Talk:2060 Chiron

From Wikipedia, the free encyclopedia
Jump to: navigation, search
WikiProject Astronomy / Astronomical objects  (Rated C-class, Mid-importance)
WikiProject icon 2060 Chiron is within the scope of WikiProject Astronomy, which collaborates on articles related to Astronomy on Wikipedia.
C-Class article C  This article has been rated as C-Class on the project's quality scale.
 Mid  This article has been rated as Mid-importance on the project's importance scale.
Taskforce icon
This article is supported by WikiProject Astronomical objects, which collaborates on articles related to astronomical objects.
 
WikiProject Solar System (Rated C-class, Mid-importance)
WikiProject icon This article is within the scope of WikiProject Solar System, a collaborative effort to improve the coverage of the Solar System on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.
C-Class article C  This article has been rated as C-Class on the project's quality scale.
 Mid  This article has been rated as Mid-importance on the project's importance scale.
 
For more information, see the Solar System importance assessment guideline.

Comments[edit]

The page says that it will eventually fall into one of the gas giants. Is enough known about its orbit to guess when this might happen and which gas giant might consume it? Inquiring minds want to know. KellyCoinGuy

Judging by the fact that it says it approached Saturn to within 16 million KM in 1664 and that's considered a big deal, it's probably safe to assume that if it's believed that it will fall into a gas giant it's because comets (asteroids) simply have a tendancy to do that eventually, and it you might expect it to happen some time in the next million years or so!   freshgavin TALK    04:45, 20 January 2006 (UTC)
I think it is far more likely that a close giant planet flyby changes its orbit dramatically, possibly ejecting it from the Solar System altogether.--Jyril 16:15, 20 January 2006 (UTC)

Cleanup[edit]

Did a major reorginization of the article, with the new layout modeled on the article for 90482 Orcus. I'm intending to get this article fixed up, so it can be used as an example for repairing the current state of the centaur articles. shaggy 12:26, 14 March 2006 (UTC)


The sections should NOT be merged into one, as the two articles are about in fact two different astronomical bodies. Instead, why not merge this one (hypothetical moon) into a Saturn article, if it absolutely must be merged with something? —Preceding unsigned comment added by 78.52.162.59 (talkcontribs) 12 April 2010

Astrology[edit]

Is the astrology section sourced in the Guinness Book? If not, it needs to go completely. Captainktainer * Talk 09:18, 9 September 2006 (UTC)

The Astrology section should either be moved to Planets_in_astrology or removed completely. Other comparable scientific articles e.g. Pluto don't have an astrology section. --Mojoh81 10:38, 1 November 2006 (UTC)

Wrong predictions 1664BC[edit]

I checked the article's statement It has been calculated that in 1664 BC Chiron approached Saturn to within approximately 16 million kilometres... with SOLEX. The other was from Kowal There is no agreement about any of the approaches between the two sources. It's not so much that SOLEX 9.1 has 30 yr more recent orbital elements. The researchers had considered perturbations of the five outer planets only. Simulations by SOLEX show that removing just Venus or Mercury completely changes the list of close approach years. So I removed the statement. Saros136 (talk) 18:49, 10 February 2008 (UTC)

Using SOLEX again, I checked to see what reliable close approach predictions can be made. SOLEX has a clone feature, for asteroids. It generates orbital elements for a number of fictitious asteroids, very similar to the first. How similar depends on the estimated uncertainty in the real elements. The only close Saturn-Chiron close passes all the clones made or will make are in May 720, at just under 30 Gm, October 3544, at 137 Gm, and January or February 4606-103 Gm. The predictions hold up if I remove the big three main belt asteroids (Ceres, Pallas, and Vesta) or Pluto(or all four), or if I add all of the biggest ones. Saros136 (talk) 13:29, 11 February 2008 (UTC)

(Note to myself) Horizons shows that Chiron came within 1.84476155AU (275,972,399 km) of Saturn on 1899-Aug-25. -- Kheider (talk) 15:41, 15 March 2009 (UTC)
Solex gives 1.84470677 au, same day. Saros136 (talk) 07:20, 17 March 2009 (UTC)
One of the sources (the Kowal one) gives an approach of 0.1AU from Saturn in the year 1664. If we're going to talk about close approaches to planets, it would be best to stick to ones explicitly stated in published sources. Personally, I don't like the idea of using computer programs to generate facts for articles. It's difficult to properly cite them and, more importantly, it's getting into WP:OR territory. Routine calculations like converting between miles and kilometers is one thing, using advanced software to predict events is something else. Reyk YO! 11:25, 17 March 2009 (UTC)
Their prediction was for 1664 BC, not AD, and was made with an invalid model.
Personally, I don't like the idea of using computer programs to generate facts for articles.. All predictions are made with computer programs, and predictions by Solex and GravSim are as accurate (or more so) as any published ones. I don't know much about GravSim, except that it is very good, but Solex is the creation of one of the leading experts in the field. His thorough testing shows it is very accurate, and its long term predictions of events match those already accepted as true. A Solex or GravSim citation has as much weight as any other source. Saros136 (talk) 07:36, 18 March 2009 (UTC)


The problem with the 1664BC passage is (1) it was generating using older orbital data from the 1970s (2) it only took the 5 outer planets into consideration (Page 247; Paragraph 3). (3) Even Kowal says, "the earlier motion must be considered rather uncertain". The modern programs Solex and Gravity Simulator are far more reliable and have been used in FA articles like Mercury (Paragraph 3, Ref 78) and Mars (Ref 68). -- Kheider (talk) 15:19, 17 March 2009 (UTC)
This doesn't matter now, but it was the Wikipedia article that said the prediction was for 1664BC. Not true. The year was given as -1664, which in astronomy is 1665 BC.Saros136 (talk) 07:44, 18 March 2009 (UTC)
I used the newest versions of the SOLEX/EXORB software, together with the original observation data from AstDys, to determine the data of closest approach in 720. It turns out that there is significant uncertainty in timing and distance resulting in different semi-major axis value prior the event. The reason for the difference to the "old" approach is that the clone feature of SOLEX alone does not always result in statistically reliable values. The use of observation data with EXORB results in more reliable data. I changed the article according to this.Renerpho (talk) 03:51, 12 July 2015 (UTC)
Thank you for re-visting the question. More eyes is always better. -- Kheider (talk) 14:33, 12 July 2015 (UTC)

Dead link[edit]

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!

--JeffGBot (talk) 05:16, 19 June 2011 (UTC

Dwarf planet[edit]

It is misleading to show an image of Chiron that suggests it is a dwarf planet without explaining in the text that it is near the lower limit to qualify as such. Even the article on larger 10199 Chariklo does not mislead people so much. -- Kheider (talk) 22:15, 3 October 2015 (UTC)

The image's caption already says it is unknown whether it is in HE. DN-boards1 (talk) 22:24, 3 October 2015 (UTC)
You have been going around Wikipedia claiming many things are/were a dp. You have even made such a claim at Phoebe (moon), which I have aggressively reverted. Mike Brown's GENERIC website claims everything from 200 to 400km is *possibly* a dwarf planet. But anything less than ~250km in diameter is not likely to qualify as a proper dwarf planet. -- Kheider (talk) 22:36, 3 October 2015 (UTC)
No RS states that it is 250km. The RSes all give a minimum of 200km. DN-boards1 (talk) 22:46, 3 October 2015 (UTC)
@Kheider: Here I have to concur with DN-boards1 for once. I don't know where you got that 250 km and we even have an example of a body that was once round below that: Phoebe. I don't care much about the image. I even removed it was because it displays more than we know about it (i.e. the round part; it could be, but we don't know). --JorisvS (talk) 22:59, 3 October 2015 (UTC)
Put simply 250km is damn small and most objects of that size will not be in current HE. -- Kheider (talk) 23:02, 3 October 2015 (UTC)
How do you know that most will not be in HE? --JorisvS (talk) 00:40, 4 October 2015 (UTC)
For starters many will be rubble piles/binaries broken-up by large impacts. 250km does not give a dp much room for error once it solidifies. -- Kheider (talk) 00:49, 4 October 2015 (UTC)
Okay, for binaries and the Haumea family we can expect a thermal history more like that of Proteus, rather unlike that of Phoebe. But beyond that, we don't know how many with thermal histories like that of Phoebe are disrupted sufficiently due to impacts, do we? --JorisvS (talk) 00:58, 4 October 2015 (UTC)
In an old (1980's) book, Cole calculated a minimum of 320km for when the pressure at the centre of an object is enough to break the material bonds (for ice, rock is higher). You can see an excerpt here, or find a really good library. (Aside: In a paper, Mike Brown referenced Cole's book, which is how I found it.) Additionally, Lineweaver and Norman calculated a size of ~400km based on the overburden pressure of a bump of 10% of the radius being enough to break the material bonds at the bottom of the bump. Brown based his 400km on Mimas, which has since been shown to not be HE (and he ignored potatoey Proteus). Also note that round alone does not mean HE. A HE body will return to round after a collision. Phoebe and Vesta not being round any more shows that they weren't in HE at the time of the collisions that de-rounded them (probably: slight caveat if the collision is big enough to knock off enough mass to lower the object below the threshold). So the reliable sources are above 300. You can consider smaller objects if the size is not well known, such that the error bars might put it above the threshold. Chiron's size is well enough determined to say that it is not one of these. Tbayboy (talk) 23:37, 3 October 2015 (UTC)
I've seen that. The only way to reconcile that with the observation of Phoebe having once been round is that early on it was so warm that its material strength was very low. Nowadays, it would not re-round (and it hasn't), but so wouldn't big Iapetus (which has triaxial dimensions significantly deviating from those expected for HE)! I don't know how that can be reconciled with their theoretical argument, but that just is the observation. If re-rounding is the criterion, we could seriously doubt the DPness of even Makemake and Haumea. And if it isn't, then there is the possibility of a whole bunch of non-battered Phoebe-like objects in the Kuiper belt, and in fact the possibility of Chiron and Chariklo being DPs. --JorisvS (talk) 00:40, 4 October 2015 (UTC)
We still do not have RS that states Phoebe (moon) was a dp. The 2012 source states that Phoebe was a round planetesimal. -- Kheider (talk) 00:58, 4 October 2015 (UTC)
How could it have been round without at least at some point having been in HE? --JorisvS (talk) 01:01, 4 October 2015 (UTC)
Exactly, JorisvS. DN-boards1 (talk) 01:02, 4 October 2015 (UTC)
"Nearly round" is not the same thing as HE, and does not mean the object fully differentiated. -- Kheider (talk) 01:06, 4 October 2015 (UTC)
Phoebe is (partially) differentiated[1][2] and Callisto may not even have differentiated much, so differentiation is not a requirement. [3] also says 'Phoebe was spherical and hot early in its history'. Spherical, but never in HE, is that even possible? --JorisvS (talk) 01:34, 4 October 2015 (UTC)
Callisto, IIRC, hasn't differentiated AT ALL. Its surface has been solely shaped by impacts. The only things in it are a core, a crust, and an internal ocean. No layers besides those three. DN-boards1 (talk) 01:43, 4 October 2015 (UTC)
I phrased it like that because there are measurements consistent with an subsurface ocean, which requires at least a little bit of differentiation. Its article says Callisto's rock content increases with depth, i.e. there is partial differentiation. Note that what you say is what differentiation is. --JorisvS (talk) 01:47, 4 October 2015 (UTC)
Cole's theoretical argument is when the very centre is capable of breaking the material. He doesn't say how quickly that fluid centre increases in size as the object size is increased. I don't recall what temperature he used for the ice (if he even said; same for Lineweaver-Norman) -- ice gets harder when the temperature drops. I agree that Phoebe was probably soft enough in her youth to have been in HE, and also Vesta. We all tend to lose our lovely shape as we age.
Iapetus might demonstrate the issue I mention about Cole's calculation. The HE centre might be deep enough to allow the veneer of non-HE crust to maintain the bulge from the earlier era, before it de-spinned.
Also note that the DP criterium is not HE, but that it has enough gravity to overcome rigid-body forces. HE is a consequence of that, but it's possible to have HE without satisfying the criterium: see Methone.
Haumea is much more massive (almost Rhea and Iapetus together), hence more gravitational force to crush itself, so I think it's safely a DP. Makemake and Ceres could be suspect (and those canyons on Charon, if you want to consider it for binary DP). It also depends on where you draw the line. A rock on the Moon won't ever crush or sink (without help from bombardment), but we still consider it HE. Lineweaver allows a bulge of up to 10% of the radius to still count as DP, but the Saturn-moon-shape paper used a much tighter criterium to exclude Iapetus from HE, under 1% I think. The transition from non-"round" to "round" happens slowly, and it seems as arbitrary as just picking a number for diameter. Tbayboy (talk) 04:03, 4 October 2015 (UTC)