Talk:(308933) 2006 SQ372

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Untitled[edit]

The Universe Today article says that "Scientists believe the object is only 50-100 kilometers (30-60 miles) across." Despite the title of the article, this is not a minor planet.

DanDixon (talk) 19:15, 18 August 2008 (UTC)[reply]

Minor planet does not mean dwarf planet. Minor planet, AFAIK, is a denomination given to every small body orbiting the Sun. --Cyclopia (talk) 09:02, 19 August 2008 (UTC)[reply]

A Centaur?[edit]

An edit by Kheider classified 2006 SQ372 as a Centaur, basing on the classification by Marc Buie.

However, 2006 SQ372 seems not to fit the definition of centuar as from the WP article as "Centaurs orbit the Sun between Jupiter and Neptune, crossing the orbits of the large gas giant planets." - 2006 SQ372 aphelion is wildly beyond Neptune.

I undid the Kheider edit, but I want to state that the edit seems perfectly legit by itself. I just undid it to "freeze" the thing before the discussion is settled. So, is our object a Centaur, a TNO, both, or none of these? Or is the definition of Centaur wrong? --Cyclopia (talk) 16:07, 5 September 2008 (UTC)[reply]

Per wiki-definitions SDOs are suppose to have perihelion distances of greater than 30 astronomical units (AU). 2006 SQ372 is really more of a Centaur since it radically crosses the orbit of Neptune and is also under the influence of Uranus.(Nathan Kaib) -- Kheider (talk) 05:44, 6 September 2008 (UTC)[reply]
Thanks a lot, now the article really clarifies the ambiguity. Too bad natural objects do not strive to fit our discrete, comfortable classifications! :D --Cyclopia (talk) 10:41, 6 September 2008 (UTC)[reply]

It is NOT Centaur because its semi-major axis is behind Neptune. It is SDO. — Chesnok (talk) 17:23, 13 September 2008 (UTC)[reply]

I don't agree. What reference do you have that it is ONLY a SDO and is not a centaur? It comes inside the orbit of Neptune. This object blurs the definitions that are in use. DES treats it as a Centaur. -- Kheider (talk) 17:29, 13 September 2008 (UTC)[reply]
Per your edit, I would just like to say that there are 3 centaurs (Chiron, 60558 Echeclus, and 166P/NEAT) (all perihelion < 8.6AU) that are classified as Comets. Moving deleted (though perhaps useful) external link to talk page: Huge Comet Discovered. Some day 2006 SQ372 may be caught outgassing, though its current perihelion distance is likely too far from the Sun. -- Kheider (talk) 11:08, 14 September 2008 (UTC)[reply]
Asteroidal object 2006 SQ372 was NOT (yet) observed with cometary activity, it is NOT a comet[1], and that link gives us misinformation and should be deleted. Except few cases, comets classified ONLY as comets. I think, Centaurs have no official definition. There are some objects classified both as comets and asteroids (95P/Chiron, 174P/Echeclus, 176P/LINEAR). — Chesnok (talk) 14:46, 15 September 2008 (UTC)[reply]
Chesnok, could you please specify what is the problem? Kheider deleted the stuff and agrees that no one can say 2006 SQ372 is a comet, as far as I can understand. --Cyclopia (talk) 17:02, 15 September 2008 (UTC)[reply]
Now it's all right. It was one external link named "comet 2006 SQ372" and I deleted it. — Chesnok (talk) 08:58, 16 September 2008 (UTC)[reply]

Orbital period?[edit]

In the header: Its orbit takes between 22,000 and 32,000 years to complete.
In the infobox: 35607.89 a
Which one is right? Other is a range of 10,000 years and the other is exact value (significantly higher) with two decimals... 85.217.46.254 (talk) 07:25, 21 January 2011 (UTC)[reply]

Orbital parameters are epoch dependent, especially when dealing with Centaurs and Scattered disc objects that just passed perihelion and have been subject to perturbation. With a 2005 epoch the object had an orbit of about 22,000 years. It came to perihelion in 2006 and now has an orbit of about 32,000 years. Osculating elements at a given epoch are always an approximation to an object's orbit (i.e. an unperturbed conic orbit or a "two-body" orbit). -- Kheider (talk) 09:59, 21 January 2011 (UTC)[reply]
Well, then what is the 35,607 number? According to your answer, I assume the 32,000 should be the maximum of the range. Infobox number is little over 3600 years larger, over 10 percent. I think that is quite much, or what? 85.217.37.129 (talk) 02:54, 23 January 2011 (UTC)[reply]
Using a 2009 epoch, a quick and dirty 2-body solution (Sun+object) would predict an orbital period of 35,000 years. As the planets also pull on the object (n-body solution) the true orbital period will be somewhat less. -- Kheider (talk) 03:07, 23 January 2011 (UTC)[reply]
I cannot find the 35607 figure outside of Wikipedia. Does anybody have a source for it? Otherwise it should just go (and the current period estimate needs to be sourced). --Cyclopiatalk 03:36, 23 January 2011 (UTC)[reply]
It is likely a 2009 epoch. JPL is now using a 2011-Feb-08 epoch. The old jpldata was entered on 19 August 2008 using an epoch of May 14, 2008. IP 83.149.3.16 changed the period, aphelion, and added a mass on 30 September 2009. (which is ironically shortly after the last reported observation of this object.) A quick run with JPL Horizons On-Line Ephemeris System shows that using a 2009-Sep-01 epoch this object did have an AD (aphelion distance) of 2.145385313128136E+03 with "PR=1.30499E+07"/365 days=35753 years. So the edit looks like it was legit when using a 2009 epoch. If you push the Epoch out a few hundred years the aphelion and orbital period start falling much closer to the lower numbers. With a 2012 epoch this object will show aphelion around 1834AU. -- Kheider (talk) 05:52, 23 January 2011 (UTC)[reply]
Understood. I see two options 1)either we source it to some online calculator and we clarify which epoch the numbers refer to or 2)we just remove it due to it being somehow WP:OR and substitute the published range. I'd prefer 2, but both are reasonable. --Cyclopiatalk 12:51, 23 January 2011 (UTC)[reply]

I have changed the wording some. I am not sure what numbers appear unreferenced. The infobox numbers are referenced to jpldata (reference #1) with an epoch of 2011-Feb-08 (top of the blue box). The DES/Buie numbers show an epoch of 2005/09/07 Keep in mind that in ~6 months JPL will use a different epoch. -- Kheider (talk) 16:40, 23 January 2011 (UTC)[reply]

Ok, thanks. However I have a question: Is the orbital period estimate in the infobox meaningful? I mean, if it is going to change anyway, does it make sense to put it with such precision? Looks misleading to me -this is a numerical estimate but the real error is high (also due to the fact that perturbations on such long orbits are quite likely). Doesn't it make more sense to put the range published in the paper? --Cyclopiatalk 18:32, 23 January 2011 (UTC)[reply]
I have added the "Solar Systems Barycenter" as the primary reference point/value since it is much more stable. Is the heliocentric orbital period meaningful or misleading? Hard to say since it is correct for the 2011 heliocentric epoch referenced. Every orbit will vary with the epoch used, it is just more obvious with an object that has an extreme eccentricity. I have left the value in the infobox as (Heliocentric 32347 yr) so that the reader knows that we are aware of the "alternative" value. -- Kheider (talk) 15:17, 24 January 2011 (UTC)[reply]
My question was of a more general order. What we're doing is, if I understand it (I'm a researcher but not an astronomer; correct me if I'm wrong), extracting a value from a fitting procedure. WP:OR concerns aside, there's two things. First, basically, what are the error bars of the fitted value? Second, and most importantly, if different fits give substantially different values depending on the epoch, this means that we have, practically, quite a large uncertainity, even if each fit gives us a very precise value. So I don't see a value detailed down to year precision as a meaningful value -what practically we know is the range of the orbital period. I hope to have been clearer. --Cyclopiatalk 15:44, 24 January 2011 (UTC)[reply]
I'm not an astronomer either. But remember that the calculated fit is for an unperturbed orbit between only the center of Sun and the object. It does not consider any of the gas giants so it is only an approximation by definition. The "real-world" error bar would be a function of the epoch and how close the object is to the gas giants, but since the approximation is a 2-body solution, the heliocentric solution (as calculated) is correct. The two-body solution using the Solar System barycenter + the object is much more reliable since the barycenter of the Solar System includes the mass of all the planets. Obviously the larger the mass pulling back on the object, the shorter the orbit will be. -- Kheider (talk) 16:25, 24 January 2011 (UTC)[reply]
The simple answer is that the object does not have orbital period. It moves along an unclosed chaotic trajectory, which is not an ellipse, so such thing as orbital period (and other standard orbital elements) is meaningless for it. (Strictly speaking all Solar System objects move along unclosed trajectories, but corrections are usually small.) So, the field in the infobox should be left empty. Ruslik_Zero 19:28, 24 January 2011 (UTC)[reply]
That's, strictly, very true, but just to give an idea of the time scale of the recurrence of the object in the closer regions of the Solar System I see nothing wrong in giving a time range (say 20.000-30.000 years) to the reader in the infobox, and then discussing the issue in the article text. --Cyclopiatalk 20:10, 24 January 2011 (UTC)[reply]

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