obrazell
March 7th, 2021, 08:52 AM
Abell 31
Sh 2-290
R.A. 08h54m13.2s
Dec. +08°53'53" (2000)
Magnitude: 12.20
Size: 16.8'
Mag CSPN 15.5
Cons Cancer
4237
Abell 31 in Cancer is one of the brighter of the Abell planetary nebulae, although of course this term is relative.
I am slightly surprised that it has not been covered before in the OOTW series. Abell 31 is thought to be about 2000
light years away and is thus perhaps 10 light years in diameter, making it very large for an object of this class.
The GAIA distance of 504pc would put it perhaps slightly closer and thus smaller. I note however that there do
seem to be some discrepancies between the HST parallax distances and the GAIA ones.
4238
On the sky this makes it almost as large as the Helix nebula, NGC 7293, making it one of the largest planetary nebulae
on the sky The planetary is also strongly interacting with the local ISM as can be seen from the bow shocks, as seen
in this image http://www.chart32.de/component/k2/objects/planetaty-nebulae/abell-31-planetary-nebula-in-cancer.
The southern limb is seen to be much sharper and the northern limb more diffuse, indicating the direction of travel
through the ISM. There is an interesting collection of images of A31 in different wavelengths at
http://sharplesscatalog.com/sharpless/SH2-290.aspx. The central star is probably off centre as it will not be
slowed by the interactions of the envelope with the ISM. It is probable that A31 belongs to the thick disk
population of our galaxy.
The central star of A31 is still pretty hot however with a temperature of around 94000K and with a mass of
perhaps 0.6 solar masses. It is suspected to be part of a binary system.
The amateur observation history of this object seems to go back a long time with a mention (under its other
name of Sh2-290) in the NSOG where it is suggested that it should be faintly visible in 20cm class instruments
with an OIII filter. I must admit that my observations of it with a 50cm scope and an OIII filter would suggest
that, at least from the UK, it would require a larger telescope. I did however see it as a crescent shaped object
with banded structure. I note that most observations suggest it should be seen as a fairly round object. The size
indicates that you are going to need a low power eyepiece to see the whole of the nebula.
As always give it a go and let us know.
Sh 2-290
R.A. 08h54m13.2s
Dec. +08°53'53" (2000)
Magnitude: 12.20
Size: 16.8'
Mag CSPN 15.5
Cons Cancer
4237
Abell 31 in Cancer is one of the brighter of the Abell planetary nebulae, although of course this term is relative.
I am slightly surprised that it has not been covered before in the OOTW series. Abell 31 is thought to be about 2000
light years away and is thus perhaps 10 light years in diameter, making it very large for an object of this class.
The GAIA distance of 504pc would put it perhaps slightly closer and thus smaller. I note however that there do
seem to be some discrepancies between the HST parallax distances and the GAIA ones.
4238
On the sky this makes it almost as large as the Helix nebula, NGC 7293, making it one of the largest planetary nebulae
on the sky The planetary is also strongly interacting with the local ISM as can be seen from the bow shocks, as seen
in this image http://www.chart32.de/component/k2/objects/planetaty-nebulae/abell-31-planetary-nebula-in-cancer.
The southern limb is seen to be much sharper and the northern limb more diffuse, indicating the direction of travel
through the ISM. There is an interesting collection of images of A31 in different wavelengths at
http://sharplesscatalog.com/sharpless/SH2-290.aspx. The central star is probably off centre as it will not be
slowed by the interactions of the envelope with the ISM. It is probable that A31 belongs to the thick disk
population of our galaxy.
The central star of A31 is still pretty hot however with a temperature of around 94000K and with a mass of
perhaps 0.6 solar masses. It is suspected to be part of a binary system.
The amateur observation history of this object seems to go back a long time with a mention (under its other
name of Sh2-290) in the NSOG where it is suggested that it should be faintly visible in 20cm class instruments
with an OIII filter. I must admit that my observations of it with a 50cm scope and an OIII filter would suggest
that, at least from the UK, it would require a larger telescope. I did however see it as a crescent shaped object
with banded structure. I note that most observations suggest it should be seen as a fairly round object. The size
indicates that you are going to need a low power eyepiece to see the whole of the nebula.
As always give it a go and let us know.