Talk:Orbital eccentricity

message: what about Eccentricity (mathematics) ? there's other equation, which is wrong ?
:They are both right, they are just calculating the eccentricity using different variables/parameters so it is a different function.  But they will both give the same answer if you use parameters from the same orbit.
:RBarryYoung (talk) 12:48, 15 August 2020 (UTC)
thread_title: Other eccentricity

message: The effect of excentricity on insolation is missing.  —Preceding unsigned comment added by 130.184.251.50 (talk) 22:28, 26 October 2009 (UTC)
thread_title: Missing info

message: I just reverted the article to an earlier version because of inserted vandalism. The value of the eccentricity of Earth's orbit was also changed in the same vandalism. I assume the previous value was correct but I'm uncertain so it should be checked by someone who knows better than I. --Pigman (talk • contribs) 21:17, 26 November 2006 (UTC)
thread_title: Checking Facts After Reverting to Older Version

message: Is that part about eccentricity and longer winters "favorable for triggering the next ice age" actually true?  It set my bogometer off, so I thought I'd ask if anybody else has heard that theory.  The only reference in the paragraph is that AOL page, which seemed a little un-scientific and POV.  --W0lfie 20:26, 8 December 2006 (UTC)
replies: text: The piece of text mentioned above seems to be referring in some way to the well-known (in climatological circles anyway) Milankovitch hypothesis - plenty of references to this can be found on the Wikipedia Milankovitch cycles and related pages. Hays, Imbrie and Shackleton Science 1976 is a good place to start http://www.es.ucsc.edu/~pkoch/EART_206/09-0303/Hays%20et%2076%20Science%20194-1121.pdf, but there are plenty of subsequent papers, both pro and anti, but the current consensus would be that eccentricity variations did play a significant role in the timing of late Pleistocene glaciations up to the present time. CF a very recent paper examining how this could play out through the dynamics of ice sheets: http://www.nature.com/nature/journal/v500/n7461/full/nature12374.html Some, of course, would beg to differ, but not me. You can certainly call it a hypothesis. It's perhaps worth noting that the next ice age may well have been, so to speak, put on ice for a while: http://www.cam.ac.uk/research/news/ice-age-interrupted. Orbitalforam (talk) 15:21, 19 June 2014 (UTC)
thread_title:  Ice Age? 

message: I reckon that this formulation is somewhat wrong:
"Planet Neptune's largest moon Triton is believed to be the only astronomical body that has a perfectly circular orbit with an eccentricity of 0."
Is it not quite harsh to claim that Triton is the only body in the entire universe to have a perfectly circular orbit? Either it should be stated that it is in our Solar system or it should state that it's the only know body... or both.
--Bilgrau 11:46, 23 June 2007 (UTC)
thread_title:  Only known or only one? 

message: Am I wrong, or is there no actual definition of eccentricity given in this article?
I read the whole thing, but I still have no real idea how it is defined. --01:13, 16 December 2009 (UTC)
thread_title:  Definition Missing 

message: Graph of the variation of eccentricity of rocky planets (Mercury, Venus, Earth, Mars)  does
not agree with upper value for Earth in the text beside the graph, assuming the heavy 
curve is for the Earth. (I  do not know if there is a problem with the other three planets, obviously Earth is most important from human perspective.)  If the upper value in the text 
occurs outside the time span of the graph, an explanation would be in order.
G Warren Coleman wd4nit@yahoo.com  — Preceding unsigned comment added by 76.105.116.92 (talk) 05:45, 16 November 2011 (UTC)
thread_title: Graph 

message: Regarding the definition in the lead, the orbit of stars and clusters through the galaxy follow a non-Keplerian rosette path. This orbit can still be assigned an orbital ellipticity, even though it isn't used in the same mathematical sense. Regards, RJH (talk) 17:02, 11 August 2012 (UTC)
thread_title:  Rosette orbits 

message: The graph is hard to fathom.  The vertical scale at the origin disagrees with the vertical scale on the right by X10.  Is this an error?.  If not, an explanation is needed on what the two scales mean.  Also, what is the meaning of the four arrows on the diagram?  SpinningSpark 10:12, 1 November 2013 (UTC)
replies: text: The arrows point to which of the two scales to use. The eccentricity of Mercury and Mars are much higher than Venus and Earth. -- Kheider (talk) 11:49, 1 November 2013 (UTC)
replies: text: Well I think that needs explaining in the caption.  Even better would be a plot to a log scale which would give a true picture of which planets were more eccentric.  Do you have data or algorithms that would allow this to be replotted in another application?  It needs redoing anyway, it's a bit pixely and it is already tagged for recreation as an SVG. SpinningSpark 20:34, 1 November 2013 (UTC)
thread_title:  Graph again 

message: Under climate it states "Apsidal precession slowly changes the place in the Earth's orbit where the solstices and equinoxes occur (this is not the precession of the axis). Over the next 10,000 years, northern hemisphere winters will become gradually longer and summers will become shorter. Any cooling effect in one hemisphere is balanced by warming in the other—and any overall change will, however, be counteracted by the fact that the eccentricity of Earth's orbit will be almost halved[citation needed], reducing the mean orbital radius and raising temperatures in both hemispheres closer to the mid-interglacial peak.". This seems presumptuous and remains uncited. While the total solar insolation may balance out, Many factors could influence the effects on the climate such as exposure to land vs water etc. Unless a counter argument can be posed i think it should be removed or reworded. Nickmista (talk) 09:10, 14 February 2015 (UTC)
thread_title:  Removal of potentially misleading climate statement 

message: If an orbit is one dimensional (like an object in vertical freefall), its semiminor axis zero, so the eccentricity=1, while I'd still call it an ellipse. So it seems like we have to say eccentricity=1 AND semimajor axis=infinity as both needed to define a parabola. Tom Ruen (talk) 04:48, 21 January 2017 (UTC)
thread_title:  Eccentricity 1 can be an ellipse? 

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thread_title:  External links modified (January 2018) 

message: The claim that... 
"Comet McNaught has a hyperbolic orbit while within the influence of the planets..."
... is not supported by the citation for that sentence.  The cited article makes no mention of "hyperbolic"  — Preceding unsigned comment added by 23.119.204.117 (talk) 21:10, 28 April 2018 (UTC)
replies: text: JPL shows that in Nov 2006 the orbit of 2006 P1 was hyperbolic. That does not mean the orbit will be hyperbolic when outside the influence of the planetary region of the Solar System. -- Kheider (talk) 17:57, 16 August 2020 (UTC)
thread_title:  Claim not in cited work 

message: This article lists the eccentricity of Neptune as 0.0086, while the Neptune page has 0.009456. I don't know which is correct.  — Preceding unsigned comment added by Probablyarobot (talk • contribs) 08:56, 3 November 2018 (UTC)
replies: text: Different epochs (dates) will generate different values. Neptune's heliocentric eccentricity varies from 0.0069 (2029-Aug) to 0.0146 (2023-Jan) as a result of Jupiter's 12 year orbit. Neptune's barycentric (Sun+Jupiter) eccentricity is a more stable 0.0087.  -- Kheider (talk) 14:33, 16 August 2020 (UTC)
thread_title:  Eccentricity of Neptune disagrees with Neptune article 

message: The animated gifs, https://upload.wikimedia.org/wikipedia/commons/a/ae/Binary_system_orbit_q%3D3_e%3D0.gif, do not represent realistic motion because the periods of both orbits are shown as the same, whereas in reality the one with a longer major axis has longer period, according to Keplers laws. IMO, these gifs are likely to cause more confusion than any benefit because orbital eccentricity is a property of the whole orbit and animation is really unnecessary, but a wrong animation is worse than unnecessary. I am deleting them. Kotika98 (talk) 15:49, 12 August 2021 (UTC)
thread_title:  The animated gifs are unfactual? 

message: I'm having difficulty reconciling the two equations for e in the Definitions section.  They differ where one has EL²/mα² and the other has εh²/μ².  I'm reading ε = E/m, h = L/m, and μ = Gm.  When I plug these three values into the second definition I get EL²/m³α² instead of EL²/mα².  Why am I getting this extra m² in the denominator?  Should μ = G instead of μ = Gm or h = L instead of h = L/m or what?   Vaughan Pratt (talk) 07:22, 2 February 2022 (UTC)
replies: text: Thanks, I see my mistakes: I used M for the reduced mass, and neglected to include the potential energy in E.  Very out of practice. Vaughan Pratt (talk) 20:43, 2 February 2022 (UTC)
thread_title:  m² discrepancy in the Definitions section? 

message: To be more precise, μ = GM, the mass of the body being orbited (the center of mass), and hence ε h² / μ² = ( E / m ) * ( L / m )² / G² M² = E L² / G² M² m³ = E L² / ( G² M² m² m ) =  E L² / α² m. where I have used M as the mass of the body being orbited (the center of mass), and m as the reduced mass of the orbiter, mred , as it appears in the article. In addition, please keep in mind that in all of physics, bound states (such as closed orbits) have total negative energy. Therefore, the total energy, E, as a quantity is a negative number with the following bounds  - G M m / r < E < 0. It never gets more negative than zero kinetic energy ( v = 0 ), and is never less negative than approaching zero, which at E = 0 the orbit stops being bound and becomes an escape parabola, consistent with e = 1.
MMmpds (talk) 15:09, 2 February 2022 (UTC)
replies: text: Thanks, I see my mistakes: I used M for the reduced mass, and neglected to include the potential energy in E.  Very out of practice. Vaughan Pratt (talk) 20:43, 2 February 2022 (UTC)
thread_title:  There is no discrepancy