SELECTED SOUTHERN DOUBLES and VARIABLES
R.A. 11 Hours

HJ 4432 (11212-6441) is a particularly bright double star in the very far western corner of Musca being some 1.6'S of the Crux and 18.4'E of the Carina borders. It can also be found some 1.3°NW from the planetary nebulae He2-68.
Discovered by John Herschel in 1836 and somehow missed by James Dunlop, these 5.7 and 6.8 mag. stars are separated by 2.4 arcsec along PA 310°. I first examined this pair in 10.5cm refractor in early 1981 and easily separated the duo at medium magnification. I would think that any aperture above 7.5cm should be able to split the two. I thought the primary was bluish and the secondary white, though on a second occasion in March 1985 I saw them as both white. Peter Williams comments on this pair in “Telescopic Targets” (Universe, 32, 7, July 1985) saying;

“Moving from IC 2948 [in Centaurus], almost 2.5° sp. is an attractive multiple star just within the bordering constellation of Musca. This pair, HJ 4432, is a close and uneven pair lying in a field of fain and scattered stars. A magnification of 100X sows this is a close but clearly separated pair in which the companion lies a little north of preceding. Both stars are white in colour.”

Of the twenty-six measures so far the 2.4 arcsec has not changed, but the P.A. has increased from 288° to 310°. The primary is listed as HIP 55596/ T8967:1170(2)/ SAO 251383/ PPM 358676, and the Hipparcos Catalogue gives the distance of 145pc or 470ly. from the parallax of π=6.87±0.59mas. At this distance the true separation is about 4.8 billion kilometres - approximately the distance between the Sun and Neptune. It is likely this pair is associated and by calculating using simple Keplerian motion, suggests the period is over 180 years. This pair will make an interesting object to observe during the 21st Century.

NZO 23 (11327-6552) is a reasonably bright pair requiring 15cm under steady conditions and high power, and is easily to resolve in 20cm. NZO 23 is a close 8.3'NE (PA 42.1°) of the planetary nebulae He2-68, and was discovered in 1914 at New Zealand’s National Observatory in Wellington. Presently the stated magnitudes of the blue and white pair in the WDS96 (Washington Double Star Catalogue) are 8.8 and 9.2, respectively. Visually, I though this to be about right. Separation is about 1 arcsec along PA 239° that was last measured in 1983. From the three measures so far acheived, the apperance has changed very little. NZO 23 lies in an interesting find. Within 2' is small circular telescopic asterism of eight or nine 14th magnitude stars that appears to the 1.5' NW. This little asterism is quite obvious on dark nights in 20cm and above.

HJ 4460 (11392-5744) is another pair, 1.7°SEE of the planetary nebula NGC 3198. It is brightish pair of 7.7 and 8.9 (7.2V and 8.2V) mags. separated by 8.6 arcsec at PA 177°. Little has changed in the positions since the first measures by H.C.Russell on the 9th June 1874 using the 7.25-inch Refractor at Sydney Observatory. So far the only spurious observation of the eleven known measures was made by Hargrave who measured 8.0 arcsec on the very same telescope on the 6th June 1879.
Russell described both stars as white, but I see them as bluish. Proper motion are likely too large a difference for this to be a real double, however, HJ 4460 lies in an elegant starry field and is worthy to glance. (Updated 08/09/03)

I 890 (11449-5528) lies in Centaurus and in the next field some 36'W of COO129 with I 891 some 2.6' NNE (PA 20°). I 890 is a 7.6 and 10.4 mag. pair separated by 2.1 arcsec along 301°. Since discovery the PA has decreased 9° and if this pair is associated, as the proper motions seem to show, then the orbit is likely to be prograde and about a thousand years long. This white A1V pair is easily split in 10.5cm.

I 891 (11450-5525) lies in some 36'W of COO129 along with another second fainter pair I 890 some 2.6' SSE (PA 200°). This 10.5 and 11.0 (11.25V and 12.43V) mag. pair is separated by 2.8 arcsec along 28°. Since discovery the PA has cahnged little but the separation has increased by +0.3 arcsec (1991) This pair is almost certainly associated. It is likely visible 10.5cm or 15cm with care, but did appeared quite faint in 20cm. This is an attractive field along with the second pair I 890.

COO 129 (11455-5530) appears in the eyepiece field some 14'NW from the open cluster NGC 3960 I saw the components colours as white and perhaps yellowish in 1981, for this 9.0 and 9.9 mag. pair whose separation is 2.4 arcsec along PA 79°. Both are listed as a single 8.3 mag. star in the SAO Catalogue Spectral type is A3m and the B-V colour index is 0.372.

COO 129 was discovered at the Cordoba Observatory in Peru in 1913 and little has changed. The WDS 2001 notes an increase of 1° and a decrease of 0.1 arcsec, but such changes are insufficiently accurate to offer any conclusions. If these stars are truly attached then the period must be certainly long. (Updated 08/09/03)

λ Mus / Lambda Muscae/ HJ 4471/ HIP 57363/ SAO251575/ HD102249 (11457-6644) is bright 3.63 mag star that is also a wide pair 3.3°NWW (PA 288°) of Epsilon Muscae or 5.3° NWW of Alpha Muscae. Alternatively, HJ 4471 can be also found 1.9°ESE of NGC 4071 along PA 285.9°. This pair is 3.6 and 12.8 mag. and is separated by 40.6 arcsec along PA 275°. I could easily see the companion in 20cm and estimated that perhaps 10.5cm should have no problems - though any 7.5cm might have problems with the Δm is 8.8.
Looking at the Hipparcos 1991 data, the distance of the bright star is 39.29±3.84pc. or 128.1±12.6ly. Parallax (π) of 2.545±0.540 mas. Furthermore the proper motion of the star is quite high in RA. (pmRA=-100.42 mas and pmDE=33.21 mas.) Interesingly this motion is roughly shared with both ε Mus and ε Cru. This maybe no coincidence! HJ 4471 is very likely a chance alignment, although this white pair has changed very little since discovery.

R179 (11460-5805) lies 1.1°SSW (PA 213°) of NGC 3918. Appearing in a moderately starry field, it shares its position with the triple HU 1485 and the pair JSP 499. (See Below) R177 was discovered by H.C. Russell from Sydney Observatory using 18cm (7.25-inch) Merz refractor (at 159x) on the 1871.369 Russell describes the equal 9th magnitude pair as "yellow", he measured the separation as 5.07 arcsec along PA 355.2° Of the nine separate occasions that the pair has since been measure little has changed in the separation, which remains as 5.1 arcsec. The current position angle is given as 176°, which is 180° from Russell's designated value. Usually the discoverer’s designation dictates the nomenclature but in this case it has been ignored. The 1937 discovery of the small Δm of only 0.1 magnitudes, which forced the PA to be changed by 180°. Stated magnitudes in the WDS2001 are 9.24 and 9.38, respectively.

My own observations in 1981 found both these stars as bluish-white, which matches well with the B2/3Vn spectral class. This is an interesting pair and worth searching for even in small apertures.

HU 1485 (11465-5802) is a triple star merely 4.5'NE (PA 44°) from R179. HU 1485 AC was the fist discovered by Hussey in 1895 and HU 1485 AB was later found by him in 1913 when he reinspected the field. It is surprising how Russell missed this system - especially during the time he was looking for faint triples in the 1880’s. The likely explanation is that Russell never returned to R179, and the 18cm (7.25-inch) Merz Refractor was too small to see HU 1485’s components.
HU 1485 AC system is the easiest to resolve and may be split in 15cm or possibly even 10.5cm. From the primary the companion is located some 7.9 arcsec along PA 276°. Colours are bluish and white. Measures suggest that the two stars are widening, changing between 7.0 and 7.8 since discovery some 110 years ago. (2001).

HU 1485 AB is separated by 2.9 arcsec along PA 320°. This close pair has a significant Δm of 4.25 mag. therefore challenging observers using less than 20cm. Easily seen in 30cm. Its position is about a third-the-way between the 'A' and 'C' stars whose angle is just slightly offset. I saw the primary as blue and the companion as whitish. Since discovery, little has changed in these two stars relative positions.

Observationally, this HU 1485 system is one of the only triples I know that appears as a line instead of usual three pinpoints under low magnification! It would be worthwhile trying to find the true threshold where all three components can be seen.

Magnitudes of the stars are; 'A' is 7.72 (7.7), 'B' is 11.97 (12.0) and 'C' is 10.57 (10.6). Both the earlier WDS1996 and WDS2001 show that all of these stars are brighter than initial estimates. Differences between these two values are extraordinarily large, +0.28, +0.53 and +0.93 mag., respectively. Furthermore, 'B' is 1.4 mag. fainter than 'C' - questioning Hussey’s designation. It is possible that 'B' or 'C' is variable, though no one (including the WDS) has suggested this possibility. Observers might like to look at this system from time to time to see if they can detect any differences between the three stars. True Gravitational connection to all three stars is still uncertain and perhaps another century from now when we find the nature of this system.

JSP 499 (11469-5807) is the third pair alongside R179 and HU 1485. This close pair lies some 7.3'ESE (PA 110°) from R179 or alternatively 6.8'SE (PA 148°) from HU 1485. Here there are two stars of 9.6 and 11.6 mag. separated by 19.2 arcsec. The brighter star is the pair JSP 499. Separated by merely 0.9 arc sec, this slightly unequal bright pair is roughly aligned north-south along PA 170°. Spliting this duo would likely be impossible with 20cm and maybe only just in 30cm. I saw the near merged pair as both yellow, though this was by no means certain regarding the companion star.

When discovered, the magnitudes were given as 10.1 and 10.8, but later photometric observations gave the more precise values of 10.19 and 10.66, reducing the Δm from 0.7 to 0.47. Since discovery by M.K. Jessep in 1929, little has changed in the position. If this is binary, we may ] have to wait sometime for any indication of motion.

TX Mus (11471-6524) is an RR Lyrae "AB" type variable some 7.5'SW further from B2730. This 12.4 magnitude star is positioned 3'N of the 9th mag. PPM 778644 / HD 102466 (11472-6527). Varying between 12.4 and 12.8 magnitude in 0.473226 days or 11h 21m 26.7s, whose 0.4 rise in brightness occurs in about 13.6 minutes. The most recent epoch is 19th April 1925 at 18h 30m UT (2424260.264), so predicting when it falls in brightness is almost anybody's guess. Visual observation could confirm a more up-to-date epoch, but this still requires observations. We know little else about this variable star.

BC Mus / GSC8981:2285 (11475-6443) is merely 1.6'N from the Centaurus / Musca border. This 12.1 mag semi-detached eclipsing binary can be seen is a moderate field, with the PNe He2-73 due south and at the bottom of the field. IC 2966 is on the eastern edge of the same field with BC Mus on the NW edge. (Actually 20'NE of IC 2966 or 26'NNW (PA 345°)) Alternatively, use the bluish 7.0 magnitude HIP 57451/ SAO 251582/ HD 102370/ BD -64 564/ PPM 358966 (11466-6446) some 6.8'NE (PA 70°) The target star is marked by the roughly 1.4' equilateral triangle of stars, whose apex points due south, with the blue-coloured star to the east being the variable.

BC Mus varies between 12.2p and 14.5:p over 3.511171 days, based at maxima on the 11th March 1927 (JDE 2424951.363), the ratio of the primary eclipse to the period is 12% over some 0.42134052 days. Seeing a deep 2.3 magnitude fall in brightness for an eclipsing binary is unusual, and to catch the magnitude drop of the eclipse the field would have to be inspected several times. Incidentally, northeast, by 10' to 15' from this triangle, is a small void almost empty of stars, while the encompassing fields are scattered with many stars below about 10th magnitude.

B 2730 (11478-6519) is the second but fainter pair placed in the same field and some 12.6'SSE of He2-73. Easily visible in dark skies using 7.5cm apertures, B2730 is a "new" double star that was first discovered by W.H. van den Bos but only measured as recently as 1987, presumable while they were measuring nearby COO 130. Separation was measured, also in 1987, as 6.4 arcsec along PA 104°, being 9.5 and 11.5 magnitude. I saw this pair coloured as bluish and colourless.

μ Mus / Mu Muscae HIP 58581/ SAO251597/ HD102584 / HR 4530 / EsB 334 (11482-6649) lies some 16' ESE of the pair of λ Musca. Although this star does not have any common name it should be perhaps be called “Mumus”, like the names given to the brightest stars in the constellation of Crux to the north. This orange 4.74 magnitude K4 III star shows a remarkable colour and spectra, which is confirmed with the B-V value of 1.522. Mu Musca's position is exactly 1.6°S of the planetary He2-73 - leaving yet another method to finding the PNe’s position. Appearing in the 19th Century “Epsin-Birmingham Catalogue of Red Stars” as ESB 344, and also appears in the updated catalogue produced by Brian Skiff “A Revised Catalogue of the Espin-Birmingham RedStars” (1998). Hipparcos measured the parallax of 7.55±0.52mas suggesting the distance is some 132pc or 432ly. This star has a moderate proper motion, being in the order of +30.77±0.45 in RA and -16.25±0.48 in Declination. These motions are quite larger than the PPM Star Catalogue - certainly an unusual discrepancy. Mu Muscae is travelling the same direction as the last proper motion star L145-141.

JSP 500 (11486-5807) was a pair I looked for after observing the previous pair JSP 499. This pair can be easily found as it is directly 13.2'E of it, but about one magnitude fainter. JSP 500 can be placed in the same field as the three pairs listed above, if JSP499 is placed about 5'W. This pair is easier to split than JSP 499 as the 10.5 and 11.4 components are separated by 1.6 arcsec along PA 188°. Although easily seen to be double under high power in 20cm, the 30cm certainly made it appear more attractive, with the colours in both apertures seen as white. Other than the small PA increased change of 2°, little has been seen to change, so any true association remains unknown.

HU 1487 (11509-5553) is another pair that lies in the eyepiece field of NGC 3960. Lying 13'S (PA 169°), the two near equal components are 9.5 and 9.9 magnitude, respectively, being separated by 0.9 arcsec along PA 238°. Visible in 20cm, and 15cm on good seeing nights, this yellow pair contrasts nicely against nearby COO 129. Since discovery by W.J. Hussey in 1913, the two stars have decreased by 0.4 arcsec(1991) in the last ninety-odd years, and it is likely these stars are gravitationally connected.

TZ Mus (11509-6508) is fainter than UU Muscae. Discovered before UU Mus, it lies 6.9'NW at PA 306° and varies between 11.16 and 12.12 in the period of 4.944885 days. Epoch 2424259.37. This yellow-orange star can be checked, because of the wide Pair 1 (11515-6504) to the NE of TZ Mus is a mere 5.3' away. This white 10.0 magnitude star is PPM 778689, and I estimated the magnitudes as 10 and 11.5, separated by c.30 arcsec at PA 20°. No one has listed this faint pair in any of the double star catalogues.

COO 130 / HIP57851 / SAO 251617 / HD103079 (11518-6512) lies in the same field as the PNe and appears as the single 4.89 magnitude star, and is plced useful for finding nearby planetary nebula He2-73. S.I. Bailey discovered this pair at the Cordova Observatory in 1894, during the required observations to produce the CD Star Catalogue beginning in the 1890's. It is really surprising that both John Herschel and H.C. Russell missed it in their double star surveys. However, it is possible that the star did appear single between 1835 and 1880. Else, the accounting for this discrepancy is hard. COO 130 is almost 20.4'E (PA 99°) of He2-73, and any low powered field marks three stars in a bent line towards the southeastern edge. These stars have respective magnitudes from south to north, of 7.5, 7.5 and 9.5, forming an odd-shaped triangle figure.

COO 130 pair is 5.2 and 7.4 magnitude, with the separation of 1.8 arcsec and PA of 159° as last measured in 1940. Resolution is possible in 15cm telescopes but this becomes much easier in 20cm. AOST2 claims this is “...just possible...” in 7.5cm, but my four different observations between 1978 and 1981 using the 7.5cm f/10 reflector and 10.8cm Refractor, clearly could not resolve the pair - even under good seeing. I saw the colours as bluish and white, or perhaps blue and white, which is about right when compared with the primary's B4V spectra. This is another classic example of bright prominent double stars that we often neglected likely just because it is not either one of the prominent Russell, Herschel or Dunlop pair. Also featured in AOST2 as #483, COO 130's connection is stated as;

“... the angle is slowly increasing but separation has not changed...Physical connection between the stars seems likely.”

HLD 114 (11551-5605) is 1.2°NE from NGC 3918, and is the "top star" of the three to find the PNe. These two yellow 7th mag stars (7.3/7.7) are separated by 3.8 arcsec at PA 169° Since the discovery by E.S. Holden in 1887, the pair has slowly widened, while the PA has decreased by some 40°. As yet it is uncertain that this pair is physically associated, but if so, it is likely a very long period.

I 892 (11552-5659) lays 22'NE of from the planetary nebula NGC 3918, being the closest star to the PNe of the three recommended earlier to find the target planetary. Discovered by Innes in 1911, the 5.7 and 11.0 stars are widely separated by 57 arcsec, these primary 11th mag star is again double, separated by a smaller 5.2 arcsec. Known as I 892b, it forms a direct line at PA 122° with the distant third component. Burnham’s states that the PA has slightly decrease since discovery, but the WDS 2001 suggests it has increased. The primary appears white in colour, while the others are too faint to tell. Since discovery, the I 892a pair has slowly increased at the rate of 1.1 arcsec per decade while the PA has changed very little. It is likely this is an optical triple.