Talk:Pluto (planet)
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On Template:March 19 selected anniversaries
I think that it is well worth including an account of the discarded specular reflection theory as an illustration of the point that although scientists have many neat ideas, the neat ideas that actually work are a painfully small minority. -- Alan Peakall 12:45 Feb 21, 2003 (UTC)
This sentence is silly:
- There is mounting evidence that Pluto may in fact be a member of the Kuiper Belt, only one of a large number of distant icy bodies.
...because the definition of the Kuiper belt, "an area of the solar system extending outwards from the orbit of Neptune (at 30 AU) to 50 AU," clearly inclueds Pluto.
Perhaps the sentence should read:
- There is mounting demand among astronomers that Pluto should no longer be classified as a planet but only a member of the Kuiper Belt.
--Uncle Ed 18:22 Feb 26, 2003 (UTC)
Or maybe:
- There is mounting evidence that Pluto should no longer be classified as a planet, but only a member of the Kuiper Belt.
otherwise these pesky astronomers seem to be demanding on a whim! -- Tarquin 19:10 Feb 26, 2003 (UTC)
- However, there is no real reason not to also call Pluto a planet, since the definition of "planet" is "whatever IAU points to and calls a planet". The debate has never been over whether to "demote" Pluto, but rather whether to add a category which it falls into. I think that the existing wording is just fine. Bryan
"Pluto orbits in a 3/2 resonance with Neptune." -- what does that mean? resonance doesn't seem to be about orbits and planets. -- Tarquin 11:02 Mar 28, 2003 (UTC)
- When Neptune approaches Pluto from behind, they start to pull on each other slightly, and you get one of those complicated interactions of the same sort that produce Trojan points, L4 & L5, etc. Since the orbits are eccentric, the 3/2 periodic ratio is favoured because this means Neptune always passes Pluto when they're almost furthest apart. On the other hand, half a Pluto orbit later, it seems like Neptune's about to catch up to Pluto, but Pluto speeds up with the acceleration from the Sun, stays ahead of Neptune, and pulls ahead, until they meet again on the other side of Pluto's orbit.
- So while it isn't one of the more common uses of the term resonance, it is a resonance. -- John Owens 11:27 Mar 28, 2003 (UTC)
Thanks. I was asking more for the benefit of the Constant Reader than myself, so the above is best off in the article :-) -- Tarquin 15:59 Mar 28, 2003 (UTC)
- ... ah, I see someone has linked to Orbital resonance. cool. :-) -- Tarquin 16:00 Mar 28, 2003 (UTC)
Would someone please shuffle around the paragraphs of Pluto (planet), so all the debate over "planet vs. Kuiper Belt object" is in one place? I think our readers are more interested in its location, orbit, and other characteristics; followed by how the heck those science johnnies found it in the first place; and also might be amused by the Great Status Debate -- but let's not scatter all the planet vs. object stuff all throughout the article. --Uncle Ed 20:22 Apr 4, 2003 (UTC)
Does anyone know why the picture of Pluto is all red and orangey? What kind of camera/imaging technique was used? --dave
- I have no idea what the case is for this particular picture, it could be a false color image, but I recall reading in multiple sources that Pluto really does have a reddish color. The red comes from complex organic compounds formed when methane ice on the planet's surface is hit with ultraviolet light. Bryan
From what I've read Pluto doesn't reflect much light, and just shows up as grey/white. [1] (http://spacekids.broaddaylight.com/spacekids/FAQ_42_2034.shtm) -- User:goatasaur
Yeh. I've read it's grey. -PY
According to http://webs.wichita.edu/lapo/o40.html it's red. Perhaps it's a matter of whether the atmosphere is frozen out or not. Bryan
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You have got to be kidding.
The statistics on Pluto show:
Mean radius 5.91352×109 km
Divide that by one million and you at least have the right order of magnitude. Whether the figure is right in that case, I don't know, but the order of magnitude is majorly wrong.
- That's the orbital radius (it's under the "Orbital characteristics" heading). The planet radius is correctly reported as ~2300 km. At18 12:09, 23 Nov 2003 (UTC)
Pluto's moon section
Had this in it:
(this is due to the fact that Charon's period of revolution about Pluto and the time it takes for Pluto to turn once on its axis are almost identical - though not exactly identical: At the time of Pluto's discovery in 1930, Charon happened to be positioned directly behind Pluto as seen from Earth, preventing it from being discovered; over the next 48 years, however, the infinitesimal difference between the periods of Charon's revolution and Pluto's rotation had sufficiently built up to allow Charon to "peek out" from behind Pluto from a terrestrial perspective, enabling Charon to be discovered then)
As far as I can tell, this entire parenthetical is inaccurate. Charon is completely tidally locked with Pluto, not just nearly so. It wasn't discovered initially because telescopes just weren't that good back then, not because it was hidden behind Pluto. Even if it was its orbital period is 6 days, so it wouldn't take anywhere near 48 years for it to "peek out" from behind Pluto. Bryan 08:44, 26 Mar 2004 (UTC)
- Yeah, it seems that way. —Bkell 09:22, 26 Mar 2004 (UTC)
Not a "smoking gun", but...
This appears on page 662 of the 2004 World Almanac:
"At the U.S. Naval Observatory in Flagstaff (Arizona), in 1978, James Christy obtained a photograph of Pluto that was distinctly elongated. Repeated observations of this shape and its variation were convincing evidence of the discovery of a satellite of Pluto, now named Charon." (Presumably previous photos of Pluto taken between 1930 and 1978 did not show this "distinct elongation" - and if not, why not?).
- Because telescopes weren't good enough before then. Look at the best photograph we have now in 2004—it's a blurry circle. I doubt telescopes in the 1940s were able to see Pluto as anything more than a dot.
- Charon goes around Pluto in fewer than seven days. If you have a telescope that can resolve Charon, you would be able to observe a complete revolution in a week, not 48 years. Christy was able to observe the variation in the shape, after all; there would be no variation to observe if it took years and years. The reason Charon wasn't discovered until 1978 is that telescopes weren't good enough, not because Charon was hiding behind Pluto. —Bkell 10:44, 28 Mar 2004 (UTC)
This was not my contention at all; what I was trying to assert is the possibility that, say, Pluto's rotation period could be something like 6 days 9 hours 17 minutes and 36.2435 seconds while Charon's revolution period might be 6 days 9 hours 17 minutes and 36.2436 seconds or something like that. Over many (Earth) years, this difference would have eventually caused the apparent relationship between the two bodies to change ever so slightly - much like the difference between the Julian calendar and the actual solar year caused the seasons to change ten days too early by the 16th Century.
- Erm, what? That would only change which face of Pluto faces Charon. How would it have anything to do with the "distinct elongation" that would be visible in the 1978 photograph? I don't follow your reasoning at all. —Bkell 12:22, 28 Mar 2004 (UTC)
- The reasoning just isn't right. An astronomer can observe Pluto at any time (any phase) in its rotation period. We aren't forced to look only when one spot on Pluto is underneath the Sun. Thus, in the last 74 years, Pluto has been observed many times with Charon on one side, with Charon on the other side, with Charon hidden, with Charon in front. -- hike395 15:16, 28 Mar 2004 (UTC)
Possibility of rings
On page 409 of the 2004 TIME Almanac, there is a horizontal row in the table marked "(Number of) Rings." Under Pluto a "?" appears - in stark contrast to the definitive "0" entered for Mercury, Venus, Earth and Mars (the numbers for Jupiter Saturn, Uranus and Neptune being 3, 1,000, 11, and 4 respectively).
In addition, Pluto's density of 32% of Earth's is far closer to that of Jupiter, Saturn, Uranus and Neptune (the four known ringed planets, with density ratios of 24%, 12%, 23% and 30% of Earth's respectively) than to that of Mercury, Venus and Mars (at 98%, 95% and 71% respectively). Since Pluto seems to take after the other outer planets in this respect, shouldn't the possibility exist that it also takes after them as per other characteristics as well (the existence of rings)?
- Pluto is not a planet. Are there any other planetoids (asteroids, KBOs etc.) with rings? — Jor (Talk) 12:35, 28 Mar 2004 (UTC)
- Don't forget that Pluto is very different to the other outer planets - the four ringed planets are extremely massive compared to the five smaller planets, and Pluto is a midget compared to the latter five. I'm no expert on planetary rings but I would guess that there's a good reason why none of the smaller planets have rings - probably something to do with the smaller Roche limits of those worlds. It seems very improbable to my mind that Pluto has any rings, so I would guess that Time is playing safe: we know for sure that eight of the nine planets have rings but we don't know this for sure yet in Pluto's case. -- ChrisO 12:45, 28 Mar 2004 (UTC)
- I agree with Jor and ChrisO. A question mark in the Time Almanac is not a definitive source for rings. How about a scientific paper? Rings only occur in the super massive planets. The density of the planet is irrelevant. Finally, scientists do have occultation data for Pluto... If there were a ring system, it would occlude the starlight in a special pattern. This is how the rings of Uranus were discovered. No such pattern has been discovered, hence there is no evidence of rings. --- hike395 15:09, 28 Mar 2004 (UTC)
On Template:March 19 selected anniversaries
I think that it is well worth including an account of the discarded specular reflection theory as an illustration of the point that although scientists have many neat ideas, the neat ideas that actually work are a painfully small minority. -- Alan Peakall 12:45 Feb 21, 2003 (UTC)
This sentence is silly:
- There is mounting evidence that Pluto may in fact be a member of the Kuiper Belt, only one of a large number of distant icy bodies.
...because the definition of the Kuiper belt, "an area of the solar system extending outwards from the orbit of Neptune (at 30 AU) to 50 AU," clearly inclueds Pluto.
Perhaps the sentence should read:
- There is mounting demand among astronomers that Pluto should no longer be classified as a planet but only a member of the Kuiper Belt.
--Uncle Ed 18:22 Feb 26, 2003 (UTC)
Or maybe:
- There is mounting evidence that Pluto should no longer be classified as a planet, but only a member of the Kuiper Belt.
otherwise these pesky astronomers seem to be demanding on a whim! -- Tarquin 19:10 Feb 26, 2003 (UTC)
- However, there is no real reason not to also call Pluto a planet, since the definition of "planet" is "whatever IAU points to and calls a planet". The debate has never been over whether to "demote" Pluto, but rather whether to add a category which it falls into. I think that the existing wording is just fine. Bryan
"Pluto orbits in a 3/2 resonance with Neptune." -- what does that mean? resonance doesn't seem to be about orbits and planets. -- Tarquin 11:02 Mar 28, 2003 (UTC)
- When Neptune approaches Pluto from behind, they start to pull on each other slightly, and you get one of those complicated interactions of the same sort that produce Trojan points, L4 & L5, etc. Since the orbits are eccentric, the 3/2 periodic ratio is favoured because this means Neptune always passes Pluto when they're almost furthest apart. On the other hand, half a Pluto orbit later, it seems like Neptune's about to catch up to Pluto, but Pluto speeds up with the acceleration from the Sun, stays ahead of Neptune, and pulls ahead, until they meet again on the other side of Pluto's orbit.
- So while it isn't one of the more common uses of the term resonance, it is a resonance. -- John Owens 11:27 Mar 28, 2003 (UTC)
Thanks. I was asking more for the benefit of the Constant Reader than myself, so the above is best off in the article :-) -- Tarquin 15:59 Mar 28, 2003 (UTC)
- ... ah, I see someone has linked to Orbital resonance. cool. :-) -- Tarquin 16:00 Mar 28, 2003 (UTC)
Would someone please shuffle around the paragraphs of Pluto (planet), so all the debate over "planet vs. Kuiper Belt object" is in one place? I think our readers are more interested in its location, orbit, and other characteristics; followed by how the heck those science johnnies found it in the first place; and also might be amused by the Great Status Debate -- but let's not scatter all the planet vs. object stuff all throughout the article. --Uncle Ed 20:22 Apr 4, 2003 (UTC)
Does anyone know why the picture of Pluto is all red and orangey? What kind of camera/imaging technique was used? --dave
- I have no idea what the case is for this particular picture, it could be a false color image, but I recall reading in multiple sources that Pluto really does have a reddish color. The red comes from complex organic compounds formed when methane ice on the planet's surface is hit with ultraviolet light. Bryan
From what I've read Pluto doesn't reflect much light, and just shows up as grey/white. [2] (http://spacekids.broaddaylight.com/spacekids/FAQ_42_2034.shtm) -- User:goatasaur
Yeh. I've read it's grey. -PY
According to http://webs.wichita.edu/lapo/o40.html it's red. Perhaps it's a matter of whether the atmosphere is frozen out or not. Bryan
You have got to be kidding.
The statistics on Pluto show:
Mean radius 5.91352×109 km
Divide that by one million and you at least have the right order of magnitude. Whether the figure is right in that case, I don't know, but the order of magnitude is majorly wrong.
- That's the orbital radius (it's under the "Orbital characteristics" heading). The planet radius is correctly reported as ~2300 km. At18 12:09, 23 Nov 2003 (UTC)
Pluto's moon section
Had this in it:
(this is due to the fact that Charon's period of revolution about Pluto and the time it takes for Pluto to turn once on its axis are almost identical - though not exactly identical: At the time of Pluto's discovery in 1930, Charon happened to be positioned directly behind Pluto as seen from Earth, preventing it from being discovered; over the next 48 years, however, the infinitesimal difference between the periods of Charon's revolution and Pluto's rotation had sufficiently built up to allow Charon to "peek out" from behind Pluto from a terrestrial perspective, enabling Charon to be discovered then)
As far as I can tell, this entire parenthetical is inaccurate. Charon is completely tidally locked with Pluto, not just nearly so. It wasn't discovered initially because telescopes just weren't that good back then, not because it was hidden behind Pluto. Even if it was its orbital period is 6 days, so it wouldn't take anywhere near 48 years for it to "peek out" from behind Pluto. Bryan 08:44, 26 Mar 2004 (UTC)
- Yeah, it seems that way. —Bkell 09:22, 26 Mar 2004 (UTC)
Not a "smoking gun", but...
This appears on page 662 of the 2004 World Almanac:
"At the U.S. Naval Observatory in Flagstaff (Arizona), in 1978, James Christy obtained a photograph of Pluto that was distinctly elongated. Repeated observations of this shape and its variation were convincing evidence of the discovery of a satellite of Pluto, now named Charon." (Presumably previous photos of Pluto taken between 1930 and 1978 did not show this "distinct elongation" - and if not, why not?).
- Because telescopes weren't good enough before then. Look at the best photograph we have now in 2004—it's a blurry circle. I doubt telescopes in the 1940s were able to see Pluto as anything more than a dot.
- Charon goes around Pluto in fewer than seven days. If you have a telescope that can resolve Charon, you would be able to observe a complete revolution in a week, not 48 years. Christy was able to observe the variation in the shape, after all; there would be no variation to observe if it took years and years. The reason Charon wasn't discovered until 1978 is that telescopes weren't good enough, not because Charon was hiding behind Pluto. —Bkell 10:44, 28 Mar 2004 (UTC)
This was not my contention at all; what I was trying to assert is the possibility that, say, Pluto's rotation period could be something like 6 days 9 hours 17 minutes and 36.2435 seconds while Charon's revolution period might be 6 days 9 hours 17 minutes and 36.2436 seconds or something like that. Over many (Earth) years, this difference would have eventually caused the apparent relationship between the two bodies to change ever so slightly - much like the difference between the Julian calendar and the actual solar year caused the seasons to change ten days too early by the 16th Century.
- Erm, what? That would only change which face of Pluto faces Charon. How would it have anything to do with the "distinct elongation" that would be visible in the 1978 photograph? I don't follow your reasoning at all. —Bkell 12:22, 28 Mar 2004 (UTC)
- The reasoning just isn't right. An astronomer can observe Pluto at any time (any phase) in its rotation period. We aren't forced to look only when one spot on Pluto is underneath the Sun. Thus, in the last 74 years, Pluto has been observed many times with Charon on one side, with Charon on the other side, with Charon hidden, with Charon in front. -- hike395 15:16, 28 Mar 2004 (UTC)
Possibility of rings
On page 409 of the 2004 TIME Almanac, there is a horizontal row in the table marked "(Number of) Rings." Under Pluto a "?" appears - in stark contrast to the definitive "0" entered for Mercury, Venus, Earth and Mars (the numbers for Jupiter Saturn, Uranus and Neptune being 3, 1,000, 11, and 4 respectively).
In addition, Pluto's density of 32% of Earth's is far closer to that of Jupiter, Saturn, Uranus and Neptune (the four known ringed planets, with density ratios of 24%, 12%, 23% and 30% of Earth's respectively) than to that of Mercury, Venus and Mars (at 98%, 95% and 71% respectively). Since Pluto seems to take after the other outer planets in this respect, shouldn't the possibility exist that it also takes after them as per other characteristics as well (the existence of rings)?
- Pluto is not a planet. Are there any other planetoids (asteroids, KBOs etc.) with rings? — Jor (Talk) 12:35, 28 Mar 2004 (UTC)
- Don't forget that Pluto is very different to the other outer planets - the four ringed planets are extremely massive compared to the five smaller planets, and Pluto is a midget compared to the latter five. I'm no expert on planetary rings but I would guess that there's a good reason why none of the smaller planets have rings - probably something to do with the smaller Roche limits of those worlds. It seems very improbable to my mind that Pluto has any rings, so I would guess that Time is playing safe: we know for sure that eight of the nine planets have rings but we don't know this for sure yet in Pluto's case. -- ChrisO 12:45, 28 Mar 2004 (UTC)
- I agree with Jor and ChrisO. A question mark in the Time Almanac is not a definitive source for rings. How about a scientific paper? Rings only occur in the super massive planets. The density of the planet is irrelevant. Finally, scientists do have occultation data for Pluto... If there were a ring system, it would occlude the starlight in a special pattern. This is how the rings of Uranus were discovered. No such pattern has been discovered, hence there is no evidence of rings. --- hike395 15:09, 28 Mar 2004 (UTC)
The Image?
Well, the image that is there is a blatant lie. There is a far better image of Pluto (in color no less) over at some nasa site (http://antwrp.gsfc.nasa.gov/apod/ap010319.html). However, being a n00b, I haven't the slightest clue how to not violate copyright. So someone either needs to get that image, or to change the caption on the current one. Ctachme 04:02, 8 Apr 2004 (UTC)
- Nice! If it's a NASA image it is likely in the public domain. Anyone see any reasons why it might not be? Bryan 04:07, 8 Apr 2004 (UTC)
Pluto a KBO?
Who says what is a planet and whats not? some stupid astronomers that dont even know what planet means? There are also theories to classify as planets those objects that have more than 360km of diameter, the size enough when gravity pulls in the way that a planet gains round shape. And I strongly agree with this. Pluto can be a KBO, that is a new type of planet. Why pluto shouldnt be a planet and jupiter should? Jupiter is mostly just gas, pluto is rocky ice. Then why Earth is a planet when is much smaller than Jupiter? Why Ceres isnt? In these day everything is so mess up, that even rocks are classified has moons and with unpronunsable manes! Astronomy sucks these days. Where did the good managers of names and classification go? :( -Pedro 22:32, 16 Jun 2004 (UTC)
- Calm down, and don't get too worked up about a classification issue like this. (And if you do want to get worked up, then it might be good to actually look into just *why* Pluto is considered a Kuiper belt object by some ^_~) -- Schnee 00:33, 17 Jun 2004 (UTC)
Exploration info
Some of the info is taken from a public domain text at.
http://www.vectorsite.net/taxpl_f.html
Distances in AU?
I think it would be very helpful if planetary distances were specified in AU units (in addition to the current metric distances, see the article on Earth). That way it would be much easier to relate facts about the Kuiper belt (30-50 AU) and the Oort cloud to the mean distance of planets like Pluto.
But maybe this suggestion should be made elsewhere?
Help!
I am doing a project on Pluto and I have a question... How many seasons does Pluto have and what are they called/how long do they last? Please help!
- Seasons would be named and defined the same way as here. Plutonian Spring would begin when the Sun goes through Pluto's equatorial plane into its northern celestial hemisphere, and so on. Each season would normally last 1/4 of an orbit, but since the orbit is quiet eccentric, this will lengthen some and shorten others. The Pluto article gives the co-ordinates of Pluto's pole and its complete orbital parametres, so you should be able to compute this for yourself...If you have the math for it, of course. ;-)
- I think you'll find this article (http://www.lowell.edu/users/buie/pluto/chphases.html) on the phases of Charon quite interesting too.
- Urhixidur 23:22, 2005 Jan 11 (UTC)
- The seasons on Pluto will be a bit different from those on Earth in terms of climate due to the high eccentricity of the planet's orbit. When the planet is close to the Sun the temperature of both hemispheres rises and when it's farther away the temperature of both hemispheres drops - enough that the planet's whole atmosphere freezes out as snow when it's farther away. This is a change in the planet's average temperature, independant of the seasonal changes in temperature that each hemisphere experiences. Bryan 00:38, 12 Jan 2005 (UTC)
- The expected temperature variation, given the albedo of 0.30, would be 66 K at perihelion and 51 K at aphelion. Not a large difference (29% energy difference), but then the atmosphere is so thin that the effects can be substantial.
- Urhixidur 03:12, 2005 Jan 12 (UTC)
Orbital period?
I've seen Pluto's orbital period listed as 247.7 or as 248.54 Earth years. Converting from Julian to Gregorian won't account for this discrepancy, or with the value 248.09 Julian years in the article's table. Can somebody clarify?--192.35.35.35 20:52, 14 Feb 2005 (UTC)
- Well, I checked out JPL Horizons (http://ssd.jpl.nasa.gov/horizons.html), and it turns out that Pluto's orbital elements are considerably affected by perturbations. The instantaneous orbital elements (what they would be if no further perturbations were ever received) show the following orbital periods at different times:
- 1920: 91438 d
- 1980: 91828 d
- 2005: 91115 d
- 2040: 90210 d
- 2100: 90065 d
- The variation here is almost 3 1/2 years. So maybe the figures quoted represent some kind of average... but I wouldn't be surprised if that average also varies slowly over time. -- Curps 02:35, 15 Feb 2005 (UTC)
- Then what is the value 90,613.3058 d in the table? Genuine result of a careful computation, or wildly unjustified precision? Do we really know the period down to the nearest 10 seconds, or only within ± 2 years?--192.35.35.34 18:00, 15 Feb 2005 (UTC)
- At any given time, we know Pluto's orbit with extremely high accuracy, it's just that that orbit changes over time as a result of perturbations (but again, we can predict those perturbations with extremely high accuracy). So I'm sure this figure represents a valid result and the digits after the decimal point represent the actual precision... I'm just not sure what result it represents. -- Curps 19:36, 15 Feb 2005 (UTC)
- Let's see. The JPL data tables give the semi-major axis with ten digits of precision, and we know the heliocentric gravitational constant and the value of the AU to twelve digits. Nine digits of precision on the period (more accurately, the instantaneous mean orbit for J2000) is what the error bars give.
- Urhixidur 01:32, 2005 Feb 16 (UTC)
- The upshot I get, then, is that these superprecise results are not actual real world orbital periods, but extrapolations fraught with uncertainty over what the actual perturbations will be in the long long run. I, too, can apply Kepler's law and get 9 decimal places, but I'm ignorant of what 240-some years of perturbations do to the final orbital period or the accuracy with which it is known.--192.35.35.36 15:43, 2 Mar 2005 (UTC)
- Not quite. The instantaneous orbit is very well known, and so is its future evolution over a fairly large time span, since we know the masses of all main objects quite well, down to the larger asteroids. Uncertainty creeps in, but before it can make a detectable difference probably takes on the order of a million years or more. Note that an orbit may also vary "chaotically" but within very well-defined bounds. Search the ADS, there may be some papers on the long-term orbit of Pluto already in there.
- Urhixidur 23:04, 2005 Mar 2 (UTC)
Other symbols
See Symbols.com (http://symbols.com/encyclopedia/54/5434.html)
On Pluto's Name
The article mentions that the grandfather sent the idea for Pluto's name to a former Astronomer Royal. Does this refer to Frank Dyson, as he was the only retired Astronomer Royal at the time?
Pluto's composition
Is there any more information available about Pluto's surface/interior composition? Right now it just mentions nitrogen and carbon monoxide ice. Surely there's more information than that. Kaldari 18:28, 23 May 2005 (UTC)