Talk:Centaur (minor planet)

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Curps: Good edit on comet/asteroid mixture of 2060 Chiron. It looks like the CFA prefers to list SDOs and Centaurs in reverse chronological order, for some reason. There is a de facto standard for listing objects in Wikipedia in decreasing diameter (see Kuiper belt, Natural satellite, first table in List of noteworthy asteroids) or sometimes chronological order (see second table in List of noteworthy asteroids).. I was trying to not use a third ordering. It would be cool to get diameters on these objects, by the way. -- hike395 05:17, 12 Apr 2004 (UTC)

In this case, I imagined future maintainers of the page would click on the external link to look up any updated info. For lists of more than a few elements, it can be very confusing to compare them if one is in the opposite order of the other (assuming the list on the Wikipedia page might grow considerably). So that's basically the reason I kept it that way. I don't know the diameters of the other objects, maybe the info is out there somewhere. -- Curps 05:45, 12 Apr 2004 (UTC)
That makes sense. -- hike395

Removed to where?[edit]

"Centaurs are not in stable orbits and will eventually be removed by the giant planets." Removed to where? Could someone who knows their stuff clarify this sentence? The Singing Badger 16:15, 26 Sep 2004 (UTC)

Centaurs will be removed from the solar system either by impacting on a planet, perturbed into a sungrazing object and destroyed by impact on or disruption by the sun (like the Kruetz family of Sun-grazing comets) or will be perturbed by one of the planets onto an orbit that will escape the solar system (the most likely removal route...). Most asteroids and Kuiper Belt objects are on orbits which are relatively stable and will last for billions of years, orbiting far enough from the planets so that their orbits will not be drastically perturbed. But in the case of planet crossing asteroids (like Centaurs or Earth-crossing asteroids), the planets (especially Jupiter) will cause drastic changes to the objects orbit, including total ejection from the solar system when the object passes relatively close to the planet in question. Typical dynamical lifetimes of Centaurs are around 1 million to a few 10s of millions of years depending on the specifics of their particular orbit. Jim 00:22, 28 Sep 2004 (UTC)
Cool! That's what I wanted to know. :) The Singing Badger 17:24, 28 Sep 2004 (UTC)

Removed line[edit]

"In 2010, the New Horizons spacecraft is expected to perform a distant flyby of a centaur, (83982) 2002 GO9."

This statement was earlier removed from the New Horizons article and appears to untrue/speculation. Rmhermen 19:14, 17 January 2006 (UTC)

10199 Chariklo[edit]

I got rid of the ugly red link to 10199 Chariklo in the "notable centaurs" section. I wasn't sure how much information on centaurs is appropriate to add there, so any input would be appreciated! shaggy 23:07, 1 March 2006 (UTC)

Yes, I believe that while the articles related to TNO/Centaurs are growing in substance we should review the distribution of the content among different articles to allow a logical, progressive digging into details while providing a quick essential read to a casual visitor. An experienced editor with not too much background in the subject would be the best, IMHO. As examples of simple common sense rules could be: let’s do not make the reader to open the link just to read the definition. Another one: if the diameter is say: 300km, let’s be nice and add whether it is huge or small for the given class of objects. Eurocommuter 11:00, 2 March 2006 (UTC)
I think some of the more well-done KBO articles could be a good model for this. The really important things to cover (and for many of these objects, the only information available) are things like the date of it's discovery, where it orbits, and (usually) color data is pretty easy to find. 90482 Orcus is a pretty good example, I think, of a non-stub outer solar system minor planet article. shaggy 15:14, 2 March 2006 (UTC)

Incomplete article[edit]

This article could be expanded to include data about the color of Centaurs. Also, there's no mention of the relationship between centaurs and the Scattered Disc. Other articles on KBOs reference the "red color of KBOs and Centaurs", so there's gotta be a source for this information on wikipedia already. I would fix it now, but I don't have time. shaggy 15:18, 2 March 2006 (UTC)

Indeed. I’m collecting some references to the articles on colour for TNO. I’ve got only tangent interest in colour, in relation to the models of the origin and classification of TNO/centaurs but I’ll be hopefully extending this aspect in the near future. TNO/centaur connection is an interesting one and so far underexposed in our articles. Eurocommuter 17:15, 2 March 2006 (UTC)
Also, a table of notable Centaurs similar to the list at Kuiper belt would be an excellent addition. shaggy 19:47, 2 March 2006 (UTC)


Is the colour section misleading to the layman? When a Centaur is described as "intensely red" do we mean that literally, or do we mean it's intense when compared to other astronomical bodies? Also, the diagram of colours shows bright purple Centaurs. Surely they're not really as purple as that? Any suggestions for how to make this clearer? The Singing Badger 12:52, 14 March 2006 (UTC)

I understand that broadband colour indices are not equivalent of three monochromatic pictures to be combined into a natural colour, as for the fantastic satellites’ pictures for example. I have a problem how to expression the colours and perhaps I’ve exaggerated (a bit?). The problem is not simple (see colour related articles). I did indeed enhance the colours to make the point and avoid dim, dirty spheres by aligning the luminosity and ignoring the albedo. (Albedo is known only for a few of them, anyway). Pholus is indeed the most red observed object (quoted refs). I’m not so bothered with the purple, it is after all on blue/red diagonal, but I should probably add more green to have the blue less blue and more grey/blue. Please consider this as a draft. I’ll be most grateful for any technical note how to combine V-B and R-V into RGB (you probably see different colours on your monitor than me, anyway). Eurocommuter 14:06, 14 March 2006 (UTC)
I think saying that the colours are enhanced is all that is necessary. It looks better already. I'm afraid I can't help with the technical side. :( The Singing Badger 14:33, 14 March 2006 (UTC)
Well, in addition to the voluntary enhancement I found a program bug shifting the colours into hellish hues. I discovered it while my rendering of Pluto did not want to match Nasa’s idea of the hue. My apologies Eurocommuter 22:49, 16 March 2006 (UTC)
looks much better now. I could almost believe those are the actual colors! Are you working on similar diagrams for the other TNO groups? shaggy 23:57, 16 March 2006 (UTC)

lead; Chiron[edit]

Mentioning Chiron’s double life as a comet so early in the lead bothers me a lot, as it could mislead into thinking that cometary activity is typical for centaurs. (maybe it is but yet to be observed for others). Perhaps we should move it into a small subsection, further on. Eurocommuter 13:50, 14 March 2006 (UTC)

I was thinking of trying to fit it into the physical characteristics section later today. It's really the only place I could think of to move it. I did substantially re-organize 2060 Chiron earlier, so we might think about moving most of that information over there. shaggy 13:59, 14 March 2006 (UTC)
Looking at it more, I think this is now one of the worst leads I have ever seen on wikipedia. I'm gonna take a crack at re-writing it. shaggy 20:09, 15 March 2006 (UTC)

Distinguishing Centaurs from TNOs[edit]

I'm wondering about the classification of the distant bodies in Image:TheKuiperBelt_55AU_Centaurs.svg as Centaurs. (The ones that cluster just inwards of the plutinos). A lot of them look rather like TNOs to me -- They don't even cross Neptune's orbit. Take, for example, 2004 TY364. While there is apparently no agreed-upon definition of what is a centaur and what isn't, I would have thought that you at least should be within Neptune's orbit some of the time, otherwise you're obviously a trans-neptunian object. Is some other definition being used? Deuar 10:16, 27 March 2006 (UTC)

That’s an old graph…(lame excuse).Good point; I promise to check; having a heavy week in real life but I’ll look into it on Saturday. My program(s) is taking the data from MPCORB database. Back then, I did not have a module checking and correcting the types with the current MPC circular for the orbit classification (as I do now, for example in the case of the orbit plots for plutinos). I will re-generate this diagram with the current modules.Eurocommuter 18:46, 28 March 2006 (UTC)
Indeed, MPCORB (the database, not html on the Web) lists 2004 TY364 as Centaur (type 10 in column 162-165 as per format description. The MPC Circular X77 I have used for other graphs does not qualify the orbit, by the way. My program followed MPC type qualification (blame yours truly, not the poor Java). As per consensual no-nonsense definition, centaurs orbits have aCentaur < aNeptune. My apologies. Thanks Peter! Will be fixed. Eurocommuter 20:09, 29 March 2006 (UTC)
Funny MPCORB qualified it that way. I seem to recall they mentioned in a summary sheet somewhere that the flags they have are not to be trusted, but I didn't really believe that before ;-) This is fun isn't it! Deuar 21:40, 29 March 2006 (UTC)
Fixed this one but a few others are affected as well.Eurocommuter 06:33, 30 March 2006 (UTC)
Looks good. I hadn't realised that Pholus is also bigger than Chiron. Deuar 10:27, 30 March 2006 (UTC)
See Talk:trans-Neptunian object#The objects between Neptune and Pluto for further discussion. Eurocommuter 11:02, 1 April 2006 (UTC)

Centaur list[edit]

Hello Centaur enthusiasts ...... I've been studying the IAU list of Scattered Disk Objects and Centaurs, and am wondering how to tell which is which! Does anyone know the location of a simpler list which clearly designates information about ONLY Centaurs, whether officially named or not? Would be much appreciated. Thanks.

Later + more searching. Check out for some great lists of information.

C'mon, that's an astrology page.
Anyway, a rough rule of thumb for Centaurs is that their semi-major axis is smaller than Neptune's. Deuar 18:09, 14 October 2006 (UTC)

You might try the JPL Small-Body Database Search Engine and specify: "Constraints: orbital class (CEN) and q > 5.5 (AU) and a < 29.7 (AU)". I came up with 64 matches.
1. Under "Limit to selected orbit class(es):" Put a check on Centaur.
2. Use the 2nd pull down to select "q (au)" > 5.5 (Aph-Jup) and click Add.
3. Use the 2nd pull down to select "a (au)" < 29.7 (Peri-Nept) and click Add.
4. Under "Pre-defined field sets:" select "Asteroid - Basic" and click "Append Selected".
5. Under Table Format, select "50 rows per page max."
6. Click "Generate Table".
You can tweak the options as you get use to using it.
Kheider 08:42, 19 October 2007 (UTC)

Deleting sections without discussion[edit]

I would like to see discussions before whole sections are deleted just because there are no citations. -- Kheider 06:27, 10 October 2007 (UTC)

The editor, Daniel Bush, made similar changes at Neptune, Asteroid, Ceres, and Small Solar System Body. He's been asked to explain these edits. --Ckatzchatspy 07:10, 10 October 2007 (UTC)

move & copy edit[edit]

Since it's not agreed that centaurs are asteroids, and not all are large (which "planetoid" implies), I moved this to "Centaur (minor planet)".

I also changed the definition of centaur in the lede. It stated that centaurs are MPs that cross the orbit of a gas giant. However, Hidalgo crosses the orbit of Jupiter and is not considered a centaur. Should it be "Saturn-Uranus crossers"? Are Neptune crossers sometimes considered centaurs and sometimes TNOs? I know the classification of a couple has changed; maybe that's the reason?

kwami (talk) 22:50, 29 September 2008 (UTC)

944 Hidalgo is listed as a centaur by JPL.
(160427) 2005 RL43 is listed as a Centaur by MPC, JPL, and DES. 2005 RL43 does not cross the orbit of either Uranus or Neptune.
(2002 PQ152) only crosses the orbit of Neptune. Both JPL and DES list it as a centaur. Thus centaurs basically have orbits that cross those of one or more of the giant planets. -- Kheider (talk) 23:27, 29 September 2008 (UTC)
Okay, the first centaur was discovered in 1920, then.
Several do not cross any planet, such as 2005 VB123 and 2001 XZ255, yet JPL classifies them as centaurs too. "Planet crosser" would seem to be a misnomer, then.
Do any have a semimajor within Saturn's and do not cross Saturn's orbit? kwami (talk) 00:24, 4 October 2008 (UTC)
Between Jupiter (q>5.5) and Saturn (Q<9) is a rough neighborhood. But 29P/Schwassmann-Wachmann and 2000 GM137 qualify. 52872 Okyrhoe is also an interesting object. -- Kheider (talk) 15:26, 4 October 2008 (UTC)
I agree that the intro needs some work. I agree that traditional centaurs basically orbit between Jupiter and Neptune, but I also believe calling them planet crosses helps the layman understand why the orbits are unstable. There will be exceptions to either version. Physical Properties of Kuiper Belt and Centaur Objects (2007) says, "The Centaur objects, with orbits that cross those of one or more of the giant planets, are thought to be the dynamical progeny of KBOs"
The MPC does not list 944 Hidalgo as a centaur, so I am not sure we should list it as the first official centaur. I am not ready to re-write history. We could list Hidalgo as the first centaur like object. I do not like 2005 VB123 because it has an orbit quality of E (error too large because only observed for 29 days). 2001 XZ255 is a good example of a centaur that is currently a non-planet crosser, but DES also lists 01XZ255 as a centaur. -- Kheider (talk) 03:38, 4 October 2008 (UTC)
Okay. The intro originally said that centaurs are planet crossers, period; I changed that to 'most' and wanted to back it up with an example. Maybe we could explain in the intro that orbits within or in resonance with Jupiter are stable (Trojans, Hildas, Main belt), as are orbits beyond or in resonance with Neptune (N trojans, plutinos, cubewanos), but that things between are unstable over long time scales and this transient population are the centaurs. kwami (talk) 05:57, 4 October 2008 (UTC)


If we're just going to make up terms, we have to define them for the poor reader, who is unlikely to be an astrophysicist conversant in the latest jargon. What in blue blazes does "dynamical lifetime" mean? And while we're at it, is there really "an unstable orbital class" of minor planets or is that just bad writing? --Milkbreath (talk) 23:58, 30 December 2008 (UTC)

Before going into a rant, it's less embarassing to do at least a modicum of checking. "dynamical lifetime" leads one rapidly to a number of explanations, including International Astronomical Union Colloquium, Zoran Knežević, Andrea Milani (2004). Dynamics of Populations of Planetary Systems: Proceedings of the 197th Colloquium of the International Astronomical Union Held in Belgrade, Serbia and Montenegro August 31 - September 4, 2004. Cambridge University Press. p. 182. ISBN 052185203X.  LeadSongDog (talk) 01:36, 31 December 2008 (UTC)
I love to rant—nobody gets hurt, do they? And I don't see how your link helps. Googling is worse than nothing, too. What you're not getting, I'm afraid, is that I don't care what it means. I do think, though, that many people who read this article will, and the article should include some way for them to find out, or, better yet, either tell them or use a phrase that's understandable on its face. I was just surfing around Wikipedia, hitting "random article" and copyediting like I do, when I stumbled upon this "centaur" business. I'm always pleased to discover a whole thing I didn't know about, and I went to copyedit when I ran into the "dynamical" wall. I've written this here in the hope that someone who knows what "dynamical lifetime" means will either tell me or fix the article. Dynamical lifetime is no help, either, by the way. I know because I tried that first. --Milkbreath (talk) 02:37, 31 December 2008 (UTC)
Yeah, there's too big a gap between the info in that article and how we're using the phrase here. Someone correct me if I'm wrong, but I understand the dynamical lifetime to be how long a dynamic system can be expected to remain stable. None of the centaur orbits are stable over the life of the Solar system, unlike, say, Earth, which can be expected to still be here in 5 Gyrs. So yeah, the centaurs are an unstable orbital class. kwami (talk) 07:08, 31 December 2008 (UTC)
Now, if you'd said Dynamical lifetime redirects to something off-topic, I'd have known what you meant. If you'd deleted the redirect there would have at least been a red link to clue us in. Anyhow, I've replaced it with an on-topic stub.LeadSongDog (talk) 20:08, 31 December 2008 (UTC)
Now we're getting somewhere. Thing is, nobody knows what a "mean motion resonance" is. And I don't delete things I don't understand. You must be at a computer, and most computers have mice, so it was reasonable of me to suppose that anyone interested in why dynamical lifetime was of no help would have clicked on the link. Let's not fight, my son. There is science to be elucidated for the masses. --Milkbreath (talk) 20:48, 31 December 2008 (UTC)
So who's fighting? Fixed the red link by piping mean motion resonance to orbital mechanics.LeadSongDog (talk) 21:27, 31 December 2008 (UTC)

The first paragraph at "THE DYNAMICS OF KNOWN CENTAURS" states, "over their dynamical lifetimes these objects diffuse". This is caused by perturbations. I do not think that orbital resonances are needed. Comets get perturbed all the time. The same source also says, "there is essentially no penetration of these objects into the main region of resonant and classical KBOs". Resonant orbits are much more stable, and thus centaurs have unstable orbits with short dynamical lifetimes. 10199 Chariklo is near the 4:3 resonance of Uranus and has a much longer estimated half-life than other more unstable centaurs. Most centaurs are not protected by a near resonance and are subject to perturbations that will not be corrected by a near resonance. -- Kheider (talk) 22:54, 31 December 2008 (UTC)

trans-Neptunian centaurs[edit]

It seems that 2007 OR10 is classified as both an SDO and a centaur. Marginal, or do we need to address this? kwami (talk) 07:58, 11 March 2009 (UTC)

Yes, I had noticed that in January. But now DES is showing it as a likely 3:10 resonance. Thanks for making me double check this. I suspect this issue is a by-product of the very preliminary orbit. The orbit is still poorly known (orbit quality code=5) -- Kheider (talk) 16:29, 11 March 2009 (UTC)


This article is shaping up nicely. Seems almost ready for FAC, I think. Serendipodous 08:14, 18 August 2009 (UTC)

Not quite ready. It needs additional citations. And citations should use consistent format (cite templates). Images also need alt text. Ruslik_Zero 17:35, 18 August 2009 (UTC)

Jove uncross'd[edit]

2004 YH32 follows such a highly inclined orbit (nearly 80°) that, while it crosses from the distance of the Main belt from the Sun to past the distance of Saturn, it does not even cross Jupiter relative to the plane of Jupiter's orbit.

Does this mean that the projection of YH32's orbit onto the ecliptic is entirely within Jupiter — or something else? —Tamfang (talk) 03:04, 7 December 2010 (UTC)

Picture description Jupiter's Trojans vs. the asteroid belt[edit]

I think the description saying "Positions of known outer solar system objects. The centaurs are those objects (in orange) that lie generally inwards of the Kuiper belt (in green) and outside the asteroid belt(pink)." From the picture it seems that the pink objects are Jupiter's Trojans, not the asteroid belt. Mr.dickens (talk) 09:03, 11 August 2011 (UTC)

You are absolutely right! Serendipodous 17:18, 11 August 2011 (UTC)


Besides Chiron, just how many centaurs were named in Greek mythology? I'd bet maybe a couple of dozen at best- nowhere near the potential "44,000" bodies in the neighborhood. CFLeon (talk) 05:05, 21 January 2015 (UTC)

Most of those 44,000 have not even been discovered, let alone have a well-determined orbit for a minor-planet number and being eligible for receiving a name. There are 297 known centaurs, of which 60 have received a number and of which just 22 have names.[1] One of these, Hidalgo, was discovered before the centaurs were recognized as a distinct class of minor planet, and hence was not named after a centaur. --JorisvS (talk) 11:15, 21 January 2015 (UTC)

Centaur classificaion[edit]

The dynamical definition of a Centaur is that the object orbits amongst the outer solar system with semimajor axis between Jupiter and Neptune and has perihelion larger than Jupiters semimajor axis. By that definition, Hidalgo is NOT a Centaur and should not be included as such. Any object with perihelion distance less than Jupiters semimajor axis is in a very unstable orbit and is not expected to last in that orbit for long. The Centaurs are a dynamical transition family between the TNOs (Kuiper Belt) and the Jupiter Family of short period comets. We call those objects crossing the orbit of Jupiter by a separate name, namely the Jupiter Crossers. I have removed Hildalgo from this article because of that. If you include Hidalgo, you need to include objects like (15503) 1999 rg3, 1998 QJ1 and many others. The JPL list is in error. See the MPC's list of Centaurs. -- jscotti(Talk) 20:23, 4 February 2015 (UTC)

Per the JPL Small-Body Database definition of a centuar, 944 Hidalgo is a centuar. I am not sure we can claim there is only one definition (use) of the term. None of the centaurs are in very stable orbits. -- Kheider (talk) 20:29, 4 February 2015 (UTC)
And therefore it should be mentioned. It could be accompanied with a statement that it is not centaur in all definitions, with a proper citation accompanying it. Removal is not appropriate, though, especially the way you have been doing it, Jscotti. --JorisvS (talk) 21:18, 4 February 2015 (UTC)
Moreover, we currently follow JPL's definition, as per the first lead sentence. This can be compared to the definition of the Kuiper belt that Wikipedia uses: excluding scattered-disc objects such as Eris. Eris is consistently not considered a Kuiper belt object, even though in some authors' definition, it would be. --JorisvS (talk) 10:23, 5 February 2015 (UTC)
Until we have more input, I have mentioned 944 Hidalgo in the Classification section. Besides now-a-days, the MPC often lists centaurs and SDOs as a single group. Now-a-days, I am not even sure where SDOs end and inner Oort cloud objects start. At least ETNOs seem to currently have a definition. -- Kheider (talk) 10:31, 5 February 2015 (UTC)
Yeah, these classifications are to some degree arbitrary. SDOs and centaurs have a common origin in being scattered from the Kuiper belt. But there are also differences, SDOs proper do not cross the orbits of any planets, whereas centaurs do. Then there are also the 'extended centaurs' crossing the orbits of one or more planets, but with a>aN. And these all blend into one another and into the Kuiper belt and into the inner Solar System.
With at least JPL considering Hidalgo a centaur, consistent with the definition in the lead, we cannot not mention Hidalgo here. --JorisvS (talk) 11:13, 5 February 2015 (UTC)

Half-Life (forward)[edit]

In the table of notable centaurs there is a field called half-life. Can anyone please explain what this means. The term with its relation to this topic is not explained anywhere in this article so it is not something that is understandable to the lay person outside of wild guesses. — Preceding unsigned comment added by (talk) 20:17, 10 July 2015 (UTC)

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