Pluto

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[[Image:Pluto.jpg|thumb|righ|150px|The highest resolution picture of ''Disco Pluto'', apparently taken with Charon's cellphone.]]
 
[[Image:Pluto.jpg|thumb|righ|150px|The highest resolution picture of ''Disco Pluto'', apparently taken with Charon's cellphone.]]
'''Pluto''' is <s>a planet</s> <s>a celestial body</s> <s>a plutoid</s> <s>trans-Neptunian Object</s> a ''[[dwarf planet]]'' in the [[Solar System]] named after the [[Roman]] god of the [[Hell|underworld]] (known as Hades to the [[Greece|Greeks]]), orbiting the [[Sun]] in an eccentric orbit at a distance of between 30 to 49 AU. It is believed to be composed mostly of ice and rock, is about two-thirds the diameter of the [[Earth]]'s [[moon]], and has one small satellite named Charon (notable for being the largest satellite in proportion to its planet (''or'' dwarf planet) in the solar system), two ''really'' small additional moons named Hydra and Nix, which were spotted in 2005 by the Hubble Space Telescope, and two ''even smaller'' moons named Kerberos and Styx, spotted in 2011 and 2012 by Hubble.
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'''Pluto''' is a <s>planet</s> <s>celestial body</s> <s>plutoid</s> <s>trans-Neptunian Object</s> ''[[dwarf planet]]'' in the [[Solar System]] named after the [[Roman]] god of the [[Hell|underworld]] (known as Hades to the [[Greece|Greeks]]), orbiting the [[Sun]] in an eccentric orbit at a distance of between 30 to 49 AU. It is believed to be composed mostly of ice and rock, is about two-thirds the diameter of the [[Earth]]'s [[moon]], and has one small satellite named Charon (notable for being the largest satellite in proportion to its planet (''or'' dwarf planet) in the solar system), two ''really'' small additional moons named Hydra and Nix, which were spotted in 2005 by the Hubble Space Telescope, and two ''even smaller'' moons named Kerberos and Styx, spotted in 2011 and 2012 by Hubble.
  
 
==Chance discovery==
 
==Chance discovery==

Latest revision as of 07:04, 6 March 2015

The highest resolution picture of Disco Pluto, apparently taken with Charon's cellphone.

Pluto is a planet celestial body plutoid trans-Neptunian Object dwarf planet in the Solar System named after the Roman god of the underworld (known as Hades to the Greeks), orbiting the Sun in an eccentric orbit at a distance of between 30 to 49 AU. It is believed to be composed mostly of ice and rock, is about two-thirds the diameter of the Earth's moon, and has one small satellite named Charon (notable for being the largest satellite in proportion to its planet (or dwarf planet) in the solar system), two really small additional moons named Hydra and Nix, which were spotted in 2005 by the Hubble Space Telescope, and two even smaller moons named Kerberos and Styx, spotted in 2011 and 2012 by Hubble.

Contents

[edit] Chance discovery

As with Uranus before it, Neptune's orbit was back-calculated to see if there was another planet farther out that might be perturbing it. Initial calculation showed that such perturbations were present, and predicted the position of the suspected "Ninth Planet" out past it, to a positional accuracy of a few degrees.

Astronomer Clyde Tombaugh searched the skies near the point where the predicted Ninth Planet was supposed to be, and lo and behold, he discovered there was a moving object out there. This object was named Pluto, and was initially believed to be the object that was perturbing Neptune's orbit. Only ... it wasn't. It quickly became obvious that Pluto was way too small to cause any detectable perturbations of Neptune.

Subsequent reviews of the original Neptune calculations showed that they had been way too aggressive. The amount of uncertainty in the observations of Neptune's position were high enough that the "perturbations" were entirely within measurement error. Later, more accurate observations of Neptune showed that such perturbations didn't exist.

So ... Pluto happened to be in the right place, at the right time, for someone who was looking for a non-existent planet to stumble upon. Therefore God exists.

[edit] As a holiday resort?

Due to its immense distance and small size, Pluto has never been visited by any man-made device. Neither Voyager 1 nor Voyager 2 went near the dwarf planet. However, in 2006 the New Horizons[wp] probe was launched with the aim of getting to Pluto by 2015 before moving on to try and study the rest of the Kuiper belt. As Pluto's discoverer Clyde Tombaugh said, "He's got to go one long, cold trip..."

[edit] Dwarf planet

Few people other than a couple astronomers gave much of a damn about Pluto until 2005 when the "10th" planet Eris was discovered.[1] As Eris was larger (by roughly a third, mass-wise) than Pluto but almost three times further away, speculation raged about whether the solar system had any more surprises up its sleeve and whether there could be hundreds of planets like this orbiting the sun. Indeed, two other very distant bodies, Haumea and Makemake, were discovered around the same time. Combined with the already known Ceres (the asteroid belt-dwelling planetoid) and a few other larger bodies discovered since 2000, this made the solar system look a little crowded. Thus, The International Astronomical Union (IAU) decided to coin the term "dwarf planet" and actually define "planet" for the first time—believe it or not, it really wasn't given a proper definition until that recently. Out of the various criteria proposed (remembering that astronomy is science and needs to be objective) there was no definition available that would keep just 9 planets. Either Eris, Ceres, and potentially many more would be added (noting that Ceres was classed as a planet until the 1860s and was used as evidence to support the Titus-Brode law), or Pluto would be lost. The key to this decision was the third criterion for classification of a planet: the object must have cleared its orbit of other debris and asteroids. None of the bodies in question had achieved this, and so would not be eligible for planetary status. Pluto was reclassified, leading to considerable drama both among astronomers and the general public (who probably felt sorry for Pluto or something like that).

To add insult to injury, solar system objects that aren't full-blooded planets have to have a number attached to their name, indicating the order in which they were discovered. So Pluto's official name is now 134,340 Pluto.

But let's face it. Pluto's planetary status always had a lot going against it. Its orbit is inclined 17° with respect to the Ecliptic, the orbit is so eccentric that at perihelion it's actually closer to the sun than Neptune, it's smaller than Earth's moon, and it's less than a fifth of the moon's mass.

Possibly to calm the drama amongst those weeping for Pluto's demotion, or possibly to appease those who prefer the term over "dwarf planet," another category of "plutoid" was also introduced.[2] This refers to the four dwarf planets in the outer solar system which rank alongside Pluto. Pluto was important again. Pluto was probably also demoted due to the fact that its name sounded like two famous cartoon characters.

[edit] King of the Plutinos

Plutinos are Kuiper belt objects in a 2:3 orbital period resonance with Neptune. Pluto was the first plutino discovered; the rest of the plutinos (all discovered later) are named after it.

Pluto is by far the largest of all the plutinos; the second largest plutino, Orcus, is less than half of Pluto's diameter.

[edit] A Dual Dwarf Planet?

It is argued in some circles that Pluto's largest moon, Charon, should be classified as a dwarf planet in its own right. At one sixth of Pluto's mass and roughly half the diameter, Charon is larger compared to its parent body than any other moon in the solar system. That would not be enough to argue dwarf planet status for Charon if not for the size ratio's effect on the system's barycenter, the point where Pluto and Charon's gravity balances out. Unlike other planet-moon systems, the system's barycenter is not beneath Pluto's surface as in the case of the Earth-Moon system, but in the empty space between Pluto and Charon. In this respect, Charon can not be considered to actually orbit Pluto, and some claim that it would be a dwarf planet if it were an independent object, so it should be classified as a dwarf planet in its own right.

[edit] Legislative planetology

Pluto is still legally a planet in some places - such as the state of Illinois. In 2009, the Illinois Senate passed a resolution[3] declaring 13 March 2009 "Pluto Day" in the state to honour Pluto's discovery (which is more or less OK) and re-establishing it "with full planetary status" (which is daft). The list of "whereas"-es cited in support of the decision only adds to the hilarity. Unfortunately, the resolution does not provide any instructions about how it's going to be enforced. Can you get arrested in Illinois for calling Pluto a dwarf planet?

[edit] The Plutonian language

In 1969, Patrick Moore made a one-off special for the BBC, called One Pair of Eyes, featuring what Moore called "independent thinkers." These included a man from the Aetherius Society who claimed to be able to speak Venusian and Plutonian.


[edit] External links

[edit] Footnotes

  1. Mike Brown. How I Killed Pluto and Why It Had It Coming. New York: Spiegel & Grau, 2010.
  2. Not to be confused with a "plutino", which is an object that orbits in the same 3:2 resonance with Neptune that Pluto does.
  3. Illinois General Assembly - Bill Status of SR0046, full text available.
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