Object of the Week January 8th, 2023 - Abell 8

[obrazell]

Abell 8

PN G167.0-00.9

Planetary Nebula

Auriga

R.A. 05h06m38.4s

Dec. +39°08'11"

Size 1’

Magnitude: 16.60

CSPN mag 19.7

After the inclusion of the planetary nebula Abell 7 in Lepus a week or so ago as the OOTW
I thought it would be interesting to have a challenge object for more northerly observers.
The planetary nebula now known as Abell 8 was first reported in George Abell’s 1955
paper where it was listed as number 7. In the better known 1966 paper it was renumbered
as Abell 8 which is how it is known today. There have been suggestions that Abell 8 is a
member of the sparse open cluster Bica 6 but there seems little follow up evidence on
this and clusters containing planetary nebulae are not common so I would have thought
if this linkage was secure there would be more information on it. If it is indeed a
member of the cluster, which is thought to be about a billion years old, then the
progenitor of Abell 8 was likely a star in the 2.5 solar mass range. Abell 8 is a relatively
old PN and has a fairly simple structure. The outer ring is very strong in H-Alpha
emission and the interior mostly shines in the light of OIII, however the IPHAS data
does show some structure in the H-Alpha band in the centre. Abell 8 is suggested to
be about 1.6 kpc from us, although the GAIA distance is nearer 2.0 kpc. The PN is
located in the anti-galactic centre location. There is some associated H-Alpha emission
nebulosity in the general area but this is not associated with the PN per-se but it is
likely to be the local ISM excited by UV radiation leaking from the PN, see
https://www.hansonastronomy.com/abell-8 . Otherwise there does not seem to be
much research published on this object.

a8.jpg

Observationally Abell 8 is going to be a challenge and my only observation of it was
with a 20” and an OIII filter which suggested that it was very faint disk, although
visible with direct vision. The site I observed it from was in Devon in the SW of the
UK so it is not a high altitude site, although transparent by UK standards. Alvin
Huey suggests a similar observation with his 30” and Kent Wallace also suggests a
faint disk with his 20” and an OIII filter. Uwe has some information on his
observations of it as well at http://www.deepsky-visuell.de/

And as always,

“Give it a go and let us know!”

[Steve Gottlieb]

I viewed this dim planetary back in January 1990 with a 17.5-inch at 82x and 140x and an O-III filter. At the time of the observation, Abell 8 was quite high (I wrote near the zenith in my notes).

It appeared quite faint, round, perhaps 1' diameter and encompassing a 13th-mag star on the southeast side. When I removed the filter, a mag 15 star was visible about 20" northeast of the brighter star, forming a wide pair. A 10th-magnitude star is 2.5' southeast.

[Ivan Maly]

One of the "visual" Abells, this nebula is prominent in Panstarrs G. I have the following notes and sketch.

2019-09-03, Spruce Knob, 4800 ft a.s.l. Clear, relatively dry and calm. Transparency above average, seeing 3-4 arcsec. SQM 21.7. 20" F/4. Abell 8 (PN, Aur). Invisible in 13 mm without filter. With OIII, appears round and smaller than on DSS NW of an unequal star pair (detached from it). Alternately, a larger annulus is suspected. 5.5 mm, OIII: hints of partial annulus - an arc just N of the fainter star. 8 mm, OIII: more definite arc NW of the star pair, convex to the N. Two similar close unequal double stars farther NW.

Abell 8.jpg

P.S. The inner nebulosity is unresolved light of the group of faint stars there, typically of Abell fields that are rich in unresolved starlight frequently enough clumped exactly where the nebula might be. The arc is real in g/OIII. It is part of the annulus that may be even brighter where the two bright stars are, but the stars wash it out visually. This was one of my first observations of Abells.

[Uwe Glahn]

I copy my notes of my online provided Abell-project beneath.

16", 129x, [OIII], NELM 7m2
only visible with [OIII] filter; very faint, round disk; double star NW edge

27", 172x, [OIII], NELM 7m0+
without filter decentred double star; no PN disk and no central star visible; with [OIII] filter steadily visible round disk with good defined edges; double star visible even trough filter

sketch:
Abell8.jpg
home

[Robin]

I observed this planetary nebula and open star cluster with my 20" Dobsonian at 419x magnification last weekend. For the PN, I had to use an O-III filter to detect it. It was pretty difficult. I did not see a ring, but a round and diffuse blob. To observe the star cluster, I removed the filter. Please find attached my sketch.

There is an interesting paper regarding a "likely membership" of the PN in the cluster:
https://iopscience.iop.org/article/10.1086/662663

Clear skies,

Robin