NEAT SOUTHERN PLANETARIES : 24 He2-97 in Musca
One final planetary nebulae in Musca
completes those featured here in the Neat Southern
Planetary series. This is Henize PNe, He2-97 that is placed
in the southwestern Musca, and merely 22′ west of the
shared Musca-Apus border. While it is reasonably bright
and easy to find, He2-97 is a fairly small 5 arcsec.
He2-97 / Sa2-98 / Wray 16-135 / PK 307-9.1 / PN
G307.2-9.0 (13454-7129) lies 3.4°E (PA 94°) of
pale orange 3.6 magnitude star,
δ Mus / Delta
Muscae / HIP 63613 / SB 746 / “Delmus”
(13023-7133). The immediate field appears as brightish pale
orange star some 3.3′NNE (PA 21°), being 7.2v
magnitude, HIP 67098 / HD 119286 (13451-7132). Alongside it
is a unrelated fainter field star of about 13th magnitude
just 11.6 arcsec away (PA 76°) that is readily seen in
15cm in dark skies.
Figures 1 & 2. He2-97 in Musca
Fig.1 (left) Wide field
image. Size: 12.5′×12.5′ taken from the
CDS ALADIN previewer. Image composite is Red: AAO/R/DSS2;
Blue: SER/I/ DSS2; Green: average. Red/blue image modified
by “Silvering”, and slightly reducing
saturation.
Fig.2 (right) Image size: c.30×30 arcsec, being
obtained from the wider image and blurred sightly to
eliminate some of the pixelation. He2-97 is the lower
orange-yellow object, with the higher white star being
about 13th magnitude, some 12 arcsec away in PA
76°
He2-97 was discovered by K.G. Henize in 1964 from Mt.
Stromlo near Canberra in his dedicated photographic
Hα survey in search of new
southern PNe. He2-97 shines at 12.6B magnitude, with this
tiny 5.0 arcsec plain disk appears like a tiny spherical
planetary smudge without mottling nor any features. It is
easily spotted using 10.5cm., although the disk appears far
more obvious in 20cm. or larger. The nebulosity responds
well with the [O-III] filter.
The white dwarf central star is listed as 15.35V, 15.3p,
but remains invisible to the visual telescopist. According
to Phillips (2005), the PNN Zanstra temperature from the
HeII emissions is 57,000K, with an absolute magnitude of
9.15 — or about one-hundredth the solar
brightness.
Phillips (2005) finds an enormous distance of 5.53kpc.,
which exceeds the usual more distant Henize PNe discussed
in this series by a factor of two! This quoted distance is
seemingly the only one I have found in the current
literature.
Reference
- Phillips, J.P., “The distances of less-evolved planetary
nebulae: a further test of statistical distance scales.”,
MNRAS., 293, 847 (2005)
Surrounding Fields : Visual Double Stars
Δ140
(13458-7159) is a Musca pair near the border with Apus,
being located 30′S (PA 176°) from PN, He2-97.
Its field contains several faintish stars, but locating
Δ140 is a difficult to
find pair for the lack of bright reference stars. I found
it best to use δ Mus, and
move the telescope 3.4°E and 0.2Z°S. Once found
it cannot be mistaken for any other system. This happens to
be one of the fainter and closer Dunlop pairs, being
currently listed as magnitudes 8.7v and 9.7v (8.74V &
9.70V). Separation is presently about 9.8 arcsec along PA
75°, which has widened by about 1 arcsec while the PA
has decreased by about 6°.
WDS02 actually states the PA is 0°, but this is
only because it was not initially measured by Dunlop. Later
versions of the WDS, I.e. WDS11, state Dunlop̵s PA is
now 90°. I visually saw the colours of both being
white in 7.5cm., 10.5cm. and 20cm.
Oddly this pair does not feature in Innes (1899)
Southern Double Star Catalogue, even though it is
easily within his self-imposed separation limit of
twenty arcsec and roughly 10th brightness.
It is likely that these two stars are attached, as the
proper motions are similar, but from the lack of any HIP
parallax, we can say little of the connectivity of the
system. Δ140 will be an
interesting pair to observe in the future for any change in
relative motions
HJ 4586 (13284-6752) is a bright white pair that
has been known as an attractive system for small
telescopes. It can be found 1.2°ESE (PA 244°)
from Sa2-96. Discovered by John Herschel in 1837, the 7.3v
and 9.1v (7.33V & 9.09V) magnitude pair has slowly been
decreasing. In 1837 the separation was 3.7 arcsec, while
the latest position in 1991 WDS11 was 2.9 arcsec. I looked
at this pair in 1994, and the separation did seem slightly
smaller than this. Position angle has also reduced by about
9° (PA 150° to 141°).
This duo will be interesting to watch, as the narrowing
separation will make it difficult to separate in modest
apertures. If the separation continues to decrease at this
rate, it will become an impossible target for apertures
less than 30cm in about 2090AD. Looking at the shared
individual proper motions of -51.60±0.67
mas.yr-1 and -12.19±0.49
mas.yr-1, HJ 4586 is likely a true binary
system, though it will take many centuries to tie down the
orbital parameters adequately for predicting its future
positions. Combined spectral class is A5III/IV.
Hipparcos (HIP2) measures that HIP 65719 (HJ 4568AB)
parallax as 7.04±0.67 mas., making distance as
142±14 parsecs or 463±44 ly. The maximum
projected true separation, at least when John Herschel
measured 3.67 arcsec is 521 AU, making the minimum period
at this distance as 5900 years or so. (This is not
incongruous with the observed motion, though the change of
0.7 arcsec in about 150 years seems a bit larger than would
be expected.) Absolute magnitudes are 1.3 and 2.7,
respectively, whose estimated masses are 2.4 and 1.9 suns.
Combined spectral class is A5III/IV.
A worthy southern pair to look out for.
Table 1: Selected Measures for HJ 4486
PA Sep. Year Source
149.4 3.67 1837.4 J.Herschel
148.9 3.87 1872.93 H.C. Russell
142.9 3.76 1879.4 CGA
144 3.1 1929 IDS76
142 2.8 1986 WDS96
141 2.9 1991 HIP n=16
I 923 (13216-6630) this near equal magnitude
yellow pair was discovered by Innes in 1911. The WDS96
gives 9.4v and 9.9v. Its PA of 133° has changed little
since this time, though the separation has slowly
increased from 1.3 to 2.1 arcsec. Looking at the poorly
known proper motions, it is likely this pair is an optical
one and that the angle will continue to widen. Seen with
care in 7.5cm, it should be easily visible in apertures
above 10.5cm.
Table 2: Selected Measures for I 923
PA Sep Year Source
130 1.2 1910 Innes
132 1.3 1911 Innes
132 1.7 1942 IDS
132 2.1 1989 WDS96
133 2.1 1991 HIP n=6
The rest of the new NSP series will continue
in Universe in December / January 2012 issue — and
into the future — at least fitted in by the necessary
whims of the Editor’s availability of space against
other submitted material by other authors!
NEAT SOUTHERN PLANETARIES ON-LINE !!
I have been working on the older NSP Series
and bring all of it up to date on this very website.
SO FAR I HAVE REDONE VERSIONS of
NSP’s
14,
15,
18,
19,
20,
22,
22a,
23,
and this page, NSP 24.
The BACK and NEXT buttons below will cycle through
these 9 Pages made so far.
I will add the remainder in coming weeks as time
permits.
ENJOY!
Last Update : 24th October 2011
Southern Astronomical Delights ©
(2011)
For any problems with this Website or Document please
e-mail me.
|