. It seems that Herschel's PA position is wrong, as visually the position was close to the 256° PA. Both of these components are visible in 10.5cm.

RST 136 BC : Closer inspection of the B component find it is again double that was discovered by R.A. Rossiter in 1930. These two quite faint 11.7 and 12.7 magnitudes stars are presently 0.8 arcsec along PA 85°, and I thought that these were certainly wider than this in 1993 and perhaps as wide as 1.0 arcsec. This was fairly easy in the 20cm at 333x though the faintness of the components made this more complicated in the moderate seeing. It is quite likely RST 136 is physically attached.

Note: The southern and western fields from Δ21 contains seven galaxy clusters and a dozen very faint galaxies. Those with large apertures (>40 cm) may like to inspect the field to see if they can see any of the these.

ESO 253-9 / PGC 17377 (05309-4657) lies 11'NE from Δ21. This 15.7 magnitude galaxy was not seen in the 20cm. I suspect 30cm could see this 0.8'x0.6' spiral galaxy as a faint oval smudge in the field.

I 62 (05305-4712) lies some 8.5' (PA 155°) from Δ21. This near equal pair of 8.3 and 8.9 magnitude is separated by a close 0.8 arcsec along PA 178°. I had some trouble separating the two stars in moderate seeing using 20cm but could detect only some elongation in the Airy disks using 200x. At 333x, in moments of good seeing, I could clearly see the two components. The most recent version of the WDS03 gives the magnitudes as 8.79V and 9.30V, which in my opinion does not match the visual appearance of 8.3v and 8.9v at all. The difference here does appear a little two large and almost half a magnitude fainter for both components. The primary is a nice light yellow but I could not see any in the secondary. Little has changed in the positions since R.T.A. Innes discovered the pair in 1896 except for a slight decrease from 1.0 to 0.8 arcsec in separation. True attached of these two stars is presently uncertain but they both do have similar proper motions of -21 and +25 arcsec per century. To the east by 1.5' are two stars of 12th and 14th magnitude separated by about 22 arcsec in an SSE direction. This properly identifies the field.

TZ Men (05302-8447) is an eclipsing binary EA system. This far southern system is located right on the mutual border of the constellaions of Mensa and Octans. TZ Men has a is rather solitary star field, and it shares an area within about 5° of sky with only fainter than 6th magnitude stars. Also nearby is the rather unexciting globular cluster NGC 1841, some 1.3°E of TZ Muss position.

Magnitude variations are between 6.23v and 6.9v over a 8.569 days period. Very little observationally work has been done with this star in recent years and this is probably because of its far southern declination. Times predicting for primary eclipse is certainly with significant errors.

Total mass of this system totals 6.5 ΣM⊚, with the primary at 3.6 M⊚ and the secondary at 2.9 M⊚. Relative luminosities are equally about fifty times that of the Sun. Both stars are separated by 22 million kilometres, each with respective diameters of about 3.6 and 2.7 million kilometres. Spectrally, the first surveys listed this star as B9.5 IV-V, as stated in Sky Catalogue 2000.0 but the more recent data indicates the spectral classes of A1 III and B9 V. The computed temperatures are 9 370K and 10 850K, unusual as the primary is cooler, but this is not too unique among eclipsing binaries.

Note: NGC 1841 appears as a nebulous glow of 12.2 magnitude that is unresolvable in telescopes below 30cm. They do not list NGC 1841 as mentioned above in Sky Catalogue 2000.0, but is listed in the companion Sky Atlas. Also note that the other GSC in Mensa, projected on to the Large Magellanic Cloud (LMC) is NGC 2121. This is the reverse problem of NGC 1841. They list it in the Catalogue, but not on the Sky Atlas!

Δ22 (05312-4219) is a nice pair found in southern Columba and lies 35′N from the Pictor border. The general wide field contains about ten stars of 9th, 10th and 11th magnitude stars within a circlet of stars some 20' across. Δ22 is the brightest and eastern most star of this stellar circlet. Dunlop gives this star as Δ26 Pictoris, but in his times the boundaries between the constellations were not properly organised by right ascension and declination but were often by the selection of the observer themselves. This is an easy white and yellowish pair even in 7.5cm though identifying the general field might be a bit tough from the lack of any bright stars. It is best to use the 3.9 mag. orange star Eta (η) Col and move the telescope 5.2° due west. Δ22 is listed as 6.7 and 7.5 magnitude with the two stars are separated by 7.4 arcsec along PA 169°. Proper motions suggest this pair is an optical one.

The general star field also contains the 9.7 mag reddish-orange star, HIP 25775 / PPM 309772, some 26' (PA 204°) of spectrum M0V. HIP 25775 has the parallax 51.56±3.73 and shows significant proper motion. Distance is 19.39±1.41pc. (63.3±4.6 ly.)

Galaxies in the Field of Δ22

Four faint galaxies appear in the same field as the pair. Both ESO 306-4 (05292-4213) and ESO 306-9 (05317-4210) can be seen in dark skies with 20cm, while the fainter companions require at least 30cm and possibly even 40cm. ESO 306-9 is 10' PA33° from Δ22.

Catalogue Name Name RA (2000)
hh mm ss.s
DEC (2000)
o mm ss
Mag. Size P.A. Type
ESO 306-4 VV 599 PGC 17343 05 29 13.4 -42 12 37 14.7p 1.3'x 0.6' 018 E+4 pec
ESO 306-9 Fair 1135 PGC 17396 05 31 41.0 -42 09 51 14.0p 1.3'x 1.1' 145 (R')SA(r)ab pec.
MAC 0529-4209 - - 05 29 09.8 -42 09 45 16 0.4'x 0.2' 068 ?
MAC 0531-4206 - - 05 31 22.2 -42 06 32 15 0.4'x 0.3' 054 ?

β Pic / Beta Pictoris (05473-5104) is a single star which was the first star to show the direct evidence of the possibility of other solar systems outside our own. It was revealed using both CCD-imaging and infra-red observations as first found by astronomers in 1986 from the Las Campanas Observatory in Chile. This proved that the star was surround, like the 1st-magnitude star Vega (Alpha Lyrae), by a cool disk of grainy material some 25 arcsec either side of β Pic that corresponds to some 800 to 1000 AU across. This is about sixteen to twenty times the size of our own planetary system of Sol.

β Pic itself lies 6°SWW of Canopus in a fairly uninteresting field. Listed as HIP 27321 / SAO 234134 / PPM 334622 / HD 39060 at the position of RA: 05h 47m 17.1s and Dec: -51° 04⁐ 00″ this 3.85V magnitude star is an slightly under-luminous A3V spectral class star displaying a colour index (B-V) of +0.171. Using the parallax from Hipparcos of 51.87±0.51gives the distance as 19.28±0.20 pc. or 62.9±0.64 ly. Beta Pictoris is moving at 82mas per year along PA 19°. Radial velocity is +28kms-1 away from us. Spectral class is A5V dwarf and it is a known shell star.

Southern Astronomical Delights”
© (2009)
10 Mar 2009