Talk:Planetary equilibrium temperature

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I think there is plenty of work to do on this article
... and some of it, as it stands, I find odd, to say the least. But I do not intend to spend time trying to edit it. I leave that to the local author.

Untitled
I now see that I have inadventently done some bad things which I should have left to an expert administrator. I am sorry for my mistake in this.

But I feel confident that the new title is the right one for this article. I hope a suitable administrative fix will be found.Chjoaygame (talk) 04:28, 16 November 2012 (UTC)
 * Not sure which part is odd. This was a derivation I found in one of the references, and it is the same problem I did in a thermodynamics class in college. I don't like the new title - I have never before seen it called "planetary equilibrium temperature". It is just not a term that existed before. I created the page because it was a term that I saw that didn't have a Wikipedia article. I see this is the 2nd time you have redirected a page away from "Equilibrium temperature" and I'm just not getting why. Drxenocide (talk) 03:29, 17 November 2012 (UTC)


 * Perhaps I have been hasty. What motivated my change is that there has been a persistent effort to put a table of planetary temperatures into the article on thermal equilibrium. I think that effort has been misdirected and would have been bad for the article on thermal equilibrium. My reason is that thermal equilibrium is a fundamental concept of the basic theory and axiomatics of thermodynamics, and most especially of equilibrium thermodynamics. Planetary temperatures are a more specialized matter, and are more the province of astronomy with a heavy empirical content; much about them is beyond the reach of thermodynamics. For example, planetary temperatures are partly governed by cloud formation, and that goes to questions that are more or less too hard for basic thermodynamics, even for non-equilibrium thermodynamics; I would say too specialized for an article on the general theory of thermodynamics. To put into the article on thermal equilibrium all subjects involving such specialized questions about temperature would be a mistake, I think. Therefore I prefer to see the specialized articles have their own dignities, places, and titles.


 * As I read your article, the general idea of equilibrium temperature is more a springboard for a study of planetary equilibrium temperature than it is the main focus of interest of your article.


 * What I found odd was your restriction of the concept to what would happen if the planet had no atmosphere and therefore no greenhouse effect. This strikes me as a very specialized approach, even an oddly specialized approach. I don't see why a planet with an atmosphere might not also be said to have an equilibrium temperature if one took the viewpoint of the persistent effort to put a table of planetary temperatures into the article on thermal equilibrium.


 * I think I may fairly ask, what is the fundamental drive of your article?


 * Ostensibly, your article, before I changed its structure (mangled it, perhaps you might feel?), had little to say about the basic theory of heat transfer or thermodynamics. For example, it did not mention the possibility of an equilibrium temperature brought about by conduction of heat or by convection of internal energy. This made me think that general abstract theory was not your main concern. That left your heavy emphasis on radiation for planets as the obvious candidate as your main concern or fundamental drive.


 * If you have a preferred title that accurately reflects your main concern, I am happy for you to change instead to it, which of course you are free to do whatever I might feel. My concern is to maintain the very abstract titles such as "Equilibrium temperature" with a main focus on the principles rather than on the specialized empirical applications. This is because there are very many potential specialized applications. I do not see it as wrong to mention the specialized applications in the general or abstract articles, but I do see it as wrong to have them dominate so as practically to minimize the general aspects, especially as in the present case, when only one specialized application seems to be contemplated.


 * I recall other efforts to write an article entitled "Equilibrium temperature". I recall looking this phrase up in a few textbooks and I reached the perhaps premature conclusion that it is a term used in some textbooks, but that it is more a product of the structure of ordinary language as used in physics than a special term of art of physics. For this reason I was opposed to an article so entitled, which might seem to imply that it was a special term of art of physics. You call it a "term", when I see it more as a phrase that arises in the use of ordinary language in physics, not to be unduly dignified by a few accidental uses and a new article of its own in the Wikipedia. You have a similar objection to my title "planetary equilibrium temperature". It seems you are right that is not much used; rather, people seem to speak of the "equilibrium temperature of a planet". Google tells me that some people write of 'planetary temperatures', or of 'effective planetary temperature', or of the 'emission temperature of a planet', or of the 'equivalent black body temperature of a planet'. Perhaps those might be better titles than my "planetary equilibrium temperature", which I accept just came to me as a natural use of language.


 * If you do decide to change the title, you may be wise to ask for specialist advice on how to do it. There are matters of talk pages and the like that need some skill to sort out. I regret that this time I forgot about that, and I have said above that I am sorry I did so.Chjoaygame (talk) 04:49, 17 November 2012 (UTC)


 * Ill check the internet again. I understand your concern about the specific conditions of the term (i.e. what about other heating?). From what I read, all those other heating mechanisms are used to calculate/explain the "actual temperature" (as I saw one website use) which is not calculated, but simply measured with an infrared spectrometer. I think it is possible that you are assuming that this is a term that is used in thermodynamics. While it is possible, all the references i saw use it really only in the context of paleontology. Based on the articles that link to the article, I think it should just be left as "Equilbrium temperature", since I dont see any other concept it is ambiguous with. After reading your specific concerns, i could clean up the definition a bit, but I think it is important to note that an atmosphere is not part of the calculation - indeed the "equilibrium temperature" could not be calculated for exoplanets if scientists had to know the composition and depth of the atmosphere.Drxenocide (talk) 15:31, 17 November 2012 (UTC)


 * Thank you for this reply. With respect, I think you are too close to your own interest to see it in perspective. I think you are trying to appropriate a general term of ordinary language in physics into a special term of art in physics in an inappropriate way, by restricting it to radiative calculations as you do. The ordinary language phrase "equilibrium temperature" is used in contexts wider than you are proposing. I recall someone, perhaps you, posting some calculations from a student text that were about putting some bodies together, initially at different temperatures, in an isolating enclosure, and waiting till they reached a steady temperature, and calling that the equilibrium temperature. There is a method of calorimetry called the method of mixing, that works like this. I have read your arguments above and find them tendentious and unconvincing.


 * You are writing about a very special calculation and your title should reflect that. If your title did not reflect that, you would be trying to appropriate a very generally intelligible phrase for use as a special term of art. I think that would be bad.


 * From another viewpoint, one can say that the Wikipedia is not a dictionary, and that not every phrase of that is ever used in any context can demand an entry of its own.


 * You are forcing me to spend time dealing with something that is really your own special interest. Subh83 has done some research on it, which I lift from the talk page of the article on Equilibrium temperature, at Talk:Equilibrium temperature


 * What is the """""correct""""" redirect? Best simply to delete this redirect item


 * Equilibrium temperature is not a term with special status in the area of thermodynamics or heat transfer. That is not to say that the phrase is not used, but is to say that it is not a specially defined term. On the other hand, the term 'equilibrium temperature' is a customarily used term in present-day climate science. I do not think it an improvement to put the redirect back to Thermal equilibrium. More comments from me at Talk:Thermodynamic equilibrium. My current conclusion: simply delete this redirect item. Chjoaygame (talk) 10:48, 25 December 2011 (UTC)Chjoaygame (talk) 11:39, 25 December 2011 (UTC)
 * "Equilibrium temperature" is definitely a term used in many regular texts on thermodynamics. I wouldn't recommend deletion of this redirect since someone searching Wikipedia using that term will end up wandering too much before getting to the correct article. - Subh83 (talk &#124; contribs) 17:34, 26 December 2011 (UTC)


 * A longer discussion on this redirect can be found at Talk:Thermodynamic_equilibrium.


 * "Equilibrium temperature" is a term used in many regular texts on thermodynamics (as a concept of physics).
 * Thermodynamics texts that use 'equilibrium temperature':
 * 1.  "A text book of engineering thermodynamics". By John Joseph Flather. pp. 446. (url)
 * 2.  "Principles of physics: a calculus-based text", Volume 1. By Raymond A. Serway, John W. Jewett. pp. 500. (url)
 * 3.  "A text book of thermo-chemistry and thermodynamics". By Otto Sackur. pp. 5. (url)
 * 4.  An example from a Wikipedia article: See the definition of entropy in Second law of thermodynamics.
 * There are a lot more references I can keep providing. - Subh83 (talk &#124; contribs) 20:05, 26 December 2011 (UTC)
 * Equilibrium temperature has nothing to do in specific with the climate. It is a general concept in physics. There can be a equilibrium temperature for a refrigerator, the human body, a piece of rock, a pressure vessel, etc. - Subh83 (talk &#124; contribs) 20:10, 26 December 2011 (UTC)


 * It is good to see some reliable sources. Thank you.


 * In general, I do not think that a Wikipedia article can qualify as a reliable source on a question such as this. In the particular case that you cite, the use of the phrase 'equilibrium temperature' there is not a properly defined term as it appears in your other cited sources, and is an example of the looseness of the meaning of the phrase. The sentence you cite is not as you assert a definition of entropy. The 'equilibrium temperature' examples that you quote (refrigerator, piece of rock, pressure vessel) are not just intrinsic properties of the items that you cite, but depend on their current internal states and surrounding conditions as well, to which you do not point. Wikipedia is not a textbook to cover every phrase that one may encounter, so as to necessarily demand an entry for a phrase such as 'equilibrium temperature'. People coming from talk of climate 'equilibrium temperature', such as the editor who started this discussion by inappropriately putting a table of planetary 'equilibrium temperatures' and other things into the Thermodynamic equilibrium talk page, will probably continue wander for a while before reaching the specific usage they are looking for; that may do them no harm. I will not dispute the matter further.Chjoaygame (talk) 23:58, 26 December 2011 (UTC)


 * This product of careful and valuable editorial work by Subh83 is evidence that the phrase 'equilibrium temperature' is widely used in at least one context other than the one for which you are proposing to appropriate it, and that it is not suitable to be set up as a term of art as a Wikipedia article title in the way that you are proposing. Your comment that it seems to be specific for paleontology was not adequately researched and was not accurate. A check of the internet may not be enough.


 * You did not answer directly and explicitly my question "What is the fundamental drive of your article?" In the absence of an explicit answer from you, I am left to work it out for myself. I conclude from what you write that you are fundamentally interested in the equivalent blackbody temperature of a planet.


 * You evidently do not like the title 'Planetary equilibrium temperature', which I think is ok. Instead, I think you could safely use 'equivalent blackbody temperature of a planet'. This phrase signals your specific interest, and indicates its specific character. This phrase may be found in Atmospheric Science. An Introductory Survey, Wallace, J.M., Hobbs, P.V. (2006), second edition, Elsevier, Amsterdam, ISBN 978-0-12-732951-2, in the index on page 475, and in the text there indicated, in Section 4.3.3, on pages 119–120; I think this would do well as a reliable source for Wikipedia.


 * I will continue to oppose the appropriation, for a very specialized article title, of a general phrase such as 'equilibrium temperature'.Chjoaygame (talk) 21:25, 17 November 2012 (UTC)

more general set-up for this article
I have constructed a more general set-up that seems to me appropriate for this article. The title does not pretend to be specific term of art, but is simply an encyclopaedia heading, in ordinary language, to encompass an area of interest, probably comprising several terms of art. I am not interested in trying to improve or edit or expand this article, but I am interested in protecting the structural coherence and consistency of Wikipedia article headings. I hope this is a reasonable compromise.Chjoaygame (talk) 03:00, 18 November 2012 (UTC)

reliable sources
I am not happy with some of the internet sources cited for this article. In my opinion, they do not reach a suitable standard of reliability. The main problem is that internet sources are often very hard to check as to their actual sources. Sometimes citing the internet is a sign of lazy editorial activity. As reliable sources for Wikipedia articles, I much prefer established printed textbooks which themselves cite reliable literature sources. The question is not as to the correctness of the source, but as to its further checkability. A reliable source should be reliably checkable.Chjoaygame (talk) 03:09, 18 November 2012 (UTC)Chjoaygame (talk) 03:12, 18 November 2012 (UTC)

possible inclusion of table, without prejudice
I prefer the previous more general version, but I am not interested in this topic, so I will not undo the new version.

This table was from time to time put into the article on thermal equilibrium, where it did not naturally fit. I have no idea of its possible value for the present article, but here it is, for your consideration. Those insertions were the cause of my concern with the present article.
 * Are you sure this table is correct with Venus? Please compare the discussion section down this page. Plus: most sources I find state either 260 K or 186 K. --129.13.156.13 (talk) 15:53, 17 February 2016 (UTC)

black is not grey
I agree that there is much to do on this article. It's very odd to put the equation in terms of the temperature and the radius of the star; that's not the usual way you see equilibrium temperature calculated. Temperature and radius are calculated, while the luminosity of the star is directly measured, so it's more common to see the equilibrium temperature in terms of the luminosity.

I added a section where the temperature is calculated as a function of the insolation, which is also a common calculation.

One quibble: if a planet has an albedo not equal to zero, it's not a "perfect blackbody"; it's emitting as a blackbody, but absorbing as a a grey body.

Geoffrey.landis (talk) 20:48, 25 June 2014 (UTC)
 * The statement "it's emitting as a blackbody" is wrong. The emissivity of the surface is NOT 0. The equation for radiative transfer from the surface is hence also wrong. While I'm at it, where else in the study of radiative energy transfer is the word "albedo" used? I was taught absorptivity+reflectivity+transmitivity=1. From the context of this article, it would appear that albedo is what the rest of us call reflecitvity?74.51.49.234 (talk) 15:00, 15 December 2015 (UTC)

Thanks a lot for your work. I originally started this article because I heard the term used when I was reading a journal article about one of the exoplanets discovered by the Kepler mission. There was no wikipedia article that addressed the topic so I created one. My original intention was to have a place to answer the question "How do they know what the temperature of an extrasolar planet is?"

While the other comments have maybe correctly pointed out that this article lacks generality, I found Choyagame's comments belligerent and just too much to deal with. I was also a bit offended that his comments were twice the length of the original article. I looked up information on the internet, after a question I had about a journal article, and couldn't find what I was looking for - and decided to create a wikipedia article. I think that if someone has a "What's that?" question, there should be an answer somewhere in Wikipedia. So while the article may lack generality, it does answer "How do scientists know what the temperature of an exoplanet is?" which is what I intended to write. The great thing about wikipedia is that generality and context can be added later, because there is always another editor who knows more than the author.

I'm fine with any edits except those that remove the answer to the question I came to this article with.

Drxenocide (talk) 17:01, 8 July 2014 (UTC)


 * I second to Geoffrey. I.e., this can be found in the 'albedo' article, for a black body a=0 by definition. However, in exo-planetology, a is not set to 0 => The equilibrium temperature is calculated for a grey body in reflectivity and for a black-body in emissivity. Thus, I'll attempt to account for that in the article. --129.13.156.13 (talk) 14:54, 10 February 2016 (UTC)

Equation correctly transcribed?
The equation under "Theoretical Model" give an equilibrium temperature for Venus of 186 K, but the article previous gave a temperature of 260 K. I have changed this value for the sake of consistency. — Preceding unsigned comment added by 192.91.60.10 (talk) 12:18, 19 August 2014 (UTC)

Merge needed ?
I think Planetary equilibrium temperature and the "Planet" chapter of Effective temperature are actually the same topic. Also it seems that equilibrium temperature and effective temperature are (at least in this context) the same thing. In my opinion the two articles should either be merged, or at least visible cross referenced. What's currently not good is that "equilibrium" and "effective" temperature are misleadingly defined like they would be different, while actually they are defined by the same formulas (and planetary equilibrium temperature is the same as effective temperature... for planets); in the formulas, the luminosity and albedo are notated (slightly) differently but everything else is identical, like two different people worked independently on two different articles which actually are about the same subject:

http://en.wikipedia.org/wiki/Effective_temperature#Planet vs http://en.wikipedia.org/wiki/Planetary_equilibrium_temperature#Detailed_derivation_of_the_planetary_equilibrium_temperature

-Paul- (talk) 10:44, 22 October 2014 (UTC)


 * I can plead guilty to inventing the present article title. I have no interest in the article nor in the title.


 * I did it because someone who shall be nameless continually invaded general theoretical physics articles with a table of theoretical virtual planetary temperatures. For reference and definiteness, here is a version of the dreaded table.


 * I just wanted the table to go somewhere else, to home where it would be welcome, perhaps a specialized article, so as to stop it invading general theoretical physics articles. When posted out of its native home, it was like a recurrent cancer.


 * I had asked the unnamed editor to write a suitable fresh article that would provide a welcoming home for the planetary table, but he didn't do so, and the table just kept invading physics articles. So I made up a home that I hoped would welcome the planetary table, so as to keep it away from straight physics articles. That is the reason for the present title. I learn from the above comment that perhaps the welcoming home is the "Planet" chapter of Effective temperature. As it happens, the dreaded table isn't in this present article. I have no idea where it has gone, if it even still exists.


 * I have just now glanced at the Effective temperature article's section Planet and I agree that seems rather near to the present article here. I would not have any objection to a merge to Effective temperature, or to removal of this present article, with any relevant content being sent to Effective Temperature, or any other thing you think fit, as long as you don't put the dreaded table back to where it doesn't belong, in the general theoretical physics articles.


 * I am not interested in this article, except as a way of keeping the dreaded planetary table away from where it doesn't belong.Chjoaygame (talk) 14:38, 22 October 2014 (UTC)


 * Maybe it is not such a bad idea to have two different articles, but at least some links should exists beween them, like here:
 * https://en.wikipedia.org/wiki/Earth%27s_energy_budget#See_also
 * Unfortunatelly I am hesitant to do something because I am not sure what's the best thing to do. For now, at least a "see also" would be fine, I think
 * -Paul- (talk) 08:04, 23 October 2014 (UTC)
 * Or maybe should we enlarge this article to "Planetary temperature" and add additional information (such as the "Planetary surface temperature" from the other article, and maybe some considerations about Internal Heathinh and GreenHouse Gases?
 * -Paul- (talk) 08:08, 23 October 2014 (UTC)
 * And since I've noticed the terminology was debated, I think equivalent terms are:
 * - equivalent black body temperature
 * - equivalent black body emission temperature
 * - effective radiating temperature
 * I've found these terms in various academic sources while reading on the subject. Well now I see they (or some of them) are mentioned in the :::beginning of the article.
 * -Paul- (talk) 08:15, 23 October 2014 (UTC)


 * I invented the title not pretending it as a technical term but as a sort of guide to the reader. I accept it is not an ideal title, but it was the best I could think of considering the circumstances. I would not favour enlarging this article to 'Planetary temperature' unless there is a very strong expert reason for doing so. I feel sure there are already about a million different Wikipedia articles about planetary temperature in general.Chjoaygame (talk) 08:54, 23 October 2014 (UTC)

Equilibrium Temperature of Venus?
Under the section titled "Theoretical model" an equation is given for the equilibrium temperature of a planet. In the paragraph below this equation, an equilibrium temperature of Venus of 260 K is given, however if one actually uses the equation given one finds the equilibrium temperature of Venus to be ~186K. The 260K figure only appears if one uses the diameter of the sun instead of the radius in the equation. It also doesn't make sense for Venus to have a higher equilibrium temperature than Earth for the simple reason that it absorbs less radiation from the sun; the solar constant at Venus is twice that at Earth, but Venus also reflects 90% of the light radiation that reaches it while Earth only reflects 30%. This means Earth absorbs 3.5 times as much radiation than Venus, and so in the absence of the greenhouse effect it would have a higher temperature.

I'm not sure if this qualifies as original research or not, but I think the 260 K figure should at least be removed as incorrect. — Preceding unsigned comment added by 131.111.185.47 (talk) 12:47, 9 November 2014 (UTC)


 * This NASA source http://nssdc.gsfc.nasa.gov/planetary/factsheet/venusfact.html also states 186 K. --129.13.156.13 (talk) 15:50, 17 February 2016 (UTC)


 * Update: The values for Bond albedo and temperature in the link above had been changed. I assume that the often cited value of 0.9 for Venus' Bond albedo just is wrong. Confusing stuff --129.13.156.135 (talk) 12:51, 10 January 2017 (UTC)

Concern about the accuracy of portions of this Article.
I was redirected from "Blackbody Temperature" and found myself confronted with an Article that starts thusly:

"The planetary equilibrium temperature is a theoretical temperature that a planet would be at when considered simply as if it were a black body being heated only by its parent star. ...".

So by definition of this Article a Extrasolar Planet, Sub-brown Dwarf or even a Rogue Planet doesn't have a "Planetary Equilibrium Temperature" or an Effective Temperature because it is a Blackbody without a "Parent Star".

All things (objects) hotter than Absolute Zero and with an Emissivity greater than zero emit radiation and thus have a temperature (or Black-body Radiation), objects with an emissivity less than zero are reflective and reflect heat, they are called a Whitebody.

Even a Black Hole (a perfect Blackbody) is thought to emit Hawking Radiation and thus have a temperature.

I'm not trying to split hairs, just looking for the Link I clicked on before this redirect - I wonder if Planet Effective Temperature duplicates some of this Info.

70.71.206.161 (talk) 06:21, 20 March 2017 (UTC)


 * Extrasolar planets have an equilibrium temperature because they are heated by their parent star. Brown dwarves and rogue planets don't have equilibrium temperature calculated this way because they aren't in equilibrium with incident energy-- brown dwarves are still cooling off from their gravitational collapse energy, and rogue (interstellar) planets would eventually come into equilibrium with the cosmic background radiation, but that takes a very very long time, so in general they are still cooling as well. This could be explained better in the article, though.
 * Indeed, Effective_temperature does duplicate this info. The two articles really need to be rewritten to be clearer about what is which. Skepticalgiraffe (talk) 21:34, 22 June 2017 (UTC)

Moon vs Venus
How the Moon can have higher equilibrium temperatre than Venus, given it is further from the Sun?--Reciprocist (talk) 23:12, 23 December 2018 (UTC)
 * Because it has a lower albedo. Double sharp (talk) 15:07, 20 November 2023 (UTC)

Clarifying between effective and equilibrium temperature, and more
I am going to make a few changes, mostly to clarify aspects of the article that are vague or misleading. One part that could use work is a clearer separation between equilibrium temperature and effective temperature. Equilibrium temperature is the temperature a planet would have to radiate at (like a blackbody) to produce a flux equal to the incoming flux it receives from the sun. Effective temperature is the temperature a planet would radiate at to produce a flux equal to the incoming solar flux PLUS any additional sources of energy, such as internal energy on giant planets. Lmfifer (talk) 22:10, 11 June 2019 (UTC)
 * Where are you finding these definitions? Dicklyon (talk) 22:38, 11 June 2019 (UTC)
 * Catling and Kasting's 2017 textbook, and Lissauer and de Pater's 2013 textbook both distinguish between the two, noting that in the presence of some internal energy flux that the effective temperature is greater than the equilibrium temperature. I need to backtrack on my last message though, I think it is more accurate to say that equilibrium temperature is what is required for a planet radiating like a blackbody to balance the incident solar radiation, but effective temperature is the temperature a planet (approximated as a blackbody) would require to produce the total energy flux OBSERVED radiating from the planet. Hence giant planets with internal energy sources have higher effective temperatures (derived from observations of their outgoing radiation) than equilibrium temperatures (what we expect purely from how much solar radiation they receive).Lmfifer (talk) 01:13, 12 June 2019 (UTC)
 * OK, thanks. Dicklyon (talk) 09:36, 12 June 2019 (UTC)

Removing emissivity, simplifying derivation
The mentions of emissivity during the complete derivation seem unnecessary, given that the definition of equilibrium temperature rests on a blackbody flux equaling incident solar flux, not a graybody (which is the only time emissivity should come into play).

Also in the derivation, a lot of attention is paid to the size (radius) of the star, while the equilibrium temperature could be defined more simply in terms of insolation (which the article uses earlier). Maybe the stellar properties (and orbital distance of the planet) could be introduced at the end of the derivation, as an aside? Lmfifer (talk) 02:29, 12 June 2019 (UTC)