Talk:Extinction (astronomy)

Split

Perhaps include the formula which links absolute and apparent magnitude and extinction.

$m_{\lambda }-M_{\lambda }=5\,\log \,d-5+A_{\lambda }$

Split

FTA "Broadly speaking, interstellar extinction varies with wavelength such that the shorter the wavelength the stronger the extinction." This isn't really true and I think it is slightly confusing. The link, though present, breaks down at the extremes of the EM spectrum. It is relatively weak and I think it would be more useful to have some sort of table listing the relative opaqueness of dust to X-ray, gamma, infrared etc....

What do people think on this?

Split

I wish for others to review the inclusion of Trumpler and the ref to the page and get a consensus for leaving it or excluding it.Jobberone (talk) 19:28, 10 September 2008 (UTC)

Split

I've started updating and expanding this page to be more comprehensive and include more references. This is part of a larger effort on my part to improve the information on interstellar dust in general. Feel free to add questions to this page and/or send them my way. Karl D. Gordon 14:32, 27 December 2006 (UTC)

Still todo: update section on how extinction curves are measured, add section on features other than just 2175 A bump (silicate and ice absorptions, maybe add X-ray absorptoin edges), and add more figures (UV-IR extinction curve with features labeled, figure for how extinction curves are calculated, figure with silicate and ice features).Karl D. Gordon 17:51, 1 January 2007 (UTC)

Split

I propose that this article is split into two pieces. The majority of the text would go into interstellar extinction and the remaining into atmospheric extinction. This would make more sense as the two sources of extinction arise from different physical processes. And it would make it easier to revise both pieces to be more comprehensive. Karl D. Gordon 16:50, 27 December 2006 (UTC)

N(H) vs. A_V

The mention of the ROSAT study, and only that study, for the determination of the relationship between N(H) and A_V seems to imply that it is the definitive, if not the only, measurement. Perhaps the Bohlin, Savage, & Drake (1978) reference should be stated, and the ROSAT study, amongst others, could be used to strengthen the confidence in the value. AmberRobot 17:51, 28 December 2006 (UTC)

Excellent point. I have added Bohlin et al. (1978) and the more recent Diplas & Savage (1994) to the reference list and changed the value of the relationship approximate given that these three studies did not all get the same value (1.87, 1.59, and 1.79). Karl D. Gordon 18:36, 28 December 2006 (UTC)

Dubious

The references Bohlin/Savage/Drake(1978), Diplas/Savage(1994) and Predehl/Schmitt(1995) all give different values of differing extinctions for differing wavelengths, f.ex. Predehl/Schmitt(1995) measures in X-rays, Diplas/Savage(1994) in HI, and Bohlin/Savage/Drake(1978) sums up HI and neutral H₂. The value in the text seems to give an unnecessarily rounded value for the X-ray measurement, while Bohlin/Savage/Drake(1978) gives 5.8 (not 1.8) ·10²¹atoms per magnitude. ... said: Rursus (bork²) 13:25, 18 June 2009 (UTC)

The ratio is sometimes given as H atoms/A(V) or H atoms/E(B-V). They are related by R(V) = A(V)/E(B-V). As R(V) is 3.1 for the average Milky Way diffuse dust, the measurements divided by E(B-V) can be converted to per A(V) by dividing by 3.1. The Bohlin et al. (1978) reference is per E(B-V). So dividing by 3.1 gives something like 1.87 ·10²¹atoms per magnitude. Given there is uncertainty in this measurement both observational and in the contribution of H₂ to the total H-atoms, an approximate value is probably the best thing to report. Karl D. Gordon (talk) 10:00, 26 January 2011 (UTC)

Undefined terms

The various terms R(V), A(V), E(B-V) should be clearly defined so the general reader can have an idea what the concepts mean. If they are defined elsewhere they should be wikified. The introduction is clear enough, but the whole of the article should be as clearly explained. A diagram of an extinction curve should be included, along with the mathematical relationship of the parametrisation.Puzl bustr (talk) 11:32, 8 December 2009 (UTC)

For example a quick Google found:

"A(V) The absolute extinction at the V band at 5550 Angstroms.

E(B-V) The color excess between the B and V bands.

c The logarithmic H beta extinction.".Puzl bustr (talk) 11:45, 8 December 2009 (UTC)

OK, I changed the article to make clear that R(V) is defined, not just equal to A(V)/E(B-V), and made clear that A(V) is measured at 5550 Å. Perhaps someone could add the relevant wavelength for B. Also defined total and absolute extinction, using the refs, since absolute extinction A(λ)/A(V) is on the y-axis of the later graph. The mathematical relationship between R(V) and the extinction curve is specified in the refs but alas I couldn't follow it. Something about fitting

a(x)+b(x)/R(V) to the mean of A(λ)/A(V) for various wavelength ranges, for polynomials a and b. A normalised extinction curve diagram is also included in [1] and shows the features mentioned, the knee, etc. It has 1/λ on the x-axis and E(λ-V)/E(B-V) on the y-axis. Would be great if someone could make such a plot and upload it to show the features mentioned. Puzl bustr (talk) 18:35, 10 December 2009 (UTC)

magnitude unclear

It is not written how significant is the space extinction phenomenon. It should be somehow compared with other stuff. The only explanation is 0.7 mag/Kpc. Doesn't tell me anything. It should be noted whether for some star the effect can be seen by the eye, not by a curve (does the color of the star change?). Compare with redshift, and compare atmospheric vs space extinction. Setreset (talk) 06:06, 25 August 2010 (UTC)

Atoms / cm^-2

Hydrogen atoms per square centimeter column... I don't understand this. Does it mean a square centimeter column extending from the earth to the object being looked at? At any rate, other non-astronomers might benefit from this being made explicit. 68.186.166.197 (talk) 21:41, 24 March 2011 (UTC)

It's the path integral of the number density along the line-of-sight between the observer and the source. Number density has units of cm^-3, whilst path length has units of cm. Mutliply the two together and you get cm^-2. This is called the 'column density'. Modest Genius ^talk 19:45, 26 May 2011 (UTC)

Source discuss

R.J. Trumpler is credited in the article with first discovering reddening (first reference). I cannot find anything about reddening in the source given. I might have missed it, can someone quote it and tell me the page?

Its possible he was first with:

6. The discrepancy between color-indices and spectral types observed in open clusters increases with the distance of the cluster and shows that this absorbtion of light is selective, the photographic absorbtion coefficient being about twice the visual.

(Page 187) http://articles.adsabs.harvard.edu/full/1930LicOB..14..154T

Now that may be unwittingly in part refering to reddening, but where does it refer to dust and reddening? My apology that it is eluding me, I'd be grateful if someone could point it out. Orphadeus (talk) 19:01, 21 May 2011 (UTC)

The 2nd reference is not available.

The 3rd reference is where? Orphadeus (talk) 20:05, 21 May 2011 (UTC)

That Trumpler source appears to be the original report of observation of selective absorption. This means that dust absorbs more strongly at some wavelengths, resulting in a "redder" spectrum. Take the blue line in the picture to the right, from Black body - the peak is a little over 500 nm, giving it a greenish-blueish hue. If you apply a high pass frequency filter at 500, you are left with something that looks yellowish ("redder" than the unmodified spectrum), but distinctly different from the lower temperature curves, so you can still tell what the original looked like. Light from distant clusters of course is a bit more complex, but that is the gist of it - interstellar space is observed to be not perfectly transparent. I added a more modern reference that explains the principles a bit more clearly as well as providing some historical perspective.

2: see Astrophysics Data System.

3: you link to a file named figlist, which presumably is ... a list of figures ... which is what that page appears to be. What is your question? - 2/0 (cont.) 21:25, 21 May 2011 (UTC)

Thanks for the reply. Regarding the 1st point, I have found the (writing) section about (presumably dust) cloud absorbtion:

'Wallenquist, aware of the large discrepancy between his color indices of NGC 663 and the spectral types of the same stars, and unable to account for it by observational errors, concludes: 'The most probable explanation is, perhaps, the assumption of selective absorbing clouds within (and in the surroundings of) cluster NGC 663.' That the effect is not due to an error in method is well illustrated by the fact that Wallenquist observed three clusters by the same method and instrument and that only the two more distant ones show a large color excess; the same is true for the two open clusters investigated by Shapley. In a former publication I drew attention to the large excess of Shapley's color observations in the cluster Messier 11 and, averse to the idea of a general selective absorbtion in our stellar system, took rather a skeptical attitude concerning the correctness of Shapley's results until these were confirmed by Wallenquist's observations.' (Page 165)

It appears from that that the concept for interstellar extinction should be currently attributed to Wallenquist. Orphadeus 94.194.100.228 (talk) 11:34, 22 May 2011 (UTC)

It appears someone has added another non reference (currently reference 2), which throws the list of references on this talk section out of kilter. Click on that reference and you get this. Sure theres a page number, do the search and you get nothing. The references currently at 4 (previously 3) have been altered and give the same (nothing) as does what is currently reference 2. The previous 2nd reference, currently at 3, still gives a link to a study which is 'not available'. The mild paranoia, excuse me, tells me that if I quite reasonably remove the dodgy references and attribute the concept of reddening to Wallenquist, with reference, the mafia will deal with me. Orphadeus (talk) 12:30, 22 May 2011 (UTC)

Priority in these cases is often difficult to determine; your Wallenquist material looks basically fine.

Did you check the actual source, or just the BookSources convenience link?

Please read about ADSABS, linked above. You are complaining about a non-issue. The not available at that page denotes that that particular indexing service does not have the abstract for that paper.

Please read and abide by the civility policy. - 2/0 (cont.) 22:07, 22 May 2011 (UTC)

I would have thought if the abstract for the paper is not available, it is a non link which should not be there. I recall reading Wikipedia being in agreement. As for the ISBN links, they simply do not work, even if you do the search with the reference number. They are literally nothing references, aside from which, would putting a google search engine as a source be acceptable? I think those links are indefensible. Orphadeus (talk) 17:09, 23 May 2011 (UTC)

Your repeated citing of Wallenquist is incorrect. He, like many other observers of that time including Shapley, noticed that star clusters in different directions and at different distances had different color gradients. But he did not attribute it to the correct cause. Trumpler was the first astronomer to put all the discrepant observations together and propose that there was diffuse dust in the Galaxy. That's why he gets the credit.

Your complaints about ISBN links and NASA ADS are also incorrect. The ISBN BookSources page provides a catch-all page for finding a book at many different sources. NASA ADS does not have abstracts for most older references because they were scanned in, and have not been OCRed. The NASA ADS links in this article all include a link to the required article, even if the abstract is not displayed on the main ADS page. - Parejkoj (talk) 14:09, 26 May 2011 (UTC)

Link between extinction/reddening and redshift

I think there may be some confusion regarding the current article and redshift from the metric expansion of space. Both cause spectra to appear redder in predictable ways, which means that any particular observation will need to be deconvoluted before the data are interpretable. The physical origins of the effects are, however, completely distinct. Is there some way that this could be phrased more clearly yet still succinctly in the lead? - 2/0 (cont.) 22:11, 22 May 2011 (UTC)

"any particular observation will need to be deconvoluted" - not really, unless you are talking about estimating photometric redshifts, which is a much more complicated process. Redshift changes the wavelengths of spectral lines, reddening changes the amplitude of the blue end of the spectrum relative to the red end, without changing the positions of lines. These are completely orthogonal effects, which the article describes as such. - Parejkoj (talk) 13:42, 23 May 2011 (UTC)

I like 2/0's final 2 sentences. I think someone who understands all the terminology, and is nimble, should perhaps check the study. I don't understand all the terminology but I can get the jist and it does look to me that Parejkoj is incorrect. Either way, it is not the job of Wikipedia to defend a set position. Perhaps a section on reddending and redshift may be appropriate, provided it is impartial. By the way, someone might find it interesting, I've just found this. Orphadeus (talk) 17:46, 23 May 2011 (UTC)

Orphadeus: you clearly do not understand these research papers that you keep citing. I once again advise you to look at some textbooks on astronomy before continuing, as you are just managing to get yourself more confused, and are spreading that confusion to Wikipedia pages. I don't understand why you keep bringing up Santiago et al., but it talks about how target selection for redshift surveys is affected by extinction, not that the subsequently determined redshifts change, as I've said before. Though this article could use some rewording (I've started to do so), the facts within are correct as they stand.

Your link to a "RedshiftEssay" is WP:FRINGE, and would *at best* belong on the nonstandard cosmology page. - Parejkoj (talk) 20:08, 23 May 2011 (UTC)

Regarding 2/0's suggestion, his sentence, 'The physical origins of the effects are, however, completely distinct' could be used. Orphadeus (talk) 17:59, 23 May 2011 (UTC)

@Parejkoj: I would count that as deconvoluting in the sense that if you just look at the ratio of two wavelengths it is still necessary to determine why there is more red than expected. Still, that is neither here nor there, and the last sentence in your first comment says it perfectly.

Rereading my initial comment, it looks like I was trying to be too diplomatic. Orphadeus, I think that you may be confusing two physically distinct concepts; I would like to edit this article in a way that clarifies your misunderstanding, but need help in determining exactly where it lies. I am further not sure why you think Santiago says what you seem to think it says; unless I am misunderstanding you, it does not. Physics Essays is generally not a reliable source for anything beyond the opinions of the authors; if this particular idea has received outside attention, it might be appropriate to cite it at Non-standard cosmology, though I have my doubts. - 2/0 (cont.) 21:47, 23 May 2011 (UTC)

Lets examine these two studies:

' Moreover, all the physics governing dust properties (metallicity, star formation and evolution rates, and radiation backgrounds) evolve strongly with redshift, so we would expect the properties of the dust to evolve with redshift. Evolution in the mean extinction law with redshift would be a crucial systematic uncertainty in studies of Type Ia supernovae to constrain the cosmological model (see, e.g., Perlmutter, Turner, & White 1999), since extinction modifies the apparent stretch of the light curves (Nugent, Kim, & Perlmutter 2002). http://iopscience.iop.org/0004-637X/605/2/614/59211.text.html

'Using Voyager observations, it is demonstrated that Triton's orbital light curve is strongly wavelength-dependent, a characteristic which readily explains some of the apparent discrepancies among pre-Voyager telescopic measurements. Specifically, a light curve amplitude (peak to peak) is found that decreases systematically with increasing wavelength from about 0.08 magnitude (peak to peak) near 200 nm to less than 0.02 magnitude near 1000 nm.' http://adsabs.harvard.edu/abs/1991JGR....9619211H

Am I grasping at straws? Perhaps the light curve being strongly wavelength dependant is specific to Triton's orbital? I'm wondering if theres a difference between the actual scientific mainsteam and the media's scientific mainstream. I'm wondering if the problem is specific to the UK. Orphadeus (talk) 11:06, 24 May 2011 (UTC)

You are misunderstanding both studies (so, yeah, grasping at straws): a light curve is the change in an object's observed brightness with time, which is not related to redshift or reddening. Please read an astronomy textbook before looking at research papers, as you *do not* understand the terminology. You are also cluttering these talk pages with your misunderstandings. Please study a textbook before posting further on Wikipedia astronomy pages. - Parejkoj (talk) 16:24, 24 May 2011 (UTC)

Updates - can we remove the Technical flag now?

I suppose one good thing that came from the recent erroneous changes to this page is that I've reworked it. The intro and first section should be much more readable now, and the "Technical" flag can hopefully be removed. I don't have a cite for the "0.7-1.0 mag/kpc" typical reddening in the stellar neighborhood value, so if someone could add that, it'd be great. Interstellar dust is not my area of expertise, so I haven't tried to update any references to reflect more recent literature, sorry. - Parejkoj (talk) 01:17, 24 May 2011 (UTC)

'Fitzgerald (1968) finds that there is heavy reddening (Av = 0.7-1 mag/kpc) in the regions 140-150° and 160-170° of the Perseus arm, implying that.. Page 8

I don't know if 140-150° and 160-170° of the Perseus arm is what you are looking for. Orphadeus (talk) 12:08, 24 May 2011 (UTC)

'A mean rate of visual extinction of (1.25 ± 1.08 mag/kpc) is deduced from a sample of 133 stars.' Page 244 You may also like to check Page 243. Orphadeus (talk) 11:17, 25 May 2011 (UTC)

The paragraph that begins, "Broadly speaking" is full of terms from spectroscopy, but no reference is made to that technique. Someone like me with physics background isn't fazed by that, but most of the people I socialize with would be totally baffled. Ok, I edited it. In fact, the first paragraph of the whole article would benefit from mention of spectroscopy, which technique I often find myself explaining when people ask me "but how do we know that there's this or that interesting element in that distant object which we can only observe by looking at from far away?" Outside the community of scientists and techies, spectroscopy is not a generally understood technique, certainly not to the degree that optical telescopes are understood by non-technical folks. Musicengin (talk) 11:18, 24 April 2015 (UTC)

What the reader wants

The current edit is likely exactly what readers of Wikipedia want. You~re average 15 year old who is interested in science can understand and enjoy. Anyone further advanced in science can enjoy the links. The references are all real in that article. I can~t be bothered with an edit war, but I believe I have shown what a wikipedia science page should be like. Orphadeus (talk) 19:09, 26 May 2011 (UTC)

The problem with your edits is that they are in the large part incorrect, and show a significant lack of understanding of the topic. I appreciate that you want to improve the article, but your changes are mostly spreading inaccuracies, and thus are not helping. As I said above, you do not understand the references you cite, are very badly misinterpreting some of them, and you are citing very fringe work that doesn't have anything to do with the topic of extinction. You also have not responded to any of my criticisms and comments in the past, and do not seem to have read any of them. - Parejkoj (talk) 19:32, 26 May 2011 (UTC)

I boldened something in Parejkoj's post that is verifiably incorrect. Orphadeus (talk) 10:00, 27 May 2011 (UTC)

Please do not edit other user's talk page comments like that. There's a very narrow set of circumstances where doing so is acceptable, none of which apply here. Besides, you haven't addressed their point or explained why you that that statement is incorrect. Modest Genius ^talk 13:35, 27 May 2011 (UTC)

Orphadeus has shown a complete inability to grasp WP:NPOV and WP:RS over at Talk:Number of the Beast, its article, and others. Whether its a matter of WP:CIR or WP:IDIDNTHEARTHAT, I don't know, but its interesting to see this guy is a problem on other pages as well. Although this isn't a topic I'm involved with, I'll add it to my watch list. For what it's worth, I've only had an introductory course to astronomy years ago, and the regular introduction isn't hard to read. If it was, I'd click the links involved to read about the stuff I wasn't sure about. A lot of our readers do that. I will grant the some other sections are a bit technical, but throwing out that information does not make it easier to read. Instead, less technical summaries and explanations added to the article (instead of replacing) would work better. However, these would need to meet the same sourcing standards as the rest of the article, or any other article.

I would strongly recommend that Orphadeus discuss any potential changes on the talk page before making them, as a number of other editors have expressed concern over his ability to locate and accurately summarize reliable sources. Ian.thomson (talk) 14:51, 27 May 2011 (UTC)

Very interesting Ian. (I think he's upset - and following me - because the gospel of Mark has 666 verses). Orphadeus (talk) 15:24, 27 May 2011 (UTC)

No, I'm keeping an eye on a problematic user who is rather adept at bringing up details without being able to explain their relevancy. Ian.thomson (talk) 15:27, 27 May 2011 (UTC)

So Ian, you are following me. Which details have I brought up without explaining their relevancy? Modest Genius, you are clearly a stickler for rules. My apology, I did not realise it was a crime to highlight some words someones post and clearly state, where anyone was saw the boldening would see, that I had highlighted them. Being a stickler for rules, are you satisfied with the references in the current article (not the one I wrote)? Orphadeus (talk) 15:31, 27 May 2011 (UTC)

The references are adequate, though of course could be improved. They don't seem to be good enough for e.g. GA standards, but they're decent. They could do with getting rid of all those ugly red links. But they're an awful lot better than the references in the version of the article which you wrote and described as 'near perfect'. Oh and I never accused you of a crime, I simply made a polite request and left a link to the relevant project page, which you might not have been aware of. Modest Genius ^talk 20:44, 27 May 2011 (UTC)

Your inability to assume good faith by accusing me of anger over your claim is assinine (and unreasonable when I did explain how to make your claim applicable to the article by asking you to explain how it was relevant and pointing out the guidelines you needed to follow). The relevant issue is that you have shown time and again you don't appear to have a high schooler's understanding of basic research standards, and you continually reject other editor's advice on this site's guidelines (which border on college level research standards but remain simple enough that I've seen editors in middle school handle them). You've pushed for fringe additions to a number of articles, and in the case of the Number of the Beast and your claim that the Gospel of Mark (which version?) has 666 verses, you never could explain why that was relevant. Competance is required here, and you either need to quit being a tendentious editor, accept guidance if you don't know how to, or leave. You had the talk page guidelines linked to you before, which did explain that it is unacceptable to edit other's talk page posts except under limited conditions (like posting in the archives as if one did not understand what the word "archive" meant). Ian.thomson (talk) 15:42, 27 May 2011 (UTC)

Are you here to talk about Extinction? Orphadeus (talk) 18:56, 27 May 2011 (UTC)

(Points to my first post on this page). I'm here to help improve the article (that is what talk pages are for, not general discussion, as has been explained to you before), because a problematic editor has disrupted it and other editors aren't aware of your behavior elsewhere. Ian.thomson (talk) 19:04, 27 May 2011 (UTC)

So Ian, how do you think the article can be improved? My personal opinion is that it is too technical (or too technical too early) and should be put so that people without a Phd can enjoy it and learn. I may be biased, but I thought I made quite a good go (not sure if you read the article - theres a link in the 1st post in this section). I would have thought that after that kind of explanation, if people wanted you can have a technical section (perhaps with relevant subsections) with the (to most people) incomprehansible stuff. I also think there is more accuracy in the article I wrote, particularly with the attribution of the concept of extinction and in the effect on Redshift section. Would you agree? Another problem with the artice is that there are links that seem to be to nothing. Orphadeus (talk) 19:25, 27 May 2011 (UTC)

Whilst the article could certainly be improved, wholesale removal of almost all of the information is not the way to do it. If you want to make the article more understandable, I suggest you do so one or two sentences at a time. Find something you think is phrased poorly and rephrase it to be more easily understandable. Then save the article and leave it for 24 hours to see if the other editors watching the page agree it's an improvement. Don't remove all the content, don't attempt to completely rewrite the article in one go, and instead try to gradually and incrementally improve it piece by piece. Modest Genius ^talk 20:37, 27 May 2011 (UTC)

As I said earlier "For what it's worth, I've only had an introductory course to astronomy years ago, and the regular introduction isn't hard to read. If it was, I'd click the links involved to read about the stuff I wasn't sure about. A lot of our readers do that. I will grant the some other sections are a bit technical, but throwing out that information does not make it easier to read. Instead, less technical summaries and explanations added to the article (instead of replacing) would work better. However, these would need to meet the same sourcing standards as the rest of the article, or any other article." In other words, the wholesale removal of much of the article's information on the grounds that it was too technical was far from perfect (even far from "near perfect.") Orphadeus, how about actually reading other user's comments? You won't end up looking like tendentious or incompetent. As for the redlinks, if the links are for subjects that deserve an article, a good solution would be to create the article. That's common and accepted practice, provided the articles are up to muster. Ian.thomson (talk) 21:33, 27 May 2011 (UTC)

Sorry Ian, I haven't read your post as we had an edit overlap and I'm nearly out of internet time, so I cut and paste to Modest Genius -

That may be a good idea. I think its the more difficult solution in practice. The problem is, for example, the 1st sentence is good and I don't want to change it. Its also rather technical. I was thinking along the line of laymans explanation followed by Technical ecstacy, possibly being discreet about the 'progression'. The current opening line could open the more technical section. It requires some tactical thinking as to page layout. Orphadeus (talk) 22:15, 27 May 2011 (UTC)

Hi Ian, I've read your post now and agree that 'less technical summaries and explanations added to the article (instead of replacing) would work better'. I also think that at the beginning as less technical readers are less likely to read through technical stuff to get to what they would appreciate, than vice versa. Regarding the opening, the reference to electromagnetic radiation is not good for the layman, even clicking on the link, its better opening with a reference to light, with the current opening sentence in a technical explanation later. I'm going to try to do an edit without removing any of of the current article. Orphadeus (talk) 11:30, 28 May 2011 (UTC)

You just added back in the material that was reverted not only for disrupting the page, but for being erroneous and fringe. You never addressed Parejkoj's earlier point regarding this. Also, the sarcasm of title "Technical Ecstacy" is inappropriate for an encyclopedia. If you are un such a limited internet schedule that you cannot effectively read my comments or his, or any that just happen to be something you disagree with, maybe you should reconsider if you have enough time to edit on Wikipedia. Ian.thomson (talk) 15:00, 28 May 2011 (UTC)

I certainly did reply to Parejkok's comment. If anyone checked the references, all his points were dealt. It has not escaped my attention that Parejkok is repeatedly removing sourced material. A further point is that I am doing exactly what the technical requests. Orphadeus (talk) 18:32, 28 May 2011 (UTC) Orphadeus (talk) 18:33, 28 May 2011 (UTC)

Actually it was Ian who removed it this time (sorry Parejkok). By the way, if anyone thinks they have a better heading than 'Techniacal Ecstacy', change it. Orphadeus (talk) 18:47, 28 May 2011 (UTC)

Again, the material is still what Parejkoj has pointed out is an erroneous interpretation. You do not appear to have addressed him anywhere on this matter, but simply made started a conversation only to leave when he points out the error. You have yet to address his points raised in Source discuss or Link between extinction/reddening and redshift. The user 2/0 has also pointed out that you have no idea what you're going on about. You have completely ignored both of them there and continued on despite multiple users pointing out your errors. You're proving to be an example of the Dunning–Kruger effect at work here. Quit reintroducing your erroneous material. Ian.thomson (talk) 19:00, 28 May 2011 (UTC)

Ian, theres no point in continuation of Parejkok saying 'this the links' and me saying 'that the links'. Check the references yourself. Theres page numbers given for where page numbers are required. There is one fringe theory which is stated in the article as a fringe theory and it is countered in the article by a mainstream study. I'll give you time to check the references. Orphadeus (talk) 21:34, 28 May 2011 (UTC) Orphadeus (talk) 21:37, 28 May 2011 (UTC)

Ok, a summary of your links looking over them myself:

• Fringe essay. The fluff piece you've created on Ling Jun Wang pretty much admits its a fringe work.
• Does not connect redshift with extinction, but points out the problems redshift causes in studying extinction.
• Unrelated to this article, any attempts to relate it would be original research.

Not that you're going to listen to me either. Ian.thomson (talk) 14:32, 29 May 2011 (UTC)

The Ling Jun Wang article could be improved by pointing out that the US government release on reddshift error did not disprove his theory, with reference. As for your other points, http://iopscience.iop.org/0004-637X/605/2/614/59211.text.html and http://adsabs.harvard.edu/abs/1991JGR....9619211H are not in the the article. The references I put in the article are:

• 1.^ http://www.asterism.org/tutorials/tut28-1.htm Atmospheric Extinction and Refraction
• 2.^ http://www.astro.virginia.edu/class/skrutskie/astr121/notes/redden.html Interstellar Reddening, Extinction, and Red Sunsets
• 3.^ http://www.asterism.org/tutorials/tut28-1.htm Atomospheric Extinction and Refraction
• 4.^ http://star-www.rl.ac.uk/star/docs/sc6.htx/node15.html Atmospheric Extinction and Air Mass
• 5.^ http://mintaka.sdsu.edu/GF/explain/optics/scatter.html Atmospheric Scattering
• 6.^ Attribution to Wallenquist on Page 165 http://adsabs.harvard.edu/cgi-bin/bib_query?1930LicOB.420..154T PRELIMINARY RESULTS ON THE DISTANCE, DIMENSIONS AND SPACE DISTRIBUTION OF OPEN STAR CLUSTERS. Authors: Trumpler, Robert Julius
• 7.^ http://adsabs.harvard.edu/full/1937AnHar.105..359G THE EFFECT OF ABSORBING CLOUDS ON THE GENERAL ABSORBTION COEFFICIENT. Author: Jesse L Greenstein
• 8.^ Page 18. http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.53.80 The Optical Redshift Survey II. Authors: Basílio X. Santiago , Bas'ilio X. Santiago , Michael A. Strauss , Ofer Lahav , Marc Davis , Alan Dressler , John P. Huchra
• 9.^ http://ned.ipac.caltech.edu/level5/Sept07/Li2/Li3.html DUST SPECTROSCOPY - DIAGNOSIS OF DUST COMPOSITION In "The Central Engine of Active Galactic Nuclei", ASP Conference Series, Vol. 373, Xi'an, China, 16-21 October, 2007, eds. L. C. Ho and J.-M. Wang
• 10.^ Page 99 http://iopscience.iop.org/1538-3881/125/1/98/pdf/1538-3881_125_1_98.pdf THE PHYSICAL CONDITIONS OF INTERMEDIATE-REDSHIFT Mg II ABSORBING CLOUDS FROM VOIGT PROFILE ANALYSIS. Authors: Christopher W, Churchill, Stephen S. Vogt, Jane C. Charlton
• 11.^ http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.53.80 The Optical Redshift Survey II. Authors: Basílio X. Santiago , Bas'ilio X. Santiago , Michael A. Strauss , Ofer Lahav , Marc Davis , Alan Dressler , John P. Huchra
• 12.^ Page 104 http://iopscience.iop.org/0004-637X/518/1/103/pdf/0004-637X_518_1_103.pdf THE DISTRIBUTION OF HIGH-REDSHIFT GALAXY COLORS: LINE-OF-SIGHT VARIATIONS IN NEUTRAL HYDROGEN ABSORPTION. Authors: Matthew A. Bershady, Jane C. Charlton, Janet M. Geoffroy
• 13.^ http://www.utc.edu/Faculty/LingJun-Wang/RedshiftEssay.pdf Dispersive Extinction Theory of Redshift. Author: Ling Jun Wang
• 14.^ http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2966.2010.16464.x/abstract On the impact of intergalactic dust on cosmology with Type Ia supernovae. Authors Brice Ménard, Martin Kilbinger, Ryan Scranton

Orphadeus (talk) 14:55, 30 May 2011 (UTC) Orphadeus (talk) 15:00, 30 May 2011 (UTC)

Anyone technical?

Theres a picture that can be downloaded here. I tried to get it in the article but couldn't. Perhaps someone more technical than me might like to. Orphadeus (talk) 21:42, 28 May 2011 (UTC) Orphadeus (talk) 21:44, 28 May 2011 (UTC)

Its not just an issue of Wiki-coding but copyright.Ian.thomson (talk) 14:32, 29 May 2011 (UTC)

Indeed. That image cannot be used under a 'free' license, nor could it qualify as fair-use. See Wikipedia:Image use policy. More to the point, it's massively out of date. Why would we want to use an image that shows very little, and that does not reflect current scientific consensus? Modest Genius ^talk 16:31, 29 May 2011 (UTC)

I assumed it was free to be used, thought it would add some colour to the page. My apology. Orphadeus (talk) 19:47, 29 May 2011 (UTC)

Is this fringe?

I would appreciate if someone could answer whether THE HUBBLE SPACE TELESCOPE* CLUSTER SUPERNOVA SURVEY: is fringe.

The reason I ask:

'Cluster early-type galaxies in particular form even earlier than those in the field, with most star formation occurring at z & 3 (Thomas et al. 2005; S´anchez-Bl´azquez et al. 2006; Gobat et al. 2008; S´anchez-Bl´azquez et al. 2006; Gobat et al. 2008).)'

'The highredshift cluster rate is particularly important: measurements show that most of the intracluster iron was produced at high redshift (Calura et al. 2007).'

Thats toward the end of Page 2. Is it fringe? — Preceding unsigned comment added by Orphadeus (talk • contribs) 13:10, 29 May 2011 (UTC)

That is not fringe, but it also has nothing to do with the topic of this article, which is extinction. As I have repeatedly said, you need to study a textbook on astronomy before trying to edit wikipedia pages on the topic: you are seriously misunderstanding the research papers you keep citing. - Parejkoj (talk) 14:00, 29 May 2011 (UTC)

Indeed, that paper does not discuss extinction. The subject of the paper is Type 1a supernovae in galaxy clusters, which has nothing to do with the subject of this article. Modest Genius ^talk 16:34, 29 May 2011 (UTC)

Its a fair point. However, it is relevant as it validates my interpretation of Page 104 of one of the references I used. Also, THE HUBBLE SPACE TELESCOPE* CLUSTER SUPERNOVA SURVEY:does refer to extinction on Page 7:

'However, its host is morphologically elliptical and likely at z . 0.7 based on its color. At z . 0.7, a SN Ia would have to be very reddened (E(B − V ) & 1) to match the color and magnitude of the SCP06U50 light curve. As this is very unlikely (considering that the elliptical host likely contains little dust), we conclude that SCP06U50 is also most likely an AGN.'

From a little further up the page -

'However, given that the host galaxy is likely at z . 1 based on its magnitude and color,'

- I find some evidence to suggest the mainstream survey, in a political way, states that dust effects redshift. Orphadeus (talk) 19:22, 29 May 2011 (UTC) Orphadeus (talk) 19:44, 29 May 2011 (UTC)

1) Extinction and reddening affect every photometric observation of anything beyond the Solar System, to a greater or lesser degree. Just because a paper mentions them does not mean it has important information to impart on the subject. There are thousands, probably tens of thousands, of papers which mention them, yet in almost all cases it's merely so they can correct for the effect.

2) Reddening and redshift are two totally different things. Redshift is the shifting the wavelengths of spectral lines towards the red due to the Earth and the source moving apart from each other at high velocity. For distant galaxies, this velocity is caused by the expansion of the universe. This has absolutely nothing to do with absorption and scattering by dust grains.

3) If someone thinks they know what an un-redshifted version of an object looks like, they can use photometry to estimate the redshift. That is what those authors are doing when they say 'based on its magnitude and color'. Note they are referring to the host galaxy at this point, not the candidate supernova.

4) In the discussion of SCP06U50 the authors are trying to work out whether this is a Type Ia supernova or some other type of object. The only information they have is a photometric light curve in several colours. Because all photometric measurements are affected by extinction, they have to consider the affect this might have. Their conclusion is that it would require a lot of dust for this source to be a SN Ia, so they conclude that it is probably an AGN instead.

5) If they had a spectroscopic measurement of the redshift, measured from a spectral line, it would be completely unaffected by dust.

I don't mean to be rude, but did you read and understand the contents of the whole of that paper, or were you just searching through it for any mention of extinction?

What exactly do you mean by 'in a political way, states that dust effects redshift'? In what sense does dust affect redshift? What does it have to do with politics? And how is this relevant to the contents of the Wikipedia article on extinction? Modest Genius ^talk 21:31, 29 May 2011 (UTC)

(edit conflict)"Political?" What does this have to do with the concept of the city-state or of governance? Also, No original research. That means no personal interpretations. We just summarize the source. This has been explained to you repeatedly, and you've had this site's guidelines defining original research linked to you multiple times (gee, maybe you think that's been done so you could read them and quit wasting everyone's time by spamming this talk page with stuff this site just doesn't take?). Ian.thomson (talk) 21:40, 29 May 2011 (UTC)

Why do they attempt to correct redshift measurement for extinction if the extinction has no effect? Orphadeus (talk) 21:51, 29 May 2011 (UTC)

They don't. They attempt to correct their photometry to determine whether the object is a supernova or not. That has nothing to do with their redshift determination. Did you read what I posted above? Or are you purposefully ignoring it? Modest Genius ^talk 21:55, 29 May 2011 (UTC)

Purposefully ignoring you when you show that he's got it wrong? Welcome to the club. Ian.thomson (talk) 22:22, 29 May 2011 (UTC)

Are you refering to photometric redshift? According to the article it has been replaced by spectroscopic redshift. Parajkoj has repeatedly assured us (without reference) that the spectroscopic lines are not effected by extinction. According to THE HUBBLE SPACE TELESCOPE* CLUSTER SUPERNOVA SURVEY on Page 16:

'For the color distribution, in addition to a simple shift, we also quantify the effect of including a smaller or larger fraction of SNe significantly reddened by dust. In fact, we have good reasons to believe that most cluster SNe Ia will be in dust-free environments. A large fraction of the stellar mass in the clusters (� 80%) is contained in red-sequence galaxies expected to have little or no dust. Our spectroscopic and photometric analysis (Meyers10) of the red-sequence galaxies confirms this expectation.'

That looks to me like Parajkok may be wrong. Orphadeus (talk) 22:27, 29 May 2011 (UTC)

Where does Parajkok say that the same light cannot be affected by both redshift and extinction? And what does this have to do with your previous... points? How do you not know how to form a coherent thesis? Ian.thomson (talk) 22:43, 29 May 2011 (UTC)

Yes, I am referring to photometric redshift of the galaxy. But the discussion of reddening was in the determination of the source, a completely different measurement, with nothing to do with redshift.

Photometric redshift is certainly an inferior technique to spectroscopic redshifts, but is in widespread use because it is MUCH easier to take an image through several filters than it is to measure a spectrum. The redshifts in that supernova cluster paper you keep referring to are photometric redshifts. But I don't understand what that quote has to do with anything, nor what Parajkok is supposedly wrong about. Modest Genius ^talk 22:42, 29 May 2011 (UTC)

Ian, I did not say that Parajkoj said that the same light cannot be effected by both redshift and extinction. He has repeatedly (with no reference) claimed that extinction does not effect redshift. You might notice I have specifically requested references. I find the political point is also worth answering (I am time restrained). It appears to me that the area of extinction, variously aquired redshift, intrinsic redshift, and such inter-related topics is an area of scientific uncertainty. It would appear something along the line of that a Guru 'solved it', became a mainstream book best seller, the yes men piled in and 'scientific mainstream fact' was established, at least in the media. However, taking the body of published scientific studies as mainstream science, there appears a split between media mainstream - exemplified by such as possibly Stephen Hawking and Brian Cox - and the actual scientific mainstream. Certainty sells books. I may be misrepresenting Hawking - I am going by what I have read about him rather than by him - but the point is fair with regard to Cox. It maybe that some of the actual scientific mainstream did go to the media personalities for a time, but there is strong evidence - such as a publication by the US government and also in the Hubble survey - that that is being abandoned (if it was ever accepted). However, there may be a problem in that the establishment do not want the public to laugh at science, hence the row back, if they ever were with the media personalities, is being done in a subtle manner that could be described as political. There may also be an issue with fiefdom and face saving if, for example, verifiable rubbish is being currently being taught in British Universities. Orphadeus (talk) 11:50, 30 May 2011 (UTC)

Does extinction effect redshift measure?

No talk - just reference. Please put your references with quotes to back your case. I'll get the ball rolling

http://supernova.lbl.gov/~evlinder/redsys.pdf - (Hey - its The US Government) Quote: 'In this paper we explore the effects of redshift error, not only through the luminosity distance but also through the propogated stretch, K-correction, and extinction errors.'— Preceding unsigned comment added by Orphadeus (talk • contribs)

If I'm reading it correctly (and keep in mind I haven't been called out constantly, nor do I pretend to be an astronomer after being called out repeatedly by a professional astronomer), the paper doesn't say that extinction affects redshift. "The distance modulus term is dominant at the very lowest redshifts whereas extinction errors dominate for almost all of the redshift range considered." Extinction and redshift may be confused for each other, but this confusion is an error. They may occur within the same location (an event causing extinction could be moving away from us, creating a redshift), but they are distinct. Ian.thomson (talk) 22:22, 29 May 2011 (UTC)

"The distance modulus term is dominant at the very lowest redshifts whereas extinction errors dominate for almost all of the redshift range considered." Thanks for that Ian. Orphadeus (talk) 22:31, 29 May 2011 (UTC)

(edit conflict)Actually Ian, that 'paper' does not quite say that (note I wrote this in reply to your earlier comment, which you since corrected). When measuring the expansion of the universe, it's necessary to plot the redshift against the distance. Using Type 1a supernovae, the distance can be found from the brightness, after correcting for various things (including extinction). That 'paper' discusses the various error sources for both quantities.

I say 'paper', because it is extremely short and does not appear to have been published in a peer-reviewed journal. Nor is it written by the US government, but someone called 'A. Kim' who apparently works at LBNL.

Now, to address the actual point: I just explained (section above) that if you're estimating redshifts from photometry then you have to take extinction into account. If someone actually measures redshifts from spectroscopy, dust is irrelevant. This is a key difference between photometric redshifts, which are only an estimate and even those who use them admit they aren't very accurate, and spectroscopic redshifts which are actual measurements of the affect.

So Orphadeus, what are you trying to prove? Why are we suddenly having a discussion about whether dust affects redshift? What does this have to do with the article? And why do you keep ignoring other user's points and instead start discussing something completely new? Modest Genius ^talk 22:35, 29 May 2011 (UTC)

This could do with musical accompanyment. Lawrence Berkley National Laboratory is the US government. Assuming good faith, if Modest Genius had read the report, he might have noticed it was referring to spectrometic redshift (try the introduction):

'In supernova studies the redshift measurement is typically taken from the spectrum of the host galaxy, either from sharp emmission lines or from the 4000 Å break' Orphadeus (talk) 10:57, 30 May 2011 (UTC) Orphadeus (talk) 14:14, 30 May 2011 (UTC)

I'm not going to go looking for a citation that redshift and reddening are different, because I seriously doubt any publication would go to the trouble of saying so. Their effects on the spectrum of an object are so different, your insistence that they are similar just showcases your lack of knowledge of the topic. It's like asking someone for a citation that a horse and a hearse are different things.

Your link to the short document by A. Kim about supernova talks about determining the distance modulus to a supernova from its luminosity. The luminosity is computed from the brightness in a given optical band which is affected by extinction. The redshift determination is not affected by extinction. Full stop. Modest Genius is correct above.

From what I can tell, you're just searching for documents that use both terms (reddening and redshift), and then claiming that they imply a link between the concepts, without actually understanding the documents. There is no confusion between reddening and redshift in the literature, just in your head. Two professional astronomers, both of whom use reddening and redshift in their work, have told you this. This conversation does nothing to improve the page in question, and should end now, and be archived soon, so it doesn't clutter this talk page any further.

Also, for all involved: it's parejkoj. - Parejkoj (talk) 17:21, 30 May 2011 (UTC)

This is a section for references. Median in the equation should be written small, as should spec. Unfortunately a wave above a straight line is not available - for after Median in the equation:

'Extinction is a source of confusion and makes difficult the identification of QSOs in the galactic plane; (c) the χ2 method is better than ANNs to estimate the photometric redshifts. Due to color degeneracies, the largest median absolute error (|Δz|Median ' 0.2) is predicted in the range 0.5 < zspec < 2. The method based on the Spectral Principal Components is promisingly good at recovering the redshift, in particular for V < 19, z < 2.5 QSOs.' http://gaia.esa.int/spectralib/spectralibqso/Claeskens-et-al.pdf Orphadeus (talk) 18:43, 30 May 2011 (UTC)

'However, we immediately realized in this study that the diversity existing among QSO spectra must be taken into account to realistically estimate the fraction of correctly identified QSOs and the errors on the redshift determination. Indeed, the observed spectrum of a QSO strongly depends on its redshift z, the slope of its continuum, the individual line strengths (peakto-continuum fluxes, line widths), the possible presence of broad absorption lines, absorption by intervening intergalactic clouds or extinction by dust in the QSO host galaxy or in the Milky Way.' - Page3 :http://gaia.esa.int/spectralib/spectralibqso/Claeskens-et-al.pdf Orphadeus (talk) 19:10, 30 May 2011 (UTC)

I'll just register that I changed the heading of this section (for no other reason than) to be consensual. Orphadeus (talk) 21:06, 30 May 2011 (UTC)

General response to Orphadeus

This is getting too spread out, so I'm consolidating it:

If you are so time constrained that you cannot properly answer a number of users' points or cannot read their corrections to your constant mistakes, you should leave and focus on your life instead of wasting everyone's time. Pretty much every editor you have interacted with has had to call you out for some sort of incompetance, and in many cases you only spat in their cases by ignoring their advice. All the more reason you should just leave. You are no help here.

As for your claims of "politics," Wikipedia goes with peer-reviewed journals, and books based on them. This article at no point cites Cox or Hawking or any one else like that. You are raising a strawman argument, a substitute for an actual point. All the authors of the sources for this article are non-notable individuals. Your claims of "politics" are ignorant bullshit. Having gone to a college that tried to shove the scientific and artistic communities into the same department, the scientific community actually hates scientist celebrities, so our sources wouldn't mind knocking Hawking and Cox down a peg, if they were in the least bit relevant to this discussion.

Also, as an American, I know there's a difference between "getting funding from the government" and actually being part of the government. Although the Lawrence Berkeley National Laboratory is funded by the US government, it's really run by the University of California. The Wang paper is no more a document from the US government than my homework last semester. Wang's paper looks more like homework than any peer reviewed journal article.

And I have a general message for you:

I'm an English major. My degree is in bullshit, so I know how to spot when someone else is talking about something they don't know about. I know you don't know what you're talking about. You may think you do, but you do not. Having seen you not get what an "archive" is for, I had to question your intelligence. Having seen your complete lack of research skills and inability to form a coherent thesis at Talk:Number of the Beast, I can only assume that part of your education is missing for some reason. Since an astronomer (Parajkoj) repeatedly say you know nothing about this subject, and noone called him out for saying that, I can only assume you don't know anything about this subject. Having looked at the LBNL paper, I can tell that you're getting the contents backwards and missing parts, and reading your views into it instead of what the paper says. You don't know anything about any subjects you have been talking about. You haven't shown you know any way to research. You are only making a mess and should just leave. You have only shown that you are incapable of anything useful. You are a prime example of the Dunning-Kruger effect.

If you want to prove me wrong, coherently state what you're trying to do for the articles you've been trying to work on. That is, form a thesis statment, and bring in sources that directly support that statement. This is stuff you have to know to graduate from high school, and you have demonstrated a complete inability to manage this. Ian.thomson (talk) 17:06, 30 May 2011 (UTC)

http://en.wikipedia.org/wiki/Filibuster Orphadeus (talk) 18:47, 30 May 2011 (UTC)

And again, you refuse to address any point. I give up, you're a useless and bad editor, either because you're deliberately ignorant and uneducated and cannot realize this or because you're a troll. Whatever the reason, this is the last time time I'll respond to you outside of warnings and reports. Ian.thomson (talk) 18:56, 30 May 2011 (UTC)

Units?

In the introduction, it says extinction is measured in mag/kpc. It is not clear whether extinction is A(bandpass), mentioned below and identified as "total extinction", and A's units are never unambiguously stated. However, the units in the equation for N_H/A(V) imply that A has units of mags. Does A have units of mag, or mag/kpc? Asterai (talk) 21:34, 1 July 2011 (UTC)

A has units of magnitudes. I've removed the misleading statement in the lead, and mentioned the units when A (and N(H)) is introduced. Modest Genius ^talk 23:11, 1 July 2011 (UTC)

Example

If I might make a suggestion here: put up an example or two with clearly defined terms as to how reddening is calculated locally. Pick a star say...300 parsecs out and walk the reader through the math step by step. Actually seeing an example of the equation in action, with defined terms all the way around, would help a great deal here. — Preceding unsigned comment added by 74.124.96.239 (talk) 00:25, 3 April 2013 (UTC)

Agreed, that would be helpful. Please go ahead and add one. Modest Genius ^talk 12:13, 22 April 2013 (UTC)