Talk:Eta Carinae

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May 15, 2015 Good article nominee Listed
July 26, 2015 Featured article candidate Promoted
Current status: Featured article


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Funny Statement[edit]

" 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)

Variability[edit]

"One remarkable aspect of Eta Carinae is its changing brightness. When it was first catalogued in 1677 by Edmond Halley, it was of the 4th magnitude, but later it brightened, reaching its greatest brightness in April 1843"


I don't know how to word it, but could the 2nd sentence be changed without getting too detailed, to indicate its varying brightness so readers don't think it only brightened from 1677 to 1843. Also, is it too fine a point to say "greatest *recorded* brightness in April 1843"? — Preceding unsigned comment added by Jeandré du Toit (talkcontribs) 11:16, 19 January 2003

Apparent magnitude out of date?[edit]

There are two conflicting magnitudes listed in the article. It appears eta car has apparent magnitude around 5.1: AAVSO — Preceding unsigned comment added by 132.206.150.195 (talkcontribs) 08:48, 30 May 2007

Someone should mention that this explosion is mostly harmless because main burst will not hit Earth. Even by 7500 ly we would be toasted in direct hit. Source: [here] .
"Note that the lobes appear to be tilted away from us by about 40 degrees or so. That’s a good thing. When stars like Eta Carinae explode, they tend to shoot of beams of energy and matter that, at its distance of 7500 light years, could kill every living thing on Earth. But since it’s pointed away from us, all we’ll get is a spectacular light show." — Preceding unsigned comment added by 80.51.70.116 (talkcontribs) 13:19, 21 June 2007

Right , now that's done....[edit]

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[edit]

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)
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[edit]

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[edit]

"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[edit]

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)

Pre-FAC checklist[edit]

  • Colour indices, magnitudes, etc.
I've changed this. Feel free to adjust further or comment if you don't like it. Lithopsian (talk) 18:43, 28 May 2015 (UTC)
  • Image shuffling. New starbox image? First lightcurve has been left in a precarious position. More images? Maybe do after finishing the text.
I think we have enough images maybe - yeah do text first Cas Liber (talk · contribs) 20:37, 27 May 2015 (UTC)
  • Infra-red observations. Especially important for this star, but I'll have to read up a bit.
agree Cas Liber (talk ·
I think I'm done. Hard to know when to stop, but I've hopefully written something accessible instead of an undergraduate course of Eta Car IR studies. Lithopsian (talk) 22:58, 2 June 2015 (UTC)
As somebody who has never taken a formal astronomy course (yet), I can understand it just fine. StringTheory11 (t • c) 23:41, 2 June 2015 (UTC)

contribs) 20:37, 27 May 2015 (UTC)

  • Starbox spectrum, still need to settle on a sufficiently vague and all-encompassing term. For that matter, other values like temperature and radius are equally poorly represented by either a single number or a range.
Well, "variable" it is, unless someone has a brainwave about how to express it better. Lithopsian (talk) 12:52, 31 May 2015 (UTC)
  • Reword the radio stuff. Not my field, but shouldn't be too hard.
Well I reworded it, but comments elsewhere suggest it should be expanded. Lithopsian (talk) 18:43, 28 May 2015 (UTC)
I've expanded this a little. Maybe someone else can add even more. Lithopsian (talk) 18:43, 28 May 2015 (UTC)
  • Final proof-read. It is getting hard for me to read with enough focus to spot the most obvious typos. Third pair of eyes needed? Or will it just come out in the review?
I'll find a someone good with prose who is a layperson and interested in clarity of prose at this point as they will be able to highlight accessibility issues. I know a couple of good people who'll be hard taskmasters. It would be prudent to do this before FAC in an article of this size. But will wait until content all sorted Cas Liber (talk · contribs) 20:37, 27 May 2015 (UTC)

Is there anything else? More about supernova imposters? More about the colliding winds? More about the spectroscopic events? More about the discovery of the binary companion? Lithopsian (talk) 18:59, 27 May 2015 (UTC)

I'd say - 'no', 'possibly', 'not sure too esoteric', and 'yes' respectively Cas Liber (talk · contribs) 20:37, 27 May 2015 (UTC)
I've added incidental mentions of the colliding winds and spectroscopic events, and might mention them again in the IR stuff. I've expanded the 20th century observations section to say a bit more about the binary discovery. Lithopsian (talk) 18:43, 28 May 2015 (UTC)

Casliber asked me to take a look. At this stage i've only read up to "surroundings". I expect this is all technically accurate, and pretty interesting, but it is also bordering on incomprehensible. There's a sh*tload of stuff happening in the Eta C system, and this article tends toward describing what is happening, but leaving the lay reader a bit in the dark because there's not enough text about what the science means. Here's an example of doing the right thing for the reader: "Further light echo observations show that following the peak brightness of the Great Eruption the spectrum developed prominent P Cygni profiles and CN molecular bands. These indicate that the star, or the expanding butt of ejected material, had cooled further and may have been colliding with circumstellar material in a similar way to a type IIn supernova". This is excellent; we just need more of these explanations i think.

  • "...the periastron passage of the binary orbit". No-one will know what a periastron passage is - a wikilink would be essential at minimum, but given the importance of the topic (that is, why did Eta C have peaks several years apart), I think we need a plainer English explanation in the article text. BTW periastron is wikilinked twice later in the text, but to different terms each time! (peristron, and apsis)
On wikilinks, the recommendation is only ever to link the first occurrence of a term. However, I've tended to link the first occurrence in each "section" (not exactly rigorously, but where it seems useful). Some sections in this article are larger than many entire articles, and it seems a bit unhelpful to expect someone who comes along and clicks through to "Evolution" to have to read the previous 10,000 words to know what is going on. Don't want to just get the whole thing nixed at FA review though. Lithopsian (talk) 16:44, 31 May 2015 (UTC)
  • "...this was Eta Carinae during its Great Outburst of in the 1840s" - the term Great Outburst (which sounds hilarious) has not been elsewhere used. I suggest stick to Great Eruption.
oops, my bad. changed. Cas Liber (talk · contribs) 12:11, 31 May 2015 (UTC)
  • "...expelling material that formed the Little Homunculus and Weigelt Blobs". There is a difficulty with the historical section occasionally, as in this passage (and in the earlier references to ejection of dust), where references are made to things we haven't been told about. So far, all we have been told is that we are looking at a star of variable brightness, and then that this had something to do with dust. We have no idea what kind of things the Little Homunculus and Weigelt Blobs are, nor links to them. Is there any way that a version of the first paragraph under "properties" can become the first para of the body text? Just a thought.
I've just taken those terms out. They are barely described at all in this article. Actually, reading more, I've wiki-linked Weigelt Blob once later. More generally, the lead isn't huge and maybe there could be expanded a little if some context is needed. Lithopsian (talk) 13:36, 31 May 2015 (UTC)
  • Under "visibility": how can a star possibly be "clearly non-stellar"?
It isn't a star :) We don't see a star (either of them), we only see a small blob of nebulosity. I've added cheap double-quotes to indicate this, but maybe there is a better way to structure the sentence. Lithopsian (talk) 13:36, 31 May 2015 (UTC)
  • "...the extreme P Cygni star HDE 316285 (B0Ieq)". What does it mean for a star to be an extreme P Cygni type? What is the implication of this comparison (ie. the interesting information)
I've restructured (and linkified) the sentence to hopefully indicate what it means. Lithopsian (talk) 13:36, 31 May 2015 (UTC)
  • "The spectrum is dominated by emission lines, usually broad although the higher excitation lines are overlaid by a narrow central component." What? I had no idea what this meant.The two sentences that follow have problems. Do we know what "high excitation" ionisation is? What is an "absorption wing"??
I've linked a number of terms, explained a few more. This is still going to be tough reading without a background understanding of astronomical spectra, but hopefully at least the links allow someone to gain the background. Lithopsian (talk) 13:36, 31 May 2015 (UTC)
  • "...emission in both permitted and forbidden lines". Again, what? What on earth are permitted or forbidden lines? Is this an awkward translation of a foreign text? Are these synonyms for absorption and emission? All pretty confusing. The sentences about the hydrogen, helium and nitrogen lines were pretty clear, though.
"Permitted" and "forbidden" lines are standard terms in astronomical spectroscopy. "Forbidden" lines represent atomic transitions that are extremely rare under terrestrial conditions but more common in interstellar environments; the name comes from the fact that they were originally thought to be impossible since they never occurred in the laboratory. Conversely, "permitted" lines are transitions that can be observed under terrestrial conditions. For a more detailed account check out the historical "discovery" of "nebulium." — Preceding unsigned comment added by 128.114.22.81 (talk) 23:37, 3 June 2015 (UTC)
  • an "accidental resonance"? sounds like something technological in nature (and pretty mysterious at that). Can we clarify?
Seems to have already been done by someone else. I've gone ahead and copyedited it, to make it sound less awkward, and clarified a point. StringTheory11 (t • c) 23:59, 2 June 2015 (UTC)
  • italics are being used inconsistently toward the end of the spectrum section and in the one that follows.
I de-italicised - we'll either bluelink or explain... Cas Liber (talk · contribs) 12:19, 31 May 2015 (UTC)
  • in the radio emission section, a new type of line, a recombination line, is introduced without either explanation or link. And then also added is "continuum emission" again without explanation.
Couldn't find wikilinks for these terms, so added parentheses with explanation. Lithopsian (talk) 12:58, 31 May 2015 (UTC)
I've gone ahead and added a redlink to the term. I'll probably go through this article and add some more redlinks to terms that should have their articles, to encourage article creation. StringTheory11 (t • c) 23:52, 2 June 2015 (UTC)

Thanks for the hard work on this everyone. hamiltonstone (talk) 11:41, 31 May 2015 (UTC)

This is good stuff, exactly what we need. I can't see the wood for the trees after reading the article so often. Plus I know what "P Cygni profile" and "accidental resonance" mean, and assume the rest of the world must too ;) Lithopsian (talk) 13:40, 31 May 2015 (UTC)