Talk:Eris (dwarf planet)

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Wikipedia is not a soapbox; it's an encyclopedia. In other words, talk about the article, not about the subject.


The lead says, "It is estimated to be approximately 2300–2400 km in diameter", while the infobox first lists a radius estimate of 1300. Well, 2 × 1300 = 2600. Shouldn't the estimate in the lead be 2300–2600 km? Regards, RJH (talk) 19:02, 1 June 2011 (UTC)

Spitzer estimate should probably be removed. Ruslik_Zero 19:17, 1 June 2011 (UTC)

Sadly, there are no recent peer-reviewed papers on the exact size of Eris. So yes, you can get different estimates from different sources. In the 2007 Spitzer results the lower bound is closer to 2*1200. We still have these measurements problem even with Pluto, but to a lesser extent. -- Kheider (talk) 19:25, 1 June 2011 (UTC)

Classification of TNOs: SDO vs. Detached TNO[edit]

CalRis (talk) 08:56, 25 August 2011 (UTC): I already posted this question [[1]], but didn't get an answer. Perhaps this place is more appropriate. I'm wondering about the orbital classification of Eris as a SDO-object (and the general classification scheme adopted by Wikipedia for TNOs). I am aware that the MPC lists it as an SDO. I'm only an astronomy aficionado, but the MPC's classification seems not entirely reliable. For example, according to the minor planet center, Sedna has the orbit type "Centaur", which is of course absurd (according to JPL's Small-Body Database Browser perihelion is 76 AU, aphelion is 995 AU). If you look at its "Centaur" list and briefly check its orbital elements (q, Q, a), you will find that there are other objects the classification of which seems rather doubtful (far too large q).

Anyway, which classification system/nomenclature is used by Wikipedia? Even the orbit classification of Eris in various scientific papers is varying (SDO, detached). Gladman et al. published (as part of the TNO-Bible The Solar System Beyond Neptune) a Nomenclature in the Outer Solar System which restricted SDOs to those objects which are currently scattering actively off Neptune (as indicated by 10 million years numerical integrations). They list both Eris and Sedna as detached TNOs.

The final verdict about what TNO-classification/nomenclature is going to be adopted by the scientific community is still out. So shouldn't Wikipedia be a bit more circumspect? One might include, for example, a respective hint by including a statement in the Eris-article that Eris is variously listed as an SDO and a detached TNO, according to the classification scheme used. What do you think? Salvete! CalRis

I think we need some discussion before we start adding this to articles: what we should say, how much, and where. Maybe at the astronomy project? AFAIK, the SD is generally defined to be the region which is thought to have been populated through scattering, regardless of present dynamics, and DOs are objects which cannot be explained that way. Maybe I'm wrong, but given the number of articles this would affect, I think we should hold off until we get some feedback from people who really know this stuff. — kwami (talk) 07:17, 30 August 2011 (UTC)
That's how I understand the concept. Serendipodous 07:42, 30 August 2011 (UTC)
  • CalRis (talk) 08:20, 30 August 2011 (UTC): For the basic reasoning behind my changes to the article about Eris (dwarf planet), see [[2]]. I believe that the source itself is reliable enough not to be ignored. The book The Solar System Beyond Neptune is a major publication with contributions by all the leading scientists in the TNO-field. Ignoring this until we can change all articles in one fell swoop, isn't that a bit too conservative? Wikipedia should be cautious! But ignoring reliable sources (and using ones as in the case of the possible resonance which is far less easy to be checked for reliability) seems to be overdoing it. However, I do agree with your feeling that some Wikipedia articles need a rewrite, especially those about the scattered disc and detached objects. I'm looking forward to your comments (and measures taken).
    • By the way, Serendipodous, what concept do you mean: that of the new understanding of detached objects or Kwamikagami's misgivings?
    • Also the wording in the article introduction ("native to a region of space beyond the Kuiper belt known as the scattered disc") is highly misleading, as the scattered disc is not a seperate region. Its inner part is roughly in the same region as the classical Kuiper belt.
Yes, orbital sets are often called "areas", which would be confusing to newbies.
I'm not saying all articles need to be done at once, I'm saying we should wait for confirmation that we want to change all the articles at all. If we do, then they can of course be done piecemeal. What I don't want is to start changing them and then encounter resistance to the rest, so that we're left with half disagreeing with the other half. — kwami (talk) 10:06, 30 August 2011 (UTC)
As one of the primary Wikipedia authors many objects do have multiple classifications. In a Solar System that is 4.5 billion years old, a 10 million year integration of the orbit is quite pathetic and is not very reliable long-term. I use to work on the detached object article on Wikipedia, but IMHO there are not a lot of sources to make that article of good quality (My concerns from 2009). In the last several years, the MPC has even started listing centaurs (scattered inwards) and SDOs (scattered outwards) on the same list just to simplify things. -- Kheider (talk) 10:38, 30 August 2011 (UTC)
CalRis (talk): I had a quick peek at the SAO/NASA Astrophysics Data System to find additional information concerning TNO orbit classification. I found the following paper: The Canada-France Ecliptic Plane Survey - Full Data Release: The orbital structure of the Kuiper belt. It is very recent (submitted 25 May 2011) and should therefore be relevant. Of interest to this present discussion is the second paragraph of section 6 ("The scattering disk") which has a look at the evolution of the definition of the scattering disk over the last 15 years and the problems involved. As can be seen from section 4.1 ("Orbit Classification"), the authors of this paper adopted most of the nomenclature from Gladman et al. 2008: "scattering (objects that over 10 Myr forward in time integrations experience encounters with Neptune resulting in variation of semimajor-axis of more than 1.5 AU)". One interesting change compared to Gladman et al. 2008 is the express listing of the "detached" population as part of the classical belt something only hinted at in Gladman et al. 2008. Personally I find it hard to believe that this part of the nomenclature will stand the test of time for objects like Sedna (but Sedna is, of course, an oddball). Anyway, I believe that this paper is more than enough to justify the small changes to the Eris-article. A major rewrite of the articles about the SDO and the detached objects should be considered as well, however. Bye, CalRis. —Preceding undated comment added 11:11, 30 August 2011 (UTC).
Are they distinguishing "scattering disk" from "scattered disk", or is that just a variant? — kwami (talk) 23:43, 30 August 2011 (UTC)
They call it "scattering" when they compute that the semi-major axis will change by at least 1.5 AU over the next 10My. If it doesn't change (and isn't resonant), then they call it "classical" (with further subdivisions for "inner", "main", and "outer") or "detached" (beyond the 2:1 resonance distance and with > .24 eccentricity). What is elsewhere called "scattered" might fit into any of these. So no, not the same, although there's probably a lot of overlap. Tbayboy (talk) 03:19, 31 August 2011 (UTC)
CalRis (talk): The approach linked with the "scattered disc" stricto sensu looks back and tries to include those objects originally having scattered off Neptune. Knowledge of orbital history is required for this classification, and this information is not available for a given real TNO (Petit et al. 2011. For this reason Gladman et al. chose a more practical approach based on the the object's current behaviour. Is it scattering off Neptune right now or not? There's of course an overlap between these groups, but they are not the same. Gladman et al. chose the term "scattering" with this in mind although they "acknowledge that the latter term [i.e. scattered] is entrenched in the literature." (Gladman et al. 2008) —Preceding undated comment added 07:28, 31 August 2011 (UTC).
CalRis (talk) 13:01, 14 September 2011 (UTC): What do you think? Isn't this justification enough for adapting the article?
First you should overhaul Trans-neptunian object, adding in the alternative categories. The problem there is that we would then have multiple classification systems, so it might be difficult to present without being confusing. The individual objects (this page, and all the other TNO pages) would then be updated adding in the new class per this paper. In other words, don't start with this page, get the base page (which would define the categories) accepted first.
The other problem is that this is one, newly printed paper. The classification system might not catch on, which would make all that work wasted. I would prefer to wait until there's a reference from somebody else using this scheme. Tbayboy (talk) 14:00, 14 September 2011 (UTC)

Radius of Eris[edit]

CalRis (talk) 13:01, 14 September 2011 (UTC): Hello! There is finally a published result (PDF, 187 KB) of the analysis of Eris' stellar occultation in 2010. The best fit (provided that Eris is spherical) is a radius of 1163 ± 6 km which results in a density of 2.52 ± 0.05 g/cm³. I suggest that these measurements are taken into account in the article.

Thanks a bunch! Added! :) Serendipodous 14:37, 14 September 2011 (UTC)
There's a bunch of other similar abstracts at the same place, for other presentations at that conference. E.g., one mentions Quaoar having a long chord (1100 or so) and appearing elongated, like Haumea. Tbayboy (talk) 15:54, 14 September 2011 (UTC)
Could you link to those? I don't have a logon ID to get in. — kwami (talk) 00:41, 16 September 2011 (UTC)
I don't recall how I first found them, which was a short list of the TNO ones. However, go to [3], click on one of the groups on the left side of the main column (under "Program Groups"), e.g., "Small bodies", then click either "oral progam" or "poster program", and that takes you to a list of the talks for that group that day. Each of the talks has a little pdf abstract (as above). The one on Quaoar is [4]. A bunch on Vesta are at [5]. Tbayboy (talk) 03:15, 16 September 2011 (UTC)

Is the "Thermal Measurement" section needed anymore?[edit]

I think it just confuses things at this point. Serendipodous 20:46, 15 September 2011 (UTC)

Support. Would we remove the Spitzer diam. from the infobox as well?
BTW, the New Scientist ref says "Pluto might have just regained its status as the largest object in the Kuiper Belt". Which of course means that Eris is a KBO, at least in their opinion, or the opinion of their sources. — kwami (talk) 23:41, 15 September 2011 (UTC)
I agree. The measurement is mentioned and explained earlier. We don't need the blow-by-blow. I think it should be removed from the infobox, too, unless there's a recent reference favouring it over the occultation. Tbayboy (talk) 14:26, 16 September 2011 (UTC)
Done. Serendipodous 17:25, 16 September 2011 (UTC)


Added a proposed symbol: Suggested symbol of Eris. Not the only one, but the most common, and several bodies have multiple symbols. Delete though if you think it's premature. — kwami (talk) 02:22, 16 September 2011 (UTC)

There appears to have been a recent short-lived edit war over this, chiefly over the lack of sourcing. Perhaps insertion of the symbol could be given proper context with help from the information referenced in Hand of Eris—or maybe a passing reference to that article could be made in the body text, rather than putting the (completely unofficial) symbol into the data box. Any thoughts? Majestic-chimp (talk) 06:33, 20 June 2012 (UTC)
That page doesn't give a proper reference for it, either. The image file doesn't give any real source for the image, neither for origin of the symbol itself nor for its proposal as the symbol of the dwarf planet. Who is using it as a symbol for the DP, and in which sources? I doubt it's being used in any astronomical sources, but astrological might be good enough. There should also be some kind of wide-spread consensus about it (i.e., across different factions). Tbayboy (talk) 12:37, 20 June 2012 (UTC)
Agreed. I picked the most common symbol, but no longer remember how I determined that. — kwami (talk) 20:41, 20 June 2012 (UTC)
The most substantial discussion appears to be in <>, so at the very least, there is basis for it being proposed by a group of Discordians. Whether that's sufficient to mention it in the article may still be up for debate. Thoughts? Majestic-chimp (talk) 21:41, 25 June 2012 (UTC)
See, e.g., There are several proposed symbols. A proposal by itself is meaningless, since anybody can propose it, and there is no official body to accept it (astronomers gave up on all but a few symbols long ago). Until there's some consensus amongst people who actually use a symbol for DP Eris (only astrologers?), I think it's premature to favour one here. Tbayboy (talk) 01:24, 26 June 2012 (UTC)

Surface area.[edit]

If the radius is 1163 km, then the surface area should be approximately 17 million square km, not 78.5 million. I was puzzled as to how Eris could have a diameter smaller than our moon, yet a surface area twice as big - unless it's not a sphere and has a highly irregular shape.

Yes, 17 million is right, assuming sphericity. It looks like it used an older value of the diameter (2500), not the new radius. Tbayboy (talk) 23:04, 26 September 2011 (UTC)
It looks like the old surface area number used a radius of 2500km. -- Kheider (talk) 23:32, 26 September 2011 (UTC)

Orbital period[edit]

CalRis (talk) 15:04, 21 November 2011 (UTC): Hello! While looking at some stats on the two Horizons-sites JPL Small-Body Database Browser and the Web-Interface to the Ephemerides-tool I couldn't help noticing a difference of 4.5 years between the orbital period entries in the SBDB (561,63 yrs) and the Ephemerides-tool (557.07 yrs). I sent a respective e-mail to a Senior Analyst from the JPL who was kind enough to reply in quite some detail (see here. It seems that both are right but that the value does not make all that much sense unless the relevant epoch of osculation is specified as well. What's your take on this? Should we indicate the epoch? Shouldn't we at least switch to the orbital period of the newer epoch?

The infobox currently specifies an epoch of 2006-Mar-06 for all orbital parameters. Using JPL Horizons On-Line Ephemeris System at that epoch Eris had a heliocentric orbital period of 2.033184877971827E+05 days (or 556.6 years). I personally prefer a barycentric solution of 558.4 years that is more stable over varying epochs. None of the above is wrong. Orbits are constantly perturbed and that is why accurate simulations require integrating the equations of motion. -- Kheider (talk) 17:43, 21 November 2011 (UTC)
  • CalRis (talk) 07:12, 22 November 2011 (UTC): I stand corrected (blush). Sorry for the inconvenience.

Dwarf planet candidate[edit]

(Edit: Sarcasm) Now that Eris is ONLY a dwarf planet candidate (Sheppard 2011, page 2 paragraph 2, "likely dwarf planets Eris") should we rewrite this article and/or put a POV tag on it? -- Kheider (talk) 15:18, 11 January 2012 (UTC)

If you would bother to read the paper, you'd see that when it was found it was a DP candidate, but that now he accepts it as a DP:
In these surveys tens of bright TNOs including likely dwarf planets Eris, Makemake, Haumea, Orcus, Quaoar, Sedna and 2007 OR10 were discovered. [...]
Though the dwarf planet definition is imprecise, it is clear that Ceres in the main asteroid belt as well as Pluto and Eris in the outer solar system are bonafide dwarf planets. Makemake and Haumea are also likely dwarf planets as are the next largest bodies in the outer solar system such as Sedna, 2007 OR10, Orcus and Quaoar.
So, as of July 2011, he accepted Eris but was not yet convinced of Makemake & Haumea. Of course, if you wish to push for Eris to be a "candidate", I'm sure we can accommodate you. — kwami (talk) 16:25, 11 January 2012 (UTC)
You are pretty much relying on single reference that one could argue contradicts itself. When Eris was discovered in 2005, it was a PLANET candidate. It is the 2006 IAU resolution that made Pluto, Ceres and Eris dps. -- Kheider (talk) 17:21, 11 January 2012 (UTC)
Sure, you can purposefully misunderstand it just to be obstinate. You could play WP:pointy games like that with any source or claim.
As for it being just one source, that is of course true, and should be WP:weighted accordingly. But contradicting ourselves in the lead of a FA is not acceptable. Basic coherence is required. — kwami (talk) 05:04, 12 January 2012 (UTC)
You might want to consider what you just wrote ("Sure, you can purposefully misunderstand it just to be obstinate. You could play WP:pointy games like that with any source or claim.") at Makemake and Haumea! -- Kheider (talk) 13:02, 12 January 2012 (UTC)
Unlike you, I am giving my honest opinion on those pages. I'm not playing games. — kwami (talk) 01:54, 13 January 2012 (UTC)
Myself and others have given you our honest opinions and you have called the group ignorant. Your argument against Makemake and Haumea being accepted as dps (using Sheppard's 2011 reference) is really no different than an argument against Eris. Too bad you spend so much time judging your fellow editors instead of the validity of a single sentence in a single reference that can be interpreted different ways. -- Kheider (talk) 02:59, 13 January 2012 (UTC)

Again, you apparently do not care enough to actually read what I write. That's fine, just don't misparaphrase me.

I did not call the group ignorant. I referred to one editor who does not understand HE as ignorant. There is a slight difference: I am not claiming you do not know what you're talking about re. these bodies, I am claiming that you are making contradictory statements in the lead and not following NPOV re. Sheppard.

BTW, I probably wouldn't care so much if we at least had a NPOV resolution to the DP article (one which you said you could accept), because then at least we'd have a clear context for new readers. — kwami (talk) 04:10, 13 January 2012 (UTC)


I was redirected from Xena to Eris. Maybe the older (or alternative?) name Xena should be mensioned? (talk) 01:09, 7 October 2012 (UTC)

It already is mentioned: Eris_(dwarf_planet)#Xena

"136199 Eris, is the most massive known dwarf planet"[edit]

How about Pluto? — Preceding unsigned comment added by (talk) 20:51, 22 November 2013 (UTC)

Eris is 27% more massive than Pluto. Serendipodous 21:21, 22 November 2013 (UTC)

Reader feedback: the tempricher and atmolthfear[edit] posted this comment on 19 November 2013 (view all feedback).

the tempricher and atmolthfear

Has there been research and a conclusion of the temperature and atmosphere?

NolanCRules (talk) 15:29, 30 November 2013 (UTC)

Eris doesn't have an atmosphere right now, although it may in the future as it approaches the Sun. As far as temperature goes, that's pretty straightforward, and is mentioned in the "Surface and atmosphere" section. Serendipodous 16:44, 30 November 2013 (UTC)

probability Pluto is larger[edit]

Assuming normal distributions etc. of our data, I calculate there is a 10% chance Eris is smaller than Pluto. Someone might want to check my math. — kwami (talk) 08:43, 8 January 2014 (UTC)

Where did you get the formula? Plugging the numbers into it indeed gives those numbers. --JorisvS (talk) 11:32, 8 January 2014 (UTC)
I asked at the math ref desk. (My stats are pathetic!)
The results look like they're in the ball-park. At about 1σ apart, there's ≈¼ overlap, and about half that should be Pl > Er, since their SD's are approx. equal. Not statistically significant, but a good chance that Eris is indeed the larger. — kwami (talk) 17:01, 8 January 2014 (UTC)

I think this is a little too close to WP:OR and may be unnecessary. Also the data you are using seems outdated. This 2011 paper give Eris' radius as 1,163 ± 6 kilometers. And here is a secondary source that says "The newly measured radius of Eris puts it within the error range of the accepted size of Pluto." so we don't need to do our own calculation to say that, though it was nice work.--agr (talk) 19:55, 8 January 2014 (UTC)

Oops! No, that was a copy error. Corrected.
It's no more OR than finding the surface gravity or any of the several other things we routinely calculate ourselves for our minor-planet articles.
Just saying it "could be" smaller is rather unsatisfying, IMO. Is it 50–50? One in a thousand? With a little common sense, we could conclude it should be > 5% and < 50%, but IMO it's nice to have something more precise, and many readers won't know that 5% is typically used to define significance. — kwami (talk) 22:58, 8 January 2014 (UTC)

Until we know more about the size of Eris and Pluto, the comparison to Eris in the Pluto article should consider them "roughly the same size" for now. It currently claims Eris is larger. (Pluto Talk is locked, so I commented here instead.) -- (talk) 20:25, 14 July 2014 (UTC)

Where does it say that Eris is larger in diameter than Pluto? I only found variations of "about the same size". Tbayboy (talk) 23:26, 14 July 2014 (UTC)
Also keep in mind that Eris is more massive even if Pluto is say ~10km larger in diameter. -- Kheider (talk) 14:46, 15 July 2014 (UTC)


Which variety of English are we supposed to be in here? --John (talk) 07:07, 20 January 2015 (UTC)

Never mind, it would appear to have been written originally in American English and then to have evolved to use a mixture of the two. Per WP:RETAIN I have moved all spellings to American ones. --John (talk) 07:49, 20 January 2015 (UTC)

naming conventions[edit]

We say TNOs are named after creation deities. AFAIK, that is only true for classical KBOs. Is there a convention for SDOs? — kwami (talk) 22:16, 20 February 2015 (UTC)