Talk:Dwarf planet

For the discussion on developing a strategy for naming dwarf planet articles, please see Talk:Dwarf planet/Naming

Stars, Planets, Moons and Baricenters, or Distance Matters, Too

Under the section "Planetary Mass Moons" would it not be helpful to note that the location of a baricenter is as dependent upon the distance between the objects as it is on the difference in mass between them? The only reason that the baricenter of the Sol-Jupiter system is outside the sun is because half a billion miles separates them, whereas the only reason that it does not lie outside the earth in the earth-moon system is that the two are so close together. If Jupiter's mass were to the same ratio to the sun as the moon's is to earth, then wouldn't its baricenter with the sun be further outside the sun than it is? 68.165.69.198 (talk) 16:55, 28 July 2013 (UTC)

equatorial diameters

Our diameters are not equatorial as claimed. Should they be so, or should we change the label? — kwami (talk) 02:33, 4 September 2013 (UTC)

I noticed that, too. Given the error bars on most of these, and the tri-axial shape of (at least) Haumea, I favour changing the label. It only needs to be an approximation here, anyway -- just to give an idea of the size of the object. Tbayboy (talk) 19:39, 4 September 2013 (UTC)

OK, only Ceres is still equatorial. Makemake has 2 diff diams in the same ref - which should we use? — kwami (talk) 20:36, 4 September 2013 (UTC)

They had two good fits, one circular and one elliptical, and they preferred an intermediary 1430x1502 solution. (I'm actually looking at the pre-print of the Ortiz paper, not the actual published paper.) See also "On the size, shape, and density of dwarf planet Makemake" by Brown (arXiv:1304.1041v1 [astro-ph.EP] 3 Apr 2013), a bit of a rebuttal to the Ortiz paper over the latter's density determination. Brown gets 1434x1422 (1430 as a spherical equivalent) in his analysis of the occultation data (also including other data). I think they're all in the same ballpark, so pick any one. The current 1478 actually matches the 1430x1502 as a spherical equivalent. Either seems reasonable here. Tbayboy (talk) 00:03, 5 September 2013 (UTC)

The Name Doesn't IMPLY Anything. It Explicitly States...

The Name section of the article leads off, "The term dwarf planet has itself been somewhat controversial, as it implies that these bodies are planets..."

This statement, I originally thought, was misleading, so I corrected it last week, so it said the name explicitly states that these bodies are planets, but someone undid that change. Now, I'm almost completely certain that the statement is dishonest. Let's reiterate the statement, but change a few of the details:

"The term black person has itself been somewhat controversial, as it implies that these bodies are people..."

You see the issue? To call something a "dwarf planet" is to continue calling it a planet, the same way to call something a "cotton sock" is to call it a sock or to call someone a "black person" is to continue to call them a person. The statement, "A dwarf planet is not a planet," is self contradictory. Taking away all adjectives from the sentence, you're saying, "A planet is not a planet." The thing that really scares me about this is that it leads to the bigotry in my first example.76.29.225.28 (talk) 23:15, 9 September 2013 (UTC)

Think of a dwarf-planet as a compound noun. Minor planets are not really planets either. -- Kheider (talk) 23:34, 9 September 2013 (UTC)

They also have "planet" right in the name. These names are dishonest if these bodies are really not planets.76.29.225.28 (talk) 23:47, 9 September 2013 (UTC)

You're right that the names are unsatisfactory, but sometimes language does unfortunate things like that. This has been discussed before on Wikipedia. We have to accept the names, as the IAU is unlikely to change them. Rothorpe (talk) 00:15, 10 September 2013 (UTC)

The choice of name appears to have been part of a strategy to get Pluto reinstated as a planet "through the back door". So yes, it would seem a bit dishonest. If you dislike it, I suggest you take Brown's advice and use "planetoid" instead. — kwami (talk) 03:10, 10 September 2013 (UTC)

Planetary discriminant of Sedna

I restored because the edit summary for deletion was off the mark: Eris and OR10 etc. are not is Sedna's orbital zone. But I haven't reviewed the citation as for whether there's actually a useful mass estimate of the zone to calculate the discriminant. — kwami (talk) 19:14, 30 December 2013 (UTC)

What is the reason to add Sedna in this list, but not other leading dwarf planet candidates, mainly Quaoar and OR10 which appear to be more massive? Ambi Valent (talk) 23:18, 30 December 2013 (UTC)

Sedna is the largest known body in its region, which makes it analogous to Ceres, Pluto, and Eris. It's obvious the other bodies are not going to make planetary status if their larger neighbors do not, but it's not obvious in the case of Sedna. — kwami (talk) 23:33, 30 December 2013 (UTC)

You're right about Eris and OR10: they overlap, but the period difference is more than an order of magnitude. (Cool - it's there to exclude comets, but now we're looking at comet-Sedna!) The mass estimate, though, is wildly inaccurate, since it doesn't consider any smaller (higher-H) bodies. Also, the estimate of 40 is simply based on the odds (best fit) of their seeing exactly one Sedna amongst similar objects on similar orbits -- the realistic range they give is 15-92 (1σ), so 40 is not even a good lower limit. It also doesn't consider any similar sized bodies that might be in less eccentric orbits (as they mention), hence not detectable by their surveys. The reference is not an estimate of the mass of the zone, nor intended to be. If we're okay to use it as a lower limit (say 15 Sedna-mass), then I recommend "<0.07" rather than just the bare number. Tbayboy (talk) 02:54, 31 December 2013 (UTC)

Sounds good. I was wondering if there was anything salvageable at all. Perhaps "estimated <0.07"? — kwami (talk) 04:27, 31 December 2013 (UTC)

Okay. I made the change. Tbayboy (talk) 04:47, 31 December 2013 (UTC)

But 15 is like realistically a lower limit of Sedna-sized objects. But that means that there must be many more smaller objects and possibly some larger objects. So simply "<0.07" would be accurate. --JorisvS (talk) 21:39, 3 January 2014 (UTC)

Murky

"It is estimated that there are hundreds to thousands of dwarf planets in the Solar System. The IAU currently recognizes five: Ceres, Pluto, Haumea, Makemake, and Eris.[11] Brown criticizes this official recognition: "A reasonable person might think that this means that there are five known objects in the solar system which fit the IAU definition of dwarf planet, but this reasonable person would be nowhere close to correct."[12] It is suspected that another hundred or so known objects in the Solar System are dwarf planets.[13] Estimates are that up to 200 dwarf planets may be found when the entire region known as the Kuiper belt is explored, and that the number may exceed 10,000 when objects scattered outside the Kuiper belt are considered.[14] Individual astronomers recognize several of these,[13]" This paragraph should be re-written, consolidating the estimates.211.225.34.139 (talk) 02:15, 24 January 2014 (UTC)

How would you consolidate them further? They're already consolidated in the first passage you put in bold. — kwami (talk) 02:52, 24 January 2014 (UTC)

I agree it's murky. What does "clear its orbit" mean? Pluto and Earth both have large moons, so why is Earth a planet but Pluto a "dwarf planet"? Do the Trojan asteroids in Jupiter's orbit disqualify Jupiter? 71.59.43.26 (talk) 04:00, 18 February 2014 (UTC)