Talk:10 Hygiea

Spelling

Is it Hygeia or Hygiea? I've seen both on several sites. I've also seen Hygieia referring to the Greek goddess, but which is the proper spelling for the asteroid itself?

The authority on spelling of asteroid names is Dictionary of Minor Planet Names by Lutz D. Schmadel. His spellings are sometimes different from the normal English spelling of the eponymous deity's name. Unfortunately I don't know why. --Cam (talk) 13:27, 16 March 2008 (UTC)

Mass

I have a newer source listing Mass ≈ 8.07×10¹⁹Kg [1]. I will wait 1 week for feedback before applying the updated information. Abyssoft 04:59, 4 September 2006 (UTC)

This is a very interesting reference. Great that you found it ; Here is what a search in PDS and ADS for other mass estimates turned up:

Author	Year	Mass (in Solar mass × 10-12)	note	link
Scholl et al	1987	47 ± 23		[2][3]
Goffin	1991	49 ± 21		[4][5]
Kuznetsov	2001	17.4 ± 6.8	repeated by Kochetova	see Kochetova
Michalak	2001	55.7 ± 7.0	the bolded "weighted mean without 7 Iris" on p 705	[6]
Kochetova	2004	50.1 ± 4.1	reference mentioned on the new webpage	[7]
Chesley et al	2005	45.4 ± 1.3		[8]
Chernetenko et al	2005	40.6 ± 1.9	newer calculation on the web	[9]

Apart from Kuznetsov who was out of line for some reason, the rest seem to fall in the same ballpark so the rough mass is at least pretty confident − unlike some of the asteroids. The new reference appears to give the second most precise value, but the Chesley calculation gives by far the smallest error so I think we should keep that one; The Chelsey number also appears the most trustworthy by itself because it is based on only a single very close encounter unlike the others which average over a bunch of distant encounters that singly give a very imprecise values. In my opinion, the advantages of a paper that bases itself on just one encounter is that

1. there is less chance that the perturbed body were also later/earlier perturbed by other asteroids, throwing the mass estimate off
2. one imagines that the data there was much more carefully inspected for anomalies (that may indicate a systematic error) than a big bulk calculation over many bodies.

See e.g. the influence of the 7 Iris perturbation in the Michalak paper.

:I suggest to reference the new Kochetova paper along with Chelsey in the article, but to keep the current Chelsey value and add in its error estimate. In fact I'll do that now provisionally. :Ah, and Kochetova looks like it could be a real good reference for a bunch of other asteroids. Deuar 22:29, 4 September 2006 (UTC)

Sorry, i've just realised the web page had newer calculations than the paper. So, Chelsey (current value in the article) and the newer web value of Chernetenko+Kochetova+Shor give by far the smallest error estimates, but worryingly they don't overlap. I suggest averaging these two best estimates and quoting an error in the article that roughly covers both cases. That would be 43.0 ± 3.7. Looks like a really good reference :-) Deuar 23:02, 4 September 2006 (UTC)

Images?

This page desperately needs an image...even if it is just a picture of it in a starfield. 70.177.71.206 17:28, 9 September 2006 (UTC) Possible Image per request @ http://www.ipac.caltech.edu/2mass/gallery/hygatlas.jpg Permission needs to be acquired first.

Permission is already given. Going up one level, at the bottom of the page: "Please note: The images in this gallery are released into the public domain. If any image or images are redisplayed or reproduced, please accompany the image or images with the following acknowledgment: "Atlas Image [or Atlas Image mosaic] obtained as part of the Two Micron All Sky Survey (2MASS), a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation." If pressed for space, this acknowledgment could be shortened to, e.g., "Atlas Image [or Atlas Image mosaic] courtesy of 2MASS/UMass/IPAC-Caltech/NASA/NSF." However, all or part of the full acknowledgment is preferred. This is the stated policy of 2MASS."Michaelbusch 02:44, 10 September 2006 (UTC)

Promotion

Just like 2002TX300 there is nothing here about how its up for promotion to dwarf planet status unless that data is old. Arkkeeper (talk) 19:35, 14 January 2008 (UTC)

Last primary planet

There's nothing in the linked text to support the claim that this was the last asteroid discovered to be considered a primary planet. In any event I found a later source which lists later asteroids like 11 Parthenope as primary planets. --Cam (talk) 20:42, 18 April 2008 (UTC)

GA Review

This review is transcluded from Talk:10 Hygiea/GA1. The edit link for this section can be used to add comments to the review.

Hi, I will be reviewing your article for GA. Initially, it looks very good. I will be making some comments. —Mattisse (Talk) 00:50, 7 September 2008 (UTC)

• Are you using a consistent reference format?

What exactly do you mean? All the refs are {{cite journal}} and {{cite web}} with one exception Nergaal (talk) 02:31, 7 September 2008 (UTC)

• Could you link perihelion in the text? (I noticed later that you have it linked in the template.)
• "This is much more than for the other objects in the "big four", the dwarf planet Ceres and the asteroids 2 Pallas and 4 Vesta." - needs a colon rather than a semicolon if you mean that the "big four" are the following bodies listed.
• "Aside from being the smallest of the four, another important factor to this end is Hygiea's..." - to what end?
• There are statements in Orbit and rotation that are unreferenced.

How does it look now? Nergaal (talk) 03:42, 7 September 2008 (UTC)

Final GA review (see here for criteria)

1. It is reasonably well written.

   a (prose): b (MoS):

2. It is factually accurate and verifiable.

   a (references): b (citations to reliable sources): c (OR):

3. It is broad in its coverage.

   a (major aspects): b (focused):

4. It follows the neutral point of view policy.

   Fair representation without bias:

5. It is stable.

   No edit wars etc.:

6. It is illustrated by images, where possible and appropriate.

   a (images are tagged and non-free images have fair use rationales): b (appropriate use with suitable captions):

7. Overall:

   Pass/Fail:

—Mattisse (Talk) 19:06, 27 January 2009 (UTC)

Dead link

During several automated bot runs the following external link was found to be unavailable. Please check if the link is in fact down and fix or remove it in that case!

• http://www.cfa.harvard.edu/iau/Ephemerides/Bright/2000
  • In 10 Hygiea on 2011-05-23 02:08:09, 404 Not Found
  • In 10 Hygiea on 2011-06-20 03:46:46, 404 Not Found

--JeffGBot (talk) 03:47, 20 June 2011 (UTC)

Three dimensional model

I suggest to add an image of a three dimensional model, like in the article about asteroid 5 Astraea, and to move the animated orbit diagram into the text. Perhaps the following image could be used: http://home.comcast.net/~eliws/ceres/images/LightcurveHygiea.jpg Renerpho (talk) 20:33, 22 May 2015 (UTC)

Orbital animation

The orbital animation does not appear to make sense. It shows Hygiea as moving in a small stable loop relative to a Sun-Jupiter frame, but this is not how it is in reality. The notes attached to the animation give insufficient information to allow any other meaning to be discerned. I am tempted to remove it unless it can be justified.

Ordinary Person (talk) 14:26, 29 July 2015 (UTC)

What do you mean? Hygiea's orbit is stable. --JorisvS (talk) 15:26, 29 July 2015 (UTC)

To be clear, I'm referring to the animation labelled "A rotating frame depiction of asteroid Hygeia's orbital motion relative to Jupiter". Hygiea's orbit _is_ stable by it does not form a small stable loop relative to the sun-Jupiter frame.Ordinary Person (talk) 15:31, 29 July 2015 (UTC)

The position of the planets are not shown. It is clearly not a rotating reference frame, which means that Jupiter would be seen to change position in it if it were shown. --JorisvS (talk) 13:26, 30 July 2015 (UTC)

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Jim Baer

Refname "Baer" no longer works. Jim Baer's website is not archived and the size, mass, density estimates for Hygiea may need to be revised with another source. Nrco0e (talk)

Updated.Renerpho (talk) 11:41, 28 April 2019 (UTC)

Dwarf Planet

Some scientists say that 10 Hygiea meets the conditions to be a Dwarf Planet.

https://www.eso.org/public/news/eso1918/

https://www.space.com/asteroid-hygiea-may-be-smallest-dwarf-planet.html

https://www.usnews.com/news/world-report/articles/2019-10-28/scientists-say-asteroid-could-be-smallest-dwarf-planet-in-earths-solar-system

https://www.cnet.com/news/tiny-mysterious-asteroid-is-likely-the-solar-systems-smallest-dwarf-planet/

https://news.yahoo.com/unknown-dwarf-planet-solar-system-153700978.html

https://news.yahoo.com/solar-system-family-five-dwarf-202500501.html

184.176.152.135 (talk) 04:55, 29 October 2019 (UTC)

That's hype. We don't know that Hygiea has an equilibrium shape, and even if it does, that doesn't mean it's a DP. Telescopes and even flybys won't tell us that. We'll need an orbiter. — kwami (talk) 02:57, 31 October 2019 (UTC)

A "dwarf planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite.

From the ESO website (linked above): "The final requirement is that it has enough mass for its own gravity to pull it into a roughly spherical shape. This is what VLT observations have now revealed about Hygiea."

The other DPs didn't have orbiters when they were declared DPs. When did that become a requirement?

And please don't change the title of my comment. It makes me look like I said something that I didn't say. 184.176.152.135 (talk) 05:42, 31 October 2019 (UTC)

The decision whether Huya is officially a dwarf planet or not is up to the IAU, not us. We don't know at this point whether or not Hygiea actually meets the requirements, and kwami may be right when he says that this question could require an orbiter to settle. That doesn't matter though. What we can say is that ESO has mentioned the possibility on their website, it has been discussed in a peer-reviewed paper, and it has been widely covered in the media. I think this makes it relevant&verifyable, which is what matters on this site. That said, the possibility that Hygiea might be a dwarf planet is already mentioned in this Wikipedia article, so I don't see what change you ask for. Renerpho (talk) 05:56, 31 October 2019 (UTC) edited 06:55, 31 October 2019 (UTC)

One addition: "The final requirement is that it has enough mass for its own gravity to pull it into a roughly spherical shape. This is what VLT observations have now revealed about Hygiea." That's a bold claim. It remains to be seen if other scientists agree with that conclusion. For instance, the paper says that Hygiea acquired its spherical shape at a time when it was liquified by an impact. The definition asks for it to "overcome rigid body forces", which is not proven, not even attempted, in the paper. Renerpho (talk) 05:59, 31 October 2019 (UTC)

Indeed, being round because of recoalescing after an impact is not the definition of a DP. The authors of the study don't seem to understand what a DP is. I hope that's due to hype or bad reporting rather than to actual ignorance. Of course, they could be using their own, non-IAU definition of a DP, but if so that should be clarified. BTW, the only body that the IAU has actually declared to be a DP is Pluto (and that was politics, not science).

Though, Renerpho, I disagree that deciding on Hygiea is up to the IAU. According to the IAU, a DP is an object that fits the definition of a DP, not something that the IAU declares to be a DP. The IAU is simply one authority, and they can be just as wrong as any other. Rather, if there is consensus in the astronomical community that Hygiea fits the definition, then we can say Hygiea is a DP, regardless of what the IAU may or may not say. — kwami (talk) 06:12, 31 October 2019 (UTC)

I agree with you on the latter part. To clarify my point: What the IAU does is to "make it official". It can be a dwarf planet and not be recognised by the IAU, provided there is overwhelming consensus in the literature. We cannot fully exclude the IAU from this equation because it is their definition. If we accept their definition then we have to at least consider their authority on the matter. -- P.S. I get the impression (and sorry if I'm wrong) that you may have strong feelings about this subject. Please let's not turn this into a discussion about politics. I'd rather not discuss Pluto here except maybe when it is relevant for the subject of this article. The same is true for whether the IAU defintion is "scientific". That's a great thing to discuss elsewhere, i.e., on the talk pages about Pluto or the IAU. Renerpho (talk) 06:44, 31 October 2019 (UTC)

Whether Pluto is a planet is a different question than whether it's a DP. Personally, I think a definition of 'planet' that includes Pluto is useful for planetary geology, and a definition that excludes Pluto is useful for planetary dynamics. But that's irrelevant here. What I feel strongly about is passing off pseudoscience as science. Using an authority as a gateway for the truth is pseudoscience.

It doesn't matter if we use the IAU's definition of DP, they don't get to decide which objects qualify under their definition, any more than the IUPAC gets to decide which isotopes are radioactive. They might evaluate the evidence, and if they do a good job, we could take them as a RS. But (thankfully) the IAU is not in the business of making declarations of the truth.

You said, 'What the IAU does is to "make it official".' But that's not what they do. They decide on the subjective matters of standards, naming and definitions, not on objective matters of fact. The latter can only follow the evidence. The only DP they made official was Pluto, which is why I pointed out that that was politics rather than science. It wasn't the debate over whether Pluto is a planet I was referring to (I don't care), but that the IAU declared it to be a DP by fiat rather than because it fits their definition, which isn't science. They haven't made any of the other objects official, though it's obvious from their publications that there was consensus in 2006 on Eris and Ceres being DPs as well. Since that seems to be the consensus of the astronomical community as a whole today, that's not an issue. For Haumea and Makemake, they said they were DP's in press releases, but what that really means is that their bureaucratic solution, for who gets to name what, was for a dual committee to name those two, not that they were demonstrated DPs. If you accept them as DPs just on the IAU's say-so, then you've changed the definition of a DP to a sub-planetary object with a magnitude greater than 1. So, which definition of DP do we follow, the one published in the IAU resolution, or the potentially conflicting one assumed in a couple press releases? Also, for Haumea and Makemake we do not have consensus today that they're DPs. Indeed, there's good reason to think they may not be. And as the IAU itself said, if the evidence later contradicts their judgement and it turns out that the bodies they named as DPs are not DPs, then they're simply not DPs (though they'll keep their names, which after all are the IAU's business). — kwami (talk) 07:28, 31 October 2019 (UTC)

Additional VLT-SPHERE images

@Nrco0e: There are a lot more images available than the one used in the press release. I went ahead and processed a few of them (see here). Compare page 31 of (Vernazza et al., 2019) for the official processing of the same data. The raw data is available at this link. I think the images from the paper aren't free, but anything produced from the raw data should be suitable for Wikipedia. Do you think these make a useful addition to the article? If yes then I will upload a licensed version. Renerpho (talk) 01:29, 30 October 2019 (UTC) EDIT: Compare also Supplementary Figure 8, here. Renerpho (talk) 01:37, 30 October 2019 (UTC)

@Renerpho: It would be nice to have these images to further illustrate Hygiea's surface features especially its two craters Calix and Serpens, which should be added somewhere in the article (once it is organized). Nrco0e (talk · contribs) 02:51, 30 October 2019 (UTC)

@Nrco0e: Done. Renerpho (talk) 05:07, 30 October 2019 (UTC)

Just a question, how could the images not be free, if they're from the ESO and therefor paid for with public funds? — kwami (talk) 02:56, 31 October 2019 (UTC)

Since the images are from a paper in a journal, and are the work of the authors of that paper, they might be considered separate from the free content published on the website, just like Hubble images that are part of a paper aren't necessarily free. The raw data is less of a problem, I believe. Renerpho (talk) 03:07, 31 October 2019 (UTC)

So it's the processing that's protected? That makes sense. — kwami (talk) 03:59, 31 October 2019 (UTC)

That's what I think. Renerpho (talk) 04:30, 31 October 2019 (UTC) The processing, and the presentation. Renerpho (talk) 04:31, 31 October 2019 (UTC)

"The name was occasionally misspelled Hygeia in the 19th century, for example in the Monthly Notices of the Royal Astronomical Society."

The Planetary Society offers us "A New Look at Asteroid Hygeia". If this is notable, it might need some expansion; I'm sure someone can come up with a 20th century misspelling as well.--Prosfilaes (talk) 08:11, 2 November 2019 (UTC)

That's not misspelled. The name of the goddess is spelled various ways in Greek, Latin and English. At the time, bodies weren't given spellings, they were given names. Didn't matter all that much how you spelled the name. Now when the IAU assigns a "name", it's really assigning a spelling, but that's a modern development. — kwami (talk) 18:09, 30 October 2020 (UTC)

Hydrostatic Equilibrium and possible dwarf planet

Unlike the recent changes to the article, the cited recent article on Euphrosyne by Yang which mentions Hygeia states nothing about it being in hydrostatic equilibrium solely due to its "disruption". Rather it merely states that Hygeia was disrupted in its past, and its currently in hydrostatic equilibrium while Euphrosyne is not. There is nothing in the article that states one way or another as to whether Hygeia's hydrostatic equilibrium is due to its own self gravitation. Nor is there anything in the IAU defition of a dwarf planet that would bar an object like Hygeia from being classified as a dwarf planet if it has been disrupted and then subsequently reaccreted by having "sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium." Disruption is not dispositive of hydrostatic equilibrium through self gravitation.XavierGreen (talk) 03:52, 30 October 2020 (UTC)

No, they do not say Hygiea is in HE, they say that its shape is very close to an HE shape. Very different thing. They write,

"the SPH simulations for the case of Hygiea showed that its shape relaxed to a sphere during the gravitational reaccumulation phase, accompanied by an acoustic fluidization. The relaxation process on Hygiea could have settled down on a timescale of a few hours." 

Acoustic fluidization is HE by any normal definition, but not by the IAU's DP definition. There's nothing here about Hygiea being massive enough for gravitation to overcome rigid-body forces.

They did say, in their previous paper,

"It appears that Hygiea is nearly as spherical as Ceres (ψHygiea~0.9975; ψCeres~0.9988). Hygiea could thus be classified as a dwarf planet, so far the smallest in the solar system."

But "close to the shape one would expect for HE" is not the same as being in HE. Otherwise we would have to count things like Methone. They say Euphrosyne isn't DP because it's *too* round -- it's rotating at 2-1/2 the rate of Hygiea, but is round like Hygiea, when it should be flatter. So if were rotating slower, they would've claimed it as a DP too! If it's just round from re-accretion, and then stayed that shape despite no longer being in HE, then the same can be true of Hygiea. The authors also claimed that Interamnia looked like being a DP, only to drop the claim later. — kwami (talk) 05:02, 30 October 2020 (UTC)

But they don't say the same thing for Hygeia, thats the point, all they say is that it was disrupted and is close to the shape one would expect for Yang does not say that Hygeia is of insufficent mass to round itself through self gravitation. They do not say that it is not in HE, they don't say that a disruption event alone prohibits a body from being a dwarf planet. Read it again. There is absolutely nothing in Yang that disproves that Hygeia is a dwarf planet, and it is but one source. The article should reflect all sources on the topic. Other papers and sources have clearly stated that Hygeia could possibly be a dwarf planet. Your claims are not explicitly stated in the source, and therefore are synthesis and impermissible.XavierGreen (talk) 13:12, 30 October 2020 (UTC)

Okay, but you know full well that a body that is round for the reasons they describe does not qualify per either the IAU or Stern's def of a DP. The paper has room to put things in context, we don't, at least not in the lead. Given that the authors have a history of making such claims based on superficial measurements and then retracting them, best just to leave it out. — kwami (talk) 18:15, 30 October 2020 (UTC)

There are a whole host of sources calling Hygeia a possible dwarf planet as you well know, nothing in Yang refutes that and in fact its statement that Hygeia appears to be near HE is supportive of that contention. Nothing in the IAU definition prevludes from being a Dwarf Planet a body that is disrupted and then re-accreates into HE via self-gravitation. If your position was true, the Earth would not be a planet because it was disrupted by the impactor that created the moon irrespective of its subsequent reformation into a HE body. As reliable sources clearly state that Hygeia could possibly be a dwarf planet, that statement must be included in the article.XavierGreen (talk) 18:53, 30 October 2020 (UTC)

Of course there are -- they're all news magazines reporting on the original claim! Adding more magazines doesn't indicate confirmation, only that they picked up on the story. If you can find other researchers who have looked at the data and agree, then it's fine to say "it is considered", which implies some consensus in the field. But if one team makes a claim, it is more responsible to specify that team has made the claim. — kwami (talk) 19:58, 30 October 2020 (UTC)

The language as it stands of the time of my comment here is acceptable.XavierGreen (talk) 20:22, 30 October 2020 (UTC)

Okay. One quibble: we said it's close to HE, which isn't quite what they said, which is that it's close to the shape an HE object would have, and they're concluding that it may thus be in HE. — kwami (talk) 20:37, 30 October 2020 (UTC)

That change is also acceptable, as its reflected in the sources cited.XavierGreen (talk) 21:51, 30 October 2020 (UTC)