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Archive 1Archive 2Archive 3

The rarity and value of Sedna & the mistery of its peculiar orbit

Roentgenium & Serendipodous have had a discussion in the edit summarys about there being perhaps 40 Sedna-like objects or some other number, most of which objects are out of sight. There are reliable sources for such estimates but all sources that have been cited have a bias of wanting to show that the astronomy is important, interesting and worthy of more funding. One instance in statistics is no data. A fluke of sighting Sedna in the only part of its orbit in which it would be visible is only one of millions of possible unlikely flukes that could be observed. If probability can be trusted, we must expect to see a few flukes.

We should not expect that there must be a Nemesis-like or Planet X-like object to explain the strange orbit. After many millions of years of forming planetismals, they were stirred up by the planet that got big first. Those slow to grow to planet size were then subjected to high velocity collisions that often caused disruption rather than accretion. Sedna's strange orbit could be the relic of the last bang it received which raised its perhelion a little. It could be possible to find a reliable source that did not think Sedna so valuable if these astronomers were not so intent on patting each other's backs. -User:Fartherred from 207.224.85.91 (talk) 22:48, 14 June 2011 (UTC)

If you find a source that says so, then fine. Serendipodous 06:06, 15 June 2011 (UTC)
I should have looked over the previous talk before contributing. The section on Population and Probability touches on the same topic. Of course you are right. We can only go with the sources we can find. 207.224.85.91 (talk) 15:05, 15 June 2011 (UTC)
The possibility of violent collisions among minor planets is nothing new or without supporting references. The possibility of a collision in the history of 90 Antiope is an example. The Origin of the Double Main Belt Asteroid (90) Antiope The problem is just finding a source that relates collission to orbit modification. If ancient Sedna had a perihelion of 30.5 AU and aphelion of 940 AU, a whack from behind at aphelion by the right sized circular orbiting body could have lifted the perihelion to 76 AU. It would have to bite you to be any more obvious. Someone (myself included) ought to be able to find a reliable source somewhere.207.224.85.91 (talk) 19:24, 15 June 2011 (UTC)
A collision from another protoplanet could have disrupted a proto-Sedna, but it would not have lifted the perihelion point above the influence of Neptune. Even the collisional Haumea family have perihelion points within the influence of Neptune. -- Kheider (talk) 20:43, 15 June 2011 (UTC)
You cite no reference for your contention and I doubt you will find one. The example you give, Haumea, is quite different from the case of Sedna. Haumea has an aphelion of 52 AU and a perihelion of 35 AU. Its average orbital speed is 4500 meters per second. Sedna has an aphelion of 937 AU and an orbital speed at aphelion of 167 meters per second. The Haumea family is refered to as having an ejection velocity of less than 150 meters per second. That is vastly greater than the delta V that would account for raising the perhelion of Sedna from 30.5 to 76 by an impulse at aphelion. I have not done a celestial mechanics problem like this for many years, but I might handle it somehow. The example you give is a clue to why astronomers failed to see the obvious. They are used to thinking of inner solar system bodies that would need large delta V to make any significant change in orbital characteristics. Out where Sedna spends most of her time the celestial bodies are just crawling along and a minor change in aphelion velocity makes a big change in perhelion distance. Astronomers need to get out of a mental rut and consider the physics of the problem. -User:Fartherred from 207.224.85.91 (talk) 23:26, 15 June 2011 (UTC)
Let us know when you have a reliable source that Sedna's orbit was created via collisional interactions and not perturbations by passing bodies. Gravitational perturbation(s) are much more probable even when Sedna is near aphelion. -- Kheider (talk) 00:31, 16 June 2011 (UTC)

It is nice to know that you have backed off of your claim that a collision would not have lifted the perihelion of Sedna above the influence of Neptune, because there was no reliable source for that false claim. Now why not back off a little farther and admit that you just made up the claim that gravitational perturbations are more probable than collisional interactions. Your sorces never considered collisional interaction, so they certainly did not compare the probability of collisional interaction with anything. -User:Fartherred from 207.224.85.91 (talk) 06:05, 16 June 2011 (UTC)

A collision with an object of a similar mass near aphelion can, of course, raise the perihelion, but how likely such a collision is? The volume is vast (20003 AU3), the cross-section is small (~15002 km2), the number of objects is small (~100) and the their speeds are small too (~0.1 km/s). My estimate of the time to collision is 1027s—1 billion times the age of the universe. So, astronomers ignore this idea only because it is implausible. Ruslik_Zero 12:08, 16 June 2011 (UTC)
First, there is no need that the two objects be of similar mass. Second, only a few meters per second impulse was needed at aphelion for the observed lift of the perihelion, I will post the number when I have worked it out. Third, the required collision would not happen in today's Solar System, but some number of billion years ago when collisions were more common than they are today. Fourth, the chance that such collisions occured is 1 out of 1, as shown by 90 Antiope and 4 Vesta which have had powerful collisions in their history. So, no matter how you made your estimate it is not merely wrong but absurdly wrong. 207.224.85.91 (talk) 15:15, 16 June 2011 (UTC)
This is all very interesting and might be worth publishing somewhere. But not here, please, as this is not a forum for discussion of the topic or a place to posit new research. Jonathunder (talk) 15:30, 16 June 2011 (UTC)
I understand you Jonathunder, but I hope that I have made some case that the proposed explanation of Sedna is something that one might reasonably hope to find discussed by reliable sources. What is found should go into the article as far as it is suitable. 207.224.85.91 (talk) 16:39, 16 June 2011 (UTC)
According to my calculations a change of speed of about 0.1 km/s is required to raise perihelion from 30 to 76 AU, which is comparable to the speed of Sedna at the aphelion—0.25 km/s. As to Vesta and Antiope, they originated in a much more dense part of the Solar System. Ruslik_Zero 18:58, 18 June 2011 (UTC)

Thanks Serendipodous

Thanks for keeping Wikipedia honest as you did in reverting edits of mine in Sedna. I was hoping to stir things up and suspected it would not last. I think there will be reliable discussion of collisional orbit modification before too long whether the sources presently cited take it up or not. Wikipedia is a really great resource, and I suppose I owe good behavior and civility to Wikipedia as a minimum, regardless of anything else I might want to do. Thanks to the whole crew for Sedna. User:Fartherred from 207.224.85.91 (talk) 18:41, 16 June 2011 (UTC)

You raise an interesting point; I hope that you will be able to locate someone who has dealt with the issue. I would suggest contacting Michael Brown, Mark Buie or Alan Stern via email and ask them if they've considered it. Serendipodous 18:48, 16 June 2011 (UTC)

plutoid?

I know Sedna fits the definition of plutoid that we've referenced, but was that intended? If we find a similarly large object in the Oort cloud, would that count as a plutoid too? — kwami (talk) 08:54, 24 June 2011 (UTC)

Intended by whom? The IAU invented this term, and they did not define any upper limit for a plutoid's orbit, so it's apparently intended by them. So Sedna and even a similar Oort cloud object would be a plutoid as well, if they're confirmed to be round. De facto plutoid just means "any dwarf planet except Ceres", so it's quite a stupid definition IMHO. I'd therefore support not using this term in Wikipedia articles when we can avoid it. --Roentgenium111 (talk) 12:37, 24 June 2011 (UTC)
That's why I was asking. It's even not like Ceres isn't icy. — kwami (talk) 14:02, 24 June 2011 (UTC)

Sun's brightness in Sedna

Even as Sedna nears its perihelion in mid 2076, the Sun would appear merely as a bright star in its sky, too small to resolve with the human eye, and only 100 times brighter than a full Moon on Earth.
That doesn't make sense. First is said that it can't be "resolved" with naked eye. Then is said it is 100 times brighter than full Moon on Earth. This cannot possibly be true, the Sun's brightness would about -17 to -18, so it would be quite easy to see. If it would be too small to see, how exactly then it could be brighter than full Moon? 85.217.15.194 (talk) 22:45, 27 July 2011 (UTC)

I think it means too small to resolve a disc, i.e., the Sun would appear as a point of light, not a circle. It's a very bright point, though. Tbayboy (talk) 07:16, 28 July 2011 (UTC)

Edit warring in lead

The current edit war over the possible dwarf planet status in the lead is totally unacceptable in a featured article. It seems quite clear that contested material should be discussed and refined on the talk page before being added, so I place it here for the necessary discussion to take place.

It is thought to be "nearly certainly" a dwarf planet,[1] although the IAU has not yet formally designated it as such.
  1. ^ Mike Brown, 'How many dwarf planets are there in the outer solar system?' Accessed 2011-08-24

I will add my comments in a subsequent post, so they are completely separate from this initial request for proper discussion. --Mirokado (talk) 21:50, 18 September 2011 (UTC)

Thanks, please (if you don't mind) joint the thread at Talk:Dwarf planet as that is where the existing discussion is already in progress. (This issue pertains to several related articles.) --Ckatzchatspy 21:59, 18 September 2011 (UTC)
OK, happy to do that, but probably will not post tonight as I should read the existing discussion first! --Mirokado (talk) 22:21, 18 September 2011 (UTC)
While Ckatz was replying above, I was archiving the Brown ref so that it could be used if necessary, here, archive date September 18, 2011 (the page is updated daily so is not a reliable ref from the point of view of verifiability). I'm adding the information now so it does not get lost, not to start a discussion here.) --Mirokado (talk) 22:29, 18 September 2011 (UTC)

Origin of name "Sedna"?

Have the discoverers said which particular "Sedna" they named 90377 Sedna after? I was surprised not to find this in the article - David Gerard (talk) 12:39, 21 September 2011 (UTC)

It's in the section titled "Discovery and Naming" Serendipodous 12:42, 21 September 2011 (UTC)

Sedna in relation to the drawf planets.

A while go I put into this article that Sedna is Larger than the planets Ceres, Haumea and possibly even Makemake, but my edit was reverted as it was said there wasn't enough evidence to make this claim. However, the infomation came straight from citeed Wikipedia articles, of which say that Sedna is about 17300000km3 which is four times bigger than Ceres, a few hundred million km3 bigger than Haumea and almost exaclty the same size as Makemake, as well as proving to be larger than many moons in the solar system. It does seem obvious that it's bigger than Ceres and (perhaps slightly less obvious) that it's bigger than Haumea so I can't see any problem in inserting that into the article. Robo37 (talk) 14:18, 21 September 2011 (UTC)

Given that Sedna could turn out to be only about 1,200km in diameter (radius ~600km), it would be incorrect to assume it is larger than either Haumea (radius ~680km) or Makemake (radius ~680km). -- Kheider (talk) 15:12, 21 September 2011 (UTC)
Perhaps, but it is definitly bigger tahn Ceres nontheless. Also, the amount of space a planet takes up (which is 17300000km3 is Sedna's case) is, in my opinion, a better definition of size than the measurement of it's radius. Robo37 (talk) 07:01, 22 September 2011 (UTC)
Sedna has never been resolved as a disc. The radius is estimated based on visual and thermal readings. Astronomers measure objects by radius, not by volume. Volume estimates are even worse than average radius estimates. In 2001, 28978 Ixion was thought to be larger than Ceres, but is now believed to be roughly the same size (or smaller). -- Kheider (talk) 07:23, 22 September 2011 (UTC)
Yes, but Sedna's estimated size isn't just a bit larger than Ceres, it's calculations are fout times larger, and scientists must have made some hard scientific calculations in order to calculate these statistics, other wise they wouldn't have bothered revealing the resaults at all. Robo37 (talk) 16:37, 22 September 2011 (UTC)
Four times as large in volume means "only" about 1.6 times as large in radius - still, this is enough to support your claim, if your sources are solid and the error bars are not too large. --Roentgenium111 (talk) 16:54, 22 September 2011 (UTC)
The size of Sedna is not known. The size range mentioned in the article is just an estimate based on an assumed value of albedo. Ruslik_Zero 19:37, 22 September 2011 (UTC)

mass = original research?

The mass estimate contains a footnote: Taking Brown's estimates for the diameter of 1,200–1,600 km and assuming Pluto's density of 2.0 (<0.26 Eris). That looks like original research to me. Doesn't belong in a featured article? --Gerrit CUTEDH 12:55, 23 September 2011 (UTC)

It is a crude (assumed) range for the mass of Sedna, but I see no problem with it. If we do not put a value there, someone will come along and put even a worse estimate without any range. -- Kheider (talk) 13:13, 23 September 2011 (UTC)
It should use a density range, too. Especially for Sedna, since it has such a mysterious origin. Say, 1 to 3, for iceball to rock, so .9 to 6.4 (roughly). Tbayboy (talk) 16:47, 23 September 2011 (UTC)
I have considered a density range as well, but that would make it harder (IMHO) for the average reader to follow. The average reader often just assumes Sedna is ~1600km in diameter. But either method is acceptable to me. -- Kheider (talk) 17:58, 23 September 2011 (UTC)
Yeah, I see your point. Throwing in the density range would be more accurate (in a sense), but it also makes the result too broad to have much meaning. Tbayboy (talk) 00:15, 24 September 2011 (UTC)

So far no one has explained here why this isn't original research. --JorisvS (talk) 18:13, 6 June 2012 (UTC)

Because 2=(1+3)/2—a simple calculation. Ruslik_Zero 18:26, 6 June 2012 (UTC)
That doesn't justify assuming a density of 2 g/cm3 without a citation. --JorisvS (talk) 19:00, 6 June 2012 (UTC)
The assumed density of 2 was based on assuming it had the density of Pluto, but astronomers use to estimate the diameter as close to 1600km. Obviously the density could lower or higher. I still think it might benefit the average reader to have a ballpark figure for comparing a well known object like Sedna to other objects. -- Kheider (talk) 19:44, 6 June 2012 (UTC)
I understand the reasons, but as long as it isn't justified by a citation it is Wikipedians assuming it, which is OR. --JorisvS (talk) 20:32, 6 June 2012 (UTC)
There is, at present and, as far as can be determined, for the forseeable future, absolutely no way to determine the mass of Sedna. Unless we discover it has a tiny moon, Sedna's mass will likely never be known. The explanation is given in the text and it is far better than any guy off the street could come up with. Serendipodous 21:09, 6 June 2012 (UTC)
I'm ambivalent on the "include it or not" issue, but, if adding these numbers, I would like to see a "louder" indication of their nature. "~" usually means "approximately", which is not the same as "assumed". So, for those properties that are directly or indirectly assumed, I think something like "Mean density: (assumed) 2.0 g/cm3 ... Mass: (assumed) 1x10^21", with notes/links, would be a better presentation. Tbayboy (talk) 00:37, 7 June 2012 (UTC)
I agree that would be better. (Also, ⟨~⟩ means "not"; it's only as ASCII approximation for 'approximately'. If we're going to use it, we should use the correct symbol, ⟨≈⟩.) — kwami (talk) 00:47, 7 June 2012 (UTC)
See tilde: it has many meanings, including approximation. Anyway, ≈ is no better since it's still meaning "approximately", which is my complaint. If we must have a glyph, I prefer "?" to either, but why not make it clearer with a word or phrase? Tbayboy (talk) 02:14, 7 June 2012 (UTC)
My point was that if we're going to say 'approximately', we should use the standard symbol for approximately. That's not an argument that we should use it here. As I said, I think your wording would be an improvement. — kwami (talk) 02:29, 7 June 2012 (UTC)

It is OR, but rather innocuous OR. This is a common density to assume for large TNOs. We could probably come up with a source or two for that, even if not specifically for Sedna. — kwami (talk) 21:21, 6 June 2012 (UTC)

Yes, I would be fine with something like that or a general study comparing TNO sizes and densities. --JorisvS (talk) 21:25, 6 June 2012 (UTC)

I think it would be better to just tell the truth. "The mass of Sedna is unknown." There, simple, concise and accurate. Don't even bother with using OR and making useless estimates. And if someone really feels compelled, then more could be added into the article to explain why the mass of Sedna is unknown and why making estimates is fraught with errors and uncertainties. HumphreyW (talk) 02:40, 7 June 2012 (UTC)

Hear, hear. Rothorpe (talk) 02:47, 7 June 2012 (UTC)
This is not completely true that the mass of Sedna is not known. It is known that it can not be as massive Earth. It also can not weight 1 kg. So, the mass is known but not very precisely. The range is quite narrow: 2-2.5 times less or 1.5-2 times more than the value based on the assumed density of 2 g/cm3. So, it would be misleading to state that it is not known. Ruslik_Zero 08:27, 7 June 2012 (UTC)
All I'm asking, really, is a sourced justification for the assumed value(s). --JorisvS (talk) 20:42, 7 June 2012 (UTC)
Muriel Gargaud, Encyclopedia of Astrobiology, Volume 1, under "Kuiper Belt" (p 899), omits mass and density for Sedna, Quaoar, and Makemake in a table of properties of the largest TNOs.
Alan Boyle, The Case For Pluto (p 104) says, "The error bars on the estimates of Sedna's size and mass are still large, but the current best guesses range between 750 and 1,100 miles for diameter, and no more than half of Pluto's mass.". — kwami (talk) 20:56, 7 June 2012 (UTC)

wording

From not "formally designated" a DP by the IAU to not "recognized" as a DP. That is the wording in one of Ckatz's NASA refs. Do we have a ref for the 'designated' wording? Any reason it would be preferable? — kwami (talk) 18:55, 5 June 2012 (UTC)

The appropriate forum for this would be the dwarf planet talk page, given that the current wording has stood for quite some time - and especially given the history of this matter. Speaking personally, I have trouble with the fact that you made these undiscussed changes within minutes of your POV tag being removed from the dwarf planet article. --Ckatzchatspy 22:43, 5 June 2012 (UTC)
There's no conspiracy, Ckatz. When I'm reminded of articles, I may see other things that I think need changing is all. — kwami (talk) 22:59, 5 June 2012 (UTC)
"Conspiracy" is not what came to mind, not at all. That aside, you're familiar enough with the controversial nature of what you've been doing to understand that you should get consensus first, at an appropriate forum. --Ckatzchatspy 23:05, 5 June 2012 (UTC)
I thought it would be too trivial to bother with. I'm not trying to change the compromise Kheider and I came to in this article, but am only reflecting wording used in one of your sources, which I thought was a better choice of words than what we currently have. — kwami (talk) 23:19, 5 June 2012 (UTC)

ref

Another ref to Sedna as a DP:

Arnold Hanslmeier (2010) Water in the Universe, p 69
3.4.2 Ices on Other Dwarf Planets
The dwarf planet 90377 Sedna was detected in 2004 ...

— kwami (talk) 18:47, 7 June 2012 (UTC)

Oh for God's sake Kwami you just don't fricking get it. It doesn't matter how many astronomers say Sedna is a DP; what matters is that the majority accept it. The IAU is the voice of the majority, so their call is what we follow. You can gather as much evidence to back your case as you want, but we will never, at least not in our lifetime, have conclusive proof that Sedna is a DP. There will always be uncertainty, and as long as there is someone has to draw a line. For better or worse, astronomers chose the IAU to draw that line. Serendipodous 19:01, 7 June 2012 (UTC)
Ah, sorry. I'm not proposing a change to this article. It's fine the way it is. But there is still push-back against reflecting sources elsewhere, and this is a handy place to post the ref.
As for your points, there is still uncertainty over the IAU five, as Stern has pointed out; we reflect that in our articles. Secondly, the IAU has simply not been making these decisions. They set up the definition of a DP, but are not in the business of deciding individual cases. There were two times that they needed to make a specific decision: once to promulgate the definition itself, and once to decide which committees would get to name which bodies. Maybe some day they will act on Tancredi's recommendations, but in the meantime, for anything with an albedo greater than 1 the IAU is not even in the picture. They are not a source for such bodies, and so we must go elsewhere. — kwami (talk) 19:13, 7 June 2012 (UTC)
Serendipodous, so you are saying that, say 60 years from now, when there is good evidence for Sedna being round, including some decent pictures, and everybody commonly refers to it as a dwarf planet, but the IAU has not formally designated it as such, all the former doesn't matter? --JorisvS (talk) 19:44, 7 June 2012 (UTC)
That is a purely hypothetical question. But in the extremely unlikely event that I make it to 97, I'd be willing to give you even`odds that the IAU will have made Sedna a DP by then; after all, close up telescope images are what made the case for Ceres. Serendipodous 21:17, 7 June 2012 (UTC)
Sure it's a hypothetical question. So what if they just don't address the issue anymore, despite all that? --JorisvS (talk) 22:13, 7 June 2012 (UTC)
I don't think that situation would arise. If we had irrifutable, in your face proof that Sedna was a dwarf planet, every astronomer on Earth would be calling it a DP, and there wouldn't be an issue with its inclusion. Serendipodous 22:23, 7 June 2012 (UTC)
Where did Stern point this out? Ruslik_Zero 19:47, 7 June 2012 (UTC)
We've already been over that, Ruslik. Anyway, it won't matter if I tell you, you'll just say I'm "lying". Check the archives if you like. — kwami (talk) 20:11, 7 June 2012 (UTC)
If have nothing behind your claims that you should say this directly. Ruslik_Zero 19:57, 8 June 2012 (UTC)

Notes: mistake

One of the "Notes" at the bottom of the page has a very serious mistake. It says:

The Stern-Levison parameter (Λ) ... determines if an object will eventually clear its orbital neighbourhood..... If an object's Λ is greater than 1, then that object will eventually clear its neighbourhood, and it can be considered for planethood. Using the unlikely highest estimated mass for Sedna of 2×1021 kg, Sedna's Λ is ... 1.44×10−6. This is much less than 1, so Sedna is not a planet by this criterion.

"unlikely highest estimated mass for Sedna of 2×1021 kg" is a mistake. Sedna's mass is likely more than 2×1021 kg. In fact, if we assume its diameter is 1400 km and its density is 2 g/cm3, then its mass will be 2.87×1021 kg. If its diameter is 1500 km and its density is 2.5 g/cm3 (about that of Eris), its mass will be 4.42×1021 kg. Could someone please correct this mistake? (Sedna's Λ will still be less than 10-4, so Sedna is not a planet.)Solomonfromfinland (talk) 08:51, 19 August 2012 (UTC)

Sedna is actually very likely only ~1000 km in diameter. If we assume that it is actually on the high end (~1075 km) of its measured size and has a very high density of 3 kg/dm3 (within the range of Haumea, so possible but not very likely), then we get ~2×1021 kg. --JorisvS (talk) 12:10, 19 August 2012 (UTC)

Why?

Why is this talk empty?--Solomonfromfinland (talk) 16:01, 19 May 2013 (UTC)

Because it has been archived (look in the box to right). --JorisvS (talk) 16:11, 19 May 2013 (UTC)

Orbit and Rotation

In the orbit section, it says: "Even as Sedna nears its perihelion in mid 2076, the Sun would appear merely as a very bright star in its sky, only 100 times brighter than a full Moon on Earth..." Am I misunderstanding something about brightness or is this a mistake? It sounds like they are saying that 100x the brightness of the full moon as it appears from the Earth is as bright as a very bright star. This sentence seems at least a bit ambiguous. (Lcohalan (talk) 06:23, 19 July 2013 (UTC)).

The Moon is not actually all that bright; it's just big. Shrink the moon down to the size of a star, and it would barely be visible to the naked eye. Serendipodous 06:28, 19 July 2013 (UTC)
100 times brighter than the full moon would be about apparent magnitude -18. That would still be ~3000 times dimmer than the Sun appears from Earth. -- Kheider (talk) 12:25, 19 July 2013 (UTC)
But it would be over a million times brighter than the brightest actual star (Sirius). I think this is the source of the OP's confusion. @Serendipodous: The Moon is extremely bright because it is very big; the definition of brightness (apparent magnitude) is independent of an object's (angular) size. --Roentgenium111 (talk) 17:39, 26 March 2014 (UTC)

One of the orbit pictures screams for immediate removal

Planet Nine is a hypothetical body that has nothing to do with reality. Until it gest photographed of course, which means forever. The scientific theories or computer simulations that do not approve its theoretical existence outnumber the fairy tale by far, no matter how big the headlines it made in the press when its non-discovery was announced to the public. Please somebody remove this picture from all pages about actual solar system bodies. Unless Vulcan and Nibiru orbits are drawn as well, of course. — Preceding unsigned comment added by 95.252.62.70 (talk) 20:09, 25 June 2017 (UTC)

Mass

I restored the note about Sedna's mass on the theory that it's a routine calculation, and as such not OR per WP:CALC. Please feel free to revert my undo if you disagree. —RP88 (talk) 01:22, 27 March 2014 (UTC)

In case it's not clear, the use of Pluto's density in the calc is presumably the source of a possible claim of OR. —RP88 (talk) 01:26, 27 March 2014 (UTC)

Possible that it's not a dwarf planet??

To qualify as a dwarf planet, Sedna must be shown to be in hydrostatic equilibrium. It is bright enough, and therefore large enough, that this is expected to be the case,[56] and several astronomers have called it one.

Are there some astronomers who believe it doesn't qualify as one?? Georgia guy (talk) 14:47, 2 April 2014 (UTC)

I don't know if there are any astronomers who have unequivocally said it wasn't (I don't think they would do so without pretty strong evidence, of which there is none), but not everyone is completely ready to say that it is. Some won't be happy without a telescope image, while others are happy with a diameter estimate. Serendipodous 15:06, 2 April 2014 (UTC)
At a diameter 995±80 km, no one seriously thinks that it could be irregular, AFAIK. Note that even rocky Vesta at a diameter of 525 km is rather round, aside from Rheasilvia basin (which has precluded it from regularly being called a dwarf planet) and at a diameter of 213 km icy Phoebe used to round but was severly battered. Then again, Saturn's moons Mimas, Enceladus, Tethys, Dione, and Iapetus all are clearly round, but careful measurements of their dimensions has revealed that they deviate from strict hydrostatic equilibrium (of Saturn's moons only Rhea and Titan have dimensions in correspondence with hydrostatic equilibrium). So if you go for hydrostatic equilibrium in its strict sense, none of the IAU-accepted dwarf planets (Ceres, Pluto, Eris, Makemake, and Haumea) are really known to fit. --JorisvS (talk) 15:09, 2 April 2014 (UTC)
If 2002 UX25 has the <0.9 density that Brown says it does, it would not be a dwarf planet (since DP can't be porous). UX25 was thought to be too large to be porous: how large can a porous object get? There's also the Saturn moons, as you mention. Would Iapetus be considered a DP if it was a TNO? I think the reason that Sedna is not generally labelled a DP is a recognition of the lack of understanding of these bodies (or, rather, lack of proof of current understanding), rather than uncertainty about Sedna's size or other properties. Most days, though, I think it's simply that whether or not something is a DP is not scientifically interesting, so most astronomers just blindly follow the IAU list, or just ignore the issue altogether. Tbayboy (talk) 18:37, 2 April 2014 (UTC)
A big strike against Sedna is that since it does not have a known moon, we do not know its mass or (estimated density). -- Kheider (talk) 18:56, 2 April 2014 (UTC)
I suspect that were Iapetus in solar orbit, it would be considered a DP (but would likely also be generating discussion about that it is not technically in HE). 2002 UX25 is an interesting case! Large enough that is should be a DP, but a very low density possibly requiring porosity and lightcurve measurements that cast doubt on its DPness...--JorisvS (talk) 21:04, 2 April 2014 (UTC)
I think this should remind us that DP is a rather stupid class. It was created to save Pluto's planetary status, but since that never happened, it serves no purpose except to determine which body at the IAU gets to name a new object. Iapetus would not be a DP if it were in Solar orbit, and there's a good chance that Haumea and Makemake are not DPs either. If they aren't, then Sedna probably isn't, but they would each require an orbiter, not just a fly-by, to determine if they're actually in HE. In other words, a completely useless category.
Serendipodous, if astronomers are willing to accept telescope images, then they're effectively saying the IAU definition can be ignored.
I think we should follow Brown's rec and use "planetoid" (literally, "planet-like") for bodies which we can reasonably expect to be round (that is, to be "worlds"), without demanding that they fit an technical definition that we can't actually determine. There's no problem calling Sedna a "planetoid". — kwami (talk) 21:24, 2 April 2014 (UTC)
Well, the class is fine, but we now know that requiring technical hydrostatic equilibrium for it is meaningless, thanks to the Saturnian moons. Those are all clearly rounded and really should be considered DPs if they were in solar orbit. Looking for rounded objects, one notices also Phoebe and Vesta, both of which appear to have been battered out of a nicely round shape. Because technical HE does not do it, a simple impact on a DP should not suddenly make it lose its DPness. --JorisvS (talk) 14:42, 14 April 2014 (UTC)
Because of Saturn's moons, we know that equilibrium shape does not mean HE. But without close-up observations, it's also impossible to know if irregular bodies like Phoebe were once in HE. Certainly if a HE body were split in half, the two halves would not count as separate DPs, so where do we draw the line? What if an ex-HE body is disrupted and comes back together as a rubble pile? Or 21 Lutetia, if it proves to be the battered core of a DP? — kwami (talk) 22:09, 14 April 2014 (UTC)
See 31 Euphrosyne: With a density over 6, it must be a fragment or core of something big. Tbayboy (talk) 01:07, 15 April 2014 (UTC)

Note [b]

I find the usage of "overtake" in footnote [b] to be ambiguous. It is apparently used in reference to one object approaching nearer to the sun than another, but this is not a terminology that would be used by astronomers. (It is trivial, also). — Preceding unsigned comment added by 75.90.11.191 (talk) 02:10, 9 December 2014 (UTC)

Odd name

Other than Wikipedia no one else seems to call this anything but Sedna. Google sources and IAU seem to always call this planetoid simply Sedna. Sure it was 2003 VB12 early after its discovery but isn't its official name now Sedna? Can't we move this from its strange "90377 Sedna" where no one looks for it? Fyunck(click) (talk) 09:40, 1 March 2015 (UTC)

"90377" is simply its minor-planet number, see its use for example at JPL: [1]. All named minor planets that are not officially listed as dwarf planets are located at "[minor-planet number] [name]". The number is not necessary for identification purposes (minor planets cannot share names; only the number is also sufficient for identification purposes in the context of the Solar System), but is useful for disambiguation purposes (with at least the namesake of the minor planet and possibly others). In all, in the text, it is unnecessary to include the number, but it is useful and consistent to have it in the title. --JorisvS (talk) 10:36, 1 March 2015 (UTC)
Using that same chart Pluto is "134340 Pluto." Titles here at Wikipedia are supposed to be the common name or if disambiguation is need, and extra term in parentheses. So Pluto or Pluto (dwarf planet). The IAU does not give it an official name of "90377 Sedna"... it's simply Sedna. Makemake and Haumea are not at some minor-planet number, nor should they be. Here it should follow similar naming either just Sedna or perhaps Sedna (minor planet). The TNO object Quaoar redirect is ridiculous... no one calls it by that and it should be redirected back to its proper title. Wikipedia is supposed to title by sourced common name or proper official name...90377 Sedna is neither. Encyclopedia Britannica gives it a proper name. Only before it's officially named by the IAU should we give it an astronomical number. Fyunck(click) (talk) 11:13, 1 March 2015 (UTC)
Except that Pluto is on the official list of dwarf planets. The name is "Sedna", but its number is "90377". Numbers exist alongside names. Pluto is a case in point: It was given a minor-planet number in 2006 when it was reclassified as a dwarf planet. If numbers were only in use until an object were named, then Pluto wouldn't have needed one. "Sedna" has other uses than the minor planet, and explicit disambiguation (dab) is preferred over dabbing using parentheses: WP:DAB. Using the number is a straightforward way of avoiding parentheses in the title. --JorisvS (talk) 11:39, 1 March 2015 (UTC)

Especially now that this story is cracking open, the planet is known as simply "Sedna" (common name): [2][3][4], which would make something like Sedna (planet)—or "(dwarf planet)", if you prefer—a better article title than the number. czar 04:27, 21 January 2016 (UTC)

Except that it is not a planet, and according to the IAU it is not a dwarf planet either (and because of the HE clause, we probably won't know if it is or not for a long time.) Double sharp (talk) 07:37, 21 January 2016 (UTC)
Numbers are fine to me as quite often astronomers have nothing more than a generic license plare number like 2012 VP113. -- Kheider (talk) 07:40, 21 January 2016 (UTC)
The number does help as a disambiguation, but better choices might be: Sedna (minor planet) or Sedna (Oort Cloud object). Those are much more common names/designations for the object. Fyunck(click) (talk) 08:54, 21 January 2016 (UTC)
I agree with the idea (minor planet), much better to grasp for the layperson. prokaryotes (talk) 09:07, 21 January 2016 (UTC)
And considering the amount of laypersons, kids, non-scientists, etc... (minor planet) works and is still an official term used. Fyunck(click) (talk) 11:16, 21 January 2016 (UTC)
@Fyunck(click): Though it was sometimes called one in the past, Sedna is not an Oort cloud object. Its orbit does not reach far enough to be affected by stellar tides and with the likely existence of Planet Nine, its orbit can be readily explained. It is a minor planet, but a piecemeal move is outright stupid; we'd have to move all the thousands of articles following the convention of minor-planet number + name. --JorisvS (talk) 10:16, 25 January 2016 (UTC)
You bring up two points. First is the Oort Cloud designation. I can only go by sources and sources tell me you are wrong. We have plenty of sources that say it's an Oort Cloud object. In Nov 2015, Scott Sheppard, astronomer at the Carnegie Institution for Science in Washington, D.C, called it an Inner Oort Cloud object. "Universe Today" from Aug 2015 also talks of it being in the Inner Oort Cloud. I can only go by sources. Now with "in the past" you mean 2 months in the past, that seems a little too restricting to me.
As for point two, a piecemeal move is not stupid at all. It's actually stupid to lump them all together as if they all have the same characteristics. They do not. We would not have to move thousands of articles. It is extremely rare to find this object called "90377 Sedna" in any writing. It is almost always called Sedna or minor planet Sedna or even dwarf planet Sedna. With all the sources calling it Sedna that's what our readers (and young readers) should see as an article title. Since it can't be because of duplicate names, Sedna (minor planet) is by far the best fit. It's what the average wikipedia reader would expect. Plus the last naming that had consensus did not choose 90377 Sedna. Fyunck(click) (talk) 10:44, 25 January 2016 (UTC)
I did say that it has been called an Oort cloud object. The thing with this has always been that its orbit does not fit what would be expected for an actual Oort cloud object (does not get far enough away to be affected by the galactic tides) and all of this was before Planet Nine became such a likely scenario. Planet Nine can actually pull typical SDOs into sednoid orbits.
This article has been at this location for eons, which also falls under consensus. I would personally be fine with "Sedna (dwarf planet)" if the several objects that are equally likely to be and as often called dwarf planets are also moved; and equally fine with being conservative and following the IAU list in article titles. I'm not fine with only moving this article to a different title. It'll have to be based on a set of identifiable criteria. So, if you propose to move only a few, which clear criteria do you propose to use? --JorisvS (talk) 18:56, 25 January 2016 (UTC)
Here I would disagree with your premise that everything fits a criteria. Every wiki project has criteria for notability but we also have wikipedia's general notability (GNG) to cover things that would normally not be notable per nice neat lists. This happens with baseball players, cricket players, etc... The same type of thing is happening here. WikiProject Solar System and WikiProject Astronomy have come up with a good working article naming that fits 99% of objects. There's no real reason to mess with that. But certain objects have gotten more press and therefore more sourcing, and have become much better known to the public by a certain name. When Pluto became a dwarf planet we didn't move it to a number because it was massively well known by just Pluto. Even if the god was just as well known we would have disambiguated Pluto and called it Pluto (dwarf planet). I'm not suggesting at all that Sedna has even come close to Pluto in popularity... not even in the same zip code. But it has crossed over from being a simple catalog item to something being talked about in the main stream press.
When smaller papers like the Lexington Kentucky Herald start talking about "Sedna, a large minor planet" we need to realize that the item in question has changed. That warranted closer scrutiny here at wiki imho, and it's why I brought this RM. Will this affect one more body? Two?, Six? I'm not sure because I was looking only at Sedna. For all I know this is the only anomaly. We have perfect boxed lists in wiki sports articles I work on to put things in nice categories. It usually works. But then someone comes along and says that one personality breaks the normal mode. We discuss it, argue about it, and (often grudgingly) agree that it's a special case. We don't change the usual criteria we created, we just know that not everything fits in a neat tidy package. Fyunck(click) (talk) 19:45, 25 January 2016 (UTC)
There have to be criteria, otherwise we are left with complete arbitrariness, which is bad. If your argument is really for using simply "Sedna" (popularity≈notability→primary topic), then that's a rather different question for me, one I could possibly support, although in that case I would say 50000 Quaoar and 90482 Orcus need to moved just like this article. But moving it to "Sedna (minor planet)" A) does not make the title any simpler, and B) adds parentheses instead of using natural disambiguation, which is just violating the principles of WP:NATURALDAB. The number 90377 is simply added as a natural way to disambiguate "Sedna", which in most contexts would not even be necessary (typical scientific articles, news articles, blogs, etc., and in the body of our article). --JorisvS (talk) 17:56, 26 January 2016 (UTC)
Which is why this is a case by case occurrence. We follow the sources. I find "90377 Sedna" to be completely "unnatural" and is not what is intended by NATURALDAB. Naturaldab says that we can disdain from using parentheticals if we can find "an alternative name that the subject is also commonly called in English reliable sources." "90377 Sedna" is almost never used in any English reliable sources therefore it is not natural to call it that. We could use "Sedna (90377)" but "Sedna (minor planet)" is imho much better for our wide swath of readers who come from all walks of life, and aren't familiar with the MPN number used in catalogs. I hope whoever closes this doesn't just take a head count but actually decides on what's best for our readers. Fyunck(click) (talk) 21:01, 26 January 2016 (UTC)
It is natural because it does occur like that; not particularly often, but it does happen. Parentheses like that, however, do not occur in running text, which is why that is, in fact, "unnatural". "Sedna (minor planet)" is at least clear and follows part of our article naming conventions, just skipping any non-parenthetical option that should be considered first per WP:NATURALDAB. "Sedna (90377)" is outright ridiculous: it is not recognizable in the slightest. It does not actually disambiguate, just confuse; minor-planet numbers are not placed in parentheses after the name. --JorisvS (talk) 11:30, 27 January 2016 (UTC)

Requested move 24 January 2016

The following is a closed discussion of a requested move. Please do not modify it. Subsequent comments should be made in a new section on the talk page. Editors desiring to contest the closing decision should consider a move review. No further edits should be made to this section.

The result of the move request was: No consensus to move after over two weeks of discussion. Cúchullain t/c 15:27, 9 February 2016 (UTC)


90377 Sedna → Sedna (minor planet) – In 2004 a name was chosen for this article... Sedna (planetoid). I don't see any other RM discussions in its history to make it what it is today so I don't know who actually changed it. Now 12 years later it seems that (minor planet) is a better fit than planetoid. Per the discussion above it seems clear that the common name of this minor planet is not "90377 Sedna." Furthermore it is confusing to new readers to see an MPC designation before the name Sedna. That number may be fine for asteroids or other bits of flotsam, but this possible dwarf planet has had much talk in the news; more so lately because of a possible new 9th planet. Even our own Minor planet designation article says 90377 is more just a catalog entry than an actual name designation. Let's call it what it is, a minor planet, per this very article and the minor planet article, and most sources. If some day it gets promoted to dwarf planet we'll deal with it then. For now, with the simple name Sedna being brought up more and more often in the press it's time for a change here. Fyunck(click) (talk) 10:56, 24 January 2016 (UTC)

Survey

Feel free to state your position on the renaming proposal by beginning a new line in this section with *'''Support''' or *'''Oppose''', then sign your comment with ~~~~.
I note that 2 of them are have dropped the number 1 Ceres and 136472 Makemake. Headbomb {talk / contribs / physics / books} 13:17, 25 January 2016 (UTC)
Yes, recognized dwarf planets are excluded, as it is unclear whether they are still technically minor planets. Serendipodous 13:21, 25 January 2016 (UTC)
Just to help confuse things more: "Technically", in some sense, there is no "minor planet" category: it's either a planet, dwarf planet, or small solar system body. But they still assign "minor planet" numbers to DPs and non-comet SSBs (and comet designations to cometary SSBs), so it looks like a dwarf planet is still a minor planet. Tbayboy (talk) 19:29, 25 January 2016 (UTC)
Because of astrology, the first four asteroids *may* be notable enough to the general public, but surely 10 Hygiea, 50000 Quaoar, and 90482 Orcus are not. -- Kheider (talk) 13:37, 25 January 2016 (UTC)
  • Oppose WP:NATURALDAB. The form used is frequently found in papers, so is a viable form of disambiguation by alternate title. -- 70.51.200.135 (talk) 07:14, 26 January 2016 (UTC)
  • Comment if you think that the KBO is the most likely topic, then why not propose it as the WP:PRIMARYTOPIC and move it to Sedna  ? (without any form of disambiguation) -- 70.51.200.135 (talk) 08:07, 26 January 2016 (UTC)
  • Oppose, 90377 Sedna is widely used in scientific papers. Sedna is not a dwarf planet either, it's simply a notable KBO. Davidbuddy9 Talk  04:49, 27 January 2016 (UTC)
    Those "widely used" scientific papers that use exactly "90377 Sedna" are few and far between. Many it seems use (90377) in parentheses because of its catalog number. A million other google sources use simply Sedna while calling it a minor planet. Fyunck(click) (talk) 06:00, 27 January 2016 (UTC)
    To add to that, the usage of "90377" in scientific papers speaks only to how the scientific community uses it. Sedna is now discussed in major outlets, such as our newspaper of record, The New York Times, and is described without its number. WP is a generalist encyclopedia and is written for the general public in the voice of the general public, not only the scientific community. I am no longer watching this page—ping if you'd like a response czar 15:52, 30 January 2016 (UTC)
So what exactly should we use as a metric to determine sufficient notability for designation removal? Because I can't access the NYT from London. Serendipodous 17:34, 30 January 2016 (UTC)
  • Support. As already noted, Sedna does seem to be most commonly identified simply as Sedna in a wide range of significant and reliable sources, from Britannica to Space.com, CalTech, Universe Today, NASA, etc. While our common practice of applying the numerical minor plant designation to bodies like this is entirely reasonable, sometimes it also makes sense to depart from it and favor common usage, particularly if the body becomes widely known by it's non-numerical name alone — and Sedna appears to be in that category. ╠╣uw [talk] 18:40, 30 January 2016 (UTC)
Comment: Then we should do the same for the "very well known" Vesta. -- Kheider (talk) 18:44, 30 January 2016 (UTC)
I would agree. ╠╣uw [talk] 09:56, 31 January 2016 (UTC)
Look, if you guys can come up with some objective criterion that can define "very well known", then I'd be fine with this. I don't see how you could though. Serendipodous 10:59, 31 January 2016 (UTC)
Look up Wikipedia:Article_titles#Use_commonly_recognizable_names and use it yourself, Serendipodous|ous:
"Wikipedia generally prefers the name that is most commonly used (as determined by its prevalence in reliable English-language sources) as such names will usually best fit criteria such as recognizability and naturalness."
"it generally prefers to use the name that is most frequently used to refer to the subject in English-language reliable sources."
" the term or name most typically used in reliable sources is generally preferred. Other encyclopedias are among the sources that may be helpful in deciding what titles are in an encyclopedic register, as well as what names are most frequently used."
Some of the above comments have presented evidence along these lines - others have not. Survey the existing citations - count up the variations and titles - let's see what happens.--Smkolins (talk) 11:34, 31 January 2016 (UTC)
Recognizability and similar points are not the only points to take into account, because there are other topics that compete for the same title, "Sedna". Unless we can agree that this article is the primary topic, that's where WP:NATURALDAB comes in. And the most natural way is still by prefixing the minor-planet number, not using parentheses. This has nothing to do with, nor is supposed to say anything about, the frequency with which the string "90377 Sedna" can be found relative to "Sedna" referring to the minor planet. --JorisvS (talk) 17:55, 31 January 2016 (UTC)
I still find this to be false. If you can't call something a Mustang because of too many other uses for the term, then certainly you'd look at Ford Mustang as a naturaldab in creating the article. It is a term in common usage. 90377 Sedna is not a common term by any stretch of the imagination. It is rarely used. Minor planet Sedna gets used in conversation more often. Sedna (minor planet) just flat out works best for our readers. Fyunck(click) (talk) 19:48, 31 January 2016 (UTC)

Discussion

If we do make this change, are we going to do so for every other named minor planet article? There are quite a few, and they all follow the established convention. Or are we just going to assume that Sedna is "special"? Serendipodous 23:02, 24 January 2016 (UTC)

  • I wouldn't make this a universal standard. Sedna is a special case just like 1 Ceres. Anyway, many sources say that Sedna is most likely a dwarf planet. Praemonitus (talk) 23:36, 24 January 2016 (UTC)
    This renaming could only be done for articles which receive more coverage. prokaryotes (talk) 23:42, 24 January 2016 (UTC)
    I would agree that this is a case by case thing. Most minor planets don't get enough coverage and sourcing to warrant removing the number designation. The general population isn't looking them up on a regular basis. If they get enough press, drop the number and use (minor planet). Otherwise no change. The only RfC/RM on this subject actually decided on Sedna (planetoid) 12 years ago. But it seems today that (minor planet) is the preferred designation of sources. Fyunck(click) (talk) 23:55, 24 January 2016 (UTC)
I agree too though I think the line is dwarf planet but these are still coming along on a case by case basis. --Smkolins (talk) 23:59, 24 January 2016 (UTC)
This is not about 'receiving enough coveraget to warrant removing the number'. That is uses a number has absolutely nothing to do with the amount of coverage. Zip. --JorisvS (talk) 10:16, 25 January 2016 (UTC)
I think coverage in the press is a huge deal. It why the dwarf planets don't need a number here. Leave the catalog numbers to the thousands of minor body articles that really have no sourcing other than those catalogs. Fyunck(click) (talk) 10:52, 25 January 2016 (UTC)
The above discussion is preserved as an archive of a requested move. Please do not modify it. Subsequent comments should be made in a new section on this talk page or in a move review. No further edits should be made to this section.

Artist's conception

I'm curious why this rendering of Sedna includes a spherical planet in the background if Sedna has no known moons? (Oh - I see original copy at [8] says "In the distance is a hypothetical small moon, which scientists believe may be orbiting this distant body.") I'll add that sentence to the image description, although I'd support removing it since we have no evidence any moon exists at all. Tom Ruen (talk) 15:02, 13 February 2016 (UTC)

It's because Sedna was originally thought to have a very long rotation period, which would be best explained by a sizable moon. We now know it has typical rotation period and no moon has been discovered. The artist's impression is thus misleading and should be removed (which I've already done). --JorisvS (talk) 15:05, 13 February 2016 (UTC)
I see. The moon could alternately be digitally removed. As-is, the image is still being used in other wiki languages. Tom Ruen (talk) 15:11, 13 February 2016 (UTC)
I tried a quick moon removal to the image. Tom Ruen (talk) 15:21, 13 February 2016 (UTC)
That would make it less misleading (the surface of the dark side can be seen in it, though, as well as strange purplish clouds). Regardless, I see no useful purpose this artist's impression could have in the article, which is ultimately why one may (or may not) be in the article. — Preceding unsigned comment added by JorisvS (talk • contribs)
Seriously guys, this is an overreaction. I don't see a moon there; all I see is a star. And the image is an accurate depiction of what current understanding says Sedna looks like; red and icy. Serendipodous 13:33, 14 February 2016 (UTC)
The moon has been removed by Tom Ruen. There are still the two weird things I've pointed out above. Plus, "icy" is not something that can be seen. The main point now would be the real added value of including it. --JorisvS (talk) 13:44, 14 February 2016 (UTC)
In this case, I think the value of the artist's impression is its accurate depiction of Sedna's reddish hue and great distance from the sun. Because of quirks of human psychology, a picture of these features conveys the information much better than prose or diagrams. I don't see the purplish clouds you mention, but agree that the visibility and odd coloration of the dark side are potentially misleading. However, these features are unlikely to convey false information about Sedna - they're more just an incorrect depiction of lighting in space. Also, it's not lead image, which makes inaccuracies like this a bit more forgivable. On the balance, I would say the information conveyed by this impression outweighs its potential to mislead, which gives it positive value. A2soup (talk) 23:18, 15 February 2016 (UTC)
I support keeping the image. Although I am a little uncomfortable without explaining the moon's removal. I'd put a date on the image and state that a hypothetical moon existed and was removed and why. Tom Ruen (talk) 00:05, 16 February 2016 (UTC)
With the moon removed, it can't be seen. And if it can't been seen, there is no point in mentioning it. --JorisvS (talk) 11:12, 16 February 2016 (UTC)
The purplish cloud is part of the background, as 'nebulae'. --JorisvS (talk) 11:12, 16 February 2016 (UTC)
I don't see a moon208.114.36.44 (talk) 15:42, 18 March 2017 (UTC)

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Sedna orbit

I made a plot of Sedna's orbit with current parameters and it is shaped differently from the SVG version (2012) in the article. And the relative orientations of Sedna and pluto's orbits don't match either. Does anyone know why the eccentricity is so high there? Did estimated parameters change since 2012?! Or is it just a qualitative representation? The NASA simulator[9] agrees with mine, although a bit unwieldy in controls for such a far out object. Tom Ruen (talk) 22:58, 27 June 2017 (UTC)


SVG, Bad orbits?
PNG, simulator, 2017 positions

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Flying Dutchman?

Apparently Mike Brown had a nickname for Sedna, Dutch, for the Flying Dutchman.[10] Is that something that can go in this article? Tom Ruen (talk) 04:55, 20 October 2017 (UTC)

Good point. Added. Serendipodous 08:29, 20 October 2017 (UTC)

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Confusing aphelion text

The first paragraph under http://en.wiki.x.io/wiki/90377_Sedna#Orbit_and_rotation seems to contain contradictory information. It starts with "Its orbit is extremely eccentric, with an aphelion estimated at 937 AU...". Later the reader sees "Eris was later detected by the same survey near aphelion at 97 AU." Is Sedna's aphelion near 937 AU or closer to 97 AU? And, if Sedna has an orbital period of 11,400 years, then it is unlikely we have observed it anywhere near perihelion *and* aphelion since its discovery.

Where have I erred? — Preceding unsigned comment added by Leveretth (talk • contribs) 21:48, 26 December 2018 (UTC)

Two possible reasons why you might be confused: 1. The paragraph you cite refers to two different objects, Sedna and Eris; and 2. aphelion is not the same as current distance. Sedna's aphelion is ~937 AU, but it is currently close to perihelion at a distance of 85 AU from the Sun. Eris, on the other hand, has an aphelion of ~98 AU, and is currently close to aphelion.Renerpho (talk) 00:18, 28 December 2018 (UTC)
I have changed the wording of the paragraph, trying to make it clearer. Is this better?Renerpho (talk) 02:05, 28 December 2018 (UTC)

Orbit inconsistent numbers

The overview lists aphelion, perihelion and semi-major axis numbers that are inconsistent - the SMA should be half the sum of the perihelion and aphelion. Do we even need the redundant SMA here? Acquirium (talk) 18:08, 28 December 2020 (UTC)

For aphelion and the orbital period we are listing barycentric values as they are more reliable over different epochs. We could switch the SMA from an instantaneous (misleading) 484AU to a barycentric value of 506AU. -- Kheider (talk) 20:04, 28 December 2020 (UTC)
Astronomy Stack Exchange had a question about this. It's inappropriate to mix orbital elements with different centers or epochs. If barycentric elements are preferred for long-period objects, they should be used across the board. Mgarraha (talk) 23:05, 29 December 2020 (UTC)
This is Wikipedia so drive-by editors will make small changes using their sources. If you switch all the unexciting orbital parameters to more-stable barycentric values, someone else will probably come by and change them back to the instantaneous JPL SBDB values that change every 6 months when JPL switches the epoch that they are defined at. The position of Jupiter over its 12 year orbit will notably change heliocentric solutions, but not barycentric solutions. AstDyS and JPL SBDB give different values because they define them at different epochs. Heliocentric solutions will vary giving Aphelion of about 881AU (2019) to 1010AU (2013), while the barycentric 937AU is just simply the more stable/accurate answer. For this reason it is more useful to give barycentric solutions for the orbital period and aphelion because those are the orbital values most readers will be looking at and noticing the biggest differences. -- Kheider (talk) 23:28, 29 December 2020 (UTC)

Perihelion is also well-known. Using JPL Horizons Sedna will come to perihelion around 2076-Jul-18 19:59 @ 76.1882AU (AstDyS=76.1858AU) with an uncertainty in the heliocentric distance of ±887049 km. (There is a difference of 360000km between Horizons and AstDyS.) Since the JPL SBDB is using an unperturbed 2-body solution instantaneously defined at epoch 2020-May-31 the generic perihelion date is off by ~4 months and 10 million km. This is the reason comets have their orbits defined at an epoch close to perihelion passage. -- Kheider (talk) 00:38, 30 December 2020 (UTC)

Yes, paraphrasing Einstein "why average infobox values when you can just look it up on Wikipedia?" Sagittarian Milky Way (talk) 15:39, 3 January 2021 (UTC)

Inuit inaccuracy

The Inuit would not be the nearest polar culture to Pasadena as stated in the article. The Yupik, maybe Aleut, would be closer. Contrary to popular opinion, all three groups have been called "Eskimos".

If that is true, then Mike Brown is at fault, not Wikipedia. Serendipodous 20:00, 13 April 2021 (UTC)
Actually, all three groups "together" are still called Eskimos. Individual groups are not. I tweaked the sentence to show it was Brown's error, not Wikipedia's. Fyunck(click) (talk) 20:38, 13 April 2021 (UTC)

Is Sedna really in interstellar space?

I didn't think the boundary was the heliopause (and Mammuthus01's edits are unreferenced anyway) - ok to leave or should I revert?JojoTNO (talk) 16:07, 27 April 2021 (UTC)

spelling

By the way, like those at other fine California schools of StanFord and BereKely, those at Caltech like to see the name spelled right. Gah4 (talk) 01:23, 21 October 2021 (UTC)

@Gah4: I can not find any instance of these being misspelled in the article. In case you refer to the talk page comment that you edited recently (and which I reverted), see WP:TPO for the few exceptions when editing other user's talk page comments is considered acceptable. The comment in question is almost 6 years old. Moreover, it occurred in a discussion that is "closed", as it was part of a requested move discussion. As stated at the end of that thread: The above discussion is preserved as an archive of a requested move. Please do not modify it. Subsequent comments should be made in a new section on this talk page or in a move review. No further edits should be made to this section. So the misspelling should stand. Renerpho (talk) 01:42, 21 October 2021 (UTC)
Thanks. Yes, I was editing maybe 100 pages, and accidentally changed this talk page. And as you note, we are supposed to add new comments in a new section at the end. So I added this at the end, as requested. Gah4 (talk) 03:52, 21 October 2021 (UTC)
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