SELECTED SOUTHERN DOUBLES and VARIABLES
R.A. 06 Hours
Δ26 (06122-6532) is one of the
more interesting of the Dunlop pairs. It can be found quickly
because in is in the same field as the orange-red 5.0 magnitude
star, η² Dor / Eta (2) Doradus / HIP 29353 / SAO
249469 (06113-6535) whose spectral class is M2.5III. Δ26 is
6.8'ENE (PA 60°) from this star. Dunlop originally gave the
stars as magnitude as ‘7,8’. Modern day bright gives 7.1 and 8.5v
magnitudes with the photometric ones being 6.86V and 8.07V.
Presently (1994) the separation is 20.4 arcsec along position angle
119°. The WDS does not give Dunlop's measure as the separation
is only guessed. The initial values are that of John Herschel in
1834 who measured 113° at 23.0 arcsec, suggesting the position
has changed +5° and reduced in distances by 2.6 arcsec. I saw
both stars as yellowish. Spectral classes are F6V+F7IV. Proper
motions suggest that the stars are likely associated. Surprisingly
E.J. Hartung missed this wonderful gem, but Graham Little in his
series “Ten O'Clock High” says of Δ26;
“Another fairly
attractive double..., but again available to ’scopes 6cm and upwards. The primary star is
an F5 type, appearing as a white, mag. 7.1... Lying 20.9 arcsec away
(near enough the same separation as the two stars in Alpha Centauri)
at PA 117 is the secondary star. It is a G type star and a good
imagination can give it a yellow tinge. It glows with a mag. of 8.5.
Keep the stars close for the best effect.” Only a few stars are seen in the
fairly dull field with Δ26 itself being visible in apertures
of 5cm. The surrounding field seem devoid of any interesting pairs
of any interest to the amateur.
Δ27 / Δ27 AB / LDS 157 AC
(06163-5913) is a strong yellow pair that lies in eastern Pictor.
Both stars are 6.3v and 7.8v magnitude (6.44V and 7.76V) magnitude
and are separated by 35.5 arcsec along PA 232°. This is an easy
system even in 5cm or binoculars In 20cm I saw the colours as yellow
and white. Since discovery these two stars have been diminishing 22.8
arcsec while the PA has increased 10° in the last 175-odd years
of available measures. Both stars are likely unrelated as the proper
motions in RA are moving in opposing directions and this certainly
accounts for the apparent rapid motion. Hipparcos gives the
parallaxes of A : 27.50±0.50mas ; B : 16.11±0.66mas
giving the distances as 36.4±0.7 pc. and 62.1±2.5 pc.,
respectively.
LDS 157AC is the wider component of 14.2
magnitude that lies 40.7 arcsec away along PA 302°. Although as
double stars go this is a wide and unlikely pair the proper motions
with the primary (Δ27A) are -45 arcsec per century in RA and
-320 arcsec per century in declination seem to suggest they are
associated. The component was discovered in 1958 during the
Luyten’s proper motion surveys. Seeing
this companion requires 20cm or greater but is a bit difficult to
see under the glare of the two other stars. Using an occultation bar
in the eyepiece might help make this companion more visible.
ARTICLE
THE FOLLOWING THREE INNES PAIRS (I3, I5 and I6) ARE
NEAR Δ27.
THESE ARE GOOD EXAMPLES OF THE NATURE OF CLOSE VISUAL PAIRS
THAT APPEAR IN THE SAME REGION OF SKY.
I 3 (06125-6128) lies in southern Pictor
and was discovered by R.T.A. Innes in 1894. It is interesting to
note that I 3 is the first of the recognized catalogued Innes pairs,
mainly because both I 1 and I 2 have been deleted from the WDS as
actual pairs. This is a bit more of a difficult pair but it is at
least easier than I 5 and I 6 that we have also examined within
these pages. A 20cm is needed to split the pair cleanly. I 3 lies
4.4°W of α Pic / Alpha Pictoris or 2.3°S (PA
190°) of Δ27. Presently the magnitude are given as 7.1
and 7.6 separated by just over 1.0 arcsec along PA 5°. I saw
the component colours as bluish and white. Since discovery the PA
shows direct motion having increased by just over 15° over in
the last century while the separation continues to widen from its
original 0.8 arcsec. Based on the similar proper motions, though
containing sizable errors, makes I 3 probably a real binary.
Using the parallax is 4.31±0.78mas giving the distance as
232±45 pc. or 756±141 ly. At this distance the
projected separation is 236 A.U. or 3.5x1010 km. Stars of
the given apparent magnitude give the absolute magnitudes as +0.27
and +0.77 suggesting masses of 5.6 M⊚ divided using the MLR
Mass-Luminosity Relationship) as 2.9M⊚ and 2.7M⊚.
Periods under these circumstances derive the overall period to be
more than 1500 years.
Field of I 3
ST Pic (06140-6128) lies directly 11'W
of I 3 and appears as a yellowish star. ST Pic is an RR Lyrae
variable that changes between 9.3 and 9.8 magnitude in a period of
0.48574 days (11h 39.5m). Like the Cepheids, the rise in an RR
Lyrae’s brightness is more rapid than
the decline, increasing in 22% of the period or 0.1069 days (02h
23m).
ESO 121-6 / PGC 18437
(06075-6148) is a Sc spiral galaxy that appear as a 13.4p elongated
gossamer smudge some 3.5'x0.5' in size that is aligned along PA
40°. ESO121-6 centre lies 41'SW of I 3 and is
visible in 20cm with care but is easily seen in apertures above
30cm. The photographic image measures 4.2'x0.6'.
I 5 (06380-6132) appears
in the southeastern part of constellation of
Pictor as a yellow 6.2 magnitude star some
1.3° WNW (PA 287°) from
α Pic / Alpha Pictoris. I 5 is a good
example of an easy pair that has become
impossible to view in amateur telescopes. When
Innes discovered this pair in 1894 the
separation was 1.7 arcsec along PA 270° for
this 6.3 and 8.8 magnitude. This would have been
easy target even for amateur telescopes. In the
last decade the pair seems to be undergoing
significant motion. Hipparcos in 1991 measured
the pair as 0.762±0.002 arc seconds (PA
262°) yet by 1999 the distance has
almost halved. Since this time the pair has
continued to close and the separation has
reduced now to an impossible 0.3 arcsec.
Furthermore the position angle shows retrograde
motion changing from 270° to
255°. This star will be interesting
to watch in the coming decades when the
separation will again increase by this time on
the eastern side. Observations of the proper
motions indicate that the star are connected
physically. It is very likely this is a true
binary system.
From the general data available the period is
likely between 175 and 500 years. Using the
parallax is 46.15±0.64mas finds the
distance to I 5 is 28.67±0.30 pc. (1.4%
error) or 70.67±0.98 ly. Proper motions
are pmRA; -50.80±0.73 and pmDec;
72.69±0.66 indicating the stars are
moving NW along PA 137°. Absolute
magnitude are +4.62 and +7.12 and respective
masses of 1.0 M⊚ and 0.6 M⊚.
Using the available data prediction of the
motion of the components are listed in the Table
below;
Year Sep. P.A. Year Sep. P.A.
arcsec deg. arcsec deg.
1900 1.62 269.1 2005 0.22 254.1
1920 1.35 266.3 2010 0.15 253.5
1940 1.09 263.4 2015 0.09 252.7
1960 0.82 260.6 2020 0.02 252.0
1980 0.55 257.7 2050 -0.38 247.7
2000 0.29 254.9 2100 -1.05 240.6
Comment: This predicts the minimum separation
will be about 2023AD. However this leaves a problem with the
Hipparcos measure as this point doesn’t match the other points. If we reject this
point, the prediction calculator shows that the 1999 measure matches
many of the previous measures. (Note: The above is a linear
interpretation and the observed results maybe different because of
the eccentricity of the orbit and the inclination to the line of
sight.)
I 6 (06425-6145) is also in southeastern
Pictor but is a pair that is a challenge for the large amateur
apertures. In some way this star by separation is mid-way between I 3 and I 5. The pair can be found
between Alpha Pictoris and I 5, being either 42'WNW (PA 284°)
of α Pic or alternatively 34'ESE (PA 113°) from I 5 (*See
Below). This is a difficult pair as the 7.7 and 8.2 magnitude stars
are presently separated by 0.6 arcsec along PA 257°. Since
discovery by Innes in 1894, the PA has shown direct motion
increasing from 230° to 257° (1997) - an increase of
27° or 2.6° per decade. Furthermore, the separation has
halved in this time, changing from 1.1" to 0.6"arcsec. Presently
this is not so easy to resolve and 30cm is likely required to see
any suggestion of duplicity. By 2010 the stars will like merge as an
apparent single star in amateur telescopes. If the motion continues
as based on the sixteen (16) odd measures the pair will be closest
in 2120 A.D. Unfortunately the available data on the system is too
poor to calculate even rough parameters of the binary nature of the
two stars, yet at least, the very similar proper motions suggests
this is a true binary. Spectral class is F5 IV/V.
ζ CMa / Zeta CMa /
1 CMa / SMY1 / Furud / HIP 30122
(06203-3004) is a very wide but bright pair of
3.0v and 7.7v (2.96V and 7.81V) magnitude. It
was noted and measured by Admiral Smyth in 1833
though it was certainly known as a wide pair by
several earlier double star observers. Set along
PA 338°, the two stars continue to
widen from the 167.0 (1833) to 174.3 arcsec (1991).
With a blue primary and yellow secondary the
colours are certainly enhanced by their general
proximity especially in small apertures or
binoculars. This pair is likely an optical
system.
Listed as star No. 395 in the 9th Spectroscopic
Binary Star Catalog, the eccentricity of the
orbit is 0.57 based on periastron on 2416508.0.
It has an ω (argument of periastron) of
207° while the system’s mean
radial velocity is +32.2kms-1. This
is a fairly poor grade orbit that was first
published in 1941. ζ CMa A is a known long
period spectroscopic binary with a period of 675
days. Spectral classes are B2.5V and K0V:
JC 3 (06203-2937) is a
faint wide pair some 24'N of ζ1
CMa. This 7.9 and 9.3 mag. (8.04 and 9.36V)
orange and yellow pair is separated by 13.3 arcsec
along PA 207°. Little has change in
the position, some +2° and
+0.4 arcsec, since Jacob found the duo in 1846.
Spectral class of the primary is estimated as
K1III: Both star share the same motion so this
maybe a true system.
EsB 188 / Herschel 20 / IV CMa / NSV 2945
/ HIP 30409 / PPM 726310 (06237-2704) this 8.5v magnitude star is
29'ENE (PA 68°) from the galaxy NGC 2217. Described as “intense red”
by William Herschel this deep red star is quite startling to the eye.
I found by defocussing the star the colour becomes a little more
obvious. EsB 188 first appeared as a variable star in the NSV
Catalogue as NSV 2945 of unknown type that varies between
8.55V and 8.95V. In the recent GVSC4 the star has been accepted as
IV CMa 140239 and recent observations have confirmed it is an
SRC variable with the later fluctuations observed between 8.21V and
8.75V. These are typically semi-regular pulsating stars usually of
late spectral classes which display amplitudes of about one magnitude
anywhere between 30 days and 10 years. A classical example of the
type is Mu Cephei.
μ Cep / Mu Cephei /
“The Garnet Star” / HIP 107259 / SAO
33693 / PPM 39787 (21435+5847) that is
located within the northern part of the bright
nebula/ open cluster, IC 1396. Variations
are 3.43 to 5.1 magnitude (mean mag. of 4.3v)
shows an average period of 730 days. Spectral
class is M2sIa while the B-V colour index is
+2.242.
EsB 188 has the B-V colour index of+2.860 and is
of spectral class C6II. The only observation I
have seen is by Steve Coe, who saw EsB 188 it as
“Orange at 100X in [a] rich
field”.
ARTICLE
Colour Comparison Stars of Late Stars Near
EsB 188
While looking for EsB 188 I stumbled upon three
red stars and three orange one in the next
fields up and to the northeast. The parallax
data on these (Stars 1, 4 and 5) (See Below) all
these three stars is small and poor. A mean
distance of all three stars in about 1.0 kpc.
Stars 1, 2 and 3 all appear in a completely
straight line along PA 290°. I have
used all these stars as a useful comparison
between orange and red stars. It is quite
surprising how these stars have subtle
differences in hue and found it a worthwhile
exercise. I know of no other field that contain
seven orange to reddish star within in a
1.6° field. Except for EsB 188, all
stars are not known variable. The individual
stars are;
Star 1 :
HIP 30390 / SAO 171672 / PPM 250315
(06234-2623) is located some 42'N of EsB 188 or
57'NNE (PA 24°) in the next field
using low magnification. This 7.2 magnitude star
has a B-V colour index of +1.669 and is of
spectral type of M1 III. This appears
orangery-red to my eyes.
Star 2 :
HIP 30461 / SAO 171693 / PPM 250340
(06242-2627) lies in the field is a 6.7
magnitude orange K0/K1III+ star appears in the
same field some 11'ESE (PA 109°).
[B-V of+0.948]
Star 3 :
HIP 30288 / SAO 171642 / PPM 250283
(06223-2617) is a second 7.8 magnitude star (HIP
30288) also in the same field, but has a deeper
orange colouration. This K2III, lies 17'WNE (PA
290°) [B-V of +1.358] HIP 30288
Star 4 :
HIP 30657 / SAO 171751 / PPM 250399
(06265-2606) lies about 45'ENE (PA
68°) from Star 1 (HIP 30390).
Although fainter at 7.7 magnitude, this star
looks identical in colour to Star 1. The B-V is
+1.644 and the spectral class is M1 III
b>Star 5 :
HIP 30903 / SAO 171826 / PPM 250481
(06292-2607) lies further due east from Star 4
by some 34'. This star is the fainter of the
tree at 7.9 magnitude and matches Star 2 in
colour with the B-V of +1.633 and the spectral
class of M3III.
Star 6 :
HIP 30436 (06239-2525) is yet another
orange star some 47'N of Star 1 or 49' from Red
Star 4. This 5.6 magnitude star is a light
colour than Star 1, 4 and 5 and has a spectral
type of K5III and the B-V of +1.561
TABLE 1. CMa Orange Stars Comparison:
Decending by B-V (Red to Orange)
Star Name Position (2000) Mag. B-V Spectral
RA Dec. Class
EsB 188 06 23.7 -27 04 8.5 +2.860 C6 II
Star 1 HIP 30390 06 23.4 -26 23 7.2 +1.669 M1 III
Star 4 HIP 30657 06 26.5 -26 06 7.7 +1.644 M1 III
Star 5 HIP 30903 06 29.2 -26 07 7.9 +1.633 M3 III
Star 6 HIP 30436 06 23.9 -25 25 5.6 +1.561 K5 III
Star 3 HIP 30288 06 22.3 -26 17 7.8 +1.358 K2 III
Star 2 HIP 30461 06 24.2 -26 27 6.7 +0.948 K0/K1 III
η Mon / Eta
Monocerotis / 8 Mon / Σ900
(06238+0436) is a very pretty white and yellow
pair in a starry field about 12°N of
Beta Mon or 8°E of Betelgeuse. Since
discovered by F.G.W. Struve in 1831 the pair has
been slowly diminishing from 13.9" to 12.7", but
the PA has remained along 27° It was
uncertain if these stars were associated, as
said in “Astronomical Objects for
Southern Telescopes”; 2nd Edition
(AOST2) by David Frew and David Malin, but since
the release of the Tycho / Hipparcos data, the
respective parallaxes are 25.39±1.02mas
and 41.09±10.14mas, combined with the RA
and Dec proper motions which are moving in
opposite directions, it is likely this is an
optical double star. Σ900 is also possibly
joined to the open cluster Dolittle 23 (Do 23)
whose 18' size holds about ten or eleven stars.
As AOST2 notes that 5'NW from 8 Mon is 9.7 mag
star T141:2248:1/ SAO113805/ PPM150409.
Described as red, I saw it as certainly orange
or yellow-orange.
Owners of large Dobsonians may find in the same
field the 14.7 mag, UGC3459 / PGC18964
(06240+4243), a Sc spiral galaxy whose visually
size measures 30"x22". It is located 7.9' (PA
26°) which in the same direction as 8
Mon. I would be interested if anyone can see
this object, as I can find no references in
sighting this galaxy.
Δ28 / Δ28 AC
/ HJ 3857 AB (06240-3642) is an easy bright
triple in Columba that is visible in small
apertures or binoculars. Lacaillé was
first to identify it as a pair, and when James
Dunlop found it 1826 the wide components were
assigned to the star 11 Argûs. Only later
it was designated as Δ28 AC. It is located
some 2.3°SE of the yellow 4.4
magnitude star, κ Col / Kappa
Columbae. These two 5.7 and 6.9 magnitude
components are presently separated by 63.9 arcsec
along PA 74° (nf) (1991) and since
discovery have slowly diminished from 69 arcsec and
PA 64° (1826). I saw the colours as
deep orange and deep yellow in a field devoid of
many stars. Proper motions of these two suggest
that this is just an optical system. Some 1.2'N
of Δ28 AC is another faint 10.9 magnitude
yellow star that enhances the pair.
Closer inspection of the primary finds the pair
HJ 3857 AB. This companion is directly
opposite the ‘C’ component forming a
straight line balanced in a ratio of about 5:1.
At magnitude 9.8v, ‘B’ is separated
by 13.0 arcsec along PA 256°.
E.J. Hartung in AOST1&2 (#246)
describes this triple as;
“These are two bright orange stars
70 arcsec apart in this field sprinkled with
stars; the brighter is south-west and has a
companion described by Hartung as ashy, easily
visible in 7.5cm. No real change has occurred
since John Herschel's measures in 1836 and
similar proper motion suggest a binary
system.”
I investigated this triple for the appearance of
ashy coloured star (as well as HJ 3875 described
below). (Ashy being the colour describing a
greyish tint.)
How Dunlop missed this star is uncertain as it
is clearly visible even in 7.5cm without any
trouble. Since 1836 the pair has widened by 1 arcsec
while the PA has decreased 4°.
Looking at the proper motions it seems, unlike
Δ28 AC, that HJ 3857 AB are associated,
but if so, the period must be fairly long.
Fields Near Δ28
The visual field of Δ28 contains many
faint galaxies, the brightest being the 14.7p
magnitude, ESO
365-10 (06219-3633) some 26'WNW (PA
289°) This SA(s)b spiral galaxy
appears visually as a small smudge some
1.5'x0.3' in size aligned along PA
107°. This was glimpsed under dark
skies within the field using 20cm (65x). As for
the other ten-odd 15th and 16th magnitude
galaxies, a larger aperture is required which is
made more difficult because of the brightness of Δ28.
Within the next southern field, some 50'
containing the galaxy cluster AGC 3390 (06250-3720) which
contains some sixty-three (63) galaxies within a
diameter of 28′ of sky. This contains several
galaxies bright enough for large apertures,
however, I have not actually observed this. Some
twenty-six (26) galaxies appear between 15th and
16th magnitude centred on the AGC position given above.
Only 1.8'NE of the given centre of AGC 3390 is
the brightest galaxy ESO
365-16 / PGC 19000 (06252-3720) which is
a faint 15.1p magnitude. This is a spiral galaxy
with a small ring around it (Type: (R)SB(r)ab.)
which would likely appear in >40cm like a
smudge with two small condensation aligned almost NW-SE. In size this
galaxy visually covers about 1.0'x0.4'.
JSP 868 (06257-3620)
is the pair some 30'NW (PA 43°) which
is contained within a 4.5' slightly bent line of
four stars. The most northerly star of these is
the brightest. This is HIP 30558 being 10.0
magnitude and distinctly yellow. Moving
southwards the third star is JSP 868 that is
made obvious by the 9th magnitude star merely
27 arcsec SSE (PA 158°) JSP 868 is listed as
10.6v and 10.9v (11.0V and 11.4V) which is
divided by 4.8 arcsec along PA 230°.
Clearly split in 20cm (127×) the two would be
visible with care in 10.5cm. To me the stars
looked wider than this by perhaps as much as
0.5 arcsec. Few observations have been made of
this duo so it is uncertain of their relationship and the latest
proper motions are a least borderline.
BU 753 (06287-3222)
lies some 54'WSW (PA 247°) of HJ
3869. BU 753 is easy to find as it lies 14'NNE
(PA 26°) from the bluish 4.5
magnitude star λ
CMa / Lambda CMa / HIP 30788 / SAO 196857 /
PPM 282725 (06282-3235). This pair has
remained relatively fixed at 1.2 arcsec but the PA
has marginaly reduced from 47° to
43o since found by S.W. Burnham in
1892. Visible in 10.5cm the moderately close pair appear in a fairly
drab star field. Spectral class is B4Vnpe.
β Mon / Beta
Monocerotis / Σ919 (06288-0702) is a
triple system. The closer "BC" pair magnitude
5.7 and 6.2 and is separated by 3.0 arcsec along
PA 107° The "A" component is 5.1
magnitude and is some 10 aarcsec away at PA
125°. Another 12th mag star, making
the AD pair (BU 570), is 25 arcsec apart
at PA 56°. Although invisible to
amateur eyes, the companion of the "C" component
was discovered as recently as 1988. Known as
CHR 167 or "Cc"; the 5.6 and 6.1 mag
stars are separated by 0.3 arcsec along PA
141° This makes Beta Mon possibly
quintuplet. It is certain that the four stars
are associated, but the "D" star is still
undetermined. All stars are of B-spectral type,
and are coloured light sapphire blue. This
system is very attractive and not one to miss!
Δ29
(06291-4022) is a wide optical pair in
south-eastern Columba lying some 3.2°
NNW (PA 330°) from the blue 3.2
magnitude star, ν Pup / Nu Puppis.
Assigned as 21 Argûs by Dunlop, this
orange pair is listed as 7.5v and 7.9v magnitude
(7.70V and 7.98V) and is separated by 64.8 arcsec
along the roughly east-west position
angle of 118°. Since the time when it
was found by Dunlop in 1826, the separation has
dropped from 71.7" to 64.8" and increased from
109° to 118°. (1991). The
field is moderately starry especially to the
eastern parts and several 6th magnitude stars
lie within 1°. An easy object even in
5cm or binoculars.
Δ30
(06297-5014) is placed some 3.2°W of
Tau (τ) Puppis, or 2.6'N and a little east
of Carina's Canopus. The magnitudes of the
yellow and red-orange pair are 5.2 and 9.0,
separated by 11.7 arcsec at PA 313°.
Δ30 is a multiple star with both o the
main components show companions. Δ30
AB has an orbital period of 53 years, and
the equal 6.0 magnitude duo can be seen in 20cm.
Presently the AB system is separated by 0.8 arcsec
(2003) whose PA is c.240°. Another
invisible component ‘ABb’ is
suspected. Δ30 CD has a longer
period of 102 years, however, it is far more
difficult to see. Presently the separation is
merely 0.5 arcsec, which will slowly increasing
to 0.6 arcsec by 2017. Both equal brightness stars
are reddish. This ‘CD’ component
should be visible due south in 30cm to 40cm with
care, requiring high magnification.
No doubt all the components of this the
multiple system are gravitationally connected,
being likely a quintuplet system.
I 4 (06307-4027) is a
nearly fixed pair in the same field as Δ29 some 17' ESE (PA
103°). In the constellation of
Columba, this distinctly blue star is separated
by 0.8 arcsec along PA 306°. Innes
discovered this pair in 1894 while likely
inspecting Δ29, as he
likely did with I 3, I 5 and I 6 with Δ27. The stars are listed
as 6.7v and 6.9v magnitude (7.28V 7.50V),
however, since discovered, the stars have moved
along 4° in PA. In 20cm (333x) the
two Airy disks were separated in good seeing and
I am quite certain that smaller apertures would
have far more difficulty. Another deep orange
star lies 8' almost due south from I 4.
μ Pic / HJ 3874 / Mu
Pictoris (06320-5848) is a bluish and white
and pair in an unremarkable field some
6°S of Canopus and about two-thirds
the distance between Canopus and Alpha Pictoris.
AOST2 says “...7.5cm shows with close
attention”. I have seen this pair in
20cm, 10.5cm and 7.5cm over the years, and I
suggest that the 10.5cm clearly separated the
duo without too much difficulty. It would assume
that any 7.5cm would need good seeing to view
the pair because of the moderate difference in
magnitude. Presently (2003) each of the 5.7 and
9.4 magnitude components are separated by
2.5 arcsec along PA 230°. Little has
changed with the eleven observations to date
(2003) regrading the relative positions. John
Herschel’s measures are questionable and
the IDS in 1961 through to the WDS03 continue to
quote the 1894 measures. In comment, it is
surprising how Dunlop missed this pair, because
it was well within his grasp and certainly
bright enough.
Lawrence Hargrave observed the pair from Sydney
Observatory on the 12th January 1879 stating
Seen: “but did not
measure”,
however, I doubt he was looking at the right
star, because he describes the magnitudes as
"6,12" - decidedly underestimating the
companion’s magnitude - as John Herschel
did in 1836. Hipparcos found the parallax of
4.50±0.50mas with little proper motion
giving the distance as 222±11pc. (or
725±82 ly.) The measured separation was
2.488±0.023 arcsec along PA
2300 - the 1991 values in the WDS03.
It remains uncertain if these two stars are
really associated, but if they are, the absolute
magnitudes are -1.0 and +2.7, respectively, with
the masses around 4.1 M⊚ and 1.7 M⊚.
Projected separation of 550 A.U.
(8x1010 ly.) gives the period around
5½ thousand years. Combined spectral
class of the pair is B9Ve. Mu Pic is listed as
HIP 31137 / SAO 234564 / PPM 335251 with
a 5.69V magnitude and the B-V of -0.057.
Δ25 ? / HJ 3869
(06326-3202). Dunlop gives Δ25 position as
06h 12m 05s -32° 06' (1825) or 06h
18.6m -32° 10' (2000) No pair exists
in this location and there are no realistic
candidates here. It is likely HJ 3869 is the duo
Dunlop is talking about. HJ 3869 is some
3.0°E (PA 88°) from
Dunlop’s precessed position for
Δ25’s of 06h 18m 26s -32°
09m 55s (2000). This is likely just a
transcription error by Dunlop but his catalogue
leaves few clues, other then the magnitudes of
“6,8” for the components, of
Δ25. This pair is very likely HJ 3869 as
it matches the pair’s magnitudes quite
well. Located in southwestern Canis Major, HJ
3869 can be found some 3.3°SE (PA
127°) from the blue 3.0 magnitude ζ CMa / Furud
(06203-3004).
Magnitudes are 5.7 and 8.7 (5.68V and 7.87V). I
thought the visual magnitude for he secondary
was a bit brighter than the visual magnitudes
given above - perhaps more like 8.0 - that
agrees with the photometric magnitudes.
Separation is presently 24.6 arcsec along
258° (1991). Since discovery the pair
continues to close while the position angle has
increased some +8°. This blue and
white pair matches well with the B2IV and A0
spectral type, however, the PPM star catalogue
oddly gives the spectral class as F0. It is
still uncertain if the stars are attached. HJ
3869 is visible in small apertures and is a
delightful pair to search for and find. An
orange star 7th magnitude star lies some 15'SW
in the same star field.
I 178 (06349-3218) is
a close pair in Canis Major that is presently
separated by 0.9 arcsec along PA 194O
(1991). Innes discovered this pair in 1897 and
the pair is placed 34'ESE (PA 119°)
of HJ 3869 - Δ25?. The pair is just
visible in 20cm at high magnification if the
seeing is good, but 25cm or 30cm would be
certainly be more preferable.
Although the pair has fractionally widened while
the position angle shows retrograde motion and
has deceased by 10° in a century.
Proper motions are similar so it is likely these
is a real system. Spectral class is B5IV.
RR Pic / Nova Pictoris /
FIN 74 (06356-6238) was a very bright
nova that was discovered on the 25th May in 1925
by R. Watson from South Africa. Nova Pictoris is
positioned some 1.6°WSW (PA
242°) from 3.2 magnitude Alpha
Pictoris which for a month or two outshone this
star.
FIN 74 (06356-6238) is listed in the
WDS03 as a multiple star whose “B, C and D
components” are actually the brighter
portions of the ejecta being flung into space in
the year immediately after fading from view.
This is similar process, as the WDS Notes state,
“...similar to those made by Kuiper for
Nova Herculis (1934)”- so FIN 74 is
therefore not a multiple star at all.
Finsen made the observations several random
sets of observations and measures between 1928
and 1934 after the nova had faded below about
10th magnitude. The positions of these brighter
fragments were given in 1928 as ‘B’
72° 0.5 arcsec, ‘C’
241° 0.4 arcsec and ‘D’
356° 0.3 arcsec, with the
‘B’ and ‘C’ components
being 12.8 and 13.5 magnitude, respectively.
This is roughly distributed in a ‘Y’
formation. From the later observations it was
concluded that the material was travelling about
0.2 arcsec per year, and Finsen showed the
general motion of the material by further
measures during 1930, 1934 and 1935.
RR Pic is listed as variable star 0634-62 and
appears on the RASNZ Chart No. 269 and No. 270.
RR Pictoris is now a star of 12.5p and maybe a
recurrent nova - hence the availability of the
RASNZ variable star chart. Nova Pictoris was one
of the first novae to be scientifically observed
by astronomers.
Δ31
(06387-4813) is another bright pair some
2.5°NE of Δ30 or
3°NW of Tau Puppis. Discovered by
Dunlop in 1826, the components are 4.9 and 8.2
mag, separated by 13 arcsec at PA 320°. The
pair reminds me very much of Δ51, with a
small magnitude difference. I saw the pair also
as orange and white. No change has been observed
with the pair, so the true connection remains
uncertain. The field is quite pretty.
Δ32 (06423-3824) lies near the
western edge of Puppis, close to the Columba border, some 7°W
then 1°S of Pi (π) Puppis (Δ43). Comparing the field to
the other ones in this article, this field is quite spartan. Both
stars are white and 6.5 and 8.0 amgnitude, respectively. Since the
first observations in 1835 both the PA and separation have remained
fixed at 276° and 8.0 arcsec. A 7.5cm should see both stars with
care, though 10.5cm would be much easier.
α Pic / Alpha
Pictoris / ‘Apictor’ / HIP 32607 /
SAO 249647 / PPM 355624 (06482-6157) is a
white 3.24 magnitude star located in
southwestern Pictor and is placed 22'W of the
border with Carina. Hipparcos parallax is
presently given as 32.96±2.14mas giving
the distance as 30.34±1.98 pc. or
98.96±6.45 ly. At this distance with the
B-V of +0.225, the absolute magnitude is +0.83.
If the spectral class is A7 IV, then the surface
temperature is 7 810K giving the stellar mass as
2.6M⊚ and the radius of 1.9 R⊚. Proper
motions are pmRA -68.39±2.34 pmDec;
242.03±2.29 mas;
giving the general cpm of 251.6 mas per year along
344° PA. α Pic is very similar
in nature to the 1st magnitude star Altair or
Alpha Aquilae.
ε CMa /
Epsilon CMa / CPO 7 / ADS 5654 / 21 CMa / Adhara
/ HIP 52089 / SAO 172676 / PPM 251347
(06586-2858) is the 22nd brightest naked-eye
star in the sky at 1.5v (1.53V) magnitude star
whose absolute magnitude (Mv) is -4.4. In size,
the primary of Adhara is 22 times the diameter
of the sun or some 7.6 million kilometres.
Stellar interferometry has measured the diameter
between 7.2x10-4 and
7.5x10-4 arc seconds. Surface
temperature of 23 000K is calculated from its
spectral type. B-V is -0.132, while the
luminosity class is B2II. A parallax of
7.30±1.80, with very little proper
motion, calculates the distance as
140±36pc. or 447±117ly. (Burnham
says Mv is -5.0 and 680ly.) ε CMa shows
several oddities such as being surrounded by a
circumstellar shell and having the colour excess
E(B-V) of +0.02. Based on the general distance
and motions, ε CMa is possibly a member
OB group near Omicron CMa being a stellar member
of the open star cluster, Collinder 121
(#34).
ε CMa is the moderately close pair CPO7
was first found in 1850 by J. Maclear from the
Cape Observatory in South Africa. Separation for
the 1.5v and 7.5v magnitude stars is presently
7.0 arcsec along the fixed position angle of
161° (2000). In the 150 years still
the most recent measure in the year 2000 the
pair looks like it is continuing to become
closer. When measured In 1850 the separation was
7.7 arcsec and 7.5 arcsec in 1950. Like Rigel /
Alpha Orionis (05145-0812)(0.3 / 10.4
9.5 arcsec,201° B8Iae:) this pair is
difficult to resolve because of the overwhelming
glare of the primary hiding the much fainter
secondary. Little information is available to
declare if the two stars are associated - though
one or two sources say this is an optical pair
based in the differing velocities (v sin i)
which is 54kms-1. Projected
separation is 1600 AU.
ESO 122-11 and ESO 122-11A
(06591-5908) are two strongly interacting
galaxies that can be found 32'W of Δ39.
*(See Below) Both galaxies can be seen in
telescopes greater than about 20cm in dark and
moonless skies, but may be more difficult to see
because of the two nearby 6th magnitude star.
Observers might like to take the two stars out
by move the telescope to the southwest to
eliminate from the field some of their
overwhelming light.
Both of the galaxy centres are separated by only
6.4 arcsec aligned NW to SE. Apparent sizes
of these two galaxies are given as 0.8'x0.4' and
1.0'x0.6' (48x18 and 60x36 arcsec) but I
would expect you would see only about half to
one-third of this. I.e. 24"x9" and 30"x18"arc
seconds.
Looking at the red image, you can clearly see
the two separate galaxies. Incidentally, the
visual image is merged because of the
overexposure, but in allows you to see the
effects of the interaction with the tail
pointing to the west. These galaxies were taken
by Sue Triton on 13th January 1978 starting at
10h 44m PM using the then UK Schmidt Camera atop
of Siding Spring - the Observatory of the Anglo
Australian Observatory. The Plate Number is
J3870 and was made during the 7.5 minute
exposure.
Do you see in the telescope two galaxies or just
one big nebulous mass? Can the cores be resolved
or not? What aperture is needed to do this?
Little is known about this interactive pair
except the radial velocities are 8 360 and 8 182
kms-1, respectively, giving a mean
distance of about 127 MPc (or about 415 million
light-years).
NOTE: By coincidence the pair Δ7 in
Horologium, four hours less in right ascension,
has the interacting galaxies ESO 115-25 and ESO
115-25A near it. These are near the galaxy NGC
1096, which are all likely part of the same
multiple-galaxy group. If you are interested in
these “double galaxies”, it might be
worth seeking out ESO115-25/25A on the samenight.
“Southern Astronomical Delights”
© (2009) |
LAST UPDATED
10 Mar 2009 |
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