Talk:Sedna (dwarf planet)/Archive 1

Misc
I notice that the astronomer Micheal Brown's home page contains a graph showing pollution where he lives in California. He might be interested to know that if he buys a new SAAB, and uses it in Los angeles, it is claimed by Jeremy Clarkson in today's Sunday Times - on the very same day that it announces the discovery of his new 'planet' - that 'the stuff coming out of the back of a Saab turbo's exhaust is actually less harmful than the air that went in at the front. Like a giant vacuum cleaner, in other words'. Anyone know if that's true? Matt Stan 22:13, 14 Mar 2004 (UTC)


 * That sounds highly implausible. :-) Evercat 22:19, 14 Mar 2004 (UTC)

Drat, looks like someone may have realized that Mike's page on Sedna was getting a lot of hits for something that wasn't supposed to have been announced yet. :) The external link is now giving a 404. Hopefully it will come back online after the press conference, there was a ton of great information there. Bryan 09:04, 15 Mar 2004 (UTC)
 * Working now MPF 20:51, 15 Mar 2004 (UTC)

Announcement 15 March
The news briefing is at 2004-03-15t13:00-05:00 http://www.nasa.gov/home/hqnews/2004/mar/HQ_n04040_solar_object.html

I guess I should remove the link to Chad's page, tho it hurts to only have news reports out there when that page (which Mike also had (neither linked to it from their homepages)) has such great info. - Jeandré, 2004-03-15t09:49z

To be pedantic, the Sun would only be blocked this way if your eye's pupil (or camera's aperture) was no larger than the pin head: The sun appears so small from Sedna that it could be completely blocked out with the head of a pin, according to Brown. I guess he means the Sun subtends an angle smaller than that of a pin head held at arm's length. Wikibob 01:50, 2004 Mar 16 (UTC)

New?
Is this the same as 2004 DW? -- The Anome 13:42, 14 Mar 2004 (UTC)


 * I don't think so. Still, this hasn't been much reported yet, Google news doesn't turn up much... Evercat 19:07, 14 Mar 2004 (UTC)


 * I got some information from http://www.theaustralian.news.com.au/common/story_page/0,5744,8968352%255E29098,00.html but don't know how accurate it all is yet. Presumably there will be a flurry of updating on Monday when the press conference is. Bryan 19:17, 14 Mar 2004 (UTC)

What is it?
Some mention should be made of its highly elliptical orbit... Evercat 01:01, 15 Mar 2004 (UTC)

Or http://www.gps.caltech.edu/~mbrown/sedna/


 * Sedna is starting to sound a lot like a scattered disk object to me. Bryan 01:04, 15 Mar 2004 (UTC)

The news item actually said that NASA is going to make its announcement tomorrow. Matt Stan 01:11, 15 Mar 2004 (UTC)

Can I suggest (astronomical object) instead of (object)? - the latter is a bit.. amibguous. Ed g2s 02:01, 15 Mar 2004 (UTC)


 * Or Sedna (planetoid)? Evercat 02:16, 15 Mar 2004 (UTC)


 * I'd suggest Sedna (plutino).&mdash;Eloquence


 * On second thought, this may be inaccurate given the definition provided at plutino.&mdash;Eloquence 04:51, Mar 15, 2004 (UTC)


 * Yes the Jewitt article cited there requires a very specific orbital diameter to be called a plutino. Joelwest 13:39, 20 Mar 2004 (UTC)

re previous attempts to define "planet" : "[Michael] A'Hearn and others say it's reasonably likely that another object as big or larger than Pluto will be found orbiting the Sun even farther out. What happens then? Start the fight over again."

One definition of a planet is "any body in the solar system that is more massive than the total mass of all of the other bodies in a similar orbit.". Another "made round by its own gravity". Also, "anything as big or bigger than Pluto." - Jeandré, 2004-03-18t09:04z --- Dan Green's page says that the whole "planet" vs. "not a planet" debate is a myth of the popular press that is long discredited in astronomy. The real question is classifying major planet vs. minor planet, and a case can be made that Pluto and Sedna are both minor planets. Joelwest 13:39, 20 Mar 2004 (UTC)

Planetoid?

 * FYI some people seem to be calling Pluto also a planetoid. -- Paddu 14:56, 17 Mar 2004 (UTC)
 * Had Pluto been discovered today, it would most likely not be called a planet. According to the IAU, it is one, though.
 * That may very well be the case - but the point is - Pluto's classifaction is the subject of debate. It is not agreed whether it is a Planet/Planetoid etc. The point of the words in brackets is for disambiguation, not definition (that can be discussed in the article). Sedna (AO) distinguishes it well enough from any other Sedna without making a decision about its classification. Ed g2s 18:49, 17 Mar 2004 (UTC)

12 or 16?
Note discrepancy over official name. Brown's web site says 2003 VB12, but the http://www.spitzer.caltech.edu/Media/releases/ssc2004-05/quickfacts.shtml, bbc, etc say VB16. NealMcB 01:42, 2004 Mar 16 (UTC)


 * This BBC News article also says VB12. Except for your link I can find no other site which calls it VB16 (where at the BBC?). &#8212; Jor (Darkelf) 01:52, 16 Mar 2004 (UTC)


 * This link said VB16 when it was indexed by Google, but now says VB12. VB16 was probably an error. &#8212; Jor (Darkelf) 01:56, 16 Mar 2004 (UTC)

Voting
Vote for the article name you support most by typing the following beneath it: #~
 * Poll closes 04:00, March 21, 2004 (UTC)

2003 VB12 (2)
 * 1) Sedna
 * 2) Anthony DiPierro

Sedna (astronomical object) (7)
 * 1) Bryan 05:36, 16 Mar 2004 (UTC)
 * 2) Minesweeper 10:19, Mar 16, 2004 (UTC)
 * 3) MPF 14:18, 16 Mar 2004 (UTC) This covers all eventualities
 * 4) Anthony DiPierro 15:28, 16 Mar 2004 (UTC) Planetoid sounds stupid. Anthony DiPierro 15:28, 16 Mar 2004 (UTC)
 * 5) Ed g2s 18:01, 16 Mar 2004 (UTC) Planetoids aren't very well defined. The article says they are more like asteroids and are "much smaller than planets". Sedna is similar in size to Pluto. From what I've read, not even the experts in the field can decide on what each definition means - and therefore what Sedna is. Until they (or WikiProject Astronomical Objects) can come up with some definitions, AO is the only sensible suggestion. Anything with planetoid in it must be ruled out.Talk:Sedna_(astronomical_object)
 * 6) ChrisO 14:51, 17 Mar 2004 (UTC) Support, for the reasons given above by Ed g2s.
 * 7) Michael Warren 15:38, Mar 17, 2004 (UTC).

Sedna (planetoid) (15)
 * 1) RickK | Talk 03:59, 16 Mar 2004 (UTC)
 * 2) Davodd 03:58, Mar 16, 2004 (UTC)
 * 3) Bryan 05:36, 16 Mar 2004 (UTC) Either this or (astronomical object) is quite sufficiently vague, IMO, and fits with our disambiguation standards. But whatever gets chosen, can we please stop moving the article around every few hours? :)
 * 4) Seth Ilys 06:11, 16 Mar 2004 (UTC). A uniform article naming system for astronomical objects needs to be established, preferably through WikiProject Astronomical Objects.
 * 5) Jeandré, 2004-03-16t10:04z.
 * 6) Minesweeper 10:19, Mar 16, 2004 (UTC)
 * 7) &#8212; Jor (Darkelf) 11:42, 16 Mar 2004 (UTC) Best of the available options for now. Once more Oort objects are discovered move to Sedna, Oort Cloud object (with final name replacing Sedna).
 * 8) andy 14:54, 16 Mar 2004 (UTC) (until IAU comes up with a naming scheme for such an object, or gives it the final name)
 * 9) Timwi 15:22, 16 Mar 2004 (UTC) (good idea, better than astronomical object)
 * 10) Dmn 22:20, 16 Mar 2004 (UTC) Planetoid is an excellent word to use
 * 11) Paddu 14:56, 17 Mar 2004 (UTC)
 * 12) Rmhermen 16:27, Mar 17, 2004 (UTC)
 * 13) Michael Snow 18:13, 17 Mar 2004 (UTC)
 * 14) Texture 18:19, 17 Mar 2004 (UTC)
 * 15) Joelwest 13:32, 20 Mar 2004 (UTC) after all, that's what its discoverers use
 * 16) Ryan_Cable 12:11, 25 Mar 2004 (UTC)
 * 17) WilliamKF 22:25, 18 September 2006 (UTC)

Sedna (astronomy) (1)
 * 1) Merovingian ↕ Talk 10:30, Mar 17, 2004 (UTC) - I don't know about you, but I like simplicity.

Debate
You may want to reconsider this. As of today, there is no sufficient data to classify this object. Although its more appropiate name would be Sedna, Planetoid 2003 VB12. As far as we know, it may be named as Sedna, Inner Oort Cloud object 2003 VB12, Sedna, Oort Cloud object 2003 VB12 or even Sedna, Trans-Neptunian object 2003 VB12. Obviously, Sedna is a planetoid and a Trans-Neptunian object, but it may or it may not be an Oort Cloud object or an Inner Oort Cloud object. --Maio 05:24, Mar 16, 2004 (UTC)


 * If it's obviously a planetoid, then what's wrong with calling it (planetoid) for now since there aren't any other significant planetoids named Sedna for it to be confused with? We can move the article one last time once its classification becomes better defined, if necessary. Bryan 05:38, 16 Mar 2004 (UTC)


 * The problem is that the object could be classified as two things at the same time, a planetoid and a TNO. But since it has been called more as a planetoid, I beleive that it is more appropiate to rename it to Sedna, Planetoid 2003 VB12 to make it detailed, precise, and human-readable at the same time.   &mdash;Michael | Talk 14:23, Mar 16, 2004 (UTC)


 * Must the 2003 VB12 be in the name? Not only is a numeric string like that imnsho very ugly, but the object is also very unlikely to be ever called both Sedna and 2003 VB12 at the same time. Sedna (planetoid) with a redirect from 2003 VB12 would seem best of both worlds. &#8212; Jor (Darkelf) 14:34, 16 Mar 2004 (UTC)


 * Copy/paste from the same article: By the IAU naming conventions for asteroids, the official name is 2003 VB12, until its orbit can be established well enough. Only then do the discoverers have the right to suggest a name. So, IMHO, at the moment it should include it. Perhaps later, when the name is officially settled down, it could be moved to Planetoid Sedna.   &mdash;Michael | Talk 14:45, Mar 16, 2004 (UTC)


 * But by then it will have a asteroid number (at least if the IAU considers it an asteroid as well), and then by the naming standard for asteroids it'd have a name like 90000 Sedna. But till then Sedna (planetoid) should be the best and shortest alternative. andy 14:54, 16 Mar 2004 (UTC)


 * I think they know enough to call it a planetoid since the size is much bigger than a meteorite and about half the size of the smallest major planet, Pluto. Being both a planetoid and TNO is not a problem: most of the planetoids outside the Asteroid belt are TNO's. And if you don't classify comets as TNO's, all the TNO's we can see so far are planetoids. Joelwest 16:26, 20 Mar 2004 (UTC)

Other Suggestions
How about moving this to Sedna and moving the goddess page to Sedna (goddess) or whatever? That's basically the situation with Quaoar... Evercat 12:37, 16 Mar 2004 (UTC)
 * Not sure if that is proper, as Sedna is not yet its name. &#8212; Jor (Darkelf) 14:34, 16 Mar 2004 (UTC)

Farthest from the sun?
"...is farther from the Sun than any previously known object in the solar system."

Not for several months, now. Voyager 1 is now 91.4 AU from the sun, and Sedna is more like 90.3 AU according to Brown's paper. The article wording was "Its discovery was the furthest distance at which any  object in the solar system has ever been observed" (which still needs rewording...). So as for the time of discovery and the geocentric viewpoint, the ephemeris shows Sedna at 88.63 AU from earth when discovered (right at opposition) on Nov 14. Voyager 1 was on the far side of the sun from us then so despite moving at 3.625 AU/year, it was further from earth than Sedna then also. So I added the word "natural" to the article. I'm not sure which was further from the sun at the time of discovery - probably Sedna. NealMcB 18:30, 2004 Mar 23 (UTC)
 * So the current sentence remains correct. "natural" object -not any object and "furthest observed", not furthest object. (Of course, we can't observe Voyager 1) Rmhermen 18:41, Mar 23, 2004 (UTC)


 * I agree the sentence is correct given the addition of "natural". But Voyager 1 certainly can be observed, at radio wavelengths.  It may have recently discovered the heliopause, and we expect to talk to it for another 2 decades when it is, I guess, 150 AU away! NealMcB 16:40, 2004 Mar 24 (UTC)

Hmm, what about comets like Hale-Bopp, for instance? Is that not considered part of the solar system? Is it because of the plane? What about other Oort cloud objects which have a more even plane? Anthony DiPierro 14:04, 16 Mar 2004 (UTC)


 * It is my understanding that this is the only known Oort cloud object but I can't explain about the comets. Probably it is the furthest distance anything has been detected at, comet being too small to see at that distance with current technology. Rmhermen 15:01, Mar 16, 2004 (UTC)


 * Hale-Bopp has an aphelion of 372 AU but it will take over 1000 years from now to get there (Sedna's is 850 AU). Maybe no known comet is currently past 90 AU? Rmhermen 15:21, Mar 16, 2004 (UTC)


 * Probably both farthest detected object, and currently farthest known? Should we note that in the article and hope that someone who's sure fixes it for us? Comet Halley holds the record distance for a comet observation: 28 AU. Comet Hale-Bopp has an aphelion of 457.583 AU. "aphelion, Comet Hyakutake will be about 800 AU's". "The aphelion (most distant point from the Sun) of a long-period comet may be more than 50,000 astronomical units away." - Jeandré, 2004-03-16t15:42z


 * Hmm, OK. I thought Hale-Bopp got farther than that.  All that talk about the Oort cloud being 50,000 to 100,000 AU away and everything.  Anthony DiPierro 15:45, 16 Mar 2004 (UTC)
 * You must have missed the creation of the "new" and much closer Inner Oort cloud yesterday! I would say Sedna has the furthest detection claim for any object and the furthest perihelion. I am not sure that it is the current furthest known object. It is not clear whether Mike Brown's map of solar system objects' positions includes comets. Rmhermen 15:52, Mar 16, 2004 (UTC)
 * Actually, that's what confused me. If Sedna is only part of the "inner" Oort cloud, how could it be the furthest known object.  Either the "outer" Oort cloud is not known, or it's not part of the solar system (apparently it's the former). Anthony DiPierro 16:02, 16 Mar 2004 (UTC)


 * Yup, no outer Oort cloud objects have been discovered yet. The Oort cloud had only been predicted in theory until Sedna came along and although it looks like the theory may need tweaking, it's still pretty generally accepted. Bryan 17:48, 16 Mar 2004 (UTC)


 * Acording to Heavens above, C/1999 LINEAR S4 is currently more than 10 AU from the sun, but has an aphelion of 1 892.19 AU. So while Sedna is the farthest detected TNO, and may currently be the farthest of all known TNOs, LINEAR-S4 will eventually be farther than Sedna. I'm sure there are other comets with even greater aphelions, tho none of them may currently be beyond 90 AU. If a comet was calculated to have most of its orbit outside the Edgeworth-Kuiper belt, then Öpik-Oort cloud (which includes both inner (disk roughly on the ecliptic) and outer (the spherical cloud)) objects have been discovered before Sedna, no?. - Jeandré, 2004-03-17t11:09z


 * Marc W. Buie from Lowell Obs has 2000 OO67 with an aphelion of >1000 AU. Is this the first discovery of a non-comet inner OOCO? - Jeandré, 2004-03-19t09:56z
 * That objects perihelion is at 20 AU while Sedna is at about 76 AU. I doubt they would be considered in the same class, however stay tuned the definition are still changing. Rmhermen 14:50, Mar 19, 2004 (UTC)

I thought when they said "farthest from the sun," they were refering to average distance, or semi-major axis. However, Sedna's range from 76 to 900 AU will give it a closer average distance than C/1999 LINEAR S4. Another way to check which has farthest average distance is to look at their periods (Kepler's third law $$P^2\sim a^3$$); whichever has the longer orbital period is further away on average. Regarding Oort cloud objects, I thought the comets were all part of it? --zandperl 17:05, 17 Mar 2004 (UTC)


 * They are theorised to be, but I don't believe any have ever actually been observed 'out there', only in-system. -- Michael Warren 17:09, Mar 17, 2004 (UTC)

Some comets are thought to originate in the Kuiper Belt. Others, with a higher inclination and longer periods, are thought to originate in the Oort cloud. Some, like Halley's comet, which has a high inclination and a short period, could really have originated from either, but was thrown off its original path by later interactions. According to WP, it's came from the Kuiper Belt. Presumably we have observed comets from farther away, but it's hard to give conclusive evidence when the periods are so long. Anthony DiPierro 17:14, 17 Mar 2004 (UTC)

The idea is that the Kuiper Belt is in line with the plane of the planets, but the Oort cloud is a sphere. But now, according to the new theories (not sure how new), there is an inner oort cloud which extends in a plane to the actual Oort cloud. This part I'm still not sure of exactly what the theory is. I never learned it in my astronomy classes a few years ago. Anthony DiPierro 17:20, 17 Mar 2004 (UTC)


 * I never learned it in my astronomy classes a few weeks ago, so I wouldn't think the professionals are quite sure just yet... :) -- Michael Warren 17:30, Mar 17, 2004 (UTC)

The article says "Its discovery was the farthest distance at which any natural object in the solar system has ever been observed. ... At its discovery, it was about 90 AU from the Sun, approaching perihelion." Is this still true? I believe 2003 UB313 was 96.928 AU when it was discovered on January 8, 2005. See http://neo.jpl.nasa.gov/orbits/2003ub313.html  -  Mark Mathu July 30, 2005


 * No it's not, thus the update notice. I haven't bothered to rewrite; perhaps something along the lines of 'was the farthest when discovered' would be appropriate. kwami 06:19, 2005 July 31 (UTC)

Reason to restore photographic image
I feel like with all of the artist's renderings (which may or may not be accurate), we should include at least one *real* picture of the object, and so I've restored the photographic image with Sedna as the tiny dot. It's the most meaningful of all the images present to *me*, and I think it will be to other people as well... - Seth Ilys 03:32, 16 Mar 2004 (UTC)


 * I don't care if the picture is on the article or not, as long as the other 3 are in it. The reason why I removed it is because, to the general public, that image is just a bunch of dots with no particular meaning. Basically, it is something that any artist can produce with Photoshop by using light effects. (regardless if it is an official image) --Maio 03:56, Mar 16, 2004 (UTC)

"...may or may not be accurate" - what nonsense. The painting DOES NOT BELONG: it is pure speculation and wouldn't even qualify as a "best guess". Usually, our speculations fail to encompass the spectacular diversity of our universe.[anon]

In-progress infobox


I moved the image outside of the table so that it can be used as a thumbnail and therefore provide an intuitive link to a larger version. &mdash;Michael | Talk 14:40, Mar 16, 2004 (UTC)


 * I would personally prefer the discovery image (the 2003-11-14t06:32z photo rather than the one with the circle, since the circle seems to have 2 objects in its centre) above the table until Hubble can give us something more substantial. What arguments are there for the use of the artistic impression at the most prominent position on the page? - Jeandré, 2004-03-17t10:30z

Pics included - query
Are the various artists impressions and photos included here and under Quaoar, etc., not copyright? Has permission for their use on a free access site (from where they can, and will, be lifted by other parties and used without acknowledgement) been granted? - MPF 14:18, 16 Mar 2004 (UTC)


 * NASA images are public domain. But JPL-Caltech images aren't necessarily.  Was this image made by NASA or JPL-Caltech? Anthony DiPierro 14:42, 16 Mar 2004 (UTC)


 * Refer to about the images presented in this article. NASA can't restrict access to the general public, but they can for commercial purposes.    &mdash;Michael | Talk 14:50, Mar 16, 2004 (UTC)


 * That link doesn't work. Anthony DiPierro 14:51, 16 Mar 2004 (UTC)


 * Works for me right now. It was down a few hours ago.   &mdash;Michael | Talk 15:30, Mar 16, 2004 (UTC)


 * OK, it's up. I'll look into it.  Asking around on IRC, someone said that while images created with US taxpayer money are public domain, the US government can have copyright transferred to it.  But I can't find any direct citations which back any of this up.  Anthony DiPierro 15:51, 16 Mar 2004 (UTC)


 * Well, it's quite belated, but here it is: "A 'work of the United States Government' is a work prepared by an officer or employee of the United States Government as part of that person's official duties." "Copyright protection under this title is not available for any work of the United States Government, but the United States Government is not precluded from receiving and holding copyrights transferred to it by assignment, bequest, or otherwise." - Title 17, chapter 1, 101 and 105. anthony (see warning) 01:59, 7 Apr 2004 (UTC)

Possible moon
This article (BBC) says Sedna might have a moon. WooHoo. --Phil | Talk 16:47, Mar 17, 2004 (UTC)


 * See Sedna (astronomical object) - it's already in the article. andy 19:55, 17 Mar 2004 (UTC)

Red planetoid in Oort cloud
I don't see any reference to the red color of the planetoid in this article. I'd add that in myself but I couldn't find a good place for it. Has it been confirmed that Sedna is in the Oort cloud? That seemed to still be in disputed.

- Texture 18:21, 17 Mar 2004 (UTC)


 * Quote from M. Browns webpage: From observations at the 1.3-m SMARTS telescope in Chile, we do know that Sedna is one of the most red objects in the solar system -- almost as red as Mars. andy 19:57, 17 Mar 2004 (UTC)

It's not even confirmed that there is an Oort cloud. The whole thing is currently just theory. Anthony DiPierro 19:50, 17 Mar 2004 (UTC)

Article Naming
Should this be moved to 2003 VB16 now, as that's the official name? Sarge Baldy 13:09, Mar 19, 2004 (UTC)


 * No, official name is 2003 VB 12 - see the discussion above why 16 is wrong. But as the name Sedna has been so much promoted by the media moving it to that name would create more confusion. See also the article naming poll above. andy 13:14, 19 Mar 2004 (UTC)

http://news.bbc.co.uk/2/hi/uk_news/magazine/3515658.stm

copy & paste move?
Why has this article been moved by copy&paste rather than moving? User:Sedna is not the only contributor to this article. &mdash; Jor (Talk) 15:54, 20 Mar 2004 (UTC)


 * Furthermore, the poll is still ongoing. If it is decided the article must be moved it should be done by a sysop who can keep edit history, not by some over-eager editor destroying edit history. &mdash; Jor (Talk) 16:02, 20 Mar 2004 (UTC)

Jupiter
I removed this from page: Studying theories of the Solar System early formation mechanisms indicates that many objects would have been ejected by Jupiter and the other giant planets very early after the formation of planets, during the early bombardment phase of Earth's history. Sedna is possibly our best candidate for a detection of one of these well travelled objects, as it is in an orbit not easily explained without perturbation; Models produce nearly circular orbits, highly eccentric orbits (and Sedna's orbit is of cometary eccentricity) have to be produced by perturbation or partial ejection.

If you read the original discovery paper (available through the Mike Brown's page link in article, you find that this theory was rejected as the orbit is far too large to have been caused by Jupiter. Of course it may still be open to other interpretations. Perturbation is still the key but they are talking globular cluster interactions. Rmhermen 13:55, Mar 21, 2004 (UTC)

Moving per vote to Sedna (planetoid)
Per the vote, I am moving this article to Sedna (planetoid) - Texture 16:56, 25 Mar 2004 (UTC)

Trimmed references
Per the suggestion from Jeandre', I removed some of the references to the less technical news articles. If people find this excessively deletionist, feel free to revert --- I won't be offended. --- hike395 22:20, 7 Apr 2004 (UTC)

True or false??
True or false?? Sedna is the tenth planet from the sun. 66.245.104.154 02:18, 10 Apr 2004 (UTC)
 * True, but only for certain definitions of planet. - Fennec 02:25, 10 Apr 2004 (UTC)
 * False, for other definitions of planet. :) Bryan 04:22, 10 Apr 2004 (UTC)
 * Almost certainly false for any definition. Rmhermen 12:31, Apr 10, 2004 (UTC)
 * Absolutely False! J P 21:54, 16 January 2006 (UTC)
 * My opinion...I think it should be a planet...
 * False. By any and every conceivable definition.  Pluto/Charon and the large plutinos, as well as Quaoar, and Eris are all in line in front of it anyhow.  Sedna is much more comet-like at least orbitally.  Even 1 Ceres has a better reputation, so let's put this to rest now.  69.136.238.165 02:55, 14 September 2006 (UTC)

Pinhead comment
This parenthetical was just added by an anonymous user:


 * According to Brown, the Sun appears so small from Sedna that it could be completely blocked out with the head of a pin held an arm-length away (while it's certainly true that the sun's apparent size as seen from Sedna is smaller than the apparent size of the pin hed at arm-length, a human would still see the sun because both the human pupil and the sun are larger than a pin head).

Uh, what? The Sun's actual size is irrelevant, Brown was merely talking about its apparent size. The size of the pupil is indeed relevant, but it merely puts additional constraints on how small the Sun would have to appear to be blocked out by a pin head, it doesn't make it impossible as far as I can tell. But since I haven't done the math on this, I'm hesitant to just revert - it could well be that Brown is wrong and this parenthetical is just poorly worded. Anyone have input, or a source on Brown's comment? Bryan 00:51, 14 May 2004 (UTC)


 * The Sun's size is relevant, but not sufficient to determine whether it's blocked out. If we consider the Sun's distance to be infinity compared to the pinhead's distance, then as long as the pinhead is smaller than your pupil, the Sun will always be visible, even if it is tiny. It's difficult to word the conditions without drawing pictures though. If your pupil is infinitessimally tiny, then Brown's comment is correct, otherwise your pupil's diameter, the pinhead's diameter and distance, the Sun's diameter and its distance are all relevant. What one would see (with a proper solar filter to save your sight) is either a blurred image of the pinhead with the Sun in focus around it, or a blurred image of the Sun with the pinhead blurred inside it. Maybe a better, but not 100% comprehensive, rephrase could be "... a human would still see the sun because the human pupil is larger than a normal pin head." -Wikibob | Talk 10:29, 2004 May 14 (UTC)


 * The solution is to sidestep the issue by simply noting that the Sun looks smaller than the pinhead, without mentioning blocking. -- Curps 14:04, 14 May 2004 (UTC)


 * I removed the sentence completely; we don't need some arbitrary comparisons in some arbitrary asteroid articles just because the discoverer made some comment (which was wrong! - at least in the way it was quoted) in an interview. 193.171.121.30 00:54, 6 Dec 2004 (UTC)

Sedna's naming
Sedna has indeed officially received its name in the latest batch of new names (MPEC 2004-S75) despite some controversy on the announcement proceedings. Asteroid lists on the Minor Planet Center site weren't updated. Jyril 15:45, 28 Sep 2004 (UTC)

Inconsistencies and inaccuracies in this article
The orbital period is given as 4108714.108 d which equals 11249.28639.. years while elsewhere it states 11487 years. Figures should not be given with vast numbers of digits precision when they are so uncertain, and consistent figures should be used. The diameter is given as 1180-1800 km and then translated as 730-1470 miles. In fact 1800 km = 1120 miles so something is badly wrong. Under orbital characterists the distance is given as 76.1 to 942 AU (elliptical) and elsewhere in the table as 76.032 to 928.048 AU. Again, consistency would help with precision kept to a realistic value. User:RayTomes 7 May 2005.

Sedna good target for mission
If Sedna spends a great deal of time beyond the heliopause, would it not record brushes with supernova within some hundreds of LY, and keep a record if such effects in a kind of geological layering of cosmic rays and radiation impacts like the earth bound ice sheets record information on dust, temperature and such. Perhaps a more interesting place to go than Pluto which may have been remade with a significant impact to create Charon as I've seen suggested?

You've made a good point, and perhaps in a few years the article can add information about a speculative mission to Sedna. The extreme redness of Sedna could indicate some very unusual things, too countless to speculate, but some include ejection from the inner solar system; ejection from a different system into ours, etc. But more likely than not, there's something still more massive than Enlil (2003 UB313) lurking around that is responsible for Sedna having been scattered to this unusual orbit. In any event, getting out there and landing something on Sedna in a future generation could be very informative. --Sturmde 01:07, 22 August 2005 (UTC)


 * Enlil? I found no match for this name.  2003 UB313 is now officially known as 136199 Eris; is that what you meant?  At any rate, even detailed spectroscopy of Sedna's surface could yield some insights.  Small and distant target for a landing mission though, most likely a flyby.  69.136.238.165 02:55, 14 September 2006 (UTC)

damocloid asteroid?
Should 90377 Sedna be classified as a "damocloid asteroid"? --Hello World! 04:30, 2 August 2005 (UTC)
 * No, damocloids visit the inner Solar System, and have orbits typical to long-period comets. It very likely that they are dormant comets that have lost most of their volatile material and because of that appear asteroid-like.--Jyril 08:39, August 2, 2005 (UTC)

11th planet?
no.


 * See above, not even close. 69.136.238.165 02:55, 14 September 2006 (UTC)

Moon? Planet a not?
People say that Sedna is not considered a planet just because it does not have a moon... I think because of this, Brown say that Pluto should not be a planet...

However the truth is...all planets with solid surface has no moon (except for our Earth)

Mercury, Venus -> no moon...

Earth -> don't know where the moon came from...

Mars -> captured asteroid objects

Pluto -> captured kuiper object —The preceding unsigned comment was added by Ragnaroknike (talk • contribs) 09:39, 20 July 2006 (UTC)


 * Earth's moon's creation theory: Giant_impact_hypothesis. Sedna's and other's status as planets will be decided when IAU defines it in September, although I don't think anyone thinks Sedna is a planet (more of a large comet IMO). Also, please remember to sign your comments. DanPMK 10:24, 23 July 2006 (UTC)

I'm not clear why Sedna is considered less certain to qualify as a pluton than Xena. Is it because we don't know how round it is? HenryFlower 21:03, 18 August 2006 (UTC)


 * Well, it's not a plutino or a KBO since it's so far out. Eris (2003 UB313 "Xena") is in a resonance with Neptune (17:5) but Sedna is so distant it is unlikely to be even influenced by planetary orbits.  So classing it with Pluto-prototypes would not be proper.  69.136.238.165 02:55, 14 September 2006 (UTC)

Is it now a candidate PLANET (not just a dwarf planet)?
The definition now adopted says that something is a planet if it has cleared the neighbourhood around its orbit. Sedna looks to be outside the Kupier Belt even at its closest approach. A few small object would not count - Jupiter has its 'Trojans' etc.

Of course Sedna is suspected of being the first of a large class of such objects. But if their orbits did not overlap, that would still count.

(Of course no one has yet proved that it is spheroid, though it seems too big to be anything else.) --GwydionM 18:48, 24 August 2006 (UTC)


 * Thank you for noticing this. You seem to be the only person except me who's done so.  Its orbit is indeed cleared, and it's almost certainly round, and this makes it a planet by the new definition.
 * I'm sure the people who created that definition didn't *want* Sedna to be a planet, though, and won't bother considering it as one. Perhaps they'll say something like 'Sedna doesn't count because although Sedna's orbit is cleared, Sedna didn't do the clearing'.
 * Unfortunately putting this in the article is OR. Ken Arromdee 14:49, 26 August 2006 (UTC)
 * Yes, that would obviously be original research, and very substantial research at that. There is simply not enough information yet about whether other Sedna-type objects exist on similar orbital paths yet. It will take some time to discover anything else that might be out in that range. When writing articles on celestial bodies with 10,000+ year orbits, patience is called for. Regarding "Sedna looks to be outside the Kupier Belt even at its closest approach": that is a matter of some dispute in the scientific community; we don't really know the extent of the Kuiper Belt or the Oort Cloud yet.  Regarding "Its orbit is indeed cleared", there is simply no evidence one way or the other about that.Derek Balsam 15:00, 26 August 2006 (UTC)
 * It would be exceedingly unlikely that Sedna is only such body. What comes to its Oort cloud membership, it probably is far too close to Sun even at aphelion. I'm quite convinced that it represents a yet-to-be-found population of intermediate objects between the Kuiper belt and the Oort cloud.--JyriL talk 15:11, 26 August 2006 (UTC)

.

Refs
Some of the "external sites" are the actual references to be quoted in the article; some are now obsolete news to be removed. Cleanup required, I believe. Current refs (scientific papers) were missing; I added a few but the article need to be refreshed IMHO. Eurocommuter 13:17, 16 September 2006 (UTC)
 * The objective of is precisely that, find a new ref. For example the paper it comes from, not necessarily the old article from Planetary Society. Eurocommuter 14:14, 16 September 2006 (UTC)

I didn't look, but I'm assuming the statement supported by the old news article? If so, it's a fair temporary ref until a better ref is found. fact is for statements that have no reference at all. Also, when the Planetary Society 404 ref was deleted, a sentence of content and a second (live, not 404) ref to NewScientist were also deleted. The fact tag was then added to the phrase that the NewScientist ref had supported. Gimmetrow 15:01, 16 September 2006 (UTC)
 * My apologies; indeed, unintentionally I deleted more than I wanted. My intention was to find and replace 404 with the original scientific paper(s) for the same statement. Regards Eurocommuter 15:19, 16 September 2006 (UTC)

Replace image with HST image
I think a better more representative image of Sedna would be the cropped HST image1 in the article2. Should someone replace Image:Sedna-NASA.JPG? -- Kheider 18:44, 1 November 2006 (UTC)

Albedo
If 90377 Sedna has a much redder color index plot (1.24,0.78) than 20000 Varuna (0.93,0.64), and Varuna has an albedo of 0.04, why does Sedna have its albedo listed as ">0.2?"? -- Kheider 08:32, 8 November 2006 (UTC)
 * Because there has been no detection of Sedna in the thermal IR. That sets an upper bound on its size and a lower bound on the albedo.  Color doesn't enter into it: a redder surface doesn't necessarily have a lower broad-band albedo. In an extreme case, my red shirt has an albedo of say ~0.4 and is redder than either Sedna or Varuna. Michaelbusch 18:05, 8 November 2006 (UTC)

History of Sedna's Orbital Period
10,500 01:37, 15 March 2004 11,487 00:17, 6 April 2004 64.228.80.85 11,249 23:51, 27 January 2005 Urhixidur 12,050 00:43, 17 January 2006 24.201.139.114 12,059 12:40, 13 August 2007 JamesFox Lowell DES

Which is considered better Lowell DES or Horizons? DES gives the current 12,059 and Horizons shows 10666.77±119.3. -- Kheider (talk) 04:39, 19 November 2007 (UTC)

Planet
At best Sedna is likely less than 42% the mass of Eris. Sedna could have a radius of only 590km with a density similiar to Tethys (moon) at 0.97 g/cm^3. This would yield a mass of only 8.3 kg. The IAU will not give planetary status to any small object with a poorly known diameter. Either way, it is not massive enough to be have cleared its orbit of other objects comparable in size to itself. -- Kheider (talk) 21:38, 16 February 2008 (UTC)
 * I've added a note about Sedna's Stern-Levison parameter (which described how gravitationally dominant it is in its orbit). (I don't believe that this classifies as Original Research, since it is simply plugging some numbers into an equation.) Bluap (talk) 23:11, 16 February 2008 (UTC)

Sedna claimed to reach Perehelion by 2075. Please don't delete this
I notice that the source for this is source 5 but it doesn't say anywhere that it will reach Perihelion in 2075. It does say that Sedna will beat Eris in 2114 as the farthest object from the sun but the Perhelion date of 2075-2076 is not listed in source 5, which is the source it is supposed to come from. -Thank You.Maldek (talk) 07:19, 16 May 2008 (UTC)

Hello Maldek. I am the person that actually put that content in the article.
 * Ref 1 from the Lowell DES website shows, "Time of Perihelion: 2479283.2278". (Ref 6 shows how to convert the number to 2075-12-11.)
 * Ref 5 is generated by JPL's Horizon program and shows a perihelion date of 2076-Jul-13. The reason the programs come up with slightly  different dates is because they use slightly different numbers to do the calculations.  Keep in mind that Sedna is very far away and has only moved a little bit over the 17 years (see precovery) that they have photos of it.  They still do not know the orbit well enough to know if it takes 10 thousand or 12 thousand years to go around the Sun.

I just re-ran the numbers with Horizons (using Soln.date: 2007-Nov-26 / 64 obs / last obs: 2007-11-08) and it now comes up with a perihelion date of 2076-Jul-18 instead of the older value (from 2007-11-19) of 2076-Jul-13. But that is still only a rough estimate until the orbit is better determined. I cite both years because they come from two different sources. -- Kheider (talk) 08:13, 16 May 2008 (UTC)

Missing context.
This sentence seems doesn't seem to follow on from the previous sentence an makes little sense as it exists: "A number of explanations have been put forward since, including a passing star and a distant, planet-sized object."

Can someone fix it? Duggy 1138 (talk) 03:18, 7 June 2008 (UTC)

What's further?
This article, and several others that reference Sedna, are worded in a way that suggest that further solar system objects have been observed. That's the first I've heard of this (last I heard Sedna was still the furthest found to date). If there has in fact been further objects found, there should be a more clear link to the applicable articles. 68.146.41.232 (talk) 19:43, 11 June 2008 (UTC)

Eris (dwarf planet) is currently further from the Sun (96AU), because Sedna is currently near its closest point to the sun (88AU). See: Talk:(148209) 2000 CR105 -- Kheider (talk) 19:54, 11 June 2008 (UTC)

Absolute Magnitude
The absolute magnitude mentioned in info box is absolutely wrong. m-M=5logd-5 (m: Apperant mag, M: Absolute mag, d:distance-as parsec-). Here is the absolute magnitude equation. You do not need to solve such equations. Also there is a simple comperation to see the mistake: The absolute magnitude of sun is 4,85m. So compared to Sun's M value, 1.56 means that Sedna is brighter than sun. So, is it? --Azizkayihan (talk) 21:29, 4 September 2008 (UTC)


 * You are incorrectly comparing a stars absolute magnitude (M) to a planets absolute magnitude (H). The Planet infobox link really does need to be updated to reflect this common mistake. -- Kheider (talk) 22:34, 4 September 2008 (UTC)


 * Yeah, i see, my mistake... Sorry :( --Azizkayihan (talk) 01:52, 5 September 2008 (UTC)

Fix?
Hey guy, will you fix this page so Sedna isn't hidden behind the picture of the Oort Cloud and the other SS views? Thanks. This comment by 71.232.40.177 was originally in the article. I'm moving it here. Reyk YO!  04:47, 19 September 2008 (UTC)

Where is Quaoar's moon?
In the Classification section there is an illustration of the largest Kuiper Belt objects with their moons. However, Quaoar's moon has been left out and should be added. —Preceding unsigned comment added by 208.73.31.50 (talk) 17:56, 26 May 2009 (UTC)
 * The Quaoar page does not mention any moon. HumphreyW (talk) 18:49, 26 May 2009 (UTC)


 * Quaoar does have a moon. "IAUC 8812: Sats OF 2003 AZ_84, (50000), (55637),, (90482)" mentions a satellite, but I don't think many details are known about it.


 * The real question would be how small to make this poorly known moon? -- Kheider (talk) 23:02, 26 May 2009 (UTC)


 * We still don't know the true size of Eris' moon Dysnomia. I think the best moon for Quaoar would be a clone of one of Pluto's little moons so as not to detract from the greater status/knowledge of Orcus and its moon.  But that method is just a best guess. -- Kheider (talk) 04:30, 27 May 2009 (UTC)

Orcus's moon got added when its name was confirmed, so I think Quaoar's moon will be added when it gets a name. The real question for me is why Varuna's still up there when we already have a larger object (2007 OR10) on the list.  Serendi pod ous  05:43, 27 May 2009 (UTC)
 * Because Varuna is named, and 2007 OR10 hasn't even been numbered yet? I mean, give enough time for Hubble to get back into service so it can be checked out properly...it hasn't been on the MPC list that long. Iridia (talk) 07:16, 27 May 2009 (UTC)
 * I also believe that once 2007 OR10 has a real name that most people will forget that it was every 2007 OR10... -- Kheider (talk) 15:07, 3 June 2009 (UTC)
 * While on the subject I suspect that the moon of Orcus may be somewhat undersized in the image. I don't think a moon really needs to be named to be added to an image representing the general knowledge of larger dwarf planets...  I would like to know more about the size of 2007 OR10 though... But a lot of this is just guessimates.-- Kheider (talk) 14:29, 27 May 2009 (UTC)
 * I went ahead and gave Quaoar a small moon... -- Kheider (talk) 14:52, 27 May 2009 (UTC)

Bigger than dwarf planets
The low end of the estimates for Sedna in the article show a smaller mass than either Ceres or Haumea and a smaller diameter than Haumea (mean). So I fail to see how the statement "It is, in fact, bigger than 2 objects that have already been classified as dwarf planets; Haumea and Ceres." is true. It may be true, but the dimensions of Sedna need to be better established first. I'm deleting the statement. --Aranae (talk) 18:02, 20 August 2009 (UTC)


 * I got that straight from the article List of Solar System objects by size, you can see Sedna placed above Haumea and Ceres in the table.


 * Robo37 (talk) 18:20, 20 August 2009 (UTC)

If you look at the key, for Sedna it states *AR meaning:
 * * Radius is known only very approximately
 * R Radius has been determined by various methods, such as optical (Hubble), thermal (Spitzer), or direct imaging via spacecraft
 * A Assumed mass

These are only estimates with noticeable error bars. Other than Sedna, the error bars could easily place any of the other TNOs as smaller than Ceres. For example, I created the article 2005 QU182 (with no scientific papers) and gave it a range of 638-1425 km. The 1050km figure is true only when asssuming an albedo of 0.09. I really only did that because many generic Wiki-created TNO articles have a tendency to assume a generic albedo of 0.09. Note that around a size of ~1200km there is tendency for the albedo to spike from 0.09ish to 0.3+. It is common for the size of a TNO to only be known (estimated) with an accuracy of a factor of 2. -- Kheider (talk) 19:48, 20 August 2009 (UTC)

Gathering sources in preparation for expansion

 * Schwamb 2009 (A Search for Distant Solar System Bodies in the Region of Sedna)
 * Google Search


 * you'll also want this. Iridia (talk) 00:37, 26 July 2010 (UTC)

OK; this is confusing

Brown/Schwamb's original paper says,

Figure 3 plots the fraction of simulated surveys that produced a single Sedna detection as a function of NH≤1.6. The best fit value gives 40 bodies that are brighter than or equal to Sedna, with the largest body in the population having a H≃-1.0, which is approximately the absolute magnitude of Eris. At the one-sigma confidence level we can rule out a population larger than 92 and smaller than 15 Sedna-sized or bigger objects on Sedna-like orbits. For comparison, the total number of bodies Sedna-sized or larger in the Kuiper belt is ∼5-8 (Brown 2008); there may be an order of magnitude more mass residing in the Sedna region than exists in the present Kuiper belt.

but the new paper says,

The best-fit values for the number of objects brighter than or equal to Sedna with 95% errors are 393 +1286 −264 and 74+279 −47 for the hot and cold brightness distributions respectively. The lower and upper 95% confidence levels limits reported are one-sided statistics found by computing the interval over which the integrated probability distribution 0.95 respectively of the total area. The survey simulator assumes all simulated Sednas that land on our images and are above the image limiting magnitude would be detected in the survey. The effect of a less than 100% survey detection efficiency is non-negligible. The reported size estimates represent a lower-bound on the size of the Sedna population. Assuming a uniform detection efficiency which drops to zero at the image limiting magnitude, the best-fit value and 95% limits for NH�1.6 is scaled by the inverse of the survey efficiency. For our nominal detection efficiency of 0.66, the best-fit values for the number of objects brighter than or equal to Sedna are 595+1949 −400 and 112+423 −71 respectively for the hot and cold brightness distributions. Figure 9 plots the fraction of simulated surveys that produced a single Sedna detection as a function of NH�1.6 the 104 M�/pc3 cluster environment for our nominal survey detection efficiency.

those results are different by an order of magnitude. So either they've radically altered their results in the last year or I'm not getting something.  Serendi pod ous  06:20, 26 July 2010 (UTC)


 * The 2009 paper seems to mention objects with perihelion (q) > 70AU of which we only know of Sedna. The 2010 paper seems to look for any eccentric body with perihelion (q) > 45AU of which we know of (4) bodies: Sedna@76AU, 2004 VN112@47AU, (145480) 2005 TB190@46AU, and 2004 XR190@51AU.  The next most eccentric object with q>45AU is 2000 PD30 with an eccentricity of only 0.02 and aphelion@48AU. -- Kheider (talk) 09:31, 26 July 2010 (UTC)

Orbital characteristics
Should we use DES data for the orbital characteristics in the infobox (as is currently used), or should we use jpldata as almost all minor planets seem to? The DES uses an epoch of 1990/09/26 while JPL uses a more recent epoch of 2010-Jul-23. -- Kheider (talk) 01:53, 19 July 2010 (UTC)
 * Given that Sedna's orbital characteristics are still being refined, I think that the most recent data are always best.  Serendi pod ous  06:16, 19 July 2010 (UTC)

Atmosphere
This quote:

"Although similar ices [to Ttriton and Pluto] have been detected on Sedna, its surface is likely distinct from these other bodies. A comparatively low visible albedo and very strong red spectral slope indicate a much higher concentration of dark organic material. The CH4 bands at the 2.3 micrometre on Sedna are rather weak, perhaps suggesting an absence of atmospheric volatile transport and redeposition that sets the stage for the long pathlengths necessary to explain the much deeper CH4 bands on those other outer Solar System objects"

is saying, I think, that because the methane bands are so weak, it means that it is not likely that methane has been evaporated into an atmosphere and then refrozen to the surface, as it has on Pluto and Eris. Am I right? Also, does the presence of organic material simply mean that there is no methane frozen on the surface, or is it that all the methane has been converted into complex organics by sunlight?  Serendi pod ous  16:44, 21 July 2010 (UTC)
 * It means that at the surface methane ice is mixed with a dark material. In such a mixture the grain sizes of the methane ice are small, which results in weak methane bands. Methane bands are strong only when grains are large and so the light can propagate a long distance inside them resulting in strong bands. Large grains can only form in either a pure methane ice or in nitrogen ice with some methane dissolved in it. However a pure ice can not exist for long without renewal. Sooner or later it will be polymerized by UV radiation or simply mixed with the underlying dark material by impacts. So, if a pure ice exist it means that it has been deposited relatively recently. On Sedna it is not possible as the temperature is very low. Ruslik_ Zero 19:00, 21 July 2010 (UTC)

Kozai mechanism
As an alternate explanation for the orbit of Sedna.

These two articles may be of use, but I cannot access them from my terminal.  Serendi pod ous  08:21, 7 August 2010 (UTC)
 * The article actually says that Sedna can not be explained by this mechanism because it has a low inclination. Ruslik_ Zero 17:16, 7 August 2010 (UTC)
 * Sorry if I'm being a twerp about it, but that might be worth adding anyway. :)  Serendi pod ous  17:17, 7 August 2010 (UTC)
 * It is only worth adding that standard mechanisms invoked to explain Scattered disc's origin does not work for Sedna. Ruslik_ Zero 13:14, 8 August 2010 (UTC)
 * OK, well the article already says that pretty much anyway.  Serendi pod ous  13:17, 8 August 2010 (UTC)

Sedna's Stern-Levison parameter and planetary discriminant
The Classification section mentions that Sedna has a Stern–Levison parameter (Λ) estimated at between 8 × 10−5 and 6 × 10−3 times that of Pluto. I think this is incorrect. The Note for it is all wrong, confusing the Stern-Levison parameter and Soter's planetary discriminant (μ). For example, it talks about dividing Sedna's Λ by the Λs of all the other bodies in its zone and comparing that to 1; however, it is Λ itself that has to be compared to 1, and it doesn't require any info about other bodies. μ does, but all it compares are masses, and the resulting ratio there should be > 100 for planethood, not 1. There's no reason to divide by Pluto's Λ at all, since they're not in the same zone (and I don't see why the mass of Earth is in there at all!).

I can calculate Sedna's Λ=.000018; all you need is the mass and the period (or semi-major axis), and K from the Stern-Levison paper. However, we can simply say that since Sedna is almost certainly lighter than Pluto and farther away (longer period), each of which reduces Λ, and since Pluto is not a planet, therefore Sedna could not be a planet (by the Λ criterion). Or just point out that Eris is in Sedna's zone, and almost certainly bigger. This has the benefit of not needing to explain where the K of the Λ equation comes from: it's not anywhere on Wikipedia, and you have to do some calculations to convert to whatever units you want to use, which might be a bit too much like original research.

I prefer to let this sit a bit before making the change, to give the original author a chance to explain, and to see if there are any objections on the OR aspect (although that barn door seems already open here). Tbayboy (talk) 01:03, 14 August 2010 (UTC)
 * S-L paper contains no such parameter as K. I also see nothing inappropriate in dividing one parameter by another if both have the same dimension. I fixed an obvious error where &Lambda; was mixed up with mass, but I do not see any other problem. Ruslik_ Zero 13:29, 14 August 2010 (UTC)
 * You're right that S-L doesn't use K, they use a complex formula (they refer to it as "the term between the square brackets" in equation 4) which is "approximately constant" (in Soter's words). It is Soter that represents it as a K, and that is how it is represented in Clearing the neighbourhood. This article (Sedna) doesn't mention this K term, and the calculation doesn't use it, with the result that there is no conversion for units and so the final Λ is not scaled to a proper likelihood where a value of 1 means that the body will clear its neighbourhood. Another obvious error here is that it states that Pluto's lambda 1.95{{e|−8}, whereas S-L says it is .004 (Soter's paper calculates it as .003, which is what I get, too). The raw Λ is meaningful and is to be compared to 1. If you divide then you must also change the comparison from 1 to 1/(whatever you were dividing by). Finally, the planetary discriminant μ is to be compared to 100 (per Soter's paper) for planethood, not 1 as stated here. μ not really relevant here, though, since so little is known of Sedna's orbital zone. (I'm wrong about Eris above: it's not in Sedna's zone because of the order-of-magnitude requirement!) Tbayboy (talk) 14:57, 14 August 2010 (UTC)

Caused Pluto's downgrading
The discovery of Sedna led to Pluto's loss of planetary status. Shouldn't this be mentioned prominently in the lede? It does not appear anywhere in the article now. Kauffner (talk) 07:01, 1 September 2010 (UTC)
 * Sedna led to a discussion by the IAU on the possibility of defining planet, but no decision was reached. It was the discovery of Eris, not Sedna, that led to Pluto's demotion.  Serendi pod ous  07:08, 1 September 2010 (UTC)
 * In 1999 The IAU postponed indefinitely all discussions on Pluto and official planet definitions. At that meeting, a proposal to grant dual status to Pluto as both a planet and a Kuiper Belt Object was debated but not adopted.  Many IAU members came down on the side of not changing Pluto's status, mainly for historical reasons.  The discovery of  Eris, which is larger and more massive than then-planet Pluto, forced the issue, not Sedna. -- Kheider (talk) 07:24, 1 September 2010 (UTC)

FAC discussion
Carrying over discussion from the FAC:


 * Ref 35 should be removed, and its citations replaced by citations to the peer-reviewed articles on that survey, which are already references.
 * That ref is citing information that is, as far as I can tell, unique to it; specifically the effects on a population of the various formation scenarios.  Serendi pod ous  07:46, 18 August 2010 (UTC)
 * I see only two chapters in The Solar System Beyond Neptune referenced, with no page numbers, where some chapters are 20+ pages. That book is the most recent comprehensive overview available, with field-wide author diversity. It should be used a lot more, as it is a secondary source, and the article is relying heavily on primary sources, some of which supersede each other. Iridia (talk) 02:56, 18 August 2010 (UTC)
 * Both those references have page numbers. I'll skim the book but keep in mind that it's basically a collection of primary sources, not all of which are about Sedna. Serendi pod ous  07:49, 18 August 2010 (UTC)
 * Oh no, it doesn't have an exclusive focus on Sedna by any means. It's just that it's the current field review article collection publication. I wouldn't normally consider a review article to be the same thing as a research article, hence my distinction between its articles and the majority of the sources in this WP article. Iridia (talk) 00:04, 30 August 2010 (UTC)
 * Also, having page numbers for the book's article is not quite the same as having page numbers for the citations within the book. Unless the ways in which books are cited can vary that much? Iridia (talk)
 * I really don't think that is important, especially considering that both those refs link to searchable documents.  Serendi pod ous  11:58, 30 August 2010 (UTC)
 * "The MPC formally accepted the name in September 2004" Hmm - the IAU CSBN judges and accepts names, the MPC publishes them. That should cite MPC 52771, which can be found here, not its Editorial Notice (an MPEC).
 * Done.  Serendi pod ous  11:58, 30 August 2010 (UTC)
 * Want to mention why a moon would produce a long rotation period?
 * Done.  Serendi pod ous  11:58, 30 August 2010 (UTC)
 * Could put a footnote giving the limits that HST put on detection of a moon.
 * Can't find the technical specs of the Hubble search. Just its result.  Serendi pod ous  11:58, 30 August 2010 (UTC)
 * Found it and added it. Iridia (talk) 12:42, 30 August 2010 (UTC)
 * Should mention how tholins are formed. The intro section of Emery et al has a few nice points for this.
 * Done.  Serendi <sup style="color:#bb0000;">pod ous  12:28, 30 August 2010 (UTC)
 * Surface composition: while this part is quite clearly written, it would be good to frame it with its missing point: all the observers' models have had to be quite complex, reflecting low S/N spectra of a surface of multiple materials. Until we get an ELT spectrum, surface modelling is half an art, and giving the precise fractions of materials becomes somewhat deceptive. I don't think the paragraphs convey that uncertainty. Also, Trujillo et al had a low S/N compared to the later confirmations, so it would be good to place their initial upper limits in that context.
 * I assume S/N means "signal to noise", not "sulphur to nitrogen" or "since to now"? That point is too general for me to make without some kind of specific reference. Keep in mind that this isn't an FAC. The onus isn't just on me now; you can contribute too. If you know of sources we could use, please post them.  Serendi <sup style="color:#bb0000;">pod ous  12:09, 30 August 2010 (UTC)
 * yes, signal to noise. I think the text of Emery et al would allow that to be done: might need to be drafted first since it could be a bit messy.
 * Will do if I think of anything. I'll probably keep making comments/notes here as I go just to keep track of any larger issues I come across. Iridia (talk) 12:42, 30 August 2010 (UTC)


 * "its deep red spectrum" should be "deep red spectral slope", and then spectral slope needs either an explanation or a footnote.
 * Done.  Serendi <sup style="color:#bb0000;">pod ous  11:58, 30 August 2010 (UTC)
 * Oh good, there is a link for that - think a few other TNO articles might need it too then. Iridia (talk) 12:42, 30 August 2010 (UTC)
 * Iridia (talk) 05:51, 30 August 2010 (UTC)

Main page
November 14 will be an anniversary of the discovery. Should we nominate it for the main page on that day? Jonathunder (talk) 22:55, 12 October 2010 (UTC)
 * Sure, if you like.  Serendi <sup style="color:#bb0000;">pod ous  19:53, 13 October 2010 (UTC)
 * ✅ Jonathunder (talk) 23:56, 13 October 2010 (UTC)

Unreferenced claim in "Exploration"
This section currently states: "Sedna's perihelion will be reached within this century, after which it will move back out and farther away from the Sun again for another ~12,000 years. Though an exploration target within the Solar System,[47] NASA is not considering any type of mission at this time." There is no reference for the claim that NASA is not considering a mission. I found this (see answer to question 8) that shows it is not a target for New Horizons, but that isn't the same as no mission at all. Also, i can't seem to access the one reference that is used in that para. hamiltonstone (talk) 23:17, 13 October 2010 (UTC)


 * Even Mike Brown, the discoverer of Sedna agrees that a mission to either Eris or Sedna would do very little to forward our knowledge of the solar system at this time. A mission out to 76AU is just too much work with current technology and funds, and we would gain little from a mission that would take 20 years to "bare fruit". -- Kheider (talk) 23:34, 13 October 2010 (UTC)


 * Well, it's not an exploration target in the Decadal Survey, which determines where the planetary mission money goes. An outer-system mission is quite expensive, and the fuel for the only feasible power source, a RTG, is in horribly short supply and not yet back in production. Haumea isn't on the table either, and it's a little more "accessible". But I doubt there would be a possible citation for this kind of information.
 * No, New Horizons can't go anywhere near it: their possible diversion cone post-Pluto is a tiny spot on the sky, and they'll have target determination for that sorted out in the next two years or so, probably a cold classical if they're lucky and there's something there before they run through the Kuiper belt and the object density thins out. Iridia (talk) 23:35, 13 October 2010 (UTC)
 * Look, I completely agree - my point is we need a ref - not whether or not it is true... hamiltonstone (talk) 00:14, 11 November 2010 (UTC)
 * The required no-visit-planned ref is probably this (3 MB pdf), I think. The current ref doesn't go to a relevant page. Iridia (talk) 00:42, 11 November 2010 (UTC)
 * I ran with this instead, as it is more current than 2006 and seems to more concisely offer evidence of the same conclusion. hamiltonstone (talk) 04:47, 11 November 2010 (UTC)

Roentgenium111's objections
I still don't understand what his problem is. The IAU has said that only those objects with an absolute magnitude of +1 or higher be included as dwarf planets. Sedna's absolute magnitude is lower than +1. Therefore, unless the IAU changes its practice, Sedna cannot be considered a dwarf planet.  Serendi <sup style="color:#bb0000;">pod ous  15:50, 10 November 2010 (UTC)


 * The IAU didn't make such an exclusion -- there is no "only" in their statement regarding the brightness. The +1 is only for purposes of naming, not classification: it allows them to name something under dwarf planet rules before they know from direct evidence whether or not it is round. Otherwise naming could become completely stalled for all but the dimmest objects. They are assuming that brighter than +1 is sufficient proof of roundness. It is not exlusive: they don't say that objects dimmer than +1 are not dwarfs (i.e., they don't say that only those bright objects are dwarfs). Tbayboy (talk) 17:53, 10 November 2010 (UTC)
 * But the article, as rewritten by Kheider, currently allows that interpretation.  Serendi <sup style="color:#bb0000;">pod ous  18:05, 10 November 2010 (UTC)
 * The "automatically" indicates the intent (i.e., that further evidence of roundness is needed), but I agree that it's poorly phrased. I also think "composition" is irrelevant. Tbayboy (talk) 21:02, 10 November 2010 (UTC)
 * No it isn't. Icy objects become rounded by thier own gravity more readily than rocky objects. And how would you rephrase it?  Serendi <sup style="color:#bb0000;">pod ous  21:03, 10 November 2010 (UTC)
 * Yes it is. :-) Irrelevant to Sedna, I mean. There's no satellite (or nearby friends to perturb), so there's no way to get the mass, hence density, hence a guess at composition. Given the rocky natures of Haumea, Quaoar, and now Eris, you can't even assume icy for TNOs, let alone a complete mystery like Sedna. As for the wording, I'll give it a try. Tbayboy (talk) 23:47, 10 November 2010 (UTC)
 * Telescopes can reveal details on the surface composition. Most TNOs do appear to have bright icy surfaces (with 2002 TC302 being a possible exception). So yes, surface composition matters. Newer observations could (even if unlikely) reveal a small moon at some point. -- Kheider (talk) 00:07, 11 November 2010 (UTC)
 * I suspect it'll take until the GMT/TMT/E-ELT are built to get any super-tiny moons. See note (e) in the article. Perhaps that note should be promoted to a sentence in the body text? Iridia (talk) 00:37, 11 November 2010 (UTC)
 * The point of those three is to show that rocky bodies can be covered by thin icy surfaces, so you can't really go by surface composition. Tbayboy (talk) 00:55, 11 November 2010 (UTC)


 * Thanks to Tbayboy for explaining my "editing motivation" (which, however, I thought to be quite clear from my edit summaries). As I said there, the IAU reference given is only about naming objects, and Sedna had been named "Sedna" long before 2008. The naming guideline was only ever invoked for Haumea and Makemake, as far as I know. (BTW, Serendipodous, I would have preferred a more informative and less "accusing" thread title.) --Roentgenium111 (talk) 21:53, 12 November 2010 (UTC)
 * Well, the current edition seems fine. Sorry if I came off a bit brusque there, I was fighting three edit wars simultaneously when I made it.  Serendi <sup style="color:#bb0000;">pod ous  22:38, 12 November 2010 (UTC)

"farther away from the Sun again for another ~12,000 years"
I dispute this edit by Kheider:
 * Sedna's perihelion will be reached within this century, after which it will move back out and farther away from the Sun again for another ~12,000 years

Sedna will only be moving farther away from the Sun for ~6,000 years; for the ~6,000 years after that it will be moving back towards the sun. I presume the intended point of this sentence is something like "Sedna is closer to the Sun this century than it will be at any time in the next 12,000 years, so if we want to explore it, we should grasp the opportunity soon." If that is the point, and if it is one worth making, then it needs to be expressed less ambiguously. jnestorius(talk) 07:45, 14 November 2010 (UTC)
 * Feel free to re-word it. But after perihelion in 2076, Sedna will not be this close to the Sun again for ~12,000 years. -- Kheider (talk) 07:50, 14 November 2010 (UTC)
 * The larger question is whether that's relevant at all (in a section called "Exploration"; it's already implicit from the information in the section "Oribit and rotation"). It will be closer to Earth than at present for the next 66 years, and for the 66 years after that; that's a 132-year window, which doesn't suggest any urgency at all. What would be lost by simply deleting the entire sentence?
 * One negative is that it would from result in leaving a one-sentence section, but that could be fixed by explaining the apparent contradiction in the second sentence: what does it mean to be an "exploration target" when there is no mission under consideration? jnestorius(talk) 09:58, 14 November 2010 (UTC)
 * Would this read better: Sedna's perihelion will be reached around 2075-2076, so if astronomers want to study Sedna while it is near closest approach to the Sun, it might be best to send a mission there in the next 100 years or so. Though listed on NASA's solar system exploration website, NASA is not considering any type of mission at this time. -- Kheider (talk) 10:15, 14 November 2010 (UTC)
 * It would read better, but needs a source to avoid OR. jnestorius(talk)

"so if astronomers want to study Sedna while it is near closest approach to the Sun, it *might* be best to send a mission there in the next 100 years or so." This is the only part that borders on OR, but since perihelion is in 2075-2076, I am hoping this falls under common sense. Assuming a ~20-30 year flight time, I do not see a reason to rush a mission to Sedna in the next 40 years. Though with Sedna being so far from the Sun, it might be scientifically useful for the next generation to insert a long-term orbiter to study Sedna's surface composition and any hint of an atmosphere while Sedna is near perihelion, instead of the quick flyby that New Horizons will be around Pluto. -- Kheider (talk) 17:30, 14 November 2010 (UTC)


 * Ah. I think the edit by CuriousEric cleaned it up nicely. -- Kheider (talk) 18:06, 14 November 2010 (UTC)

Why just explore it. This is a free spaceride to the outer solar system. It should be more of a priority than Mars. I mean at the very least we should put a base on it or at the very least a permanent Voyager type probe/message. In 6,000 years it could make the ultimate launchpad/stopover for interstellar missions and exploration base for the Oort Cloud. --EvenGreenerFish (talk) 03:45, 15 November 2010 (UTC)
 * Interesting idea, but it's harder to land on a distant object than to just keep moving on beyond it. And spacecrafts like New Horizons move much faster away from the Sun than Sedna does. (Actually, Voyager 1 and 2 are already farther away from Earth than Sedna, and will never be overtaken by Sedna since they're much faster.)--Roentgenium111 (talk) 18:12, 16 November 2010 (UTC)

Resolution power
I am translating this article for the French wikipedia and I am a little puzzled by the following sentence. the Sun would appear merely as a bright star in its sky: with an angular diameter too small to resolve as a disc, it would be only 100 times brighter than a full Moon on Earth.. I don't really like (but maybe don't really understand) the bold part of this sentence. The resolution power reference corresponds to a human eye I guess. Isn't it quite too hypothetical (because it supposed that a man could get on this object and will likely not happen in the next xxxx years) ? I just don't see the point on this part. Poppy (talk) 23:03, 7 December 2010 (UTC)
 * It's just hypothetical, to give an idea of where Sedna is in relation to Earth. On Earth, the Sun is a blazing disc, on Sedna, it would be a bright smear of light in the night.  Serendi <sup style="color:#bb0000;">pod ous  00:57, 8 December 2010 (UTC)
 * I would favor the wording "...bright star in its sky, too small to resolve with the human eye..." The more technical sounding "...with an angular diameter too small to resolve as a disc..." does not add anything that those familiar with astronomy need to know and it might confuse some with just a little knowledge of astronomy.  They might think the sun could not be resolved from Sedna with a 2 meter reflector. Also, I prefer keeping closer to the meaning of the reference. - User:Fartherred from 207.224.85.91 (talk) 02:25, 15 June 2011 (UTC)

2006 SQ372
The text in this article says Barring comets, Sedna has the longest orbital period of any known object in the Solar System, calculated at between 11,800 and 12,100 years. Shouldn't we mention 2006 SQ372 which has a longer period (it is uncertain whether it is a comet or not) ? Poppy (talk) 23:23, 7 December 2010 (UTC)
 * Not sure. It seems like a super-centaur. I'll need to do some reading up on it. Should merit a footnote at least.  Serendi <sup style="color:#bb0000;">pod ous  00:59, 8 December 2010 (UTC)
 * I have added Note F: Small Solar System bodies such as 2010 EC46, 2006 SQ372, 2005 VX3, (87269) 2000 OO67, 2002 RN109, and 2007 TG422 have longer orbits. -- Kheider (talk) 02:00, 8 December 2010 (UTC)
 * I added that they may or may not be comets.  Serendi <sup style="color:#bb0000;">pod ous  09:35, 8 December 2010 (UTC)

More questions
Dear all,

thanks for the previous answers. I have more questions in order to translate accurately to French : Thanks in advance. Poppy (talk) 16:55, 15 December 2010 (UTC)
 * then Sedna's population would all possess relatively low inclinations and range from 100–500 AU : I find the end of this sentence not completely accurate. Are we taking of perihelion, aphelion, "average" orbit ? Because, Sedna is part of this population and its perihelion is 76 AU and aphelion 900 AU, so out of the range.
 * The gravity of perturbing stars would produce a wide range of perihelia and inclinations, each dependent on the number and angle of such encounters. I am not completely clear on this one : does this mean that given an history (1 precise history of perturbation by stars), the population has a wide range of perihelia and inclinations (my guess) or does that mean that due to the large number of possible histories, there are a lot of perihelia and incliations possible but the whole population has similars parameters.
 * point 1: unfortunately the source isn't clear on this either; however I think semi-major axis is meant in this case.


 * point 2: Your guess is correct.  Serendi <sup style="color:#bb0000;">pod ous  17:34, 15 December 2010 (UTC)
 * Thanks :). Poppy (talk) 00:31, 16 December 2010 (UTC)

Population and Probability
Currently, the article says, "Sedna's highly elliptical orbit means that the probability of its detection was roughly one in 60, suggesting that, unless its discovery was a fluke, another 40–120 Sedna-sized objects should exist within its region." I made a change a month ago, but another source was added and it was changed back. But I still have the same complaint, so I thought I should explain my thought process better.

My first issue was with "one in 60" claim. I would have expected one in 80, because that is midway between 40 and 120. But, I know that probability doesn't always work like you think, so I read the cited source. It does say between 40-120 Sedna (or larger) objects. They said that Sedna would only have been detected during the 150 years it is near perihelion out of its 11,000 year orbit. They never cite one in 60, and these values give something closer to 1 in 70. The new source uses the same logic, but with different numbers to explicitly say Sedna could only be detected during ~1% of its orbit, suggesting a population of ~100. So if anything, the sources contradict the one in 60. I still say one in 80, which would make sense using 150/12000 = 1/80.

The second was a bigger issue with me: Using the word "fluke" doesn't really make sense with probability. I think I understand what you really mean though-- that it might not be a part of a population (or that its population is thinner than we would expect) and we were just "lucky" to discover Sedna. But it's not like it's a fluke if we roll double sixes on our first time-- low probability things just happen sometimes. Anyway, to make a long story short, I think the article will be improved if we want to change it so it makes sense. Thanks. Slim (talk) 05:26, 14 January 2011 (UTC)
 * if the source says 150 years, rather than 200, which is the usually cited figure, then it should be 1/80. As for "fluke", well, I didn't intend to imply the existence of luck- I meant it as you said. Sometimes low-probability things just happen. I'm looking for another word ("statistical anomaly" doesn't really fit), but I think that clause has to be there, because when it wasn't, readers complained they couldn't see the connection between probability and population.  Serendi <sup style="color:#bb0000;">pod ous  11:20, 14 January 2011 (UTC)


 * I would humbly suggest to use Brown's most recent estimates (expected number 40, range of 15-92 objects within one sigma) (from 2009, ref. [41] in the article) more prominently in the article, and cut down (or even remove completely) the mentioning of the outdated (2004) estimates you discuss here.--Roentgenium111 (talk) 00:06, 15 January 2011 (UTC)


 * In 2004 Brown was still hoping to find more Sedna's, but by 2009 (or even 2011), he nor any else has. -- Kheider (talk) 00:19, 15 January 2011 (UTC)


 * Let us make it clear lest readers get the wrong impression, the rarity of Sedna-like bodies within the observable portion of their orbits is completely consistent with there being 1-120 Sedna-like bodies in the unobservable portions of their orbits. They might start popping into view any century now.  -User:Fartherred from 207.224.85.91 (talk) 19:44, 15 June 2011 (UTC)

Tm, Gm, Mm, km
In the Infobox I think AU should be listed first since that is what the sources use. The question is do we want to keep both metres and Tm or should we convert to km? It is very redundant (IMHO) to list both. A similar conversation took place at: Talk:Eris (dwarf planet) -- Kheider (talk) 17:01, 26 January 2011 (UTC)
 * Yes, AU should be listed first. Ruslik_ Zero 19:31, 26 January 2011 (UTC)

Furthest presently known spherical minor planet in 2114?
We currently have a note (note b) that says...


 * Sedna will overtake Eris as the farthest presently known spherical minor planet in 2114.

That's what the source says, yes; but I'm not convinced it's accurate (sorry Kheider). We don't know for sure that Sedna is spherical (I'll assume "spherical" is here used to mean "spheroidal" or "in hydrostatic equilibrium"). OK, so it's a near-certainty. But it's also very likely that 2007 OR10 (at absolute magnitude ~1.7, compared to Sedna's ~1.6) is in hydrostatic equilibrium. 2007 OR10 will be close to aphelion at ~100 AU in 2114, compared to ~80 AU for Sedna.

Seems to me the farthest presently known spherical minor planet in 2114 will not be either Eris or Sedna, but rather 2007 OR10, which will overtake both. Sideways713 (talk) 11:07, 17 February 2011 (UTC)


 * Oops, you are correct. When I originally made the list in Nov 2007, 2007 OR10 had not been announced yet, so I overlooked it.  I will update the file.  Ironically in the OR10 article, I list the fact that OR10 It will be further from the Sun than Sedna in 2013. -- Kheider (talk) 13:39, 17 February 2011 (UTC)


 * "Spherical minor planet" should be shortened to "dwarf planet"; a dwarf planet is, by definition, a minor planet that is rounded under gravity.--Solomonfromfinland (talk) 17:16, 31 May 2012 (UTC)


 * If you do that you may need to expand it "dwarf planet/dwarf planet candidate". Sedna is technically only a strong candidate. -- Kheider (talk) 17:47, 31 May 2012 (UTC)

Orbital period
Good catch Kheider. On Solex, last aphelion to the next was 11,399.5 years, from -3638 to 7761.

Another reason for rounding is when the quantities change fast. As of April 27, the period is 12,243 years. On Jan1 1, 2012 it will be 12,557. There is no point in using all five digits, in the name of accuracy.

I think we should forget the elements and use the 11,400 year figure. Maybe with a note that this is the aphelion-to-aphelion gap. Saros136 (talk) 05:35, 27 April 2011 (UTC)
 * The clone feature and the twinlib feature in Solex make this predictions fairly reliable. Saros136 (talk) 05:37, 27 April 2011 (UTC)
 * Next perihelions, 2076-7-18.4 and 13480-5-4. 11,404 years apart. Where did you find the 11,400 year solution? Saros136 (talk) 06:06, 27 April 2011 (UTC)
 * I used JPL Horizons to compute the barycentric value of ~11,400 years. This is also how you compute the best-fit for a long-period comet such as Elenin. See: Barycentric coordinates (astronomy) for more details. Should we change the article to reflect the more stable barycentric value? -- Kheider (talk) 18:53, 28 April 2011 (UTC)
 * That would make a great change, both in the box and text. I think we should change other things. The Bowell and AstDys databases give near identical elements that agree with the other sources. And the clones, as made by Solex but also by that other page, support that the orbit is securely calculated. I think we could at least be as specific as a July 2076 perihelion and about that 76 or 76.2 Gm distance. Saros136 (talk) 05:32, 30 April 2011 (UTC)