PAGE INDEX
SOUTHERN DOUBLES
B831 TrA
B832 TrA
Δ194 / SLR 11 TrA
SOUTHERN VARIABLES
X TrA / EsB 422
BRIGHT STARS
None Given
OTHER DOUBLES and VARIABLES
None Given
DEEP SKY
None Given
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NOTES 1
Positions given as;
I.e. (13583-6018), are;
RIGHT ASCENSION
13h 58.3m
DECLINATION
-60° 15'
EPOCH
2000.0
This follows the current
WDS Conventions. |
NOTES 2
S E P A R A T I O N
" or "arcsec
In arc seconds or
' or 'arcmin
In arc minutes or
mas - milli arc seconds
POSITION ANGLE
( ° ) Angle in degrees.
Measured from
North through East
M A G N I T U D E S
v - visual (naked-eye)
p - photographic
V - Photometric Visual
B - Photometric Blue
MV - Absolute @ 10pc.
ABBREVIATIONS
pc. - parsecs
ly. - light-years
AU - Astronomical Unit
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NOTES 3
O R B I T A L
E L E M E N T S
T: Periastron (yr.)
P: Period (yr.)
a: Semi-Major Axis (arc sec.)
e: Eccentricity
i: Inclination
Ω: Orbital Node (°)
ω: Angle True Orbit (°)
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SELECTED SOUTHERN DOUBLES and VARIABLES
R.A. 15 Hours
B831 (15085-6438) in TrA is
17.0'W of B832 by and 3.0'N of the planetary nebula NGC
5844. The magnitudes are 8.7 and 10.9 respectively,
separated by 2.6 arcsec towards PA 108°. Little has
also changed with this pair in the last seventy years
since its discovery. I see both stars as yellowish-white.
Located 13′NEE (PA ~55°), and centred on the
position 15h 12m 23s Dec. -64° 32′ 29″
is a lovely asterism of eight stars and finding it is easy.
This object has no common name, and is not listed as a
multiple star. The two brightest and closest stars
(GSC9029:374 and GSC9029:167) are 7.4 and 7.8 mag. All the
other stars are between 9.8 and 13.8 mag in an area of
about 4.0'. It would take 20cm in dark skies to see them
all, that is best viewed using medium magnifications.
(c.200×)
B832 (15109-6439) in Triangulum
Australe is 4.0' from the planetary nebula NGC 5844. Both
stars are 9.4 and 11.4 mag, respectively, appear as yellow
and orange. Since the first measure in 1927, little has
changed with these stars that are separated by some 4.8 arcsec
at PA 79°.
Δ194 / SLR 11
(15549-6045) is a stunningly brilliant multiple star,
1.0°NE of NGC 5979. The primary pair, SLR 11
(AB) has the components as 6.5 and 8.8 magnitudes, being
separated by 1.3 arcsec at the due east PA of 93°.
To me the primary is yellowish, and the secondary is blue in
colour. Spectrally this star is given as B9 II, but there
is some doubt, I.e. the WDS Notes, that suggests it maybe
more like a K-type star. A 20cm telescope, using medium to
high magnification and good seeing will just easily
separate the pair. 25cm or 30cm will perhaps separate the
pair more easily. Since the first measures by Sellors in
1891, the separation has slowly increased by 0.4 arcsec -
with the last reliable measure made in 1962. The
‘A’ component is an unknown type suspected
variable NSV 7310, displaying a small magnitude range of
6.11v to 6.15v. It is also a spectroscopic binary of
uncertain period - making this a likely triple.
Two fainter yellowish companions are associated with the
main pair that was discovered by Dunlop at Parramatta
Observatory in 1832. The brightest lies north followed by
the principle pair. Δ194 (AC) has the additional C
component at 9.1 mag, some 45.0 arcsec apart at PA
48°. Since the first measures by H.C.Russell in
1883, the separation has increased by 1.5 arcsec while
the PA diminished by merely 3°. The second star
is Δ194 (AD) lies south preceding. At 8.7 mag, it is
separated by 48.1 arcsec at PA 225.7°. Since 1883,
the separation has diminished by 1.2 arcsec. Due to the small
motion of these stars, little is known of the true connect
of these outlying stars. The ‘C’ and
‘D’ components display opposite common proper
motions. They maybe orbiting in a very long period - but
it is more likely they are mere field stars.
Overall the multiple star of Δ194 makes an attractive
set of stars in a prolifically starry field.
X TrA / EsB 422 / SAO253062 /
(15146-7004) lays 1.4° SSW of the third
magnitude star Gamma (γ) TrA, and 24' from the
Triangulum Australe and Octans border. Positioned on the
western corner of TrA, it can be easily found by moving an
equatorial mounted telescope directly 9°W from
the planetary Sa2-162. I came across the deep red
star while journeying in the southern part of the
constellation. Its redness is obvious when once seen. It
is similar to the garnet star EsB 365 next to β
Crucis. The variable star classification of X Tra was made
during the turn of the century, and was classed as a Lb
type irregular variable - so it tends to exhibit slow
changes in brightness. In X TrA case, the brightness
variations seem to be between 5.0v and 6.2v magnitude or
8.1p to 9.1p magnitude. One reference to this star is
found in Webb's “Celestial Objects for Common
Telescopes”'; Vol 2. under “Stars with
Remarkable Spectra”. The EsB is the
Epsin-Bimingham '“Red Star Catalogue”'
produced photographical and visual observations in 1897,
yet EsB 422 was by discovered by Fleming in 1895. It also
has a large B-V magnitudes of 2.7. Spectrally it is
classed as Nb, which was later upgraded to a carbon star
of spectral type C5,5, corresponding to a surface
temperature around 2 500K. Interestingly, Webb states 6.2
mag, however, visual estimations of red stars are
notorious for being unreliable. This 6.2 mag 'minima' are
still quoted in the magnitude range, though it has never
been this faint since this time. (Note: Espin Updated
Addition of the Handbook was made in 1917. The observation
by Epsin was actually made by Innes.)
“Southern Astronomical Delights”
© (2009) |
LAST UPDATED
10 Mar 2009 |
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