Southern Doubles, Stars and Variables
10 Mar 2009
RA : 10h
Dec : -30° to -90°
Constellations : Ant, Vel, Car, Oct.
Best Observed : Jan - Jun (Text Ordered by RA)
RA : 10h
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

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. 10 Hours

S Car (10094-6133) is a red Mira-type variable star that is likely one of the first variables stars that southern amateurs select, when embarking on observations of variables. It lies 1.1°N of IC 2553, or conversely, using S Carinae also finds the planetary nebula. Variations follow regular pulsations of about 149.49 days, often somewhere between 4.5 and 9.9 mags. During maximum the spectra class displayed is M4 that decreases to M6 towards the minima. Also throughout the cycle some emission lines are more prominent in the spectra.

HJ 4306 (10191-6440) is a bright and fairly equal 6.5 mag pair that Sir John Herschel discovered and measured in 1836. In a wonderful field, HJ is visible in 10.5cm, and easily through 15cm. To my eyes both stars are bluish-white. (A0V/ AIV) Burnham incorrectly gives both stars as 7.0 magniude. H.C. Russell on the 24th March 1873 saw both stars as yellow. He described it as Very beautiful, well defined. In the last 166-odd years (2003), the separation has increased from 2 to 2.5 arcsec and the PA of 139° has decreased to 134°. From the similar common proper motions, and the closeness of the two stars, it is likely they are physically associated. This pair will be worthwhile watching in the 21st century.

R140 (10191-5601) is another pair in the same field of J Velorum, and 12'W. Discovered and measured by Russell on the 20th June 1881, this moderately bright pair, at 7.8 and 8.3 magnitude, is separated by 2.8 arcsec at PA 279°. It is amazing that neither John Herschel, Dunlop nor Rümker saw this obvious pair, and unless of course if the stars were much closer in the 1830s, but this one is hard to reconcile. Since Russells measures ρ=2.88 arcsec and θ=277.1°), little has changed in the measured positions. A 10.5cm can probably separate the duo with care, though it was easy in the 20cm at 127x. This field, including J Vel, has a rough north-south line of stars that divides the field in two.

RST 3692 (10203-6240) is a faint pair that is in the same field some 12'E of NGC 3211. Although it is in a very starry field, RST 3692 is the northern object of two 10th mag. stars, some 80 arcsec apart. Discovered by Rossiter in 1936, the pair is a close 0.8 arcsec at PA 65°, that incidently points directly to NGC 3211. Both have stated 9.8 and 11.8 mag, respectively. In 20cm, I could clearly separate the pair at 310X, and suspect that any well-aligned 15cm may also see both stars.

J Velorum / Rmk 13 (10209-5603) is a spectacular triple which lies in a dense stellar field, some 2.6°WSW from x Velorum (or 2.5° WNW from Sa2-64). Unlike most systems, Rumker discovered the AC pair first in 1835, and the AB pair a year later. I suspect he may have missed the brighter AB pair, because of bad seeing and not necessarily carelessness. The main pair is 4.5 and 8.4 mag. and is separated by 7.2 arcsec at PA 102°. I see the colours as blue-white, and could discern any colour difference. AOST2 describes them as white saying ...this is a beautiful object. Spectral types for the two giant stars are B4 and B9.5. This pair is visible under medium to high power in 10.5cm, and medium power in the 20cm. Difficulty in the separation for smaller apertures is more from the Δm of 3.9, than the quality of the telescope. Component 'A' has been found to have a variable spectrum, and a possible suggestion says that this maybe either a yet undetermined spectroscopic binary, or that RMK 13A has some peculiarities. Some 37 arcsec ESE (PA 102°) of the main pair is a 9.8 mag star. (SAO 277958) This wider star is easy in 7.5cm, and I see the colour as yellowish-white. Little has changed in the relative positions, so it is uncertain if the stars are physically associated.

R146 (10263-5529) appears as a pleasing pair some 1.84°W, and fractionally north of x Velorum. Russell found it on the same night as R140. The light yellow pair is 8.7 and 9.2 magnitude, though I thought Δm was 0.8 magnitude, either the primary being a main sequence F5-F6 star. In the last 112 years, the pair has significantly increasing in separation. When Russell discovered R146, the separation was 11.6 arcsec at PA 99°. In 1998, the separation has doubled to c.20 arcsec, and the position angle has decreased by 5°. Proper motion shows a large differential in right ascension, so we can say R146 with certainty to be an optical double star.

R 149 (10288-6642) appears as a moderately faint pair some 2.2°SW of the Southern Pleiades (IC2602) that is visible as an easy pair in small 7.5cm apertures. Discovered just before midnight on the 14th (1874.284), and first measured on the morning of 7th May 1880 (1880.347), this is fairly easy pair in the 7.5cm to 10.5cm range. He puzzlingly gives the pair magnitudes as but it is obvious this is a gross overestimate. I checked the presented RA and Dec and the measured positions and concluded this is the correct pair.

R 149 is presently the separation is 3.7 arcsec along PA 138°. Since 1880, the PA has increased by +4° while the separation has diminished from 4.2" to 3.7" arc seconds. Magnitudes were recently downgraded from 8.83V and 9.80V (1991) to 9.23V and 10.06V (1992). Both stars are likely of B6 spectral class.

Russell also describes the nearby field stars to the pair;

...Three stars within 12s in R.A. and almost exactly in a line when the wire bisects the first and second; the third is 0.5 arcsec south of the line.

Russels third star (Star 3) is 11.1 magnitude and has been left behind by the primarys rapid northwesterly proper motion of -32 and +33mas. Star 3 now lies 1.7' NNW (PA 338°) (10287-6640) Catalogued as T2 8968:747:1 this star is certainly not associated. The secondary position has remained relatively fixed.

A fourth 11.7 magnitude star (Star 4) exists 33 arcsec NE (PA 34°) from Star 3. Identifying the field, some 19' SSE (PA 155°) from R149, is the bluish-white 6.2 magnitude star HIP 51425 / SAO 250989 / PPM 358033 / HD 91272 (10301-6659)

The system is likely an optical double.

Δ85 (10288-6235) is found by continuing to move the telescope eastwards of planetary nebula NGC 3211 from RST 3692 by a further 1°17'E or 77'E, and perhaps fractionally more north. This is the pair Δ85. Respective, magnitudes of these two bluish-white stars are 8.8 and 9.2. Since discovered and measured by Herschel in 1837, little has changed in either the separation of 21.8 arcsec or the PA of 220°. Earlier the obtained spectra placed the pair as both main sequence A0 stars, but recent observations suggest they are slightly hotter B6s. Some 3'N is the white 8.3 magnitude field star, SAO 250977. A nice moderately faint pair.

Δ87 (10307-6122). Some 1.2°N of Δ85 is another fainter pair Δ87. First found by Dunlop at Parramatta in 1835, this is a charming colour contrasting pair and is a wonderful object even in the smallest of telescopes (and possibly even binoculars). The bright 6.43 and 7.6 magnitudes stars, respectively. Separation is 82.6 arcsec at PA 75°. Colours are red and blue, reflected in the spectral classes of M2 III and B9. Little has changed in the system, and the proper motions of both are almost stationary. It is likely this is an optical pair. Some 2.5'NW of Δ87 is the 7.5 mag blue (B9) star SAO 250491, enhancing the beauty of the object.

HJ 5444 (10318-8155) The pair is bright and wide, and is listed as 7.0 and 9.5 mag, separated by 41.9 arcsec at PA 235°. Measures in the last 85 years have shown little change. The last measures in 1983, as quoted in the WDS96 Catalogue, gives a separation of 41.8 arcsec with the PA of 223.5°. Later observations have give the spectral class an upgrade in temperature, and the primary is now considered a subgiant B5 III-IV star instead of lust B3. Based on the common proper motions of the two stars it is likely just an optical double star. The pair is visible even in 7.5cm. My observations describe the colours as bluish and yellowish. A neat pair!

ZZ Vel (10379-5557) is another detached main sequence EA-type eclipsing binary. It can be found some 30'NNE of Sa-66, and 20'SSE of x Velorum. Magnitudes vary between 9.93v and 10.39v in the period of 2.87615 days. The primary is a blue A0V. Duration of the primary eclipse is 11h 02.6m (0.460184 days), last adjusted made on 8th October 1923 (JD=2423700.42). Although, the magnitude difference is merely 0.45, observers may like to check ZZ Vel over an observing night if they can detect any variations with any of the other stars in the field.

Fig010a x Velorum / Δ95 (AB) and HJ 4341 (BC) (10393-5536) is third in my Top 5 of favourite double/ multiple stars. I have named it Albireo Australis. (Alpha Centauri is first, Gamma Velorum is second, Beta Cygni is fourth, Acrux is fifth.) In 1826, James Dunlop discovered the wide and bright AB components (4.4 and 6.6 mag) at Parramatta Observatory. Separation is 51.9 arcsec at the position angle of 105°. (See Figure.) Little has change in the relative positions of the two stars since the Dunlops first measures. The ASNSW Double Star Section during the Double Star Colour Estimates Programme (DSCE) in 1979-81, saw the star colours as orange-yellow and pale blue. The thirty-six members of the ASNSW and other contributing Societies assessed this. H.C.Russell on the 21st March 1873, described the colour as straw yellow and greenish blue. He comments also that Glimpse several minute points near this. The colour difference is magnificent, significantly enhanced by an optical illusion - reflect by stars spectral classes; G2-3 Ib and B8 V. Δm is 1.2, though the twelve observers in this part of the programme overall estimated the difference is closer to 1.8. Closer inspection reveals that the blue component is again double, and Sir John Herschel discovered this pair, HJ4341, some eight years later than Dunlop. Burnhams incorrectly names it Δ95b, and saying the primary AB is HJ 4341. Russell also incorrectly assumes that the HJ 4341 was the AB system, though Herschels observation implicitly refers to the BC system. Such a discrepancy is difficult to explain satisfactorily, as the AB pair is too obvious. The third 11th mag yellowish star is found opposite to the A component, at PA 176°. We measure separation of 20.2 arcsec as one third the distance between A and B. This can glimpse this in 7.5cm, though a 10.5cm will prove better in seeing the component from the bright glare of the B component.

Table 1 : Δ95 Vel / x Velorum

Magnitudes : 4.36V / 6.06V Spectral Class : G2-3Ib n=19


Table 2 : HJ 4341 BC

Magnitudes : 6.24V / 12.11V : Spectral Class : B8V n=3


All three stars have the same common proper motion, so it is still possible that this might be a physical system. However, if it is, the periods are likely to be very long time. The general field is dense with stars, and contains another 8.2 mag star some 6' at PA 120°. This colourful triple is one of the most attractive objects in the south - even for the smallest of telescopes.

μ Vel / R 155 / Mu Velorum (10468-4925) is a bright 2.6 magnitude star that lies some 10°N of the Eta Carina Nebula or 6.7°N of the colourful x Velorum. Deep yellow in colour, Mu Vel appears as written text in Burnhams Celestial Handbook Vol.3. p.2038.

Mu Velorum is a rather difficult binary, first measured by H.C.Russell in 1880 when the separation was 2.8 arcsec in PA 55°; it has since closed down to about 0.7" in PA 90° (1942) and, according to a note in the Lick Index Catalogue of Visual Double Stars in 1961, has not been seen with certainty since. The computed distance of the star is about 110 light years, and the total luminosity about 75 times that of the Sun. The star shows an annual proper motion of 0.08"; the radial velocity is 4 miles per second in recession.



Double and Multiple Stars in the Inner Eta Carinae Nebula

NGC 3372 / Eta (η) Carinae Nebula (10440-5930) is the brightest of the emission nebulae in the southern skies, whose diameter extends more than more than 3° of sky. Is very centre is found near the open star cluster Tr14. (See Below.) This region abounds with bright and dark nebulosity and the edges contain many bays and complex structures. In small telescopes it is extraordinary in the space it occupied, covering at least eight times the area of the Great Orion Nebula, and which all southern observers know pales the Orion Nebula to second grade. Eta Carinae and the star that gives the name to the brightest, and I dare say also the best nebulae in the sky.

Eta Carinae and the environs it appears to contain many astronomical objects including many pairs and open star clusters. In most cases nearly all are easily visible to the amateur. The region contains enough objects and structures worthy of several nights observing.

In Webbs Celestial Objects for Common Telescopes, the southern addendum Appendix II, quotes;

Great diffused branching milky nebulae with interior dark around η Argús.

In Astronomical Objects for Southern Telescopes, E.J. Hartung describes;

η Car with its associated star clusters and the great diffuse gaseous nebula enveloping it form one of the finest telescopic objects; on a clear dark night the region is beautiful beyond description, even for small apertures.

Distance of the nebulosity from us is between 1 800 to 2 500 pc. (6 000 to 8 000 ly.) being within the Carinae arm of our Milky Way galaxy. In size the true nebulosity is perhaps some 400 ly. across, some ten to twelve times the area of the Orion Nebula. If it were at the same distance as the Great Orion Nebula M42, it would cover the entire area of Orions Pot or Venuss Mirrors and be an shine incredibly bright at -2.4 magnitude!

See 123 (10440-5932) is the faint pair of 9.6 and 12.2 magnitude pair separated by about 7.0 arcsec along PA 330°, which I roughly estimated in 1997. Last measures were made in 1934, when the positions were 4.5 arcsec and 311°. This bluish or bluish white pair lies merely 1' from the cluster's centre and both appear as a lovely sight against the backdrop of nebulosity. Easy enough for 10cm.

HJ 4353 (10437-5935) is a solitary faint pair of 10.8 and 10.5B magnitude, and I estimated about the same for the visual ones. This pair is not among the stun-wahs in the many pairs that I have observed, yet it does lie within the same field of Trumpler 14 - even though it might not be a true cluster member. Since discovery by Herschel in 1837, it has shown clear tendencies of increasing in separation, but the PA of 180° (due south) has not changed at all. The WDS01 shows that the last measure was in 1959 with the given separation of 4.9 arcsec. In my eyes the separation was in 1994 beyond 6 arcsec. I saw both these star without colour (white perhaps) and easy in the 20cm.

Smaller apertures as low as 10.5cm should be able to see this duo - perhaps even 7.5cm with care. This star is also not mentioned in AOST2.- Nothing really to write home about though!

HJ 4356 (10440-5933) lies in the very heart of Tr 14, making it its brightest star. John Herschel discovered this pair in 1836 and little has changed in the positions at all. These two stars are a little closer together than the rest whose 9.0 and 10.4 components are separated by 2.8 arcsec with the PA being in a SE direction at 149°. Any 7.5cm telescope should be able to see both white stars which make up the AB system. There are another two visual companion stars nearby.

HJ 4356 AC is 13.0 magnitude and is about 5.0 arcsec following PA of 270° (West). I glimpsed this once in the 20cm C8 under very good seeing, though 25cm or 30cm might make this easier. My notes says that I looked at this pair with 30cm in 1986 and that I could not see it - I didnt write much on the conditions so Im unsure why I did not see it. Yet another companion- the AD system. The D star is an even fainter 13.5 magnitude star along PA 187° with the separation of 3.0 arcsec. This star was a little tougher because of the δm of 4.5 magnitude. In the same evening using the 20cm it appeared elongated with the A component even using high 333× magnification and I thought I glimpsed it once in a period of about five minutes. This is not an easy pair to see as it is almost in-line with the C component. This did not seem much better in 30cm, for the same reasons above, but this time A, D and B had merged into a small line of haze - something Ive never seen before. I also suspect this star was harder to see than I suspected and it might actually be closer than what the WDS is saying. I would love to see this in 40cm or 50cm Dobsonian. The A and B star are mentioned in AOST1, but the other two are not, even though they should be visible in 20cm to 30cm telescopes. What is also mentioned in this same reference is the primary A component which is quite rightly brought to the attention of astronomers.

This star is HD 93129A / SAO238396 / PPM 339375 and has a given spectral class of O2 If* - with a measured B-V of -0.206, it suggesting a late B spectral class star. However the difference here is suspected only because there is much obscuration from the surrounding nebulosity meaning that the star light has been reddened somewhat. All these stars here seemed white to my eyes.

HJ 4356 A / HD 93129A appears in several professional papers being described as one of the most luminous stars known, and ranks in some ways, like Eta Carinae itself. This star shines very brightly in the ultra-violet and has the unusual spectral lines of highly ionized N IV, C IV and N V, that are more characteristic of the central stars of planetary nebulae.
According to Simon, K.P., A&A., 125, 345 (1983), by mass all the stars within HJ 4356 total some 60M⊚, each having; HD 93128 HD 93129A HDE 303308 the respective radii of 11±1R⊚, 21±2R⊚, 13±2R⊚ and having the luminosities log 5.7L⊚, 6.2L⊚ and 5.8L⊚ Teff 48 000±3 000K, 45 000±2 000 and 45 000±3000K Like most high temperature stars they are rapidly losing mass from their surfaces at a prodigious rate - something in the order of 10-4 to 10-6 M⊚ per year! According to Benaglia, P.; Koribalski, B. Radio Observations of HD93129A : The earliest O star with the highest mass loss.;A&A., 416, 171-178 (2004) the measured mass loss was 5.1x10-5 M⊚ per year. They also found a distance of 2.8kpc. From the observed spectra, the gas outflows from HD 93129A are can change anywhere between 2 000 and 3 000 kms-1.
According to Brian Skiff (2004) HD 93129A was recently resolved as an astrometric binary using the Fine Guidance Sensor of the Hubble Space Telescope. If this is so, then HD 93129A may not be as massive as once thought.

In all, HJ 4356 is an interesting quadruple system, and if they are all truly associated, the periods may be very long. We know little of the distance to these stars as the parallaxes are far too small, though some work has been done on the galactic cluster Tr14 and the nebula itself, giving the distance around 3.2 to 3.3 kpc.

Other Stellar Heavyweights

Zeta Puppis / HIP 39429 / SAO 198752 / Noas (08037-4000) is suspected by astronomers to possibly outshine HD 93129A. This really monstrous O5Iaf star by some estimates could range in mass anywhere between 50M⊚ and 70M⊚. Others suspect it could be even heavier. At the magnitude of 2.2v, this supergiant star has an absolute magnitude (Mv) of -7.4 and lies at the very top left-hand corner of the HR Diagram. Surface temperature of Noas has been estimated to be in the order of 38 000K to 41 000K. Its spectra also shows bright emission lines of He II and N III. Strong variable stellar winds have been observed to average around 2 300 kms-1. Mass loss is estimated by Schaerer ApJ.Let., 484, 153-156 (1997) as 2.7x10-6 Msolmass.yr-1 and by Lammers and Cassinelli "introduction to Stellar Winds" Cambridge Uni Press (1999) as 2.4x10-6 Msolmass.yr-1. Distance is about 735pc. or 2 400ly.
Telescopically, Noas to me appears ultra-blue, though other amateurs like Les Dalrymple of the Sutherland Astronomical Society, see it more as a powdery blue colour.

γ1 Vel / Gamma (1) Velorum (08095-4721) is another example of another rival star is the 4.25 magnitude which has a similar temperature, distance and absolute magnitude to Noas. A small spectroscope or direct-vision prism on either of these stars show bright lines of oxygen, nitrogen and helium. There is very little doubt that these stars will sometime in the future end their lives as Supernovae Type IIs - with the catastrophic explosion rivalling the brightness of the Moon for the peoples of the Earth.

NAME Δ85 AB Δ85 AC Δ85 AD Δ85 BC Δ85 CD I 1175 DE Δ85 Aa
Mags. 1.8 / 4.3 2.2 / 8.5 2.2 / 9.4 6.0 / 8.0 9.0 / 11.0 9.4 / 12.8 1.79
DATE 1826/1980/2002 1835/1907/1991 1846/1902/1985 1835/1885/1991 1826/1846/1976 1926/1949 1997
Sep. 41.3/41.4/41.8 62.3/62.1/62.5 93.5/93.5/93.6 61.0/60.8/60.9 33.3/33.9/33.9 1.5/1.5 4.7
P.A. 220/220/219 151/149/152 141/141/142 112/113/113 125/123/124 150/144 146

NOTE: Both Zeta Puppis and Gamma Velorum lie within the enormous Gum Nebula - a supernova remnant. γ2 is not a member of the foreground open cluster Cr 173, and there continues to be some debate on whether it is attached to the Vel OB2 association. However, γ2 Vel is one of the main ionising sources of the Gum Nebula. ζ puppis lies at the back of the Gum Nebula and lies at a disance of 429±120pc.

HJ 4360 (10441-5935) is likely the prettiest pair of the four pairs we are discussed here, but it is as just as interesting as HJ 4356 mentioned about because it is another multiple with five stars this time. HJ 4360 lies in the same field as the other three pairs so far mentioned, and lies some 2.2'SE (PA 140°) from HJ 4365.

HJ 4360 AB is the main pair is a near equal 8.59 and 8.64 magnitude, though AOST2 for some reason gives the bright values of 7.8 and 7.8 - and I could not find its original source. Both stars are separated by 2.1 arcsec along PA 117°. The two are easily seen in good conditions in 7.5cm telescope. Like HJ 4365, the primary 'A' is another O6 spectral class star. Little has change in these two except for perhaps a minute decrease in apparent distance.
HJ 4360 AC is another internal pair that is little easier to see, as it is 12.5 arcsec apart along PA 289° (WNW). Easily seen in 7.5cm, and possibly even 5cm with due care, these 8.59 and 7.89 duo appear to me white and yellowish-white. Over time it seems that the PA is increased by about 1° per fifty years or so, while the separation has reduced by 1.1 arcsec since discovered in 1835 by J. Herschel. All three of these stars are very attractive for the observer with small instruments. All these main stars remind me of a miniature Alpha Crucis except that all the stars are either white or yellowish - again reddened by interstellar absorption of starlight.

HJ 4360 AE is the fourth companion of the system. This is another bright star that is aligned nearly parallel the close AB pair. Users of Megastar 4.0 & 5.0 should note that HJ 4360 AE is wrongly identified as the principal AB pair in this system, and this might have discouraged a few southern observers not to view this multiple at all. This time the 'E' component is 9.0 magnitude add lies along the easterly PA of 97° and is separated by 7.7 arcsec. These stars are also easy to spot in 7.5cm, though it was certainly more impressive in 20cm. I saw 'E' as white as well.

FIN 412 CD can be seen if you look carefully at the C component the star splits in two with apertures around 20cm or more. Discovered by Finsen in 1934 it makes the D component of the system. This time the alignment roughly matches the AC system where the separation is some 2.4 arcsec along PA 305°, which I estimated in mid-1984. It seems these stars are showing the most movement of all the components, where the PA (my estimation) has increased by 11° in fifty years since 1934. This is the only star to show significant motion of these components in all these pairs we have so far discussed. This star has the best chance of being the true binary, however the proper motions and parallax are essentially zero. It may take some time to prove it has physical connection as a binary. I would be interested to hear if the PA has continued in its motion or not, and if so, it would be encouraging to see some new measures of this duo. Looking in January 2002 the distance seemed just a little wider. The distance is likely to be the same as the stars in the open cluster Tr 14 and the other pairs mentioned above. All in all this is a nice easy system for small to moderate apertures. But even in larger telescopes and applying moderate magnification this pair is further enhanced, as the nebulosity nearby is bright and adds much to this truly majestical and regal field.

Gaspingly beautiful!

Components PA Sep. Mv(1) Mv(2)
HJ 4360 AB 117 2.1 8.59 8.64
HJ 4360 AC 288 12.5 8.59 7.89
HJ 4360 AE 097 7.7 8.59 9.0
FIN 412 CD 299 2.9 8.4 12.5

Tr 14 / Trumpler 14 / Cr230 (10439-5933) within the Eta Carina Nebula contains some twenty (20) brightish stars all within an area of 5' and is something akin to the area seen with the Jewel Box (NGC 4755) Tr 14 contains the pair See 123, and possibly the other pairs of HJ 4353, HJ 4356 and HJ 4360. All of these are visible in 10.5cm with care.

Tr 16/ Trumpler 16 / Cr233 (10452-5943) is within the η Car Nebula. Tr 16 is estimated to has an average O5 spectral type star and contains about fourteen (14) others. Covering about 10', the total integrated magnitude is 5.0 magnitude. In age of this cluster is about ten million years old.

Δ98 / DUN 98 Aa-H (10451-5941) was discovered by Dunlop in 1826. This is the wide pair that includes the magnificent star η Car and the nearby bright star H. The wide 8.14 magnitude companion star that lies 60.7 arcsec along the P.A. angle 17° (1991). Observations have shown a very slow increase in separation by 0.5 arcsec and the PA increasing from 11° to 17°. As the proper motions are small and we assume that the two stars are at a distance of the nebulosity, it is almost certain that this is just an optical pair.

Southern Astronomical Delights”
© (2009)
10 Mar 2009