Talk:Cat's Eye Nebula

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Featured article Cat's Eye Nebula is a featured article; it (or a previous version of it) has been identified as one of the best articles produced by the Wikipedia community. Even so, if you can update or improve it, please do so.
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Ambiguous sentence[edit]

From the article:

The image reveals two 'caps' of less ionised material at the edge of the nebula

Should it be read as that the material in these regions are less ionised compared to other regions; or that the concentration of ionised particles is lower, or something else?

If it is singly ionized nitrogen; does it have to be mentioned at all? In such case it is already mentioned in the text that green represents singly ionized nitrogen. Gunnar Larsson 19:03, 14 September 2006 (UTC)

Images[edit]

Why have they suddenly all disappeared? Several beautiful NASA public domain images have been deleted for no apparent reason.

The question has been here for a month, and no explanation offered.... were they just deleted for fun, then? 81.179.65.38 00:22, 23 December 2006 (UTC)
You don't want to have too many images--that's what Wikimedia Commons is for. I will add one more, though. It certainly is a beautiful thing.--MrFishGo Fish 18:55, 7 May 2009 (UTC)

Age[edit]

Could someone please explain the discrepancy between the distance of 3300lj and the stated upper limit of the age for NGC6543 of only 1000 years? We would not be able to see this nebula if those values were correct. —Preceding unsigned comment added by 80.187.102.108 (talk) 12:22, 8 May 2011 (UTC)

There is no discrepancy. The light that we are now seeing left the nebula 3300 years ago, when the nebula was 1000 years old. The stated age of astronomical objects almost never refers to their actual age. It always refers to their apparent age as viewed from earth, which is actually the age they were when the light we are viewing left them. Only occasionally, usually only with very distant objects, is the true age mentioned, and even then only to emphasise the huge distance and/or to note that the object may no longer exist.At least I try (talk) 12:58, 16 May 2016 (UTC)

This Article is an Utter Shambles[edit]

I've read this article three times now, and have found more than fifty mistakes here. Most of the facts are either mixed-up, incorrect or just plainly misconstrued. Note: Anyone reading the Wiki article on Planetary Nebula could fix these errors!!

Even many of the cited references don't actually say what is written here. Worst, most of the references are either out of date, or are not primary sources. I.e. SIMBAD quotes Stanghellini, L.; Shaw, R.A., Villaver, E., “The Magellanic cloud calibration of the Galactic planetary nebula distance scale.”, AJ., 689, 194 (2008), saying this distance is 1623 parsecs (1.62 kpc.)being 5323 light-years, rounded to 5300 light years NOT 3000!!


Paragraph 3

1) "The intricacy of the structure may be caused in part by material ejected from a binary central star, but as yet, there is no direct evidence that the central star has a companion."

What? Theory says that the shapes could be caused a binary star, but the majority planetaries we observe have not detected a binary star. Much of the problems are due to the distances to planetary nebulae!

2) "Also, measurements of chemical abundances reveal a large discrepancy between measurements done by two different methods, the cause of which is uncertain."

Again this is mostly due to distance, especially mostly as chemical abundance comes from spectra. Worst, What two methods? Is this any less more problematic to NGC 6543 compared to other planetary nebulae?

3) "Hubble Telescope observations revealed a number of faint rings around the Eye, which are spherical shells ejected by the central star in the distant past. The exact mechanism of those ejections, however, is unclear."

This applies to the majority of planetary nebulae, not just NGC 6543! The shells are not caused by ejections but by variable mass loss rates in the so-called superwinds, they are likely formed by snowplough theory, where the wind encounters the slower material forming them into multiple shells.

Paragraph 3 should be deleted, unless it can be proven to apply to NGC 6543. Else it should be in the Planetary Nebula page.

Under "General information" this article refers to Moore (2007) three times. I.e. Moore,S.L.(2007),"Observing the Cat’s Eye Nebula", Journal of the British Astronomical Association 117 (5): 279–280, Bibcode:2007JBAA..117R.279M

Yet the reference article does not mention 'surface brightness' nor anything about the "high declination" as stated!

Amazingly much of this article and the problems here stems from User:Worldtraveller between 2nd January 2005 to 5th September 2006 (He has not posted since 3rd March 2007. His User talk:Worldtraveller says retired.

Solution. Unless there is strong objection, much if this article needs revision and need to be written clearly to distinguish between facts relating to directly to NGC 6543 and planetary nebulae in general. I.e. The article is about NGC 6543 NOT planetary nebulae as a subject. Arianewiki1 (talk) 21:10, 31 October 2014 (UTC)

This article had a Featured Article Review in 2009, see Wikipedia:Featured article review/Cat's Eye Nebula/archive1 (nothing to stop another one though if you feel the problems are systemic enough). Ruslik0 is still active on wikipedia and so might help with this. I guess all articles need some context. I haven't read it yet to determine my feelings on the matter. Cas Liber (talk · contribs) 01:54, 1 November 2014 (UTC)
It is perfectly ok to mention that there are rings around NGC 6543, and the suspected reason for them. How else am I to find out that there a concentric rings around this nebula? Go to the nebula article and dig through that until I find a list of planetary nebula with rings? Perhaps you would like all references to the fusion of hydrogen inside the sun to be removed from the "sun" article and placed in the "star" article. It's certainly not unique to the sun.

The mention of facts concerning this nebula in this article that also apply to most nebulae does not make this an article about nebulae in general. Indeed, your wish to distinguish facts relating specifically to NGC6543 from those relating to nebulae in general will actually make this article a de facto article about nebulae in general. I agree the article is a bit of a mess, but not because it mentions aspects of NGC6543 that also apply to nebulae in general. At least I try (talk) 13:30, 16 May 2016 (UTC)

PNN[edit]

Hey people, I was the original anonymous editor for the PNN thing, I did not realize I was not logged in. I just wanna say, I am glad that the article is clearly better now. I think my original concern still stands, i.e. an abbreviation that isn't used makes the article worst, but it has been nicely addres…sed now. Dravick (talk) 14:49, 19 May 2016 (UTC)

So pleased that you have said this. You were correct to pint out the flaw of this not being mentioned in the article, so I added, referenced it, and used it multiple times. The PNN is mostly called this because of the thick atmosphere, leaching out the dregs of the gas diffused in the core, is the transition between a star and a white dwarf, whose extreme temperature radiates in the ultra-violet and illuminates the nebulosity. When the temperature drops below a certain threshold, the the PNN cannot illuminate the nebula. The moment it does this it becomes an ordinary white dwarf. The period the PNN exists is about 10,000 to 50,000 years or so.
Again, I appreciate your sentiments, hence the explanation here, and reaffirms the policy here to gain consensus when editing. Cheers. Arianewiki1 (talk) 16:34, 19 May 2016 (UTC)
I agreed with Dravick's original edit for the reason he gave, that it was not used (that it might be common outside the article seems supremely irrelevant), and this is why I reverted whoever it was that reverted that original edit. It's different now because the abbreviation is indeed used, so I agree with those changes too. Dondervogel 2 (talk) 21:39, 19 May 2016 (UTC)