Talk:Eta Carinae/Archive 2

Archive 1

Archive 2

Archive 3

Pre-GAN things to do

Right, going through it and thinking about things to do/find.... Cas Liber (talk · contribs) 22:39, 20 April 2015 (UTC)

• Need to find best ref discussing Carina OB1 association and membership thereof - had a brief look late last night, so that the tag can be reffed...

I Might have to reword that bit. Although it agrees with the Carina OB1 article, some research suggests it isn't clearcut, possubly not true at all. Lithopsian (talk) 23:17, 20 April 2015 (UTC)

Removed all reference to Car OB2. Not really associated with the Carina Nebula, just nearby in the same spiral arm, so nothing to do with Eta Car. Lithopsian (talk) 20:01, 21 April 2015 (UTC)

• Should periastron link to Argument of periapsis?

It appears to redirect? Not really the same thing. It should probably redirect to Periapsis which is currently a redirect to Apsis. Lithopsian (talk) 23:17, 20 April 2015 (UTC)

aha, good idea/done Cas Liber (talk · contribs) 00:56, 21 April 2015 (UTC)

• Isn't the adjective "bolometric" implied when we use the term luminosity?

Usually. It doesn't hurt to mention it when there could be possible confusion, but maybe that word isn't necessary in the lead. Lithopsian (talk) 16:09, 21 April 2015 (UTC)

I took that word out of the lead, and slightly modified that sentence to be sure it referred to both components combined. I think this is OK now. Lithopsian (talk) 09:49, 29 April 2015 (UTC)

• Added a to classification section.

Added a reference for that paragraph. Lithopsian (talk) 16:10, 21 April 2015 (UTC)

• I can't see where we discuss distance anywhere.....

Distance? Such a minor thing :) I'll have to add a section for that, especially since it is known reasonably well. Lithopsian (talk) 16:09, 21 April 2015 (UTC)

The distance was already in the starbox, but formatted incorrectly. Do we need a section about it? The derivation of the distance is quite interesting and unusually accurate for such a distant object. Or just mention it somewhere like the surroundings section? Lithopsian (talk) 20:01, 21 April 2015 (UTC)

I think it is worth discussing as yes it is interesting - already seen other stuff in the discussion on trumpler 16 going over some of the estimates too. I did wonder whether the properties of the stars were maybe better organised into a section each on star A and star B as much of the material on classification and temperature particularly could be more coherent this way. Cas Liber (talk · contribs) 22:55, 21 April 2015 (UTC)

I'm not sure how best to organise this. There are only a handful of things known (or guessed) about the secondary, and any sections about them would be very minimal. I was also thinking that a section about the orbit itself might be helpful. There's some raw data in the starbox, but I don't think that really gets across the relationship between the two stars (eg. how close they are at periastron). Lithopsian (talk) 12:25, 22 April 2015 (UTC)

I'm calling this one done (probably needs proofing!). I've added a section discussing methods to derive the distance, which should provide some insight into both the techniques and the uncertainties involved. Lithopsian (talk) 13:24, 24 April 2015 (UTC)

• Section "Observational history"? Seems like the first sub-section is history, but the rest not really. Is this the best title? Lithopsian (talk) 12:22, 24 April 2015 (UTC)

I was comparing with Betelgeuse, Sirius and Vega (all FAs) - have rearranged like them - visibility needs some basic stuff like where it can be seen from etc and how to find it. I put surroundings in its own section. Cas Liber (talk · contribs) 13:55, 24 April 2015 (UTC)

Better arrangement. Can Surroundings go back into the new Visibility section?? Where should Distance be? Lithopsian (talk) 18:44, 24 April 2015 (UTC)

NB: Just started reading more (using books.google.com.au I can see first 2 chapters of Eta Carinae book, can you see different ones?) ...this article could get quite a bit bigger (groan..) Cas Liber (talk · contribs) 13:55, 24 April 2015 (UTC)

Could be, but I think we have most of what the article needs now. Eta Carinae may be the most intensively studied star in the sky, a quick non-scientific check shows more journal references even than Betelgeuse. Lithopsian (talk) 18:44, 24 April 2015 (UTC)

NB:The dying words of Priscilla Fairfield Bok are pretty cool too, be nice to shoehorn them in somehow. Cas Liber (talk · contribs) 14:09, 24 April 2015 (UTC)

Story also in Bok's biography and elsewhere, with some variations. Lithopsian (talk) 18:44, 24 April 2015 (UTC)

• A light curve. We have the thousand words describing the brightness variations, a picture would summarise them nicely. I rememver looking and not finding one in Wikipedia, but surely there is something out there we can use? Lithopsian (talk) 20:55, 25 April 2015 (UTC)

Yes - there is one in the Frew reference. If someone can re-draw it like we do maps then we're in business. Page 13 of this/here :) 21:00, 25 April 2015 (UTC)

I added TWO! Lithopsian (talk) 16:38, 28 April 2015 (UTC)

Cool! Cas Liber (talk · contribs) 03:31, 29 April 2015 (UTC)

• Pronunciation? Lithopsian (talk) 16:38, 28 April 2015 (UTC)

of what? I've never bothered....Cas Liber (talk · contribs) 03:31, 29 April 2015 (UTC)

OK, lets not bother. Latin pronunciation is a nightmare anyway, everyone has their own way, and here might not be the place to explain how to pronounce Greek letters. Lithopsian (talk) 12:51, 29 April 2015 (UTC)

@Lithopsian: are you happy with the comprehensiveness now? I can't think of anything important we've missed but will read more and have a think. My only niggle is a concern that we should rearrange the Properties section so that its subsections are Orbit, Primary Secondary and Mass loss and material is reorganised accordingly, but am not convinced either way.....otherwise we can just sling it up at GAN and see how it goes. Cas Liber (talk · contribs) 05:52, 29 April 2015 (UTC)

Yes, I'm happy with the completeness, although I might think of a few more little things. I do still have a few corrections to make in the new Future section though, so don't nominate just yet. I'm not really happy with the section layout though, and not just the Properties section. Are you suggesting just three (four?) sub-sections in Properties? One for the orbit, then one each for all the properties of the primary and secondary? And a separate one for mass loss? Lithopsian (talk) 09:47, 29 April 2015 (UTC)

Yes, Like in the article Sirius. Cas Liber (talk · contribs) 11:43, 29 April 2015 (UTC)

I can see the niggle, and I can see how it works well in Sirius (although some other parts of the article seem poor - bit-rotted over time?), but I'm not seeing a solution for Eta Carinae. I tried to rearrange the Properties sub-sections and just got a mess. Some of the existing sub-sections are quite small, but an Eta Carinae A properties sub-section becomes a massive amount of words all in one lump. Also it is hard to separate the properties in some cases, after all we've never come close to seeing the secondary. I tried a different arrangement of sub-sections elsewhere which 'm a bit happier with, but still not sure about Distance. Lithopsian (talk) 12:51, 29 April 2015 (UTC)

Distance is a hard one - it's sort of linked with visibility, possibly more so than properties. I think it is at a point where GAN is worth a shot for some outside eyes anyway. I reckon if you feel comfortable with its comprehensiveness (and I think I do to), and I've tried to copyedit and link then it's time for some outside eyes. My choice is GAN, then if it gets a ral good going-over at GAN, I usually send to FAC. If not, a PR might be good, or I will just ask a couple of folks to take a look at it (one lay-person and one astronomer)...Cas Liber (talk · contribs) 14:42, 29 April 2015 (UTC)

Give me two weeks and I'll give it a thorough read-through (assuming the GA review gets completed by then). StringTheory11 (t • c) 15:30, 29 April 2015 (UTC)

I agree it is ready to be a Good Article now. Lithopsian (talk) 15:00, 29 April 2015 (UTC)

homunculus nebula and great eruption

I think we should make separate sections on the great eruption and homunculus nebula. hi (talk) 14:53, 2 May 2015 (UTC)

I think we should let the GA review take place without pulling the rug out from under whoever is trying to read the article. 21 edits in one day for no gain is just the thing to make a reviewer reject the article out of hand. Lithopsian (talk) 20:17, 2 May 2015 (UTC)

I am. furhan. agree with Lithopsian - we've all been staring at this article for days and days. Just pausing and getting a fresh set of eyes is extremely important here. This is the best thing about the review. Then we move on from there. I've done this a few times and will give us the best end result. Cas Liber (talk · contribs) 22:32, 2 May 2015 (UTC)

Mass and luminosity

Check this. It says Eta carinae's luminosity is ~4,000,000 L_☉.

Answered on my talk page, but it needs comment here too. I don't see anywhere in the paper that says the luminosity is ~4,000,000 L_☉. One of their models gives a value near this, the other models less near. Note that the models are not intended to give accurate values for the luminosity of Eta Car, only to provide validation of the models themselves, although they do offer an interesting insight into the nature of the object and the radiation it is emitting. The only value I can see in the paper that might be intended as an actual statement of the luminosity of Eta Car is the HR diagram (no source given) which suggests an offbeat value below 2 million L_☉, which I can only assume is a mistake. Lithopsian (talk) 21:03, 25 April 2015 (UTC)

Page 14 of this book gives some figures - currently around 501,000, peaking at around 5 million. There is some good consensus stuff I am trying to read in it. Cas Liber (talk · contribs) 21:16, 25 April 2015 (UTC)

This has some interesting information. Reply back if you think I am right. hi (talk) 21:58, 25 April 2015 (UTC)

This and this say that eta carinae A's mass is ~>90 M⊙, the best estimate for the radius is ~60 R⊙, its mass loss rate is ~8.5 × 10^-4 solar masses per year, and its wind velocity is ~420 km/s. eta carinae B, however, is now throught to be a Wolf-Rayet star or an O supergiant with a mass of ~40-50 M⊙, and a mass loss rate of ~10^-5 solar masses per year, and a wind velocity of ~3000 km/s. They also say;

"The angular momentum transfer scenario appears conceivable since η Car’s rotational velocity is likely close to the orbital velocity of the companion star, i.e., v_rot ∼ 0.8–0.9 × v_crit ∼ 240–270 km s⁻¹, whereas v_orb ∼ 250–300 km s⁻¹ (with a companion mass of ∼ 40–50 M⊙ and an orbit eccentricity of 0.8 or higher)."

Some of these numbers aren't in the article so maybe we could put them in.

Yes, I've seen those numbers and some consensus material uses them. Will take a look at them soon. Cas Liber (talk · contribs) 20:46, 27 April 2015 (UTC)

Problem with this one is that it cites an article from a 2001 paper, which predates confirmation of binary status. This one only touches on that -and is really focussing on the periastron its significance in the evolution of the system. Still looking....Cas Liber (talk · contribs) 02:46, 29 April 2015 (UTC)

You seem to be getting hung up on this mass number of 90. Even though one of your quoted papers says >100. 90 is a "hard" lower limit for the mass, with the calculation that it would simply blow itself apart if it were any less massive. So we have "> 90", and occasionally "> 100" based on slightly different calculations. That might be 120, 150, 250, or 1000! A good consensus estimate (best guess!) appears to be 120 and recent comprehensive papers most frequently use this number. It is even harder to pin a single number on the radius, perhaps entirely meaningless, read the text for discussion. 60 R_☉ is an entirely arbitrary number for an entirely unseen and unseeable supposed "core" at a particular density and temperature. The number 60 is mentioned in the text with an explanation of what it means. Be very careful about pulling individual numbers out of context and throwing them into Wikipedia as if they were hard facts. Lithopsian (talk) 10:10, 29 April 2015 (UTC)

@Lithopsian The paper said that the most likely number would be ~60 R_☉ so maybe we should put it in the starbox. hi (talk) 14:42, 8 May 2015 (UTC)

I assume you're talking about the 2014 Hamaguchi paper? Anybody's guess, but I'll go with that for now. So you're pulling out the number "60" without understanding what is going on? What is so special about that number quoted from a paper 15 years old (pre binary), but not the values actually derived in that paper itself?

So, I'll try to explain since you can't be bothered to read the literature yourself. Although the 60 R_☉ value is from an old paper, it is in many respects still as valid today as it was 15 years ago. Did you read the Hillier paper? You should, it puts that number into context, no more and no less special than several other values. 60 R_☉ is the size of an arbitrary "quasi-hydrostatic core" at 35,000K. We can't see the core and there is no real reason to assume it exists, but it isn't incompatible with other extreme LBVs such as Car 83 and HD 5980. Several authors use the number, it is convenient and useful in the right context, although it is worth noting that the temperature of the actual "star" before all the trouble started is thought to be 20,000-25,000K (equating roughly to 100 R_☉)rather than 35,000K.

The definition of the radius, and the temperature, of Eta Carinae is far from obvious. The Hiller paper discusses this and I have attempted to explain in this article. Eta Carinae may or may not have something resembling a "surface", a rather discontinuous boundary between a quasi-hydrostatic interior "star" and much more tenuous "atmosphere". It certainly doesn't have a traditional photospheric surface like our sun. What it does have is a dense opaque stellar wind, possibly entirely indistinguishable from the denser deeper layers, but in any case it is all we can observe. Defining the wind surface itself is somewhat arbitrary because it is heavily influenced by the secondary, indeed at times it completely envelops the secondary. Leaving aside just where you want to pick a "surface" between the top of the wind and the core of the star, neither the wind nor the star are remotely spherical. The star is thought to be heavily deformed by near-critical rotation. The wind is *known* to be nowhere near spherical even before it is mashed by the wind from the secondary. Incidentally, it is slightly odd that the Hamaguchi researchers seem bemused that the numbers they derive for the size of some x-ray blocking structure does not match the 60 R_☉ value, because there really isn't any reason it should.

So give up your search for some magic number, and definitely stop fixating on particular numbers without understanding the context, because Eta Car isn't a ball bearing. The numbers in the starbox for radius and temperature both come with cited papers, both of which explain the context and reference other possible definitions including the 60 R_☉ number. One possible valid criticism is that the starbox temperature and radius are not from the same paper and are not strictly compatible with eachother. I wrote three paragraphs in the article about the difficulties of defining the size (did you even read that?) to try and put this into some context, although obviously I could write a lot more. Lithopsian (talk) 19:47, 8 May 2015 (UTC)

This is confusing. The article said, "As a single star, an initial ≈150 M☉ star would typically reach core collapse as a Wolf Rayet star within 3 million years", yet the article said that Eta Carinae is <3 million years old! I know this means "less than", but it obviously means that it is very close to 3 million years, so the reader will assume that Eta Carinae will reach core collapse within a very short period, or perhaps no time at all. Someone should correct this error. hi (talk) 20:21, 28 April 2015 (UTC)

Why are you guessing that less than 3 million means very nearly 3 million? It says less than because it means less than. It might be 1 million, 2 million, or very nearly 3 million. Nobody is prepared to make a strong estimate on any particular number so < 3 million is the best we have. Lithopsian (talk) 09:36, 29 April 2015 (UTC)

Starbox image

A few days ago I added a small star map showing the location of Carina and of Eta within it. I put it above the starbox, moving the pretty picture elsewhere. Now we have a Visibility section and it strikes me that the little map might be better there instead. So what do people think should be at the top of the starbox: striking picture; or useful map. Lithopsian (talk) 18:53, 29 April 2015 (UTC)

@Lithopsian: - torn on this. The image looks great but could be used in the article when discussing surrounding nebulosity...Cas Liber (talk · contribs) 00:40, 25 May 2015 (UTC)

GA Review

This review is transcluded from Talk:Eta Carinae/GA1. The edit link for this section can be used to add comments to the review.

Reviewer: I am. furhan. (talk · contribs) 20:09, 29 April 2015 (UTC)

Yes, it should be a good article.

@I am. furhan.: it's supposed to be someone uninvolved with the article who reviews it, sorry. Thanks for the vote of confidence though. Cas Liber (talk · contribs) 20:31, 29 April 2015 (UTC)

@Casliber:, if you consider me uninvolved enough, I could take up the review in a week and a half or so if nobody else has done so by then. StringTheory11 (t • c) 12:36, 30 April 2015 (UTC)

Hmmm, from looking though the history, all you've done is some very minor formatting and cat fixing, so I'd consider you uninvolved WRT article content as a whole, so, yeah, if no-one has picked it up when you're free we'd be happy to have you look it over. cheers, Cas Liber (talk · contribs) 12:42, 30 April 2015 (UTC)

@Casliber:, I'll start the review tomorrow! StringTheory11 (t • c) 02:42, 12 May 2015 (UTC)

Great! much appreciated. Cas Liber (talk · contribs) 02:43, 12 May 2015 (UTC)

@Casliber:, @Lithopsian:; quite a good article overall; does a nice job of making a technical subject non-technical for the laypeople. There are only a few minor issues that need to be solved before GA.

• I've done some minor copyedits; revert if you disagree with any.
• What do you mean by "emit natural LASER light"? Do you mean the light is polarized like the light from some lasers is, or do you mean that the process is similar to how light from lasers is produced? I'm a little confused. I also don't see this mentioned anywhere in the body.

This is a throwaway factoid that I left in because some readers will no doubt have heard it mentioned. The light is actually from stimulated emission, with a (usually forbidden) meta-stable transition being pumped by another strong emission line. I can describe it (where?) or just remove it. Lithopsian (talk) 16:29, 12 May 2015 (UTC)

How about in the High energy radiation section? StringTheory11 (t • c) 18:00, 12 May 2015 (UTC)

I've put a paragraph in the Spectrum section. It fits well there, although someone looking for laser information might have to search for it. Lithopsian (talk) 18:58, 13 May 2015 (UTC)

• "Further sporadic observations over the next 70 years show that Eta Carinae was probably around or below 4th magnitude". Do you mean the 4th magnitude as in the magnitude 3.3 mentioned above, or do you mean the modern 4th magnitude?

I've re-read the reference and worded this more clearly. Lithopsian (talk) 21:06, 12 May 2015 (UTC)

• "In 2010, astronomers Duane Hamacher and David Frew from Macquarie University in Sydney showed that...". I think this might go better in the Cultural Significance section.

I moved this from there as it seemed to slot nicely chronologically into the Brightness section, where it has more context than just being one of a bunch of factoids in a Cultural Significance section. However, the Cultural Significance section is a bit slim. Happy to move if everyone else thinks better in latter place Cas Liber (talk · contribs) 01:42, 13 May 2015 (UTC)

I've been torn on this, but I've decided moving it out is better. That snippet adds nothing to a section called "Brightness", even though that Cultural Significance section is a bit of a loose end. I also want to edit it slightly to clarify that the Chinese names are "modern", 17th century, since Eta Carinae is not included in the original mansion-based constellations. Furhan has re-organised things though. I'm tempted to undo the whole lot, but that may be too harsh. The headings are no longer appropriate, there is some dubious poorly cited material, and some (accidental, I think from sandbox working) reverts of previous copyedits. I can add back some useful changes afterwards, for example some image shuffling. Lithopsian (talk) 18:49, 13 May 2015 (UTC)

@Lithopsian:, I think undoing the whole edit is probably the best idea at this point. Furhan is definitely a good faith editor, but I'm not seeing any improvement from the edits and I'm seeing lots of deprovements. StringTheory11 (t • c) 18:15, 14 May 2015 (UTC)

Undo and moved that block of text, plus minor edits to the Chinese asterisms paragraph. Lithopsian (talk) 21:53, 14 May 2015 (UTC)

• Probably good to define the acronyms EHF, SHF, and UHF.

Done. Lithopsian (talk) 22:32, 12 May 2015 (UTC)

• "looking distinctly orange within the dark "V" dust lane". I would think that Eta Carinae is currently much too dim to be able to see color with the naked eye; am I missing something.

Agreed, those details are not visible with the naked eye. I'll try to clarify the text. Lithopsian (talk) 16:29, 12 May 2015 (UTC)

StringTheory11 (t • c) 15:35, 12 May 2015 (UTC)

All queries have been addressed, and I now believe this meets the GA criteria. Pass. StringTheory11 (t • c) 01:28, 15 May 2015 (UTC)

There are masses of Eta Carinae images. I just wanted some eye candy at the top, not necessarily this particular image. You can move any images that go with a particular section, there will always be good ones to go in the starbox. Lithopsian (talk) 10:42, 25 May 2015 (UTC)

Error

The starbox says that the spectra is F but then says that the temperature is 15,000 K.aaaaaaaaaaaaaaaaaaaaaa (talk) 01:11, 26 May 2015 (UTC)

That's a weird Simbad-style composite spectral string from a catalogue showing several different spectral types. I should probably change it, but its hard to know what would be better. The current day spectrum defies classification, partly because nothing resembling a star is actually visible. The last published spectral type saying anything more than just "peculiar" is F5 from 1893. There's an "OBe pec" from 1971, but that's just a cursory global survey of many stars. I notice that Simbad doesn't even list a spectral type for Eta Car A any more. As we've discussed before, none of the physical parameters for Eta Car can be taken at face value (except maybe the luminosity), certainly not the spectral type and temperature, that's why there is so much text describing them. BTW, obfuscating your user-name isn't clever. Lithopsian (talk) 13:38, 26 May 2015 (UTC)

Yes - often with weird stars you really have to read (and explain in the article} alot as it is more complex than just listing the letters and numbers - a similar situation exists with the R Coronae Borealis variables, which SIMBAD often lists as C, yet they have temperatures sitting in the F range...and some are described as such. And agree with changing your signature back please. Cas Liber (talk · contribs) 20:30, 26 May 2015 (UTC)

Why not just list it as 'variable' or 'peculiar'? Any interested reader can consult the Classification section for the details. Modest Genius ^talk 21:30, 26 May 2015 (UTC)

Heh, that's what the little 'p' is for....(chuckle) - depends on the situation. I've stuck in ranges for Cepheids and RV Tauri variables FWIW. Cas Liber (talk · contribs) 01:04, 27 May 2015 (UTC)

Ranges are OK for some variables, but can't be used here. I tend to just put "LBV" for LBVs, which isn't a real spectral type but nicely encapsulates the particular type of spectral variability, but Eta Car doesn't obey those LBV rules. I'd put "variable" except the spectrum isn't really variable (isn't really even visible!) - it has changed over the decades but is relatively stable on shorter timescales (some high energy features,x-rays especially, change during the orbit). I feel footnotes coming on, but I really feel they are an admission of failure to properly describe the subject. Note that the secondary spectrum is also far from being a hard fact, it could well be a WR star, the luminosity class is unclear, and the exact subclass isn't known. Lithopsian (talk) 11:43, 27 May 2015 (UTC)

Non-visual colours

At the moment the starbox has a fairly complete list of colour indices (U-B, B-V, J-K, etc). These are valuable to an astronomer for analysis, but would the simple apparent magnitudes in each filter range be more helpful to the average reader of this article? Lithopsian (talk) 18:47, 25 May 2015 (UTC)

Not sure either is hugely accessible really - possibly a wikiproject issue as it might involve looking at all starboxes and what is in them? Cas Liber (talk · contribs) 20:49, 25 May 2015 (UTC)

The fields are available in the starbox, just not filled in in this case (or in most cases). I just think an infra-red apparent magnitude might at least mean something to some people (like "HOW bright?" in Eta Carinae's case), but how many people would know what to make of a J-K value. Lithopsian (talk) 21:15, 25 May 2015 (UTC)

My bad - if they are already available in the starbox then use them. Cas Liber (talk · contribs) 11:52, 27 May 2015 (UTC)

Funny Statement

" The primary is a peculiar star similar to a luminous blue variable." Similar? Really? There are a lot of folks who consider Eta Car to be the prototype of all LBVs. — Preceding unsigned comment added by 24.121.216.97 (talk) 04:05, 28 May 2015 (UTC)

Hardly the prototype, or they'd be called Eta Carinid variables ;) The prototypes (read LBV) were variables in M31 and M33. In fact if they are named after any star at all, they are called S Doradus variables. Eta Carinae and P Cygni are certainly considered archetypal examples of the LBV super-outburst but it isn't clear if that this is something which all LBVs undergo. Even ignoring all that, Eta Carinae does not exhibit classic S Doradus features and if it was only known from the last century would be considered a candidate LBV at best, more likely a unique object. However, rather than me disagreeing with your anonymous "lot of folks", I recommend you simply read the references from the article, they are comprehensive and will give you a better understanding of the subject. In particular, if you read only one thing, read the book Eta Carinae and the Supernova Imposters. I'll offer you one quote from the chapter on LBVs: "Eta Car is often described as an LBV, although it is a more extreme example owing to its giant eruption.". Lithopsian (talk) 11:52, 28 May 2015 (UTC)

Right , now that's done....

Right, I'll alert Mike Peel who's actually an astronomer to take a look as a Peer Review type activity.... cheers, Cas Liber (talk · contribs) 01:53, 15 May 2015 (UTC)

Hmm - Mike seems to be busy - will ask someone unfamiliar to see what we can do about accessibility as well. Cas Liber (talk · contribs) 21:44, 21 May 2015 (UTC)

Comments from Mike

Sorry for not commenting sooner. I've put some initial suggestions below; I'll add more in-line over time. Thanks. Mike Peel (talk) 20:32, 22 May 2015 (UTC)

Overall:

• I'd recommend refocusing the structure of the article a bit. 'Observational history' should cover the history of the observations and events: 'brightness', 'spectrum', 'high energy radiation' and 'radio emission' would be more natural under 'properties'. Why not have a section on the Great Eruption as a historical event, followed by when the object was discovered in different wavebands? 'Visibility' confuses two different topics: how the object looks from Earth, and what its environment is. Consider splitting those into two different sections. 'Cultural significance' could be moved into the history section.

I don't know. I've never been 100% happy with the section arrangement, but its the best I could think of. 90.216.66.95 (talk) 12:22, 23 May 2015 (UTC)

(Lithopsian is that you logged out?) I will have a play at reorganising and we can put them up side by side I guess Cas Liber (talk · contribs) 13:51, 23 May 2015 (UTC)

Ok, I have rejigged them thus - I feel happier with it this way. Surroundings was a hard one to slot into a larger topic. Now in distance - could just put it at lvl 2 header I guess too Cas Liber (talk · contribs) 14:13, 23 May 2015 (UTC)

I think maybe the surroundings section can be split. Talk about the Homunculus separately from the more distant surroundings. Could we have a section that isn't called "Distance" and have a "Distance" sub-section after Homunculus and Surroundings? Lithopsian (talk) 17:11, 23 May 2015 (UTC)

yeah I was looking at it and sort of thinking the same thing - we could either just have then distance and whatever we split surroundings in as two separate level two headings or make a level two location and surrounds header and have them all level three headings within. thoughts? Cas Liber (talk · contribs) 20:56, 23 May 2015 (UTC)

• Numbers should include uncertainties, rather than giving the appearance of being exact, or using words like "around".

Tricky. Very few of the data values have published error ranges (ie. they are assumptions or models rather than direct calculations). Even when you find an error range given, it typically applies within a single set of assumptions that are far more uncertain than any quoted error. Less weasel words would be good, but these values really are uncertain and even the uncertainties are uncertain. 90.216.66.95 (talk) 12:22, 23 May 2015 (UTC)

• A minor point: the minus symbol should be given as − rather than -

think I got 'em all... Cas Liber (talk · contribs) 00:29, 23 May 2015 (UTC)

Introduction:

• 'This is currently the only star known to emit natural LASER light in ultraviolet wavelengths.' - laser shouldn't be capitalised (yes, it's an acronym, but it's an every-day word now). it might be better to say 'known to emit ultraviolet laser emission'. The references should be in the body of the article rather than the introduction.

No refs in the lead now. No acronyms either. Lithopsian (talk) 17:11, 23 May 2015 (UTC)

• "revolve in an eccentric orbit every 5.54 years" - "have an eccentric orbit with a period of 5.54 years' (and give an uncertainty)

Added uncertainty to the starbox. 90.216.66.95 (talk) 12:22, 23 May 2015 (UTC)

changed - will look up uncertainty Cas Liber (talk · contribs) 22:15, 22 May 2015 (UTC)

Observational history:

• " In 1751 Nicolas Louis de Lacaille mapped the stars of Argo Navis and Robur Carolinum into separate smaller constellations." -> "mapped the stars ... and divided them into (two/more?) smaller constellations"

tweaked Cas Liber (talk · contribs) 00:29, 23 May 2015 (UTC)

• Radio emission: rather than using EHF/SHF/UHF (which aren't in common usage in radio astronomy), it would be better to give frequencies/wavelengths, and/or talk about Submillimetre astronomy and Radio astronomy. An average Spectral energy distribution would be nice to include if possible.

Something like this would be nice (http://asd.gsfc.nasa.gov/Rubab.Khan/EtaCarSearch/), but I never know which images have suitable copyright to be uploaded on Wikipedia. Lithopsian (talk) 23:20, 27 May 2015 (UTC)

alot of NASA images are PD - I don't think these are sadly, but not sure.... Cas Liber (talk · contribs) 03:22, 28 May 2015 (UTC)

Visibility:

• "as of 2014" is dated. Consider linking to Naked eye from the first, rather than last, usage.

removed dated bit, linked at first instance in lead and body. Tempted in this article more than any other to put "currently" - or when it became 4th mag maybe..? Cas Liber (talk · contribs) 22:15, 22 May 2015 (UTC)

Future prospects:

• "Eta Carinae is not expected to produce a gamma ray burst and its axis is not currently aimed near Earth", given this, it doesn't need to be followed by a description of what a gamma ray burst would do to Earth; just point towards Gamma-ray burst would be sufficient.

The damage description is specific to Eta Car, not GRBs in general, even if it is highly unlikely. I shortened it as much as practical because it is really just astro-porn, but people will have heard about it and want to see something. 90.216.66.95 (talk) 12:22, 23 May 2015 (UTC)

Cultural significance:

• Boorong paragraph: I'd suggest re-ordering this, as the emphasis should be on the Boorong people rather than the researchers. Consider also mentioning their observations under 'history' (or moving the section to history, as suggested above).

inverted now. Will discuss placement with Lithopsian Cas Liber (talk · contribs) 11:36, 23 May 2015 (UTC)

Back to plan B? Again? Maybe can be worked in better with a wider section rearrangement. 90.216.66.95 (talk) 12:22, 23 May 2015 (UTC)

incorporated into history now Cas Liber (talk · contribs) 14:17, 23 May 2015 (UTC)

Other points:

• These might be useful references, particularly given the 3D printing link (and also see the citations they contain): [1] and [2]. Thanks. Mike Peel (talk) 18:06, 24 May 2015 (UTC)

Interesting reading - I think these would be best covered in detail in the Homunculus Nebula article with some summary here...I guess. Need to sleep on it and read tomorrow... Cas Liber (talk · contribs) 14:35, 25 May 2015 (UTC)

I meant to do these, but got distracted. One is already a cited reference in the Homunculus nebula article. The other I'll add as an external link or further reading. The information will surely be interesting for some people but doesn't directly support claims in the article as it stands. Lithopsian (talk) 18:37, 25 May 2015 (UTC)

Yeah I was thinking that after reading them...well, maybe buff the nebula next...speaking of which, @Lithopsian: anything else you wanna add/correct/modify or is it FAC time? Cas Liber (talk · contribs) 01:09, 27 May 2015 (UTC)

Do you think it is ready? I've never been through that process. I gather being comprehensive is an important criterion? As you know, nothing short of a book would be comprehensive for this star. In any case there are still a few things to sort out yet: the colour indices in the starbox are a bit of a halfway house at the moment and need to go one way or the other (or both!): the EHF/UHF stuff still needs tweaking; and I want to beef up the infra-red observations, maybe make it a separate sub-section. Lithopsian (talk) 11:55, 27 May 2015 (UTC)

My thinking is (from now) to add everything you want to add that might be of possible interest to the layperson, then once done double-check the prose and then nominate. The idea is that once listed, the only quibbles that come up are minor things that can be dealt with quickly. So if the above things are the last things you wanna do, then nominating after a double-check then should be ok. It's no big deal anyway, if it fails it's like a big Peer Review and better for next time. Co-nominations are good as sometimes it is really good to deal with things quickly.Cas Liber (talk · contribs) 13:33, 27 May 2015 (UTC)

Comments from David

I'm a physicist, not an astronomer. I had two thoughts:

1. I see in the talk page that someone asked for a separate section on the Great Eruption and Homunculus Nebula, and I was going to suggest that as well. The first thing I wanted to know when I read the article was what caused the Great Eruption (it doesn't even say whether it was a supernova, if it was well understood by the community, and it would be nice to have a summary of the current thoughts...).

We're in a bit of a bind with the Homunculus. There is a separate article and a proposal to merge was rejected, so we're stuck with it. I've at least made that article legible, although it needs further expansion. I wouldn't want to duplicate too much of it here, but so much of what we known about the star is from observing the Homunculus. And nobody knows what caused the Great Eruption :lol: 90.216.66.95 (talk) 12:32, 23 May 2015 (UTC)

This is a pain but does happen from time to time, when a whole set of articles are interlinked - I haven't read much of latter article - will take a look and think about what to do. Cas Liber (talk · contribs) 14:10, 23 May 2015 (UTC)

we could add the basic dimensions and properties of the homunculus nebula to teh surroundings section quite easily. I think 3-4 sentences would be fine and not involve too much duplication of daughter article. Cas Liber (talk · contribs) 14:19, 23 May 2015 (UTC)

2. I wasn't sure what "Future Prospects" meant. Future prospects for observation? Maybe there's a more precise term for thinking about what the star might do in the future?

Probably. Maybe it is all "Evolution"? Or "Future behaviour"? 90.216.66.95 (talk) 12:32, 23 May 2015 (UTC)

I've just changed whole section to Evolution (or could be Stellar evolution) as that is the all-encompassing concept really Cas Liber (talk · contribs) 14:10, 23 May 2015 (UTC)

(Posted with permission. Mike Peel (talk) 21:31, 22 May 2015 (UTC))

Comment from Jayant

"It's nicely written. Distances are given in parsecs in that section. Isn't light years more appropriate here?" (copied from the Facebook thread. Mike Peel (talk) 16:52, 24 May 2015 (UTC))

doing...trying to get an approximation of an approximation is tricky... Cas Liber (talk · contribs) 00:38, 25 May 2015 (UTC)

Comment from Baerbel

Much more needs to be written about Eta Carina's radio emission - ... if only I had some time. - http://www.narrabri.atnf.csiro.au/public/images/etacarinae/ (copied from the Facebook thread. Mike Peel (talk) 08:02, 28 May 2015 (UTC))

now that animation is insane! Yes I think we need to explore this...some of it is covered in the last para of the spectrum section. Cas Liber (talk · contribs) 09:26, 28 May 2015 (UTC)

More on radio might be good, but now I'm getting really out of my depth. The radio coverage is very much about the nearby surroundings of Eta Carinae, especially the inner Homunculus region. Published research seems a little scanty compared to other types of observation, or maybe I've just tended to skip over it. Lithopsian (talk) 12:29, 28 May 2015 (UTC)