Talk:Dysnomia (moon)

redirect

The content of this article is more or less a straight copy and paste from the main article. There doesn't seem a whole lot of point in doing that, so I've changed it back to a redirect. When so little is known about the moon anyway, it makes much more sense to discuss it in the main article.

Natural satellites deserve own articles, but since there is so little information available (there's even been rumors that it isn't real after all), keeping the article only a redirect is justified.--Jyril 12:16, 6 May 2006 (UTC)

Infobox

S/2005 (2003 UB₃₁₃) 1

File:2006-16-a-full.jpg 2003 UB313 and satellite: artist's impression
Discovery
Discovered by	Michael E. Brown (using the Keck Observatory)
Discovered in	10 September 2005
Orbital characteristics
Semi-major axis (a)	30,000 - 36,000 km
Eccentricity
Orbital period (P)	~1da4 d
Inclination
Parent body	20as03 UB313
Physical characteristics			Mean diameter	300 asd- 400 km
Mass
Mean density
Rotation period
Axial tilt
Albedo
Surface temp.
Atmosphere

This image would be nice:

• http://it.wikipedia.org/wiki/Immagine:2003_UB313-Moon.jpg

2003 UB313's satellite: artist's impression

"Gabrielle_(Xena)"

"Xena"; "Ceres", "1 Ceres".

Hilarious & silly.

Miles O'Brien [ Miles_O'Brien_(journalist) ], cnn, speaking with Neil deGrasse Tyson, announced this mnemonic:

"My Very Educated Mother Just Sent Us Nine Pizzas,..."

"Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto,..."

"...'chovies eXtra."

Hopiakuta 20:43, 16 August 2006 (UTC)

Dysnomia, Lawlessness?

Am I the only one that finds this choice of name ironic? Concidering that Xena was played by a Lucy Lawless? Perhaps... Hmm, did this maybe subconciously affect their decisions for the official name of the newly designated planet? -- Lucy (Not Lawless, just coincidence) 08:16, September 14, 2006 (UTC)

You're not. The name is too obvious to be a pure coincidence.--JyriL ^talk 10:15, 14 September 2006 (UTC)

I came to this discussion page to see if anyone had already mentioned this. When I read the article it immediately dawned on me. If it is a coincidence, it's eerie. Maybe something about this should be put into the article? Hmm? Dismas|^(talk) 10:40, 14 September 2006 (UTC)

It would be original research if the one who gave the name has not provably confirmed it.--JyriL ^talk 11:04, 14 September 2006 (UTC)

Hang on. The dwarf planet is dischord. The moon now called 'lawless' was nicknamed Gabrielle, the role played by Renée O'Connor. --GwydionM 15:24, 14 September 2006 (UTC)

I suspect that Mike named them discord and lawlessness because of all the controversy surrounding them and their naming. This would need to be confirmed by Mike. Watch for interviews.Michaelbusch 15:59, 14 September 2006 (UTC)

SkyTonight.com: The satellite, now called Dysnomia, is named for Eris's daughter, the goddess of lawlessness — a tribute, says Brown, to the actress who played Xena, Warrior Princess: Lucy Lawless. The name also referes to Brown's wife Diana (cf. Pluto's Charon / Charlene). [1] --JyriL ^talk 17:59, 14 September 2006 (UTC)

Dysnomia is a memory disorder characterized by a marked difficulty in remembering names or recalling words needed for oral or written language. Uh... sorry, what was the name of this satellite again? --mglg_(talk) 17:46, 14 September 2006 (UTC)

Some articles talking about the coincidence: Dwarf Planet, Cause of Strife, Gains ‘the Perfect Name’ NY Times, Dwarf planets get new names astronomy.com, and here's one that quotes Brown: Eris, Goddess of Strife, Joins Solar System Amid Raucous Debate (The Planetary society) - but the quote isn't confirmed anywhere else Andjam 23:57, 16 September 2006 (UTC)

Bad Astronomy blog post on the naming Andjam 00:54, 17 September 2006 (UTC)

fixing

could someone fix the infobox? It's transparent..--TheFEARgod (listening) 20:43, 14 September 2006 (UTC)

Should this not be at (136199) Eris I Dysnomia?

After all, "Dysnomia" has no historic claim to the name (an argument, IMO flawed, made with 134340 Pluto), and we do have a redirect already at Dysnomia for the rare user looking for this obscure body. --John Kenneth Fisher 22:24, 14 September 2006 (UTC)

I oppose moving it there. None of the other moons in the solar system have such titles, and this one shouldn't have such at title either. Voortle 23:47, 14 September 2006 (UTC)

It's in exactly the same format as Nix (moon) and Hydra (moon), or for that matter Dactyl (moon) (which however leads off with the name (243) Ida I Dactyl). That's just how we do it here at Wikipedia. :) RandomCritic 03:35, 15 September 2006 (UTC)

Dysnomia (moon) → Dysnomia (natural satellite)

The following is a closed discussion of the proposal. Please do not modify it. Subsequent comments should be made in a new section on the talk page. No further edits should be made to this section.

The result of the proposal was No move Duja 10:44, 18 October 2006 (UTC)

---

Moon can be a confusing term --Cat out 14:42, 12 October 2006 (UTC)

How so? Michaelbusch 14:46, 12 October 2006 (UTC)

I would assume it's because the moon is commonly associated with Earth's natural satellite. I agree with the move, but weakly. --Wirbelwind 15:07, 12 October 2006 (UTC)

Aren't all the other natural satellites disambiguated by "(moon)"? Is there a reason why this particular body has been singled out? --Polaron | Talk 15:08, 12 October 2006 (UTC)

Moon is commonly used for natural satellites, there's no reason to use a more complicated term. – Alensha ^talk 16:58, 12 October 2006 (UTC)

• Oppose Moon is the common term. 132.205.44.134 00:43, 13 October 2006 (UTC)
• Oppose: Per 132.205.44.134. Even if "natural satellite" is the technically correct term, "moon" is certainly more common and that's all that matters per WP:NC. —Wknight94 (talk) 02:06, 13 October 2006 (UTC)
• Oppose - The object may be correctly referred to as a moon, and most people are smart enough to figure out that the article title is not referring to the Earth's moon. Also, please note that the rings of Jupiter, rings of Saturn, rings of Uranus, and rings of Neptune are natural satellites that cannot be considered moons. GeorgeJBendo 06:26, 13 October 2006 (UTC)
• Opppose. Page move would be pointless.--JyriL ^talk 19:13, 13 October 2006 (UTC)
• Oppose All the planet's moons are called name (moon) so this one should also unless we change them all. WilliamKF 23:26, 13 October 2006 (UTC)
• Oppose "Natural satellite" has the same ambiguity; so the proposal adds pompousness (and spelling errors) for no real benefit. Septentrionalis 20:35, 15 October 2006 (UTC)
• Oppose — if only because a multitude of other moon articles would then need to be renamed. See the links in the table on the natural satellite page. — RJH (talk) 22:23, 16 October 2006 (UTC)

The above discussion is preserved as an archive of the proposal. Please do not modify it. Subsequent comments should be made in a new section on this talk page. No further edits should be made to this section.

officially designated garbage

The lead sentence is not necessary. It's not officially named "136199 Eris Dysnomia", it is named Dysnomia.

The official name of Dysnomia is 136199 Eris I (Dysnomia), just as Phobos is Mars I (Phobos). In practice, the full name is infrequently used. Michaelbusch 01:37, 31 October 2006 (UTC)

• They're not "official" designations, they are just secondary ones. Like Mars II, Pluto II, Saturn II, Jupiter II, etc. And for the record, it's not Mars II with (Phobos) in parenthesis, it's just Mars II.

Constrain

The article says, "the satellite was used to constrain the mass of Eris". What is the meaning of "constrain" in this sentence? Is is referring to constraint algorithms? Vsst 03:02, 15 July 2007 (UTC)

Radius or diameter ?

The text in Properties says "its diameter is estimated to be less than 150 km" and in the table it says "equatorial radius 175±75 km" (= equatorial diameter 350±150 km) - a clear misfit. So which is wrong ? —Preceding unsigned comment added by Allgaeuer (talk • contribs) 23:42, 11 July 2008 (UTC)

pronunciation

I can't access the ref for the 2ary pronunciation. Is it really "dice-nomia", or is the y just long in the nickname Dy? kwami (talk) 12:16, 29 September 2008 (UTC)

I thought it would have been pronounced as "Dis-nomia" im probably wrong. Mr Deathbat (talk) 09:24, 29 January 2009 (UTC)

I was later able to confirm it. Brown (mis)pronounces the name "dice-nomia" after his wife, as Christy pronounced Charon "sharon" after his. But I don't know that Brown's pronunciation is catching on, whereas Christy's pronunciation of Charon is perhaps the dominant one. kwami (talk) 09:37, 29 January 2009 (UTC)

Eccentricity and inclination references ?

Where do the figures for eccentricity and inclination come from ? I have just read the reference fully, but there are no figures for eccentricity and inclination included in that reference. --Franklin Demenge (talk) 10:58, 3 August 2009 (UTC)

The numbers used come from the Supporting Online Material for the paper: Brown, M. E.; Schaller, E. L. (2007). "The Mass of Dwarf Planet Eris". Science 316 (5831): 1585. Looks like I used the numbers of the retrograde orbit. --Volcanopele (talk) 18:49, 3 August 2009 (UTC)

Volcanopele, those figures are not in the abstract on either of the two links for Science 316 (5831): 1585. So I read the entire paper in Science on their web site, but the two figures are not there either. Where did they come from ? --Franklin Demenge (talk) 19:12, 3 August 2009 (UTC)

Look at the Supporting Online Material at [2]. Clicking on "Download Supplement" brings up a pdf document (which I believe is publicly available, I can access from my home computer). The numbers I used come from Table S2 on the last page of that document, using orbit 2. --Volcanopele (talk) 19:35, 3 August 2009 (UTC)

The figures are all there ! Thank you for the explanation. Is that document the same as "Science 316 (5831): 1585" or it is additional to "Science 316 (5831): 1585", i.e, only "Supporting Online Material" as it's described ? It gives figures for "Orbit 1" and "Orbit 2". Please explain why there are two orbits, and why only the figures for "Orbit 2" are stated on Wikipedia ? --Franklin Demenge (talk) 20:04, 3 August 2009 (UTC)

Yeah, the Supporting Online Material is part of that paper. There are two orbits because the observations taken by Brown and Schaller could fit both a prograde or a retrograde orbit, those two solutions are thus provided as orbit 1 and 2. Only Orbit 2 is used because at the time, I seemed to remember that the retrograde solution was the more likely, though it has been so long that I don't have a source for that. --Volcanopele (talk) 20:08, 3 August 2009 (UTC)

Volcanopele, when there is uncertainty as to which of the two orbits is correct, even if one of them is more likely, should both sets of figures be quoted ?

I have not come across papers for which there has effectively been a second paper in the form of Supporting Online Material. Is this very common in astronomy ? Would such additional material come up on searches of databases such as The SAO/NASA Astrophysics Data System ?

I'd say that it's reasonably common when the journal is something like Science or Nature, where the article length is tiny and the data tables are necessary, but not printed. It would be unusual for an ApJ, AJ, or MNRAS article, which often contain large printed tables.

ADS links through to the Science page for the article (on subscriber access), which has 'Supporting Online Material' in the sidebar and at the end of the article, but it's not obvious, and is not mentioned in the ADS listing. Iridia (talk) 02:26, 4 August 2009 (UTC)

Where did you originally hear about this new research concerning Dysnomia ? I use Science Daily's Astronomy page to keep up with what is new concerning astronomy : http://www.sciencedaily.com/news/space_time/astronomy/ Do you use another source of information that would be better to use ? --Franklin Demenge (talk) 20:23, 3 August 2009 (UTC)

It depends on the level of content you want: if press-release level is preferred, then Universe Today and the Planetary Society blog are good places. If you want to read abstracts, arXiv.astro-ph is the place to be (although it doesn't get a lot of Icarus papers). Or you can get a weekly notification set up at ADS on your topics of interest. Iridia (talk) 02:26, 4 August 2009 (UTC)

Thank you --Franklin Demenge (talk) 14:56, 4 August 2009 (UTC)

Planetary adjectives

The adjective for Dysnomia is given as "Dysnomian". This is not referenced. Are adjectives for planets and moons decided by an Astronomy organisation, or are these adjectives taken from a particular dictionary ? --Franklin Demenge (talk) 18:07, 5 August 2009 (UTC)

This is a Wikipedian thing that keeps cropping up on the planetary articles. It might be grammatically correct, but it's not a usage that appears in scientific articles on these objects. Plus, it looks downright painful on the non-Latin or Greek names, eg. "Teharonhiawakian"... There are some valid adjectives that have widespread usage in the field (see the list at planetary science), but they are few in number. Iridia (talk) 00:48, 6 August 2009 (UTC)

Dysnomia data

I have collected together all of the data concerning Dysnomia from all the possible research references concerning Dysnomia. This is all that is known. Before adding any of it, I am leaving it here for a few days for possible discussion as I am not sure which of it to add. For some qualities the astronomers unusually gave two figures. I don't know what a few of the other figures mean. So I am not sure if some of the figures actually concern Dysnomia, or if they are merely figures explaining how they obtained the data concerning Dysnomia at the time.

Orbital characteristics

Orbital period [X2] : 15.772 ± 0.002 days or 15.774 ± 0.002 days

Inclination [X2] : 61.3 ± 0.7° or 142 ± 3°

Semi-major axis [X2] : 37430 ±140 km or 37,350 ±140 km

Eccentricity [X2] : < 0.010 or < 0.013

Longitude of ascending node [X2] : 139 ± 1° or 68 ± 3°

Mean anomaly [X2] : 328.6 ± 0.6° or 306.5 ± 1.3°

Argument of periapsis : unknown

Physical characteristics

Equatorial radius [X4] : ~ 50-125 km

Axial tilt (obliquity) [X2] : 78°

Others ?

Current sub-solar latitude [X2] : 39°

Year of vernal equinox [X2] : AD 2239.5 or AD 2126.5

Em [X2] : 339.3° or 251.3°

V magnitude [X3] : 18.8

• Eris has an apparent magnitude of 18.7. Dysnomia would be about apmag 23.1 (18.7+4.4). -- Kheider (talk) 05:02, 10 August 2009 (UTC)

Satellite fractional brightness [X3] : 1.9 ± 0.5 %

References

[X1] International Astronomical Union Circular [2006] 8747 (D.W.E. Green)

[X2] Science [2007] 316 (5831) : 1585 and Supporting Online Material (M.E.Brown, E.L.Schaller)

[X3] The Astrophysical Journal Letters [2006] 639 : L43-L46 (M.E. Brown, M.A. van Dam, A.H.Bouchez, D.Le Mignant, R.D.Campbell, J.C.Y. Chin, A.Conrad, S.K.Hartman, E.M.Johansson, R.E.Lafon, D.L. Rabinowitz, P.J.Stomski Jr., D.M.Summers, C.A.Trujillo, P.L. Wizinowich)

[X4] California Institute of Technology web site http://www.gps.caltech.edu/~mbrown/planetlila/moon/ (M.E.Brown)

--Franklin Demenge (talk) 18:38, 9 August 2009 (UTC)

Well, most of it is useful: have a look here if you want to compare the kind of information that often occurs (for a non-Wikipedia comparison). I'd say only the last two of the 'others' set are useful, but the rest are good. Iridia (talk) 23:12, 9 August 2009 (UTC)

There is a lot more information there than I have added. Howevever, it concerns both Eris and Dysnomia. So in order to fully appreciate and understand the data you have referred to I would need to go through all of the research papers for Eris as well. So that is what I shall now do. --Franklin Demenge (talk) 10:46, 10 August 2009 (UTC)

Mike Brown, head of the Keck team that made the discovery, wrote that "We can't tell the difference between Orbit 1 and Orbit 2, so it's best to use them both until we can tell which one it really is." --Franklin Demenge (talk) 17:40, 11 August 2009 (UTC)

CalRis (talk) 10:18, 30 November 2011 (UTC): This matter is still unsettled. I believe that the table should either cite the values of both orbits or it should use rounded values instead. The current tables implies a false certainty. Rounded values might look like this:

• "Semimajor axis: ca. 37,400"
• "Inclination: uncertain"
• "Period: ca. 15.77 days"

Who was the discoverer of Dysnomia ?

Who discovered Dysnomia ? In the article it claims Mike Brown. In the info-box there are four names including his. The research paper describing the discovery gives the names of the whole team :

The Astrophysical Journal Letters [2006] 639 : L43-L46 (M.E. Brown, M.A. van Dam, A.H.Bouchez, D.Le Mignant, R.D.Campbell, J.C.Y. Chin, A.Conrad, S.K.Hartman, E.M.Johansson, R.E.Lafon, D.L. Rabinowitz, P.J.Stomski Jr., D.M.Summers, C.A.Trujillo, P.L. Wizinowich)

However, surely they can't have all been looking through the same telescope at the same time when it was discovered ! Wouldn't the actual discoverer have been only one of them ? --Franklin Demenge (talk) 18:56, 9 August 2009 (UTC)

The discoverers are normally given in the MPC or IAU circular announcing the discovery. First announcement here, quite brief as usual for these. However, the discovery was made by the Keck AO team + the original discoverers, according to that ApJ article and also Mike Brown's webpage. The infobox currently only contains the discoverers of Eris, so that should be fixed to add all the paper authors.

(This is quite normal for astronomical discoveries: the work involves the contribution of a whole team of people, from technical staff through support astronomers, students, postdocs and the telescope-time proposal writer, so discovery credit is shared equally). Iridia (talk) 23:07, 9 August 2009 (UTC)

In the past, discoveries in astronomy would be made by lone astronomers such as Galileo by literally looking through their telescope. With some of the huge telescopes such as Hubble or those used by Keck do they still do things by this means, or are photographic images taken instead ? Is the actual discoverer of Eris and Dysnomia crediting the whole team merely in order to be nice, or are the whole team credited because observations using huge telescopes are largely done by technical means rather than actual visual discovery by just one of the astronomers ? --Franklin Demenge (talk) 10:40, 10 August 2009 (UTC)

With faint discoveries like Dysnomia, I don't think it's even possible to see it by putting your eye to a telescope. No, nowadays the light coming into a telescope is focused on a light sensitive computer chip and processed by a computer before a human gets a look. --Patteroast (talk) 13:15, 10 August 2009 (UTC)

That must be why the entire team are credited with discoveries like this. --Franklin Demenge (talk) 14:29, 10 August 2009 (UTC)

The last moon discovered visually was Amalthea way back in 1892. The human eye is just not designed for observing faint objects. Amalthea has an apparent magnitude of 14. -- Kheider (talk) 15:01, 10 August 2009 (UTC)

The procedure of finding outer Solar System moving objects like Eris is as follows. Wide-field images of the sky covering several square degrees are recorded in the visual wavelengths by a CCD in an 'imager' instrument which receives the light from the telescope (the instrument is either directly mechanically mounted on the telescope or the light is passed to its location in a different room to the telescope via an optical fiber: large modern professional telescopes have instruments mounted permanently at their various focal points and cannot be looked through directly). Computer programs such as SExtractor are run on these digital images to extract the flux and location of all the point sources of light in the image. Specialist software written by the science team is then used to match the location of all these point sources to their locations in other images of that same piece of sky, taken at a different time. The time interval used to detect asteroids is hours; for outer solar system objects, which move far slower, it is days. Any sources that move between the two images can then be verified (a person eyeballs the computer output to check it isn't a strange variable star being misidentified, etc) and then have further observations scheduled to determine their orbit. Because of this complicated process, many people have contributed to an object being found: the observers (if the telescope is not automated), the scientists, etc.

[[:File:Leda2(moon).jpg|thumb|right|Tracking Leda.]]

The process of detecting satellites around these objects is slightly different: the telescope tracks on the object's motion rate and takes images over a short period of time, allowing any background stars to move more than any satellites would move, and therefore smear. Satellites are then visible as non-smeared sources. Iridia (talk) 02:19, 11 August 2009 (UTC)

Mike Brown, the head of the team that made the discoveries of Eris and Dysnomia wrote to me that he first saw Eris, and that Antonin Bouchez first saw Dysnomia. --Franklin Demenge (talk) 17:37, 11 August 2009 (UTC)

Mike Brown added : "It's a good question, and one that we struggle with as scientists. For Eris it was easy: I saw it first, and I was the person who conceived and led the project. Dysnomia is a bit trickier. The observations were done at my request and on my behalf, but I didn't get to be the first person to look at the pictures since they were taken by an engineering team while I was not in Hawaii. I think this is more like the case of "Columbus discovering America" (or whatever he actually did). He might not have been the first to see it, but the people who did were only there because he was leading them that way. Thus we credit him as the leader." --Franklin Demenge (talk) 19:13, 11 August 2009 (UTC)

Unfortunately, personal correspondence is not valid for citation in Wikipedia: please read WP:PSTS. I am not doubting the validity of this quotation, but the information cannot be added unless it is mentioned in a secondary source. Please leave the article "as-is" until you can provide such a citation. --Iridia (talk) 23:47, 11 August 2009 (UTC)

The analogy Mike Brown used concerning discoveries in astronomy is a very good one. Today's discoverers, the equivalent of Columbus and Magellan, are astronomers, using telescopes rather than sailing ships. At the time of Columbus, it was the captains or the chief geographers - those who directed the voyages - who were credited as the discoverers. However, they were never the first to see land. That was usually who ever happened to be sitting in the "bird's nest" or instructed to stand at the front of the ship to look for land. There is therefore a distinction between the discoverer and the first observer. In previous centuries in astronomy this was inevitably the same person. Nowadays, with teams of astronomers using huge technical telescopes, the team leader is the equivalent of the ship captain and discoverer,regardless of whether or not they were the first observer. --Franklin Demenge (talk) 07:47, 12 August 2009 (UTC)

Yes - it's a nice analogy, and a good poetic way to put it. However, the person these days in the "bird's nest" is generally no passive low-level watcher - it'd be more along the lines of Columbus and a chief navigator busily conferring over charts, and one or the other running out in turn to check what's ahead of the ship. --Iridia (talk) 12:48, 12 August 2009 (UTC)

For the reference, Franklin Demenge is a sockpuppet of General Tojo, also known as Keith Bridgeman, now blocked indef. Details at Wikipedia:Long term abuse/General Tojo‎. feydey (talk) 20:18, 12 August 2009 (UTC)

Temperature?

Is there any clue or hint on how the temperature on Dysnomia is? Because I have to do a presentation about Trans Neptunian Objects for school and this is something I really need.. —Preceding unsigned comment added by 95.118.108.226 (talk) 00:08, 14 October 2009 (UTC)

The only clue I can give you is that the temperature on Dysnomia is probably about the same as the temperature on Eris, somewhere around 40 kelvin. Trewal (talk) 18:41, 14 October 2009 (UTC)

Reference for average orbital speed Comment Comment

An IP editor added a line in the infobox for average orbital speed:

   | avg_speed = 0.172 km/s

Unfortunately it seems the reference 'calculated' is never defined, leading to a 'Cite error: The named reference calculated was invoked but never defined (see the help page).'. The information added looks like it could be right, but unfortunately I can find nowhere on the Internet a source for this. It looks like the anonymous editor calculated it from the other given orbital quantities. Is this something we do? Anon423 (talk) 16:59, 5 November 2014 (UTC)

It's correct and very easily calculated. I've added the calculation in the note. --JorisvS (talk) 17:20, 5 November 2014 (UTC)

Thanks a lot! How'd you get to this so fast? Anon423 (talk) 17:57, 5 November 2014 (UTC)

Seeing it on my watchlist and a quick calculation was all it needed. --JorisvS (talk) 18:13, 5 November 2014 (UTC)

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New paper by Brown on Dysnomia (and Vanth)

This article mentions Michael Brown's claim that Dysnomia is fairly small. He's since changed his mind, and this paper should be cited and used to modify the properties section: https://arxiv.org/abs/1801.07221 134340Goat (talk) 02:23, 23 January 2018 (UTC)

Irregular or spheroid

Do we know whether Dysnomia is or could be in hydrostatic equilibrium, rounded by its gravity? This image shows a spherical Dysnomia. 212.186.7.232 (talk) 13:10, 27 April 2019 (UTC)

No. Very little is known about it. The size you see here is shaky, based on several model assumptions. They don't even have high confidence that they even actually detected Dysnomia in the data used. (Not implying there's anything wrong with it, just that nature has a habit of smashing our nice models to dust.) And if you could nail down the size, it's still in the range (Dysnomia in 300-800 km) where they don't know the likelihood of it being HE. Tbayboy (talk) 16:04, 27 April 2019 (UTC)

One should send a spacecraft to the Eris system. Eris is the only planet which hasn't been visited by a probe as yet, due to its distance and its late discovery. NASA will have an occasion to launch a probe in 2026, they could call it 'New Horizons II' like they did with the Voyager probes. Perhaps also the Webb telescope will give us more precise images of planet Eris and its moon. 212.186.7.232 (talk) 18:29, 27 April 2019 (UTC)

Well, given that we now know it managed to tidally lock its parent (so Eris–Dysnomia are mutually tidally locked just like Pluto–Charon), the answer appears to be "yes, it's almost certainly dense enough to be gravitationally rounded". Double sharp (talk) 01:41, 18 November 2022 (UTC)

How do you conclude that D is in HE from it being tidally locked? AFAICT the density [assuming the underlying assumptions are justified] only indicates that it's a solid body. Still, it's probably more-or-less round regardless. — kwami (talk) 04:17, 18 November 2022 (UTC)

@Kwamikagami: I don't conclude that it's in HE, just that it's solid (though yeah, I should've been clearer). "Gravitationally rounded" seems vague enough to be accurate, since many Saturnian moons are round enough while not being in HE, and we already use it to title List of gravitationally rounded objects of the Solar System. (Besides, everybody includes Tethys as a planemo moon anyway, even though there's some doubt about it being solid.) Double sharp (talk) 14:58, 18 November 2022 (UTC)