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 | The contents of the Vanth (moon) page were merged into 90482 Orcus. For the contribution history and old versions of the redirected page, please see its history; for the discussion at that location, see its talk page. (12 January 2017) |
 | On 14 November 2022, it was proposed that this article be moved to Orcus (dwarf planet). The result of the discussion was no consensus. |
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Added missing "." in Mass listing on table. Abyssoft 21:08, 5 July 2006 (UTC)
From “IAU's Planet Definition” Questions & Answers Sheet: [1]
(90482) Orcus 1000±200 km [Brown, Binzel, private communication (2006)]
It may be much smaller than thought.-- JyriL talk 14:04, 16 August 2006 (UTC)
So what's up with the listed dimensions for Orcus?: "946.3+74.1-72.3 km.", it looks like it could be formatted better. I'll leave the correction for someone who knows better. HunterTruth ( talk) 16:17, 26 January 2008 (UTC)
In the intro: "The diameter of Orcus is estimated to be 761 or 807 km and the diameter of Vanth 378 or 267 km respectively, depending on their relative albedos."
In the info-box: "Dimensions 917±25 km"
In the section, "Size and magnitude": "If the albedos of both bodies are the same at 0.23 then the size of Orcus is about 917±25 km, and the size of Vanth is about 276±17 km."
There's a big inconsistency between the intro and the Size&Mag section, and given the various estimates of albedo, the ±25 km in the info-box doesn't actually show the full error-range.
Additionally, the info-box should specify what the 917km actually refers to; diameter, radius, major axis, etc, not just "Dimensions". -- PaulxSA ( talk) 06:16, 23 February 2017 (UTC)
I do not believe that we should use proposals as references. After all, if an astronomer wants to get a grant/telescope time etc. he could mention the possibility that the object is … inhabited. I feel we should keep with the usual sources. Let Mr Brown publish first. Eurocommuter 16:08, 21 August 2006 (UTC)
- Agreed. It's a good example of intriguing information that could mentioned on the talk page. Suggestive/speculative information doesn't belong to article itself.-- JyriL talk 19:03, 21 August 2006 (UTC)
- I can't help but think it is a bit outrageous to suggest that Mr. Brown lied about something so important to his work just to get telescope time.
JamesFox 01:29, 23 August 2006 (UTC)
- This was certainly not my point! My point was that with Google one can find many documents and not all of them should be used as references. Astronomers have data /hypothesis they want to test. They decide what and when to publish. I simply belive that we should let them to do so and then report it. My apologies, if my comment was read otherwise.
Eurocommuter 10:10, 23 August 2006 (UTC)
- Except that from the proposal, I get the impression that the satellite of Orcus is regarded as fact by Michael Brown (just not announced), due to the phrasing used, and that the telescope time was to get data necessary to compute the orbital period, not to confirm the existance of the satellite.
JamesFox 19:24, 24 August 2006 (UTC)
- Yeah, but he hasn't published any evidence to prove a satellite. If there is one, he'll publish when he's ready. I'm sure he himself would rather confirm it first, rather than have his funding proposals used as evidence. The Singing Badger 20:26, 24 August 2006 (UTC)
- Except that from the proposal, I get the impression that the satellite of Orcus is regarded as fact by Michael Brown (just not announced), due to the phrasing used, and that the telescope time was to get data necessary to compute the orbital period, not to confirm the existance of the satellite.
JamesFox 19:24, 24 August 2006 (UTC)
- This was certainly not my point! My point was that with Google one can find many documents and not all of them should be used as references. Astronomers have data /hypothesis they want to test. They decide what and when to publish. I simply belive that we should let them to do so and then report it. My apologies, if my comment was read otherwise.
Eurocommuter 10:10, 23 August 2006 (UTC)
The discovery of a satellite for Orcus has been published in IAUC 8812, but I haven't actually seen the circular, so I have no details. RandomCritic 02:03, 25 February 2007 (UTC)
- I tried to track down info as well, but met with the same problem. Is the existence of this page, with the heading "Recently Discovered Natural Satellites and Rings of Major and Minor Planets" and the text "Satellites of 2003 AZ_84, (50000) Quaoar, (55637) 2002 UX_25, and (90482) Orcus. IAUC 8812, 2007 Feb. 22" enough to warrant a mention? Something like "An IAU circular dated 22 February 2007 announced the discovery of satellites for Quaoar and Orcus"? Thoughts? -- Ckatz chat spy 11:54, 25 February 2007 (UTC)
this change in the Albedo does not make sense. It is way too high' and I could not find any sources for it. I am changing back to the 0.09 value. Chagai 18:47, 26 October 2007 (UTC)
- It says right in the text that observations from the Spitzer Space Telescope were used to derive a size, which can the be used to get a value for the albedo, which is given in the text as ~20%. I'm going to revert.
JamesFox 02:35, 27 October 2007 (UTC)
- We need a source, and a good one.
this source is reliable, and support 0.09. If you are familiar with the term Albedo, you know that 20% is impossible! Its like a mirror, which "90482 Orcus" is not. Look at the values of other Trans-Neptun objects. They don't even come close.
Chagai 01:51, 28 October 2007 (UTC)
- See also
Bond albedo. All values are fractions. You are just putting here wrong information.
Chagai 11:26, 29 October 2007 (UTC)
- There are many, many errors in your statements. I'll list at least most of them. 1) 20% is not an impossible amount, it is not close to being a mirror. 2) 20% is a fraction, it is the same as 0.2, just as 0.09 is the same as 9%. 3) Several known TNO's have albedos higher than 0.2, or 20%. Pluto has an estimated albedo of 0.49 to 0.66 (or between 49% and 66%), Eris' albedo is given as being around 86% (0.86). 4) There is a reference for the values determied by the Spitzer Space Telescope, look at reference 1. 5) The 0.09 value should nor be considered better, since if you look at the sources, it is clear that that Albedo was simply assumed, back in the days when Astronomers thought that TNO's would have low albedos. JamesFox 14:38, 3 November 2007 (UTC)
- See also
Bond albedo. All values are fractions. You are just putting here wrong information.
Chagai 11:26, 29 October 2007 (UTC)
- We need a source, and a good one.
this source is reliable, and support 0.09. If you are familiar with the term Albedo, you know that 20% is impossible! Its like a mirror, which "90482 Orcus" is not. Look at the values of other Trans-Neptun objects. They don't even come close.
Chagai 01:51, 28 October 2007 (UTC)
Mike Brown just named Orcus's moon. But it's not official until he clears it with the IAU. So should we start making the changes now, to make things easier, or should we wait until it's confirmed beyond doubt? Serendi pod ous 20:00, 7 April 2009 (UTC)
- Technically the name has merely been submitted and could be turned down. But we should definitely mention that the name has been submitted to the IAU for review. -- Kheider ( talk) 20:14, 7 April 2009 (UTC)
Oh, if anyone wants to have a look at it, I went looking and found the discovery image of Orcus + moon here in the HST archive (Aladin Java applet will load). Iridia ( talk) 03:13, 8 April 2009 (UTC)
- I went ahead and created Vanth (moon). Didn't want to link it into this article until it was official, but that is just a technicality. kwami ( talk) 00:03, 15 April 2009 (UTC)
- Okay, I'll move it to 90482 Orcus I and we can move again if/when the name is approved. kwami ( talk) 06:54, 15 April 2009 (UTC)
The following paper:
- Ortiz, J. L. (2011). "A mid-term astrometric and photometric study of trans-Neptunian object (90482) Orcus". Astronomy and Astrophysics. 525.
Bibcode:
2011A&A...525A..31O.
doi:
10.1051/0004-6361/201015309.
{{ cite journal}}: Unknown parameter|coauthors=ignored (|author=suggested) ( help); Unknown parameter|month=ignored ( help)
suggests that the ~10h periodic variability may be caused by the orbit of the satellite and hence the rotation of Orcus might be much faster. For what it's worth.— RJH ( talk) 22:58, 7 December 2010 (UTC)
- Actually it claims that there is a 9.7 day photometric periodicity coincident with the orbital motion in addition to weaker 10h periodicity of unknown origin. Ruslik_ Zero 06:59, 8 December 2010 (UTC)
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/iauc/08800/08812.html
- In (55637) 2002 UX25 on 2011-05-20 21:18:17, 404 Not Found
- In (55637) 2002 UX25 on 2011-05-31 04:15:46, 404 Not Found
- In 90482 Orcus on 2011-06-19 21:44:28, 404 Not Found
-- JeffGBot ( talk) 21:45, 19 June 2011 (UTC)
 | The related Category:Orcus has been nominated for deletion, merging, or renaming . You are encouraged to join the discussion on the Categories for discussion page. |
To move the article without prior consensus is a complete mystery to me. The given rationale is not good enough and will cause an administrative nightmare. Guess this opens the door to endless discussions about which TNO is or is not a DP. It's crazy... -- Cheers, Rfassbind – talk 22:56, 18 September 2015 (UTC)
- This article should not have been moved and needs to be moved back by an admin. -- Kheider ( talk) 22:58, 18 September 2015 (UTC)
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New Category > Category:90482 Orcus
On 1 April 2015, the category Category:90482 Orcus has been created and added to the article's categories. Although I don't think this category makes much sense, there might be a rationale I'm missing. Can its creator, Solomonfromfinland, or anyone else help me understand? Rfassbind – talk 23:31, 2 April 2017 (UTC)
- Right now, there are only three articles in said category: this article, Orcus, and Vanth (the latter two refer to the deities, not the dwarf planet and its moon). However, having said latter two articles in said category is arguably justified; the article Orcus has an entire paragraf on the plutino (wikilinks removed):
The Kuiper belt object 90482 Orcus is named after Orcus. This was because Orcus was sometimes considered to be another name for Pluto, and also because Pluto and 90482 Orcus are both plutinos.
For the moon, see Vanth (moon).
- (Wikilink as in original; “ Vanth (moon)” redirects to “ 90482 Orcus”.) However, the number of articles in this category could be increased to four by restoring “ Vanth (moon)” as a separate article, as I think should be done; after all, we have articles on Solar System objects of which about as little is known as is about Vanth.-- Solomonfromfinland ( talk) 17:25, 8 April 2017 (UTC)
Btw, the correct date is April 2017, not April 2015. (I'm not offended by said mistake; I just wanted to point it out politely.)-- Solomonfromfinland ( talk) 17:28, 8 April 2017 (UTC)
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| GA toolbox |
|---|
| Reviewing |
- This review is transcluded from Talk:90482 Orcus/GA1. The edit link for this section can be used to add comments to the review.
Reviewer: Bryanrutherford0 ( talk · contribs) 14:18, 20 September 2019 (UTC)
- It is reasonably well written.
- a (prose, spelling, and grammar):
b (
MoS for
lead,
layout,
word choice,
fiction, and
lists):
- The article is written to a good prose standard and complies with the required sections of MoS,
with one exception: the lead section is clear and relevant but a bit too long. MOS:LEADLENGTH indicates that the lead section of an article this size should be "one or two paragraphs." The final paragraph should be cut from the lead, since it appears to only contain information about Vanth and not Orcus; that content should be moved to the section on Vanth at the end of the body, where it will give that section a little more heft (I would put it between the two existing sentences of the final paragraph of the body). - I think the third paragraph of the lead should probably be cut as well (of course keeping all of the content in the body sections on Orcus's surface and cryovolcanism). I would probably keep the first sentence ("The surface of Orcus is...") but move it to the first paragraph after the sentence that establishes the body's diameter, which would improve the size balance between the two paragraphs. The rest of the detail here probably needs to wait for treatment in the body.
- In the section "Size and magnitude", one sentence begins, "If the albedos of both bodies are the same...", but the next sentence says that a subsequent study has revealed that the albedos are not the same, requiring an upward revision of Vanth's estimated size; if that's true, then the "If they were the same..." sentence should be deleted as a distraction.
- In "Spectra and surface", The first sentence of the third paragraph begins, "Orcus straddles the edge...", but to straddle something is to be on both sides of it at once. It's not yet known with certainty whether Orcus is big enough, but in reality it either is or is not, so "straddles" sends the wrong message. Maybe "Orcus sits at the threshold..."?
- Regarding the use of Template:Minor planets navigator at the end: it doesn't seem like this footer navbox is really adding anything to the article without the adjacent minor planets included, but I see that we don't seem to have articles about either of them (and may never have, since neither may ever be especially notable). Probably this should be removed, unless it's serving some purpose I'm not seeing?
Another minor note: I would add a wikilink to psychopomp in the sentence in "Name" explaining Vanth's name, but it's not required.
- The article is written to a good prose standard and complies with the required sections of MoS,
- a (prose, spelling, and grammar):
- It is factually accurate and
verifiable.
- a (
reference section): b (citations to
reliable sources): c (
OR): d (
copyvio and
plagiarism):
- The article has citations and a reference section. The online citations included support the vast majority of the article's substantive content, and I'll AGF on some of the paywalled studies for plausible physical data. Earwig's copyvio tool shows a close match between some of this article's text about the IAU's naming conventions and some other wiki/fansites, but it looks to me like that's probably because those sites ripped off this article.
Comments: I see in the infobox that we have the margins of error for all the figures in the "Physical characteristics" section, but they seem to be omitted in the "Orbital characteristics" section. Is there a reason not to include the uncertainties with those figures as well? They seem to be included on the JPL page that's cited, in the form of standard deviations (rather than a 90% confidence interval or what have you). Also, the JPL page's orbital data seem to be based on Epoch 2019 April 27.0 (as do those on the Minor Planet Center page), but the infobox claims that its orbital characteristics figures are from Epoch 4 September 2017; where did the infobox numbers come from, and should they be replaced by the figures from the JPL site?- The section "Mass and density" speculates about the division of mass between Orcus and Vanth, but the preceding section ("Size and magnitude") seems to indicate that a 2017 study nailed down Vanth's diameter to within about ±2%. Does this datum render the talk about Vanth making up between 1/33 and 1/12 of the binary system's mass outdated? If the previous section is correct, then it sounds like the relative sizes are known to much greater precision than this now.
In "Orbit and rotation", I'm uncomfortable with the phrase "Orcus is currently 48.0 AU from the Sun"; this is a sort of claim that is certain to rapidly go out of date and need continual updating. Perhaps we could cut this out and then update the remainder of the sentence to something like "Orcus has its aphelion in 2019 and will then approach the Sun until reaching perihelion in [presumably about] 2143"? That at least would keep the article up to date for the next 124 years. The second paragraph in the same section includes the claim that a rotational period of "about 10.5 hours seems to be the most likely one." Why does that figure seem the most likely, if other studies have produced other figures? Indeed, the abstract of the cited article seems to me to suggest that its authors find the possibility of Vanth's being tidally locked to be at least plausible. This claim about likelihood doesn't seem warranted by the sources I can see (but the Ortiz et al. article is paywalled, so I can't read the full text).- I've updated the orbital parameters of Orcus from the JPL Small Body Database. About the uncertainties for the orbital characteristics, the figures in the infobox are rounded and the uncertainties listed on the JPL site are very small. There is no need to include the small uncertainties if nearly all of them don't exceed 0.001. Nrco0e ( talk) 01:59, 23 September 2019 (UTC)
- With that aside, I have resolved the rest of your assessments.
Nrco0e (
talk) 02:28, 23 September 2019 (UTC)
- Oh, I see, the uncertainty is beyond the precision you're reporting. Fair enough! - Bryan Rutherford ( talk) 14:43, 23 September 2019 (UTC)
- a (
reference section):
- It is broad in its coverage.
- a (
major aspects): b (
focused):
- The article appears to cover the major aspects of the topic, including observational history, origin of name, characteristics of the body and of its orbit, and a brief summary of information about its moon. It also doesn't generally drift off topic,
with a few exceptions: the chief is that it goes into too much detail about Vanth in the lead section (as discussed above). Another two come in the "Name" section, where the sentence describing the visual depiction of the deity Orcus in Etruscan tombs should be completely removed. In the same section, the discoverer's wife's given name isn't relevant and should be removed in the interest of privacy.
- The article appears to cover the major aspects of the topic, including observational history, origin of name, characteristics of the body and of its orbit, and a brief summary of information about its moon. It also doesn't generally drift off topic,
- a (
major aspects):
- It follows the
neutral point of view policy.
- Fair representation without bias:
- The article maintains an appropriately neutral tone and doesn't e.g. lionize the body's discoverers.
- Fair representation without bias:
- It is stable.
- No edit wars, etc.:
- No edit wars, etc.:
- It is illustrated by
images and other media, where possible and appropriate.
- a (images are tagged and non-free content have
fair use rationales): b (
appropriate use with
suitable captions):
- The images are relevant and appropriate, and they all have good licenses and helpful captions. It would be nice to add alt-text to all the images, but it isn't required for GA.
- a (images are tagged and non-free content have
fair use rationales):
- Overall:
- Pass/Fail:
- An interesting and informative article about a plutino! With a little polish, this should be able to reach the GA standard.
- Pass/Fail:
- I have edited the article according to your recommendations. I will be waiting for your next assessments.
Nrco0e (
talk) 19:07, 21 September 2019 (UTC)
- Wow, thank you for your quick and responsive editing! I'll look through the sources by the end of the day tomorrow and give any feedback there, but everything I've pointed out so far is now fixed. -
Bryan Rutherford (
talk) 20:38, 21 September 2019 (UTC)
- By the way, if you haven't known already, most of the scientific papers cited in the article can be accessed from their
arXiv preprints, which is linked near the end of the source citation. For your issue about the rotation period of Orcus, the full paper can be read at
https://arxiv.org/abs/1010.6187. I hope this helps for your future reviews on science-related articles!
Nrco0e (
talk) 02:40, 23 September 2019 (UTC)
- This all looks good! Thanks again for being so responsive; this article is hereby approved for GA! - Bryan Rutherford ( talk) 14:43, 23 September 2019 (UTC)
- By the way, if you haven't known already, most of the scientific papers cited in the article can be accessed from their
arXiv preprints, which is linked near the end of the source citation. For your issue about the rotation period of Orcus, the full paper can be read at
https://arxiv.org/abs/1010.6187. I hope this helps for your future reviews on science-related articles!
Nrco0e (
talk) 02:40, 23 September 2019 (UTC)
- Wow, thank you for your quick and responsive editing! I'll look through the sources by the end of the day tomorrow and give any feedback there, but everything I've pointed out so far is now fixed. -
Bryan Rutherford (
talk) 20:38, 21 September 2019 (UTC)
- I have edited the article according to your recommendations. I will be waiting for your next assessments.
Nrco0e (
talk) 19:07, 21 September 2019 (UTC)
https://www.youtube.com/watch?v=2rrelv96nCQ
I am not a believer in the Nibiru cataclysm, so what is in that final image? 103.38.21.38 ( talk) 05:25, 15 December 2019 (UTC)
- As it is meaningless youtube clickbait, it could be anything such as a manipulated image of the bottom of a frying pan. -- Kheider ( talk) 11:59, 15 December 2019 (UTC)
Will there be a mission to orcus? — Preceding unsigned comment added by Zachbarbo ( talk • contribs) 19:46, 9 November 2021 (UTC)
- I wish! A concept has been studied, though it also considers Pluto, Haumea, and Quaoar as possibilities. But only a concept. Double sharp ( talk) 23:06, 9 November 2021 (UTC)
How long will a flyby mission to Orcus will take? — Preceding unsigned comment added by Zachbarbo ( talk • contribs) 15:12, 10 November 2021 (UTC)
- Orcus is currently at 48 AU, Pluto at about 30. It took New Horizons almost 15 years to reach Pluto. So, all things being equal, we could expect it to take maybe 24 years to reach Orcus. But all things wouldn't be equal. A big determiner in how long a flight will take is how big a boost the spacecraft gets from its Jupiter flyby. So we'd have to fit the timing to three planets: Earth, Jupiter and Orcus, and we might need to wait years for them to align properly. Also, nothing much is going to happen on Orcus for a century or so, so IMO a bigger priority would be Eris or Sedna. — kwami ( talk) 04:23, 11 November 2021 (UTC)
There is a move discussion in progress on Talk:90377 Sedna which affects this page. Please participate on that page and not in this talk page section. Thank you. — RMCD bot 20:00, 14 November 2022 (UTC)
I tagged this sentence as failed verification: Orcus had been accepted by many astronomers as a dwarf planet, though as of 2024 that consensus has changed. [2]
@ Double sharp: responded: See below - they argue that Sedna, Gonggong, Quaoar differ from "all smaller TNOs" (which would include Orcus) in ways that imply they have undergone chemical evolution while the smaller ones have not, which is the point of the DP category
I read the paper before I tagged it for failed verification, I assume you were talking about this sentence: We suggest that these three bodies have undergone internal melting and geochemical evolution similar to the larger dwarf planets and distinct from all smaller KBOs. To nitpick, the underlined part doesn't logically imply that all smaller KBOs are definitely not dwarf planets. The rest of the text more or less puts Sedna, Gonggong and Quaoar in a third group different from both larger bodies and undiscussed smaller bodies (no evidence of neither methane nor methanol).
Not being listed in a single paper specifically focusing on chemical composition of three unrelated dwarf planet candidates to me isn't enough of a development to belong right in the third sentence for Orcus. Especially since the Dwarf planet article goes on and on about how there's no consensus on which TNOs are dwarf planets (There is no clear definition of what constitutes a dwarf planet, and whether to classify an object as one is up to individual astronomers). IvicaInsomniac ( talk) 21:40, 13 March 2024 (UTC)
- @ Kwamikagami: Pinging you for your opinion. Double sharp ( talk) 03:02, 14 March 2024 (UTC)
- Also
Exoplanetaryscience.
Double sharp (
talk) 03:03, 14 March 2024 (UTC)
- I thought we had two papers now that said this: Quaoar up look geologically active (or at least formerly so); the rest do not. The fact that they don't specifically mention Orcus is no more reason to ignore their claim than their similar failure to mention Salacia, Varuna, Ixion, etc.
— kwami (
talk) 07:04, 14 March 2024 (UTC)
- @ Kwamikagami in case it is missed (and because it is directly relevant), Ardenau4 noted that the currently measured size of Orcus is consistent with Quaoar's and Sedna's, not smaller. AstroChara ( talk) 19:09, 15 March 2024 (UTC)
- I thought we had two papers now that said this: Quaoar up look geologically active (or at least formerly so); the rest do not. The fact that they don't specifically mention Orcus is no more reason to ignore their claim than their similar failure to mention Salacia, Varuna, Ixion, etc.
— kwami (
talk) 07:04, 14 March 2024 (UTC)
- Revisiting this topic after a while. Though I do agree that Orcus's status as an unambiguous dwarf planet is on shaky ground, and really hasn't much of a better justification than Salacia and Varuna, I must agree here that the paper provided is pretty weak in arguing against Orcus's classification, especially for it to warrant declaring that 'consensus' has swung against it. To my knowledge, it has not; as recently as just last year, some astronomers have been referring to Orcus as a dwarf planet. One paper does not change consensus; this would arguably be an example of undue weight.
- I would suggest citing additional papers such as
Fornasier et al., where the authors do not refer to Orcus as a dwarf planet, to more clearly demonstrate that consensus does not (and perhaps arguably never has) favor Orcus as a dwarf planet, and that opinion is still divided.
ArkHyena (
talk) 21:34, 14 March 2024 (UTC)
- The above source does not really seem helpful, given that it does not refer to Quaoar as a dwarf planet as well. Rather, it seems more likely that the above paper intends to discuss TNOs as a whole and to not make distinctions between dwarf planets and non-dwarf planets. I also should mention that, actually, from the most recent size estimates, Sedna is slightly smaller than Orcus (but the sizes are essentially identical given the large uncertainties). It's not clear that "all smaller TNOs" should refer to Orcus, considering that Orcus is in the same size range as Quaoar and Sedna, whereas Varuna, 2002MS4, etc. are clearly smaller. Salacia once again falls within a grey area, but Salacia has not been in the list of "consensus dwarf planets" for a while now. Given this does not really make sense to say that the consensus has "changed".
Ardenau4 (
talk) 21:45, 14 March 2024 (UTC)
- Coming back to additionally note that Grundy et al. 2019 seems to provide the actual justifications as to why most astronomers classify Orcus as a dwarf planet:
- Orcus and Charon probably melted and differentiated, considering their higher densities and spectra indicating surfaces made of relatively clean H2O ice. But the lower albedos and densities of Gǃkúnǁ'hòmdímà, 55637, Varda, and Salacia suggest that they never did differentiate, or if they did, it was only in their deep interiors, not a complete melting and overturning that involved the surface.
- Combined with the above, I believe that removing Orcus from the list of consensus dwarf planets here was premature.
ArkHyena (
talk) 17:40, 16 March 2024 (UTC)
- Grundy is a co-author of the latest paper. But it's true that we don't know that he (or his 2019 co-authors, none of whom were authors of the 2023 papers) agree with this particular statement. I've seen papers on what is a planet that effectively concluded that Earth and Jupiter are not planets, which I'm pretty sure are not conclusions shared by any of the authors. (Though much more sloppily written than this one, the point is that legalistic reading of a paper may be justified when there is a single author, who we know to be precise in their writing, but not when there are several.) So maybe it was premature. — kwami ( talk) 18:05, 16 March 2024 (UTC)
- BTW, the paper in question had both Stern and Grundy as co-authors, among others, but I suspect they didn't have much if anything to do with writing it, and instead signed on to something they agreed with to help make a point. It was an opinion piece that dwarf planets should be considered planets and had no real academic content. But my point is that it defined one criterion for planethood as being a tri-axial spheroid. Since that is a mathematical impossibility, a legalistic reading is that there is no such thing as a planet. Obviously, none of the authors intended what it said. I think it's quite possible that if you asked the authors of the 2023 paper about Orcus, they'd hedge, and of course we don't know about Noll or Buie etc. from the 2019 paper.
— kwami (
talk) 18:27, 16 March 2024 (UTC)
- The point is that if it's really the case (per the 2023 paper) that Sedna, Gonggong, and Quaoar differ from "all smaller TNOs" (which would rather include Orcus under current size estimates) in whether or not they are chemically evolved, then the conclusion of the 2019 paper about Orcus is not so clear anymore. And it was specifically only a "probable" thing anyway, considering that by the 2019 criteria, Orcus has the albedo but is on the borderline for density. So I think it makes sense to consider Orcus somewhat unclear, but one step more likely than Salacia. It might take a while for a detailed study of Orcus to settle it, of course.
Double sharp (
talk) 04:04, 18 March 2024 (UTC)
- We do have a gradient of probability, which is lost when we give a specific list. Also, Vesta is chemically evolved, but we don't consider it a DP.
— kwami (
talk) 04:43, 18 March 2024 (UTC)
- That is largely due to it significantly departing from an ellipsoidal shape; if it weren't for the Rheasilvia and Veneia impacts, we would likely be identifying Vesta as a DP. Orcus may or may not be significantly out of HE, especially since 2002 MS4 demonstrates objects larger than Vesta can similarly be knocked out of HE from impacts, but then again 2002 MS4 does not appear be (as) chemically evolved like Orcus is.
- Double sharp is correct though in that Orcus's properties are quite poorly known. The justification for calling Orcus a DP largely appears to come from how Charon, arguably the most similar known object to Orcus, is very clearly of planetary nature and has sustained its own extensive geological history. This, of course, is a tentative justification though.
ArkHyena (
talk) 05:00, 18 March 2024 (UTC)
- When the IAU was discussing the DP concept in 2006 (i.e. before Dawn), Vesta, Pallas, and Hygiea were all considered candidates. So I agree with ArkHyena that Vesta without impacts would certainly be considered a dwarf. Proteus is in a similar situation, and would probably be classed as a planemo moon if its surface features had relaxed. OTOH, there's clearly some limit, as Iapetus is generally included despite the equatorial ridge.
- Charon is probably significantly larger than Orcus and orbits the largest current DP. Anyway, extrapolating from what is known will always have problems: in the past, the general consensus based on Mimas and Enceladus was that icy objects that size should generally be geologically evolved, and look how that turned out. :) Probably the best way to describe Orcus at present is to say that it's often included among DPs, but that there is some evidence that it might not be one. The current wording seems fine to me.
Double sharp (
talk) 06:37, 18 March 2024 (UTC)
- The current wording makes it sound a lot like something was majorly changed in 2023, specially since it cites a 2023/4 source, and I see we can't even be 100% positive this source intends to judge Orcus's status. Wouldn't it be better to just move the details down to "Size and magnitude" where the other dwarf planet - not dwarf planet judgements are and then shorten them into that sentence at the top of the article?
IvicaInsomniac (
talk) 00:49, 19 March 2024 (UTC)
- I can see how linking it to just one source could imply that, though this is complicated by how very few papers appear to ever discuss/debate Orcus's possible DP status head-on, and instead typically lump it in with other objects. And indeed, a better-written section on Orcus's status and its relationship compared to other large TNOs would be warranted; looking over Orcus's article as a whole, a touch-up looks needed anyways. ArkHyena ( talk) 23:21, 10 April 2024 (UTC)
- The current wording makes it sound a lot like something was majorly changed in 2023, specially since it cites a 2023/4 source, and I see we can't even be 100% positive this source intends to judge Orcus's status. Wouldn't it be better to just move the details down to "Size and magnitude" where the other dwarf planet - not dwarf planet judgements are and then shorten them into that sentence at the top of the article?
IvicaInsomniac (
talk) 00:49, 19 March 2024 (UTC)
- We do have a gradient of probability, which is lost when we give a specific list. Also, Vesta is chemically evolved, but we don't consider it a DP.
— kwami (
talk) 04:43, 18 March 2024 (UTC)
- The point is that if it's really the case (per the 2023 paper) that Sedna, Gonggong, and Quaoar differ from "all smaller TNOs" (which would rather include Orcus under current size estimates) in whether or not they are chemically evolved, then the conclusion of the 2019 paper about Orcus is not so clear anymore. And it was specifically only a "probable" thing anyway, considering that by the 2019 criteria, Orcus has the albedo but is on the borderline for density. So I think it makes sense to consider Orcus somewhat unclear, but one step more likely than Salacia. It might take a while for a detailed study of Orcus to settle it, of course.
Double sharp (
talk) 04:04, 18 March 2024 (UTC)
- The above source does not really seem helpful, given that it does not refer to Quaoar as a dwarf planet as well. Rather, it seems more likely that the above paper intends to discuss TNOs as a whole and to not make distinctions between dwarf planets and non-dwarf planets. I also should mention that, actually, from the most recent size estimates, Sedna is slightly smaller than Orcus (but the sizes are essentially identical given the large uncertainties). It's not clear that "all smaller TNOs" should refer to Orcus, considering that Orcus is in the same size range as Quaoar and Sedna, whereas Varuna, 2002MS4, etc. are clearly smaller. Salacia once again falls within a grey area, but Salacia has not been in the list of "consensus dwarf planets" for a while now. Given this does not really make sense to say that the consensus has "changed".
Ardenau4 (
talk) 21:45, 14 March 2024 (UTC)
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Added missing "." in Mass listing on table. Abyssoft 21:08, 5 July 2006 (UTC)
From “IAU's Planet Definition” Questions & Answers Sheet: [1]
(90482) Orcus 1000±200 km [Brown, Binzel, private communication (2006)]
It may be much smaller than thought.-- JyriL talk 14:04, 16 August 2006 (UTC)
So what's up with the listed dimensions for Orcus?: "946.3+74.1-72.3 km.", it looks like it could be formatted better. I'll leave the correction for someone who knows better. HunterTruth ( talk) 16:17, 26 January 2008 (UTC)
In the intro: "The diameter of Orcus is estimated to be 761 or 807 km and the diameter of Vanth 378 or 267 km respectively, depending on their relative albedos."
In the info-box: "Dimensions 917±25 km"
In the section, "Size and magnitude": "If the albedos of both bodies are the same at 0.23 then the size of Orcus is about 917±25 km, and the size of Vanth is about 276±17 km."
There's a big inconsistency between the intro and the Size&Mag section, and given the various estimates of albedo, the ±25 km in the info-box doesn't actually show the full error-range.
Additionally, the info-box should specify what the 917km actually refers to; diameter, radius, major axis, etc, not just "Dimensions". -- PaulxSA ( talk) 06:16, 23 February 2017 (UTC)
I do not believe that we should use proposals as references. After all, if an astronomer wants to get a grant/telescope time etc. he could mention the possibility that the object is … inhabited. I feel we should keep with the usual sources. Let Mr Brown publish first. Eurocommuter 16:08, 21 August 2006 (UTC)
- Agreed. It's a good example of intriguing information that could mentioned on the talk page. Suggestive/speculative information doesn't belong to article itself.-- JyriL talk 19:03, 21 August 2006 (UTC)
- I can't help but think it is a bit outrageous to suggest that Mr. Brown lied about something so important to his work just to get telescope time.
JamesFox 01:29, 23 August 2006 (UTC)
- This was certainly not my point! My point was that with Google one can find many documents and not all of them should be used as references. Astronomers have data /hypothesis they want to test. They decide what and when to publish. I simply belive that we should let them to do so and then report it. My apologies, if my comment was read otherwise.
Eurocommuter 10:10, 23 August 2006 (UTC)
- Except that from the proposal, I get the impression that the satellite of Orcus is regarded as fact by Michael Brown (just not announced), due to the phrasing used, and that the telescope time was to get data necessary to compute the orbital period, not to confirm the existance of the satellite.
JamesFox 19:24, 24 August 2006 (UTC)
- Yeah, but he hasn't published any evidence to prove a satellite. If there is one, he'll publish when he's ready. I'm sure he himself would rather confirm it first, rather than have his funding proposals used as evidence. The Singing Badger 20:26, 24 August 2006 (UTC)
- Except that from the proposal, I get the impression that the satellite of Orcus is regarded as fact by Michael Brown (just not announced), due to the phrasing used, and that the telescope time was to get data necessary to compute the orbital period, not to confirm the existance of the satellite.
JamesFox 19:24, 24 August 2006 (UTC)
- This was certainly not my point! My point was that with Google one can find many documents and not all of them should be used as references. Astronomers have data /hypothesis they want to test. They decide what and when to publish. I simply belive that we should let them to do so and then report it. My apologies, if my comment was read otherwise.
Eurocommuter 10:10, 23 August 2006 (UTC)
The discovery of a satellite for Orcus has been published in IAUC 8812, but I haven't actually seen the circular, so I have no details. RandomCritic 02:03, 25 February 2007 (UTC)
- I tried to track down info as well, but met with the same problem. Is the existence of this page, with the heading "Recently Discovered Natural Satellites and Rings of Major and Minor Planets" and the text "Satellites of 2003 AZ_84, (50000) Quaoar, (55637) 2002 UX_25, and (90482) Orcus. IAUC 8812, 2007 Feb. 22" enough to warrant a mention? Something like "An IAU circular dated 22 February 2007 announced the discovery of satellites for Quaoar and Orcus"? Thoughts? -- Ckatz chat spy 11:54, 25 February 2007 (UTC)
this change in the Albedo does not make sense. It is way too high' and I could not find any sources for it. I am changing back to the 0.09 value. Chagai 18:47, 26 October 2007 (UTC)
- It says right in the text that observations from the Spitzer Space Telescope were used to derive a size, which can the be used to get a value for the albedo, which is given in the text as ~20%. I'm going to revert.
JamesFox 02:35, 27 October 2007 (UTC)
- We need a source, and a good one.
this source is reliable, and support 0.09. If you are familiar with the term Albedo, you know that 20% is impossible! Its like a mirror, which "90482 Orcus" is not. Look at the values of other Trans-Neptun objects. They don't even come close.
Chagai 01:51, 28 October 2007 (UTC)
- See also
Bond albedo. All values are fractions. You are just putting here wrong information.
Chagai 11:26, 29 October 2007 (UTC)
- There are many, many errors in your statements. I'll list at least most of them. 1) 20% is not an impossible amount, it is not close to being a mirror. 2) 20% is a fraction, it is the same as 0.2, just as 0.09 is the same as 9%. 3) Several known TNO's have albedos higher than 0.2, or 20%. Pluto has an estimated albedo of 0.49 to 0.66 (or between 49% and 66%), Eris' albedo is given as being around 86% (0.86). 4) There is a reference for the values determied by the Spitzer Space Telescope, look at reference 1. 5) The 0.09 value should nor be considered better, since if you look at the sources, it is clear that that Albedo was simply assumed, back in the days when Astronomers thought that TNO's would have low albedos. JamesFox 14:38, 3 November 2007 (UTC)
- See also
Bond albedo. All values are fractions. You are just putting here wrong information.
Chagai 11:26, 29 October 2007 (UTC)
- We need a source, and a good one.
this source is reliable, and support 0.09. If you are familiar with the term Albedo, you know that 20% is impossible! Its like a mirror, which "90482 Orcus" is not. Look at the values of other Trans-Neptun objects. They don't even come close.
Chagai 01:51, 28 October 2007 (UTC)
Mike Brown just named Orcus's moon. But it's not official until he clears it with the IAU. So should we start making the changes now, to make things easier, or should we wait until it's confirmed beyond doubt? Serendi pod ous 20:00, 7 April 2009 (UTC)
- Technically the name has merely been submitted and could be turned down. But we should definitely mention that the name has been submitted to the IAU for review. -- Kheider ( talk) 20:14, 7 April 2009 (UTC)
Oh, if anyone wants to have a look at it, I went looking and found the discovery image of Orcus + moon here in the HST archive (Aladin Java applet will load). Iridia ( talk) 03:13, 8 April 2009 (UTC)
- I went ahead and created Vanth (moon). Didn't want to link it into this article until it was official, but that is just a technicality. kwami ( talk) 00:03, 15 April 2009 (UTC)
- Okay, I'll move it to 90482 Orcus I and we can move again if/when the name is approved. kwami ( talk) 06:54, 15 April 2009 (UTC)
The following paper:
- Ortiz, J. L. (2011). "A mid-term astrometric and photometric study of trans-Neptunian object (90482) Orcus". Astronomy and Astrophysics. 525.
Bibcode:
2011A&A...525A..31O.
doi:
10.1051/0004-6361/201015309.
{{ cite journal}}: Unknown parameter|coauthors=ignored (|author=suggested) ( help); Unknown parameter|month=ignored ( help)
suggests that the ~10h periodic variability may be caused by the orbit of the satellite and hence the rotation of Orcus might be much faster. For what it's worth.— RJH ( talk) 22:58, 7 December 2010 (UTC)
- Actually it claims that there is a 9.7 day photometric periodicity coincident with the orbital motion in addition to weaker 10h periodicity of unknown origin. Ruslik_ Zero 06:59, 8 December 2010 (UTC)
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/iauc/08800/08812.html
- In (55637) 2002 UX25 on 2011-05-20 21:18:17, 404 Not Found
- In (55637) 2002 UX25 on 2011-05-31 04:15:46, 404 Not Found
- In 90482 Orcus on 2011-06-19 21:44:28, 404 Not Found
-- JeffGBot ( talk) 21:45, 19 June 2011 (UTC)
| The related Category:Orcus has been nominated for deletion, merging, or renaming . You are encouraged to join the discussion on the Categories for discussion page. |
To move the article without prior consensus is a complete mystery to me. The given rationale is not good enough and will cause an administrative nightmare. Guess this opens the door to endless discussions about which TNO is or is not a DP. It's crazy... -- Cheers, Rfassbind – talk 22:56, 18 September 2015 (UTC)
- This article should not have been moved and needs to be moved back by an admin. -- Kheider ( talk) 22:58, 18 September 2015 (UTC)
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New Category > Category:90482 Orcus
On 1 April 2015, the category Category:90482 Orcus has been created and added to the article's categories. Although I don't think this category makes much sense, there might be a rationale I'm missing. Can its creator, Solomonfromfinland, or anyone else help me understand? Rfassbind – talk 23:31, 2 April 2017 (UTC)
- Right now, there are only three articles in said category: this article, Orcus, and Vanth (the latter two refer to the deities, not the dwarf planet and its moon). However, having said latter two articles in said category is arguably justified; the article Orcus has an entire paragraf on the plutino (wikilinks removed):
The Kuiper belt object 90482 Orcus is named after Orcus. This was because Orcus was sometimes considered to be another name for Pluto, and also because Pluto and 90482 Orcus are both plutinos.
For the moon, see Vanth (moon).
- (Wikilink as in original; “ Vanth (moon)” redirects to “ 90482 Orcus”.) However, the number of articles in this category could be increased to four by restoring “ Vanth (moon)” as a separate article, as I think should be done; after all, we have articles on Solar System objects of which about as little is known as is about Vanth.-- Solomonfromfinland ( talk) 17:25, 8 April 2017 (UTC)
Btw, the correct date is April 2017, not April 2015. (I'm not offended by said mistake; I just wanted to point it out politely.)-- Solomonfromfinland ( talk) 17:28, 8 April 2017 (UTC)
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| GA toolbox |
|---|
| Reviewing |
- This review is transcluded from Talk:90482 Orcus/GA1. The edit link for this section can be used to add comments to the review.
Reviewer: Bryanrutherford0 ( talk · contribs) 14:18, 20 September 2019 (UTC)
- It is reasonably well written.
- a (prose, spelling, and grammar): b (
MoS for
lead,
layout,
word choice,
fiction, and
lists):
- The article is written to a good prose standard and complies with the required sections of MoS,
with one exception: the lead section is clear and relevant but a bit too long. MOS:LEADLENGTH indicates that the lead section of an article this size should be "one or two paragraphs." The final paragraph should be cut from the lead, since it appears to only contain information about Vanth and not Orcus; that content should be moved to the section on Vanth at the end of the body, where it will give that section a little more heft (I would put it between the two existing sentences of the final paragraph of the body). - I think the third paragraph of the lead should probably be cut as well (of course keeping all of the content in the body sections on Orcus's surface and cryovolcanism). I would probably keep the first sentence ("The surface of Orcus is...") but move it to the first paragraph after the sentence that establishes the body's diameter, which would improve the size balance between the two paragraphs. The rest of the detail here probably needs to wait for treatment in the body.
- In the section "Size and magnitude", one sentence begins, "If the albedos of both bodies are the same...", but the next sentence says that a subsequent study has revealed that the albedos are not the same, requiring an upward revision of Vanth's estimated size; if that's true, then the "If they were the same..." sentence should be deleted as a distraction.
- In "Spectra and surface", The first sentence of the third paragraph begins, "Orcus straddles the edge...", but to straddle something is to be on both sides of it at once. It's not yet known with certainty whether Orcus is big enough, but in reality it either is or is not, so "straddles" sends the wrong message. Maybe "Orcus sits at the threshold..."?
- Regarding the use of Template:Minor planets navigator at the end: it doesn't seem like this footer navbox is really adding anything to the article without the adjacent minor planets included, but I see that we don't seem to have articles about either of them (and may never have, since neither may ever be especially notable). Probably this should be removed, unless it's serving some purpose I'm not seeing?
Another minor note: I would add a wikilink to psychopomp in the sentence in "Name" explaining Vanth's name, but it's not required.
- The article is written to a good prose standard and complies with the required sections of MoS,
- a (prose, spelling, and grammar):
- It is factually accurate and
verifiable.
- a (
reference section): b (citations to
reliable sources): c (
OR): d (
copyvio and
plagiarism):
- The article has citations and a reference section. The online citations included support the vast majority of the article's substantive content, and I'll AGF on some of the paywalled studies for plausible physical data. Earwig's copyvio tool shows a close match between some of this article's text about the IAU's naming conventions and some other wiki/fansites, but it looks to me like that's probably because those sites ripped off this article.
Comments: I see in the infobox that we have the margins of error for all the figures in the "Physical characteristics" section, but they seem to be omitted in the "Orbital characteristics" section. Is there a reason not to include the uncertainties with those figures as well? They seem to be included on the JPL page that's cited, in the form of standard deviations (rather than a 90% confidence interval or what have you). Also, the JPL page's orbital data seem to be based on Epoch 2019 April 27.0 (as do those on the Minor Planet Center page), but the infobox claims that its orbital characteristics figures are from Epoch 4 September 2017; where did the infobox numbers come from, and should they be replaced by the figures from the JPL site?- The section "Mass and density" speculates about the division of mass between Orcus and Vanth, but the preceding section ("Size and magnitude") seems to indicate that a 2017 study nailed down Vanth's diameter to within about ±2%. Does this datum render the talk about Vanth making up between 1/33 and 1/12 of the binary system's mass outdated? If the previous section is correct, then it sounds like the relative sizes are known to much greater precision than this now.
In "Orbit and rotation", I'm uncomfortable with the phrase "Orcus is currently 48.0 AU from the Sun"; this is a sort of claim that is certain to rapidly go out of date and need continual updating. Perhaps we could cut this out and then update the remainder of the sentence to something like "Orcus has its aphelion in 2019 and will then approach the Sun until reaching perihelion in [presumably about] 2143"? That at least would keep the article up to date for the next 124 years. The second paragraph in the same section includes the claim that a rotational period of "about 10.5 hours seems to be the most likely one." Why does that figure seem the most likely, if other studies have produced other figures? Indeed, the abstract of the cited article seems to me to suggest that its authors find the possibility of Vanth's being tidally locked to be at least plausible. This claim about likelihood doesn't seem warranted by the sources I can see (but the Ortiz et al. article is paywalled, so I can't read the full text).- I've updated the orbital parameters of Orcus from the JPL Small Body Database. About the uncertainties for the orbital characteristics, the figures in the infobox are rounded and the uncertainties listed on the JPL site are very small. There is no need to include the small uncertainties if nearly all of them don't exceed 0.001. Nrco0e ( talk) 01:59, 23 September 2019 (UTC)
- With that aside, I have resolved the rest of your assessments.
Nrco0e (
talk) 02:28, 23 September 2019 (UTC)
- Oh, I see, the uncertainty is beyond the precision you're reporting. Fair enough! - Bryan Rutherford ( talk) 14:43, 23 September 2019 (UTC)
- a (
reference section):
- It is broad in its coverage.
- a (
major aspects): b (
focused):
- The article appears to cover the major aspects of the topic, including observational history, origin of name, characteristics of the body and of its orbit, and a brief summary of information about its moon. It also doesn't generally drift off topic,
with a few exceptions: the chief is that it goes into too much detail about Vanth in the lead section (as discussed above). Another two come in the "Name" section, where the sentence describing the visual depiction of the deity Orcus in Etruscan tombs should be completely removed. In the same section, the discoverer's wife's given name isn't relevant and should be removed in the interest of privacy.
- The article appears to cover the major aspects of the topic, including observational history, origin of name, characteristics of the body and of its orbit, and a brief summary of information about its moon. It also doesn't generally drift off topic,
- a (
major aspects):
- It follows the
neutral point of view policy.
- Fair representation without bias:
- The article maintains an appropriately neutral tone and doesn't e.g. lionize the body's discoverers.
- Fair representation without bias:
- It is stable.
- No edit wars, etc.:
- No edit wars, etc.:
- It is illustrated by
images and other media, where possible and appropriate.
- a (images are tagged and non-free content have
fair use rationales): b (
appropriate use with
suitable captions):
- The images are relevant and appropriate, and they all have good licenses and helpful captions. It would be nice to add alt-text to all the images, but it isn't required for GA.
- a (images are tagged and non-free content have
fair use rationales):
- Overall:
- Pass/Fail:
- An interesting and informative article about a plutino! With a little polish, this should be able to reach the GA standard.
- Pass/Fail:
- I have edited the article according to your recommendations. I will be waiting for your next assessments.
Nrco0e (
talk) 19:07, 21 September 2019 (UTC)
- Wow, thank you for your quick and responsive editing! I'll look through the sources by the end of the day tomorrow and give any feedback there, but everything I've pointed out so far is now fixed. -
Bryan Rutherford (
talk) 20:38, 21 September 2019 (UTC)
- By the way, if you haven't known already, most of the scientific papers cited in the article can be accessed from their
arXiv preprints, which is linked near the end of the source citation. For your issue about the rotation period of Orcus, the full paper can be read at
https://arxiv.org/abs/1010.6187. I hope this helps for your future reviews on science-related articles!
Nrco0e (
talk) 02:40, 23 September 2019 (UTC)
- This all looks good! Thanks again for being so responsive; this article is hereby approved for GA! - Bryan Rutherford ( talk) 14:43, 23 September 2019 (UTC)
- By the way, if you haven't known already, most of the scientific papers cited in the article can be accessed from their
arXiv preprints, which is linked near the end of the source citation. For your issue about the rotation period of Orcus, the full paper can be read at
https://arxiv.org/abs/1010.6187. I hope this helps for your future reviews on science-related articles!
Nrco0e (
talk) 02:40, 23 September 2019 (UTC)
- Wow, thank you for your quick and responsive editing! I'll look through the sources by the end of the day tomorrow and give any feedback there, but everything I've pointed out so far is now fixed. -
Bryan Rutherford (
talk) 20:38, 21 September 2019 (UTC)
- I have edited the article according to your recommendations. I will be waiting for your next assessments.
Nrco0e (
talk) 19:07, 21 September 2019 (UTC)
https://www.youtube.com/watch?v=2rrelv96nCQ
I am not a believer in the Nibiru cataclysm, so what is in that final image? 103.38.21.38 ( talk) 05:25, 15 December 2019 (UTC)
- As it is meaningless youtube clickbait, it could be anything such as a manipulated image of the bottom of a frying pan. -- Kheider ( talk) 11:59, 15 December 2019 (UTC)
Will there be a mission to orcus? — Preceding unsigned comment added by Zachbarbo ( talk • contribs) 19:46, 9 November 2021 (UTC)
- I wish! A concept has been studied, though it also considers Pluto, Haumea, and Quaoar as possibilities. But only a concept. Double sharp ( talk) 23:06, 9 November 2021 (UTC)
How long will a flyby mission to Orcus will take? — Preceding unsigned comment added by Zachbarbo ( talk • contribs) 15:12, 10 November 2021 (UTC)
- Orcus is currently at 48 AU, Pluto at about 30. It took New Horizons almost 15 years to reach Pluto. So, all things being equal, we could expect it to take maybe 24 years to reach Orcus. But all things wouldn't be equal. A big determiner in how long a flight will take is how big a boost the spacecraft gets from its Jupiter flyby. So we'd have to fit the timing to three planets: Earth, Jupiter and Orcus, and we might need to wait years for them to align properly. Also, nothing much is going to happen on Orcus for a century or so, so IMO a bigger priority would be Eris or Sedna. — kwami ( talk) 04:23, 11 November 2021 (UTC)
There is a move discussion in progress on Talk:90377 Sedna which affects this page. Please participate on that page and not in this talk page section. Thank you. — RMCD bot 20:00, 14 November 2022 (UTC)
I tagged this sentence as failed verification: Orcus had been accepted by many astronomers as a dwarf planet, though as of 2024 that consensus has changed. [2]
@ Double sharp: responded: See below - they argue that Sedna, Gonggong, Quaoar differ from "all smaller TNOs" (which would include Orcus) in ways that imply they have undergone chemical evolution while the smaller ones have not, which is the point of the DP category
I read the paper before I tagged it for failed verification, I assume you were talking about this sentence: We suggest that these three bodies have undergone internal melting and geochemical evolution similar to the larger dwarf planets and distinct from all smaller KBOs. To nitpick, the underlined part doesn't logically imply that all smaller KBOs are definitely not dwarf planets. The rest of the text more or less puts Sedna, Gonggong and Quaoar in a third group different from both larger bodies and undiscussed smaller bodies (no evidence of neither methane nor methanol).
Not being listed in a single paper specifically focusing on chemical composition of three unrelated dwarf planet candidates to me isn't enough of a development to belong right in the third sentence for Orcus. Especially since the Dwarf planet article goes on and on about how there's no consensus on which TNOs are dwarf planets (There is no clear definition of what constitutes a dwarf planet, and whether to classify an object as one is up to individual astronomers). IvicaInsomniac ( talk) 21:40, 13 March 2024 (UTC)
- @ Kwamikagami: Pinging you for your opinion. Double sharp ( talk) 03:02, 14 March 2024 (UTC)
- Also
Exoplanetaryscience.
Double sharp (
talk) 03:03, 14 March 2024 (UTC)
- I thought we had two papers now that said this: Quaoar up look geologically active (or at least formerly so); the rest do not. The fact that they don't specifically mention Orcus is no more reason to ignore their claim than their similar failure to mention Salacia, Varuna, Ixion, etc.
— kwami (
talk) 07:04, 14 March 2024 (UTC)
- @ Kwamikagami in case it is missed (and because it is directly relevant), Ardenau4 noted that the currently measured size of Orcus is consistent with Quaoar's and Sedna's, not smaller. AstroChara ( talk) 19:09, 15 March 2024 (UTC)
- I thought we had two papers now that said this: Quaoar up look geologically active (or at least formerly so); the rest do not. The fact that they don't specifically mention Orcus is no more reason to ignore their claim than their similar failure to mention Salacia, Varuna, Ixion, etc.
— kwami (
talk) 07:04, 14 March 2024 (UTC)
- Revisiting this topic after a while. Though I do agree that Orcus's status as an unambiguous dwarf planet is on shaky ground, and really hasn't much of a better justification than Salacia and Varuna, I must agree here that the paper provided is pretty weak in arguing against Orcus's classification, especially for it to warrant declaring that 'consensus' has swung against it. To my knowledge, it has not; as recently as just last year, some astronomers have been referring to Orcus as a dwarf planet. One paper does not change consensus; this would arguably be an example of undue weight.
- I would suggest citing additional papers such as
Fornasier et al., where the authors do not refer to Orcus as a dwarf planet, to more clearly demonstrate that consensus does not (and perhaps arguably never has) favor Orcus as a dwarf planet, and that opinion is still divided.
ArkHyena (
talk) 21:34, 14 March 2024 (UTC)
- The above source does not really seem helpful, given that it does not refer to Quaoar as a dwarf planet as well. Rather, it seems more likely that the above paper intends to discuss TNOs as a whole and to not make distinctions between dwarf planets and non-dwarf planets. I also should mention that, actually, from the most recent size estimates, Sedna is slightly smaller than Orcus (but the sizes are essentially identical given the large uncertainties). It's not clear that "all smaller TNOs" should refer to Orcus, considering that Orcus is in the same size range as Quaoar and Sedna, whereas Varuna, 2002MS4, etc. are clearly smaller. Salacia once again falls within a grey area, but Salacia has not been in the list of "consensus dwarf planets" for a while now. Given this does not really make sense to say that the consensus has "changed".
Ardenau4 (
talk) 21:45, 14 March 2024 (UTC)
- Coming back to additionally note that Grundy et al. 2019 seems to provide the actual justifications as to why most astronomers classify Orcus as a dwarf planet:
- Orcus and Charon probably melted and differentiated, considering their higher densities and spectra indicating surfaces made of relatively clean H2O ice. But the lower albedos and densities of Gǃkúnǁ'hòmdímà, 55637, Varda, and Salacia suggest that they never did differentiate, or if they did, it was only in their deep interiors, not a complete melting and overturning that involved the surface.
- Combined with the above, I believe that removing Orcus from the list of consensus dwarf planets here was premature.
ArkHyena (
talk) 17:40, 16 March 2024 (UTC)
- Grundy is a co-author of the latest paper. But it's true that we don't know that he (or his 2019 co-authors, none of whom were authors of the 2023 papers) agree with this particular statement. I've seen papers on what is a planet that effectively concluded that Earth and Jupiter are not planets, which I'm pretty sure are not conclusions shared by any of the authors. (Though much more sloppily written than this one, the point is that legalistic reading of a paper may be justified when there is a single author, who we know to be precise in their writing, but not when there are several.) So maybe it was premature. — kwami ( talk) 18:05, 16 March 2024 (UTC)
- BTW, the paper in question had both Stern and Grundy as co-authors, among others, but I suspect they didn't have much if anything to do with writing it, and instead signed on to something they agreed with to help make a point. It was an opinion piece that dwarf planets should be considered planets and had no real academic content. But my point is that it defined one criterion for planethood as being a tri-axial spheroid. Since that is a mathematical impossibility, a legalistic reading is that there is no such thing as a planet. Obviously, none of the authors intended what it said. I think it's quite possible that if you asked the authors of the 2023 paper about Orcus, they'd hedge, and of course we don't know about Noll or Buie etc. from the 2019 paper.
— kwami (
talk) 18:27, 16 March 2024 (UTC)
- The point is that if it's really the case (per the 2023 paper) that Sedna, Gonggong, and Quaoar differ from "all smaller TNOs" (which would rather include Orcus under current size estimates) in whether or not they are chemically evolved, then the conclusion of the 2019 paper about Orcus is not so clear anymore. And it was specifically only a "probable" thing anyway, considering that by the 2019 criteria, Orcus has the albedo but is on the borderline for density. So I think it makes sense to consider Orcus somewhat unclear, but one step more likely than Salacia. It might take a while for a detailed study of Orcus to settle it, of course.
Double sharp (
talk) 04:04, 18 March 2024 (UTC)
- We do have a gradient of probability, which is lost when we give a specific list. Also, Vesta is chemically evolved, but we don't consider it a DP.
— kwami (
talk) 04:43, 18 March 2024 (UTC)
- That is largely due to it significantly departing from an ellipsoidal shape; if it weren't for the Rheasilvia and Veneia impacts, we would likely be identifying Vesta as a DP. Orcus may or may not be significantly out of HE, especially since 2002 MS4 demonstrates objects larger than Vesta can similarly be knocked out of HE from impacts, but then again 2002 MS4 does not appear be (as) chemically evolved like Orcus is.
- Double sharp is correct though in that Orcus's properties are quite poorly known. The justification for calling Orcus a DP largely appears to come from how Charon, arguably the most similar known object to Orcus, is very clearly of planetary nature and has sustained its own extensive geological history. This, of course, is a tentative justification though.
ArkHyena (
talk) 05:00, 18 March 2024 (UTC)
- When the IAU was discussing the DP concept in 2006 (i.e. before Dawn), Vesta, Pallas, and Hygiea were all considered candidates. So I agree with ArkHyena that Vesta without impacts would certainly be considered a dwarf. Proteus is in a similar situation, and would probably be classed as a planemo moon if its surface features had relaxed. OTOH, there's clearly some limit, as Iapetus is generally included despite the equatorial ridge.
- Charon is probably significantly larger than Orcus and orbits the largest current DP. Anyway, extrapolating from what is known will always have problems: in the past, the general consensus based on Mimas and Enceladus was that icy objects that size should generally be geologically evolved, and look how that turned out. :) Probably the best way to describe Orcus at present is to say that it's often included among DPs, but that there is some evidence that it might not be one. The current wording seems fine to me.
Double sharp (
talk) 06:37, 18 March 2024 (UTC)
- The current wording makes it sound a lot like something was majorly changed in 2023, specially since it cites a 2023/4 source, and I see we can't even be 100% positive this source intends to judge Orcus's status. Wouldn't it be better to just move the details down to "Size and magnitude" where the other dwarf planet - not dwarf planet judgements are and then shorten them into that sentence at the top of the article?
IvicaInsomniac (
talk) 00:49, 19 March 2024 (UTC)
- I can see how linking it to just one source could imply that, though this is complicated by how very few papers appear to ever discuss/debate Orcus's possible DP status head-on, and instead typically lump it in with other objects. And indeed, a better-written section on Orcus's status and its relationship compared to other large TNOs would be warranted; looking over Orcus's article as a whole, a touch-up looks needed anyways. ArkHyena ( talk) 23:21, 10 April 2024 (UTC)
- The current wording makes it sound a lot like something was majorly changed in 2023, specially since it cites a 2023/4 source, and I see we can't even be 100% positive this source intends to judge Orcus's status. Wouldn't it be better to just move the details down to "Size and magnitude" where the other dwarf planet - not dwarf planet judgements are and then shorten them into that sentence at the top of the article?
IvicaInsomniac (
talk) 00:49, 19 March 2024 (UTC)
- We do have a gradient of probability, which is lost when we give a specific list. Also, Vesta is chemically evolved, but we don't consider it a DP.
— kwami (
talk) 04:43, 18 March 2024 (UTC)
- The point is that if it's really the case (per the 2023 paper) that Sedna, Gonggong, and Quaoar differ from "all smaller TNOs" (which would rather include Orcus under current size estimates) in whether or not they are chemically evolved, then the conclusion of the 2019 paper about Orcus is not so clear anymore. And it was specifically only a "probable" thing anyway, considering that by the 2019 criteria, Orcus has the albedo but is on the borderline for density. So I think it makes sense to consider Orcus somewhat unclear, but one step more likely than Salacia. It might take a while for a detailed study of Orcus to settle it, of course.
Double sharp (
talk) 04:04, 18 March 2024 (UTC)
- The above source does not really seem helpful, given that it does not refer to Quaoar as a dwarf planet as well. Rather, it seems more likely that the above paper intends to discuss TNOs as a whole and to not make distinctions between dwarf planets and non-dwarf planets. I also should mention that, actually, from the most recent size estimates, Sedna is slightly smaller than Orcus (but the sizes are essentially identical given the large uncertainties). It's not clear that "all smaller TNOs" should refer to Orcus, considering that Orcus is in the same size range as Quaoar and Sedna, whereas Varuna, 2002MS4, etc. are clearly smaller. Salacia once again falls within a grey area, but Salacia has not been in the list of "consensus dwarf planets" for a while now. Given this does not really make sense to say that the consensus has "changed".
Ardenau4 (
talk) 21:45, 14 March 2024 (UTC)
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