NGC 2392
Caldwell 39
| A planetary nebula in Gemini |
| Apparent magnitude: +9.2 |
|---|
| Apparent diameter: 0.8 x 0.7 arc-min |
| Image exposure: 31 minutes | Image field of view: 39.4 x 26.2 arcmin | Image date: 2022-01-28 |
This was taken on my first successful imaging session in four cloud-ridden weeks and so it was great to spend a warm summer evening under the stars again, even if the clouds were still threatening!
In recent months I’ve been spending a lot of whatever few sessions I can get, seeking out medium mass dying stars, otherwise known as planetary nebulae.
Apart from the nearby planetaries, such as the Helix Nebula and the Dumbbell Nebula, they are pretty darn’ small in the telescope. However, they are not as hard to locate these days as they might have been when observational star-hopping was the main method of detection. ‘Go to‘ mounts with a laptop and plate solving software now make locating them easy.
So, why ‘medium mass’ dying stars you may well ask? Well, ‘high mass’ stars die in a gigantic supernova, are gone in a few weeks and there has not been a visible supernova in the Milky Way for over four hundred years. As for low mass stars, their destiny is to uneventfully die slowly and simply fade away over hundreds of billions of years. I don’t have time for that.
The distance of NGC 2392 is uncertain but one recent estimate places it as much as 6520 light years implying a radial extent of about one third of a light year from the central star. In our Solar System, such a nebula is likely in a few billion years and it would engulf all of the planets as it reaches well out into the Oort Cloud.
NGC 2392 looks a little bit lonely in the full size image above, taken with my Schmidt-Cassegrain telescope and ZWO astro-camera. So I cropped it, to double it’s size:
Stack_21frames_1890s Half size image.
19.7 x 13.1 arcmin
It was still a bit small, so I cropped it again to double it’s size again:
Stack_21frames_1890s Quarter size image.
9.87 x 6.55 arcmin.
It’s called the Eskimo because (perhaps depending on which way you look at it), it seems to resemble a face inside the hood of a parka with a furry lining. It is also commonly known as the “Clown Face” nebula. Both seem apt descriptions but the International Astronomy Union (IAU) does not recognise the names and wants us just to call it NGC 2392 – because the names are “offensive”.
Presumably to Eskimos and clowns….. 😕
The coloured gases of the nebula, (nitrogen, hydrogen, oxygen and helium) ejected about 10,000 years ago are glowing from the ionisation caused by high energy radiation emanating from the hot central star.
The central star HD 59088 is believed to be one of the brightest for planetaries. It is a massive 10th magnitude hot O-type star, clearly defined inside the shield shaped bright inner shell (representing the face), while the outer blue-green shell contains a mottled ring of a contrasting hue, (representing the fur).
The bright type A star nearby is 8th magnitude HD 59087, a variable star.
Images © Roger Powell
| Telescope: | Meade LX-90 200mm Schmidt-Cassegrain (deforked); 2000 mm f/l @ f/10. |
| Optics: | Astronomik light pollution filter. |
| Mount & Guiding: | SkyWatcher EQ6-R Pro mount. |
| Imaging camera: | ZWO ASI 071 MC cooled. |
| Astrometry: | The Blind Astronomer |
Cosmic Focus Observatory
34° South
Above us only sky….
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Cosmic Focus 
Very nice. I like your comparison of the destinies of low, medium, and high mass stars.
My scope is sitting peacefully while the weather is cold. I am not eager to be out in it. I have enjoyed watching the thinning Moon approach Mars and Venus. I can do that from within the house with a cup of coffee in hand. A window over the mantle framed the 3 nicely today.
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I don’t envy your winters! When I was taking this image it was a pleasant +25º all evening.
I’m not sure how far I would have gone with astronomy if I had to constantly deal with sub-freezing temperatures. Here at home it might occasionally drop to about +5º on winter nights; and on rare nights the Society’s observing field has been known to drop below zero. Dew is our biggest problem, not ice!
Good for you, finding opportunities from behind a window!
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You always come up with fascinating photos and explanations . Thanks for all of them.
I save your posts so I can look at them often I envy your summer temperatures. It’s -22* here.
Fran
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Thanks Fran, very much.
I don’t know if you mean -22º C or -22º F but either way it must be somewhere near the North Pole!
🙃
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You could try GigaPixel to see if you can enlarge it. I would try it, but it’s a WEBP file that is already compressed and annoying to work with.
Otherwise, interesting as always.
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Before cropping images like this I do enlarge them with an increased resolution, which does help.
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…and I agree with you, I do not find webp files an attractive proposition.
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Very nice image and explanation on the different types of mass stars.
The planetary nebula does look like an Eskimo, peaking his head out of an igloo. To explain it like this will resonate with people, including children. No kid will grow up to be a scientist because he fondly remembered seeing “NGC 2392” through a telescope for the first time.
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I’m acquainted with another amateur astronomer, an experienced visual observer, who has memorised all the NGC and IC numbers of objects that he has ever viewed. He’s a walking, talking encyclopaedia.
Unlike him, all I can remember is “M1” and about half a dozen other popular Messier objects. Names are more easily recalled, as you rightly suggest – and if I was an eskimo or a clown, I would not take offence at the names. It would be a badge of honour.
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