|WikiProject Physics / Relativity||(Rated Start-class, Low-importance)|
|WikiProject Astronomy / Astronomical objects||(Rated Start-class, Low-importance)|
- 1 Dark star
- 2 Currency of the term
- 3 Points needing fine-tuning
- 4 'Gravastar' vs 'Dark Energy Star'
- 5 Revised introduction
- 6 New dark energy star theory
- 8 Uh Oh, New astronomical use for the term Dark Star
- 9 Almost no-one is interested in this concept
- 10 Dark Energy Measurement
- 11 Assessment comment
- 12 External links modified
- Due to a page move, this is now at Talk:Dark star (Newtonian mechanics)#Dark-energy star. --Christopher Thomas (talk) 06:08, 31 March 2010 (UTC)
Currency of the term
Does anyone other than Dr. Chapeline use this term? --Wtshymanski 05:19, 8 Apr 2005 (UTC)
It seems like the article is describing what is commonly called a White Hole MikeMorley 15:43, 13 July 2005 (UTC) The latest Analog Science Fiction Science Fact pulper has an article on it. 188.8.131.52 03:50, 5 August 2005 (UTC)
- No, I don't think so, as the speculation is that emission of dark energy would be from the same event horizon, did I get this right? 'Grey hole' might be appropriate? —Preceding unsigned comment added by 184.108.40.206 (talk) 09:17, 30 June 2009 (UTC)
Points needing fine-tuning
I've put a link to this article on Wikipedia:Pages needing attention/Physics, to reflect the "needs attention" template on the article itself. Hopefully this will bring in more editors to contribute.
- Dark energy star - Needs to be overhauled by a physicist familiar with the models involved. As-is, several points in the description are inaccurate (noted in the article's talk page). The model has been published in reputable journals, if I'm remembering which one this is correctly. Still fringe science, for now. --Christopher Thomas 01:23, 21 Jun 2005 (UTC)
Back to talk page
Points that I find odd in the current write-up:
- The description of how GR treats black holes isn't quite accurate. Infalling objects appear stationary only to distant observers, and this effect is definitely only an appearance. What actually happens depends on how you choose to measure time in the vicinity of the hole, but the infalling object measures itself to have passed through the horizon very shortly after starting to fall, and any form of measurement the distant observer could try would fail to interact with the infalling object despite an image of it being present (you can't bounce a radar pulse off the image, for instance; it's just an image formed by light that took a long time to escape from the point where it was emitted).
- The description of an object "bouncing" after passing through the horizon seems odd, as if there's actually a horizon, it implies a causal disconnection between the regions outside and inside. If I recall correctly, the papers about this type of object described the resulting structure as having a region of very high density outside of where the horizon would be, but no event horizon. However, I'd be more comfortable if an astrophysicist could read the publications and adjust the write-up accordingly (I'm not one).
- More detail on the "stranger effects" due to quantum fluctuations is needed. Most people know about Hawking radiation, but it should be mentioned. I also recall mentions of a fuzziness in the exact location of the event horizon, and of certain situations causing infalling objects to encounter large amounts of matter produced by interactions between the black hole and virtual particles (I'd want to look these up again before claiming they accurately represent mainstream views, though).
- Clarification - I recall references to encountering large amounts of matter _inside_ the horizon, in the vicinity of the Cauchy horizon (as distinct from plowing through Hawking radiation of great intensity when you approach the event horizon from the outside). --Christopher Thomas 06:32, 21 Jun 2005 (UTC)
An excellent start, but could use more fine-tuning.--Christopher Thomas 01:37, 21 Jun 2005 (UTC)
'Gravastar' vs 'Dark Energy Star'
- see also Talk:Gravastar
Having read both entries and several linked pages, I am still unclear as to the distinction. Are these simply alternative names for a single concept? If so, would it not be advisable to merge the two entries?
- Please refer to discussion here for this; and to ask any further questions. - RoyBoy 800 21:50, 21 August 2005 (UTC)
- There is no useful content pertaining to the distinction between gravastars and dark energy stars on that page. Most of the thread you participated in discusses "dark stars", which are the Newtonian equivalent of black holes. Discussion of the proposed merge should either be here, or at Talk:Gravastar. --Christopher Thomas 22:22, 11 January 2006 (UTC)
"Chapline theorized that a phase transition in the phase of space occurs at the event horizon"- whats a phase of space (or am I reading this incorrectly)? "As there is no singularity to evaporate, Hawking radiation may not exist in this model of black holes." - A singularity is not required for Hawking radiation. All that is needed is a horizon. eg: see http://arxiv.org/abs/hep-th/0106111. However, I'm not sure there is a horizon. My understanding is that collapse of matter halts before the outer surface of the matter falls over the horizon radius (certainly true for a gravastar, I'm now reading to see if a gravastar is a dark star - I'm pretty sure they aren't since they have been invented by different authors). Therefore one would not have Hawking radiation. Don't merge. But the articles need major rebuilding: both are very ambiguous on the differences. Steve Max 16:10, 13 April 2006 (UTC)
- I got the impression that an observer outside the horizon could tell the difference between a dark energy star and a black hole but that a gravastar appears identical to a black hole outside the horizon. Namely, normal matter falling into a dark energy star would decay into dark energy before crossing the horizon. Protons would also first decay into observable positrons and photons. These quantum/dark energy effects would be observable even if the object were very massive and lacked the extreme tidal forces needed to be even noticeable in a system modelled on General Relativity alone (where an event horizon is not significant to a local observer). A gravastar seems to differ from a black hole only on the inside - where no singularity forms because of some sort of phase transition on space-time. So to sum up the differences: space changes inside the horizon of a gravastar, matter changes outside the horizon of a dark energy star.
A dark energy star is an alternative explaination to black holes in which instead of entering the star, matter is converted into dark energy. A gravastar however is a different explaination in which matter enters the star but, unlike a black hole, space keeps the matter from collapsing into a singularity. Instead the matter is compressed to a high density in the center of the star. In a black hole matter collapses into a singularity in the center of the black hole. —The preceding unsigned comment was added by 220.127.116.11 (talk • contribs) on 19:13, 24 May 2006.
Hi all, hypothetical speculations for possible compact objects which could avoid invoking the black hole concept which troubles so many (including some astronomers) is a legitimate topic, since this is genuine if controversial topic in the research literature. However, please try to make it clear in the first paragraph when a speculation is regarded as dubious by the majority of physicists, as is the case with gravastars. IOW, please make every attempt to keep discussion of both black holes, neutron stars, and possible other kinds of compact objects as fair and accurate as possible with regard to current scientific status. I don't want to get into Chapline et al. right now (but see recent discussion in sci.physics.research), but I took the time to try to slighly modify the introduction to better suggest the speculative status of gravastars. Even editors who feel that black holes are equally speculative should not suggest that they are not the mainstream explanation for observed black hole candidates (in fact, very few would even be as careful as I am to sometimes refer to black hole candidates rather than simply black holes). ---CH (talk) 10:35, 3 October 2005 (UTC)
New dark energy star theory
This makes for an excellent read... New Scientist Article. From my reading of that the dark energy star is a completely different beast to the gravastar or dark star which some people seem to equate it with - it should end any confusion. --LiamE 10:13, 10 March 2006 (UTC)
- Having said that a read a bit deeper it the article is rather similar to a gravastar as descibed in its article. Can someone please clarify the differences between the theories please. --LiamE 10:35, 10 March 2006 (UTC)
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Uh Oh, New astronomical use for the term Dark Star
|Centralizing discussion at Talk:Dark star|
|The following discussion has been closed. Please do not modify it.|
We need to rename and reorganize these articles: there is a third astronomical term, "Dark Star". At the moment, the Dark star article is not well-named - as in physics and astronomy classes the term "dark star" is not commonly used for Newtonian black holes. That article needs to be renamed "Newtonian black holes", or something like that. Then, we should use the title "dark star" for this newly hypothesized category of super-huge star, powered by neutralino interactions.
Current situation: Two articles, and one type of star is simply missing
Let's start discussing this. We now have two articles with similar names, for three types of astronomical objects. This is confusing not only to lay readers, but even to scientists.
This thread is duplicated across two pages. I'm archiving this copy, so that we can centralize discussion at Talk:Dark star#Uh Oh, New astronomical use for the term Dark Star. --Christopher Thomas (talk) 07:00, 23 March 2010 (UTC)
- Due to a page move, the thread is now at Talk:Dark star (Newtonian mechanics)#Uh Oh, New astronomical use for the term Dark Star. --Christopher Thomas (talk) 06:10, 31 March 2010 (UTC)
Almost no-one is interested in this concept
I wish there were some way I could say that in the article, but the comment would be reverted for sure. You can see here just one basic reason why people aren't interested in Chapline's model - it allows faster-than-light effects.
It is a sociological fact about theoretical physics that there are always people pushing ideas which no-one else is interested in and which never amount to anything. I don't just mean amateurs with websites; there are hundreds, perhaps thousands, of academic physicists around the world who have a favorite private idea, and who write series of papers across many years developing the idea, and hardly anyone even reads the papers. A significant fraction of the theory papers which appear on the famous arxiv.org site have this quality. They get onto the archive because the author is in academia - and usually that means they have done good or at least competent science at some point in their career. Chapline, for example, worked on superconductors.
Anyway, another sociological development is that sometimes a paper or a concept is lifted out of this obscurity by science journalism. Garrett Lisi's theory of everything was a big example a few years ago, but really, there are several examples each year now. A further twist is that some of these ideas which achieve media success then become popular among the many iconoclastic amateur physicists who are busy on dozens of web forums trying to overthrow relativity, quantum theory, string theory, or whatever. And another minor aspect is that Wikipedia pages get created for some of them.
It is true, of course, that obscure ideas do sometimes get discovered or reinvented many years later. But mostly it never happens. So here is the problem. There are probably many many physics articles on Wikipedia just like this one, namely, they present a speculative concept advanced by just one or two people, and there is nothing to indicate to a lay reader just how obscure and ignored the idea really is. Especially if the advocates of the idea start editing the page themselves! Mporter (talk) 09:50, 3 April 2010 (UTC)
- What might be a useful way to deal with such articles is to redirect them to an omnibus page for alternative or fringe theories of their type, and then have a few words on that page summarizing the idea in question. (I previously did this for a "Planck matter" page, which I redirected to Induced gravity. The phrase "Planck matter" is the invention of one physicist and it has no currency within the field.) Incidentally, I'm not proposing that these omnibus pages would attempt to be comprehensive lists of every alternative theory out there - it's just a way to deal with those theories that do get onto Wikipedia and aren't so obviously crackpot as to warrant immediate deletion. Chapline's theory, for example, made it into New Scientist, so I suppose people deserve to know something about it. But apart from the summary which the page currently provides, they also deserve to know that it's totally obscure and the only person writing about it is Chapline himself. (The article currently says "a minority of physicists" are interested in the idea, which is technically true, but we're talking a very small minority.) So the current page would be redirected to something like Alternative theories of stellar evolution (it looks to me like gravastar would belong there too). Mporter (talk) 10:00, 3 April 2010 (UTC)
- If the've been published in scientific literature, and have received at least a little press, I don't see the problem with them being in the encyclopedia. We don't have a page limit, after all. My main concerns would be with material that hadn't passed peer review somewhere, hadn't received any press, or was presented as being mainstream when it wasn't. I'm a bit of an inclusionist that way. --Christopher Thomas (talk) 15:44, 3 April 2010 (UTC)
Dark Energy Measurement
Unless my basic understanding of the term Dark energy is flawed, no one has been able to measure it. Dark Energy is a theory about unexplained phenomenon in Cosmology, hence "Dark". So the statement, "Dark energy is invisible to the human eye; however, it can be tracked with difficulty by gamma-ray astronomy." seems wrong to me on many levels. I put in a citation needed tag, but I think this statement needs more help than that. Silve Slade (talk) 18:58, 8 February 2012 (UTC)
The comment(s) below were originally left at several discussions in past years, these subpages are now deprecated. The comments may be irrelevant or outdated; if so, please feel free to remove this section., and are posted here for posterity. Following
|The concept of dark energy star is possibly not published in any standard journal.So we need not give importance to it.|
Last edited at 00:43, 1 January 2012 (UTC). Substituted at 12:50, 29 April 2016 (UTC)
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