Talk:Pluto

Opening Lines

There has been confusion, at my college even, about the way the article opened previously by stating that Pluto is the largest object in the Kuiper Belt but without mentioning Eris until the issue of mass came up. As far as scientists know at the moment, Eris is a slightly larger Trans-Neptunian Object. Most people (the students here, and the professors haven't mentioned it once during classes!) do not know about the Scattered Disk, and think of all TNOs as either Kuiper Belt or Oort Cloud objects. Some scientific articles even still list Eris as a KBO, not just a TNO. The earlier wording made it SOUND AS THOUGH it were trying to say that Pluto was the largest TNO because it didn't (and still doesn't at that point) say anything about a Scattered Disk. The following statement about mass did mention Eris, but made it sound like Pluto was known to be larger than Eris, just not as massive. There is more information much later, but at that point in the reading the old wording seemed misleading. It would seem unnecessary to break down the definitions of KBOs and SDOs right in the first sentences of the article, so to clarify and avoid confusion I have slightly modified the opening wording to say that Pluto is the second-largest dwarf planet, and THEN that it is the largest KBO. This sticks to all the same facts, but orders it so as to keep relevant information easier to read and understand. MXVN (talk) 21:55, 5 May 2015 (UTC)

The definitions are broken down in the handy footnote right after the first mention. Serendi^podous 22:06, 5 May 2015 (UTC)

The scattered disc is really a quite distinct population. That said, the Kuiper belt consists of several distinct populations, with the hot-classical population possibly more closely related to the scattered disc than the cold-classical population. As for Pluto vs. Eris: Eris is 27% more massive than Pluto, but Pluto is possibly the larger of the two (we'll know for certain this summer after New Horizons has flown by. You should tell your teachers that you've learned that what they teach is too incomplete to paint a correct picture of the situation and that they should get their terminology straight: the Kuiper belt is just one region of the entire trans-Neptunian region. --JorisvS (talk) 08:42, 6 May 2015 (UTC)

Orientation of Pluto's spin axis

I'm surprised to find the article doesn't seem to mention the unusual orientation of the spin axis pointing almost towards the sun. Also the article on Pluto's moons doesn't seem to mention it either, at any rate I didn't see it, unless I'm missing it.

I'd have thought this was an important aspect that should be highlighted. Especially now in build up to the Dawn mission so that the readers can understand its unusual orientation for the mission (with one of its hemispheres currently in permanent darkness, so will need to be photographed using Charon to illuminate it).

See http://spaceplace.nasa.gov/ice-dwarf/en/

for a diagram we could use.

Also for the new horizons mission, another diagram showing both Pluto and it's moons orientation along with the spacecraft's trajectory: http://qph.is.quoracdn.net/main-qimg-8fb3242b253733195de88814ba36453a?convert_to_webp=true

I'd edit it right away, but this surely must be a very high profile astronomy article with lots of editors and watchers, so maybe I'm missing something, as it is such a significant feature of Pluto. Has it has been discussed and there is a reason for not mentioning it? Or is it just an omission, if so then we should "be bold" and just add it in. Any thoughts? Robert Walker (talk) 03:09, 24 May 2015 (UTC)

It's mentioned in the "Rotation" section. Serendi^podous 07:25, 24 May 2015 (UTC)

Oh, so it does, thanks! How about adding the diagram from http://spaceplace.nasa.gov/ice-dwarf/en/ to that section? I mean this image here:

http://spaceplace.nasa.gov/review/ice-dwarf/pluto_orbit.en.gif

It's a NASA image so should be no problem including it, and it might help draw attention to the section as well as helping the reader.

What do you think about that idea? Just a thought. Others might miss it as I did. Robert Walker (talk) 11:45, 24 May 2015 (UTC)

I moved an animated image to the location. Given that all the other images are animated, it makes more sense. Serendi^podous 12:09, 24 May 2015 (UTC)

Okay great, thanks! Yes that's fine, an image helps draw attention and to understand the concept, and an animation is even better. As observed from New Horizons which is approaching Pluto from the direction of the sun. Just a thought, but probably most readers would understand this, could say "taken by New Horizons from the direction of the sun" or some such. Robert Walker (talk) 12:14, 24 May 2015 (UTC)

Possible observation of polar ice cap

Also wondered, what about the possible polar ice cap? I did a search of the page for "ice" and didn't find it. Is it mentioned?

I'd have thought there was enough attention in the news for this hypothesis to be worth a mention, even though of course whatever we write now is liable to be changed within a few weeks, what do you think?

NASA's Best Photos of Pluto Yet Show Possible Ice Cap (Video)

Pluto may have ice cap at pole

Just a suggestion again. Robert Walker (talk) 12:14, 24 May 2015 (UTC)

Well, we'll know for sure in 50 days, so maybe just wait. Serendi^podous 12:25, 24 May 2015 (UTC)

Okay :). Robert Walker (talk) 13:14, 24 May 2015 (UTC)

NASA-Audio (06/03/2015@1pm/edt/usa) - Moons of Pluto - "Surprising" Finds.

NASA-Audio (Wednesday, June 3, 2015@1pm/edt/usa) - Panel of experts to discuss latest "surprising" findings by the Hubble Space Telescope of the Moons of Pluto. - Enjoy! :) Drbogdan (talk) 12:07, 29 May 2015 (UTC)

References

When should we start moving material to daughter articles?

This is already becoming an issue, and it will explode once the New Horizons flyby ends, so we need to start thinking about it now. Serendi^podous 08:20, 4 June 2015 (UTC)

The "Satellites" section is fairlymuch too long. It can be trimmed, with the material moved to the already existing moons of Pluto if it is not there already."

I also think that the "Classification" section is rather long, with some material bordering on off-topic.

The information on its atmosphere and its geology/surface features can be expected to be expanded considerably, which may make it a good idea to split these off to Atmosphere of Pluto and Geology of Pluto (these are currently redirects). --JorisvS (talk) 09:57, 4 June 2015 (UTC)

I have trimmed the "Satellites" section to an appropriate size, though it could still be structured better. --JorisvS (talk) 16:16, 13 June 2015 (UTC)

I have pruned the "Classification" section somewhat, improved its structure and move it to the encompassing "History" section, with which its content groups naturally. --JorisvS (talk) 10:12, 15 June 2015 (UTC)

I have split off atmosphere (almost a week ago) and geology (just now) articles. --JorisvS (talk) 12:25, 7 July 2015 (UTC)

Directly?

Doesn't this; "Pluto and Charon are sometimes described as a binary system because the barycenter of their orbits does not lie within either body." contradict this "directly orbiting the Sun"? Directly means directly after all. If it is orbiting a point outside its barycenter then surely that's its primary orbit, as much as the moon orbits the Earth. If not, why not?121.73.221.187 (talk) 20:52, 6 June 2015 (UTC)

Personally I think orbiting an empty point in space doesn't really count as "orbiting something". Serendi^podous 20:58, 6 June 2015 (UTC)

It's not orbiting an empty point in space; it and Charon are orbiting each other. In exactly the same way in a binary star system the stars orbit each other (where their respective masses places the barycentre outside the bodies of each that is).121.73.221.187 (talk) 21:02, 6 June 2015 (UTC)

In that case, it is directly orbiting the Sun; it's just orbiting the Sun with Charon. Serendi^podous 21:13, 6 June 2015 (UTC)

Then that's not it itself orbiting 'directly'.

di·rect·ly

adverb

adverb: directly

1.without changing direction or stopping.

2.with nothing or no one in between.121.73.221.187 (talk) 21:24, 6 June 2015 (UTC)

Yup, definition #2 applies. If pluto was orbiting a point inside of another body, then it would be orbiting that body rather than the sun (as the moon orbits the earth). VQuakr (talk) 22:45, 6 June 2015 (UTC)

No it really doesn't. Orbiting means going around, it's not directly going around the sun as its primary orbit (any more than Earth's moon is), it and Charon are directly orbiting each other. That orbit is between their orbit and the orbit with the sun.It makes no difference if the centre of that orbit is inside a body or not, it's still the orbit that they have a primary direct relationship with. An orbit is not defined as being within the body of an another object, it's defined by the curved path the body is following. Otherwise you couldn't say binary stars were orbiting each other.121.73.221.187 (talk) 23:00, 6 June 2015 (UTC)

You asked the difference between Pluto and earth's moon; this was answered. VQuakr (talk) 23:05, 6 June 2015 (UTC)

I didn't ask for a difference between Pluto and Earth's moon. I pointed to how they're similar as the defining point of what does and doesn't constitute directly orbiting the sun. The barycenter of both is outside of the body in question, it's the barycentre that's the centre of their orbit, so that's their primary and direct orbit, around each other. The argument that the centre of the orbit is not within another body is moot, as that's nothing to do with the definition of an orbit, as demonstrated by binary systems where stars orbit each other.121.73.221.187 (talk) 23:27, 6 June 2015 (UTC)

I think I kind of agree. If someone describes the Pluto–Charon system as a binary, then each is rather a satellite of the other, and they cannot be said to really orbit the Sun directly, though together they still do, of course. That said, in the (current) IAU definition, Charon is a satellite of Pluto, not a dwarf planet, so it is Pluto that orbits the Sun directly. The phrase "directly orbiting the Sun" is worded per the IAU definition, whereas "Pluto and Charon are sometimes described as a binary system because the barycenter of their orbits does not lie within either body." only says that sometimes people consider it a binary. Without the word "sometimes" they would contradict each other, but they do not really do now, only for the people who actually consider it a binary, but they still live in a world where the majority does not. --JorisvS (talk) 09:04, 7 June 2015 (UTC)

@JorisvS: Thank you. In addition, Jupiter's barycenter with the Sun is above its surface. Jupiter is still a planet and is still "directly orbiting the Sun", isn't it? Obviously, the location of the barycenter alone does not adequately define what qualifies as planet or a moon. --Cheers, Rfassbind -talk 17:41, 8 June 2015 (UTC)

I completely agree with that. What makes the problem with a simple barycenter definition even clearer: The greater the distance from the primary, the less massive the secondary needs to be for the barycenter to be outside the primary, which means that if a not-so-massive object orbits very far from its primary, it is possible for the barycenter to be outside the primary. --JorisvS (talk) 20:20, 8 June 2015 (UTC)

@Rfassbind. The difference with the example of Jupiter you raise is that its direct relationship is still the sun. Just as Pluto and Charon could be said to be orbiting each other, Jupiter is orbiting the sun, even if the sun is orbiting Jupiter to a very very small degree.

@JorisvS, your argument regarding Charon being officially defined as the satellite of Pluto seems valid. Though it still seems strange that it would be defined that way, over-riding the primary definition of what a satellite is if you see what I mean. (And I'm not sure it changes what's meant by 'directly' in of itself, but I'm not going to make a big deal about it. Just raising it for consideration).121.73.221.187 (talk) 14:49, 13 June 2015 (UTC)

The IAU working group's initial definition of planet included Charon for precisely that reason, but it was voted down. I don't know why; perhaps they blanched at the idea of having to explain it to the public over and over and over again. Serendi^podous 15:17, 13 June 2015 (UTC)

@Anon, the simple barycenter definition is flawed: Whether a binary objects is a primary–moon or a double should not depend on their separation. Also, it is not the primary definition of what a satellite is, because only some people use it.--JorisvS (talk) 15:43, 13 June 2015 (UTC)

It's not a matter of an arbitrary definition, there's nothing to be 'flawed', the barycenter is objectively the centre of the orbit by definition; A natural satellite by definition is a body that orbits a primary body such as a planet/dwarf planet/small solar system body. It's not merely a difference in separation, but of what they're actually doing. If you were standing still and I was walking around you (with you slightly leaning towards me as I went around), that's significantly different to if we were both walking in a circle around a particular spot.121.73.221.187 (talk) 11:48, 14 June 2015 (UTC)

The barycenter of a primary–satellite pair is never exactly at the primary's center. The greater the satellite's mass, the farther it is from the primary's center. But also, the greater the separation between the primary and its satellite, the farther the barycenter is from the primary's center. This means that the barycenter can be located outside the primary for a smaller body further from the primary, but not when they would be closer together. This is not something that should factor in whether something is a primary–satellite or a double. --JorisvS (talk) 12:00, 14 June 2015 (UTC)

Also the barycenter of most asteroid moon systems is also outside the primary. Yawn. -- Kheider (talk) 13:35, 14 June 2015 (UTC)

"The barycenter of a primary–satellite pair is never exactly at the primary's center." -And no one said it was, -it's irrelevant to the point, there's an objective difference between two objects revolving around each other and one object orbiting another. If the barycenter is within one that's objectively the one being orbited. The relationship between two objects defines their relationship, that's tautological. Otherwise what's to stop us saying Charon is the Dwarf Planet and Pluto its satellite. What you're asserting has very little to do with the point raised. I.e. the use of the word 'directly' in relation to the word 'orbit'. It doesn't matter if you call Charon a satellite or blancmange. The objective fact of the orbit is what matters. They're spinning around each other in an orbit. No matter what you want to call them. Labels are all well and good, but they don't change what the objects themselves are actually doing.

And Kheider there's absolutely no need for the addition of comments like 'yawn'. -If you read the article you linked you'd see they're also sometimes referred to as binaries, including the MPC's/IAU's terminology being "binary companions" where a binary nature has been established (or even triple component systems). 219.88.68.195 (talk) 00:13, 15 June 2015 (UTC)

And yet that very link calls Charon a satellite... -- Kheider (talk) 01:01, 15 June 2015 (UTC)

Already been over why that's irrelevant to the point being raised, and it wasn't point you were making that I was addressing.219.88.68.195 (talk) 23:00, 15 June 2015 (UTC)

Anon, there is no break, or what you call "objective difference" between orbiting a barycenter inside or outside a primary. Instead, there is a continuum, with all possible separations between the center of the primary and the barycenter equally possible. And what makes Charon the secondary (satellite) regardless of anything is that it is unambiguously less massive than Pluto. "They're spinning around each other in an orbit": That's what all primary–satellite pairs do, just usually to a lesser degree. Whether the barycenter is just above or below the surface of the primary makes no physical difference. --JorisvS (talk) 09:19, 15 June 2015 (UTC)

Of course there's an objective difference between orbiting a barycenter inside or outside of another body. It's literally right there in what you said. Being inside or outside is an objective difference. And it's an objective difference that defines what is being directly orbited. There is a difference between two objects revolving around a point between them, directly orbiting that point, and one circling the other (even if it gives the primary a wobble); As here, those are two different things.

"Instead, there is a continuum, with all possible separations between the center of the primary and the barycenter equally possible."

By that argument you could say the earth is orbiting the Moon, it's just the barycenter is so far outside the body of the primary on this continuum that it's actually inside the Earth. -If 'all possible separations' are the equally possible.

"And what makes Charon the secondary (satellite) regardless of anything is that it is unambiguously less massive than Pluto."

-Again, you're missing the point. This discussion about labels is irrelevant. It doesn't change the fact of what is actually being directly orbited. Though (and again, this isn't the point) that isn't unambiguous as a definition of a satellite; there isn't a definition relating to relative size afaics, everything references the relationship in regard to orbit as the defining property; and it's also why their relationship is often described in terms of being a binary. And I've already accepted that the de facto labeling of Charon as a Satellite. I'm not arguing that at all.219.88.68.195 (talk) 23:00, 15 June 2015 (UTC)

It is different to you, but not to nature. If the barycenter is close to the surface of the primary, changing its density slightly while keeping its mass the same can mean that the barycenter ends up at the other side of the surface of the primary. No meaningful difference to nature, the objects still orbit with the same semi-major axis and orbital period. But I get the feeling that you think you're right and everyone who disagrees with you is wrong, no matter their arguments. Else, you would have simply understood that the satellite/secondary cannot be the more massive of the pair by definition of the words. --JorisvS (talk) 08:32, 16 June 2015 (UTC)

And if it had much less mass the satellite would spin off by itself, and if it had much more they'd crash into each other. Talking about what ifs doesn't change what is. Inside and outside are objectively different, you surely can't argue with that. Making what is being orbited different. If one body is orbiting a point inside another, then it's perfectly straight forward to say it is orbiting that body; If they're both orbiting a point outside of themselves, between them, that's not so straight forward. -Again, the definition of the words rely on the relationship of the orbit in regard to one another. I understand why that means the more massive of the two will be the primary; I was using the example to point out why your argument about a 'continuum' with "all possible separations between the center of the primary and the barycenter equally possible" was flawed.

And more to the point, this is still on the point about labels. -It's irrelevant to the point that's been raised about the use of the word 'directly'.121.73.221.187 (talk) 10:58, 16 June 2015 (UTC)

My point of the example is that there are no physical breaks anywhere that can non-arbitrarily be used in a definition. When looking from afar, the primary will be seen to wobble with respect to the background whether the barycenter is just inside or outside, and the degree to which it does will be virtually the same in those two cases. The simple barycenter definition depends positively on the density of the primary and the semi-major axis of the secondary, which are rather weird parameters to factor into what is a double or isn't. You can disregard this, but it won't get you anywhere. --JorisvS (talk) 11:50, 16 June 2015 (UTC)

How is being inside or outside not a non-arbitrarily physical break. -It doesn't matter how that hypothetical situation looks from a distance, we know it's outside in the case of Pluto and Charon. The IAU take the idea seriously and have explicitly stated that reclassifying Charon as a Dwarf planet may be considered. -Even explicitly saying they orbit each other (see 'Is Pluto's satellite Charon a dwarf planet?' here (and that constitutes an WP:RS)) -which is the point I'm raising about the world 'directly'; they cite their comparable size, and refer to the barycentre residing in the free space between them.

-Binary star systems exist with different size stars. The larger is just labeled the primary and the smaller a companion. That doesn't mean they're not in a binary relationship. Density/axis aren't weird parameters; the definition of what constitutes a binary relates to the relationship of the orbit. But -not that it matters, because again, it doesn't matter what we label them, -the point being raised is what they're actually doing in terms of what each is directly orbiting. -And we know they orbit each other -there's a reliable source right there. I'm not questioning the de facto present labeling at all.219.88.68.195 (talk) 21:52, 16 June 2015 (UTC)

Back to the original question - yes, Pluto directly orbits the sun. If Charon were reclassified as a dwarf plant, Pluto would still directly orbit the sun, with Charon. In your binary star analogy, if a star were, say orbiting a super-massive black hole, it would be doing so directly whether or not it had a binary companion. VQuakr (talk) 00:38, 17 June 2015 (UTC)

Thank you for addressing the actual question. But why is that 'directly' when you wouldn't say a moon was directly orbiting the sun? In both cases they're orbiting something else which is closer, while still going round the sun. What's the distinction? I can see how you could say the binary system was orbiting the sun, but they're individually speaking directly orbiting each other, as much as a moon orbits its primary. Like you could say the Moon and the earth orbit the sun together, but if you were talking about the Moon individually you'd say its direct orbit was around the earth. If you see what I mean.219.88.68.195 (talk) 04:06, 17 June 2015 (UTC)

The Earth/Moon comparison is not exactly accurate. In the case of the Moon, although it is directly orbiting the Earth its orbit is also at all point concave to the Sun and so it could just as accurately be said to be directly orbiting the Sun. I do not think this is the case with the Pluto/Charon system.EJM Missouri (talk) 17:06, 23 June 2015 (UTC)

Updating inflation

The article (currently) says "£5 (equivalent to £282, or $430 USD in 2015),", whose code is "equivalent to £{{formatnum:{{Inflation|UK|5|1930|{{CURRENTYEAR}}|r=0}}}}, or $430 USD in {{CURRENTYEAR}})", which looks like the current value in pounds is updated automatically, but not the current value in U.S. dollars. I'm not familiar with these templates, but is there a way to get the US-dollar version to also update automatically using these and maybe another template? --JorisvS (talk) 16:47, 14 June 2015 (UTC)

Rock and ice fractions

The original about Pluto's density and composition said "Observations by the Hubble Space Telescope place Pluto's density at between 1.8 and 2.1 g/cm3, suggesting its internal composition consists of roughly 50–70 percent rock and 30–50 percent ice by mass.". However, its density is known much more precisely than that (which I have corrected), but this means that the mentioned rock and ice fractions do no longer correspond to the density value. Pending a proper source for these, I have hidden this part. Does anyone know of a source that can be used to this end? --JorisvS (talk) 16:22, 18 June 2015 (UTC)

I don't think that precise answer is correct; the only way to determine density is to divide mass by volume, and we don't know what Pluto's volume is, because we don't know what its radius is, thanks to its atmosphere. Serendi^podous 17:54, 18 June 2015 (UTC)

We may not know it exactly, but we do have a good estimate, as the uncertainty in the density shows: 2.03±0.06 g/cm³. The most difficult part would be which densities to use for the components. I've think I've seen 1 and 3.5 g/cm³ somewhere. This would give the equations 3.5a+b=2.03±0.06 and a+b=1, and hence a rock fraction of a=0.412±0.024 and an ice fraction of b=0.588±0.024. However, I don't know if these densities are much good, and hence not how accurate the calculated composition would be. --JorisvS (talk) 09:23, 19 June 2015 (UTC)

Combining the history section

While that is tidier, it does mention Pluto's position in the Kuiper belt before Pluto's position in the Kuiper belt is properly explained in the origins section. Serendi^podous 18:07, 25 June 2015 (UTC)

We could move it if that makes more sense. Then again, "History" sections tend to be the first section in articles. Ours does say "From 1992 onward, many bodies were discovered orbiting in the same area as Pluto, showing Pluto's place within the Kuiper belt", which should be enough for readers to understand the point, IMO (although it could be phrased better, I'll do that in a minute). --JorisvS (talk) 09:59, 26 June 2015 (UTC)

equatorial spots

Anyone want to venture they're a crater chain from the impact of an inner moon? — kwami (talk) 23:59, 2 July 2015 (UTC)

Images for the infobox

• 
  Coloured
• 
  Not coloured

The colouration of the LORRI images degrades the contrast of the image (check the comparison on the right). Although the colour information provided by MVIC is valuable and relevant for the infobox, it is of a much lower resolution than the brightness and shape information provided by LORRI. I don't think they look particularly pretty, either, and since they sort of reduce the actual resolution of the image, I don't think we should have coloured LORRI images for the infobox.

According to this information, a colour image of Pluto from MVIC (i.e. a "real" colour image) where Pluto will be 480 pixels across will be downlinked on 16 July. This might be usable for the infobox. Other than that, we will have to wait until September for better colour images from MVIC.

We'll also probably soon (like tomorrow) be at a stage where raw images will likely be the best images for the infobox, by the way. --Njardarlogar (talk) 11:07, 7 July 2015 (UTC)

Of course this whole discussion will be completely moot in just over a week. However, in the meantime a color image reflects what Pluto is like much better than a greyscale image, even if it is of a somewhat lower resolution. --JorisvS (talk) 11:52, 7 July 2015 (UTC)

As per what I wrote above, due to the downlinking schedule, this debate can be relevant all the way until September, October or even later. :-) In terms of downlinked data, most of the flyby happens in September and the following weeks/months, not next week. --Njardarlogar (talk) 12:14, 7 July 2015 (UTC)

Again we are having some issues. The highest-resolution image released to date, is the image from 8 July, not 7 July. One must not confuse the resolution of the image file and the spatial resolution of the image. It's easy to blow up the 8 July, should that be preferable, but it is, either way, the best image we got of Pluto at this point. --Njardarlogar (talk) 12:48, 10 July 2015 (UTC)

Why don't we just use the color image until we get the final full frame pictures and then use that? This is all about esthetics after all, and the color one looks cooler. Cool trumps all. We have a few days to think about it....Ericl (talk) 12:28, 11 July 2015 (UTC)

I am not sure which images you are referring to now, the image we currently have for the infobox is positively the coolest picture planetary science has produced for quite some time (and we have no colour version of it). --Njardarlogar (talk) 12:47, 11 July 2015 (UTC)

I am beside myself with excitement. We are seeing things no person has ever seen before. History before our very eyes (and constantly updating on Wikipedia!). Anyway, I vote monochrome for now :)82.71.30.178 (talk) 22:03, 12 July 2015 (UTC)

NASA-TV - Pluto Flyby - Updated Schedule (7/12/2015) of Media Coverage

NASA-TV - Pluto Flyby - Updated Schedule (7/8/2015) of Media Coverage. - Enjoy! :) Drbogdan (talk) 11:59, 9 July 2015 (UTC) - UPDATE (7/12/2015) of Media Coverage. - Enjoy! :) Drbogdan (talk) 17:51, 12 July 2015 (UTC)

References

Hypothetical human perspective of the Pluto landscape

I notice this article is a bit lacking in description of what it would be like for a human to look at the landscape. There is reasonable detail at http://pluto.jhuapl.edu/common/content/FAQ.php , but it has some issues. To begin with, it uses a figure of 900 times dimmer than sunlight but 300 times brighter than moonlight that seems to disagree with the million-to-one ratio we have at moonlight. More to the point, I keep thinking there must be some kind of comparison we can use, maybe from around sunrise/sunset or from a particular near total solar eclipse that we have pictures of. I'm not sure - just feel like there must be a better didactic approach. And then there's the issue of the eye damage. Wouldn't it do terrible eye damage if you simply looked at the Sun from somewhere as far away as Pluto? I'm thinking the pinpoint of light is just as hot as when seen from Earth (inverse squares cancel out...) and the relaxed irises in low light are a danger, just as when people watch a near total solar eclipse here. Also, the way the source I cite puts it is "In the dim Pluto daylight, the astronaut may be able to see that the landscape has a yellowish or pinkish color..." which unfortunately is unclear whether it is hard to see color in the ambient light or if they simply didn't know at the time what color Pluto would be. I sometimes feel like colors are ever so slightly visible in moonlight - I think that at even 300 times brighter they should be unmistakeable?? Anyway, we need all this sort of stuff from some usable reliable sources for the article - it can't just be original research. Wnt (talk) 21:18, 9 July 2015 (UTC)

Plutodolia

<3 <3 <3 (yup, this is relevant, these astronomers could've sworn they saw a heart on Pluto.) — Rickyrab. ^{Yada yada yada} 04:18, 10 July 2015 (UTC)

More to the point, should we mention this bit of pareidolia in the article? — Rickyrab. ^{Yada yada yada} 04:23, 10 July 2015 (UTC)

I don't think so unless it legitimately ends up being what people remember about the mission. I would give it a week or two after the closest approach to see if anyone still remembers. A2soup (talk) 07:35, 10 July 2015 (UTC)

Rotation and the north pole

From recent images we see Pluto's north pole on top and rotation direction is counter-clockwise as viewed from above. But rotation period of Pluto is negative, so it should rotate clockwise, i.e. from east to west as viewed from the northern hemisphere of the Earth. Does this mean that on images we see Pluto upside down and north pole should be on the bottom if seen from the northern hemisphere of the Earth, not on top as on images? Should these questions be clarified in now small "Rotation" section of the article?188.69.214.120 (talk) 07:48, 12 July 2015 (UTC)

Properly, the north pole is where the thumb points if you follow the direction of rotation with the fingers of your right hand (the right-hand rule). Then, the rotation period is always positive, and a minus sign only used to stress that the obliquity of the body's is larger than 90°. So, when viewed from a body's north pole, it will by definition of what is its north pole rotate counterclockwise. (This would not be the case in the competing usage, though, which is that north is the pole on the same side of the ecliptic as Earth's north pole (which follows the right-hand rule regardless). This one is less simple, easier to confuse poles, and less universally applicable and hence less useful) --JorisvS (talk) 09:32, 12 July 2015 (UTC)

So, as Pluto's obliquity is 120 degrees, its north pole from the nortern hemisphere of the Earth should be seen in the lower part of Pluto's disc,not in the upper, as on recent images, Pluto is upside down on images, as I understand. 188.69.214.120 (talk) 11:01, 12 July 2015 (UTC)

As seen from Earth, yes. But images taken by New Horizons may be (often?, always?) rotated to have north up. --JorisvS (talk) 11:19, 12 July 2015 (UTC)

I think virtually every image official image release (i.e. non-raw image) since May or so has north as up (in the 'polar cap' release from April, the orientation was different). --Njardarlogar (talk) 11:29, 12 July 2015 (UTC)

Australians (and others in the southern hemisphere), I think, see north pole up, as they do see the Moon upside down.188.69.214.120 (talk) 11:45, 12 July 2015 (UTC)