Why some scientists and the mainstream media "demoted" Pluto: psychodynamics
The "demotion" of Pluto and other Kuyper Belt bodies, e.g., Eris, Huamea, etc., from planetary to "dwarf" status, wasn't particularly intelligent, nor was it scientifically justified. For the details of that, see, e.g., pluto and hades. Suffice it to say that calling a body that has achieved hydrostatic equilibrium a "dwarf" doesn't tell anyone anything useful about it, though it suggests that the one doing the telling has nothing but contempt for it.
Much more useful definitions and classifications of Solar System bodies do exist, e.g., one classifying them according to where they are in the Solar System and the general population of other bodies they belong to:
1) The small, rocky planets (Mercury, Venus, Earth, Mars);
2) The Main-Belt asteroids (Ceres, Vesta, Juno, Pallas, etc.);
3) The gas giants (Jupiter, Saturn);
4) The ice giants (Uranus, Neptune);
5) The Kuyper-Belt bodies (Pluto, Eris, Haumea, etc.);
6) The Centaurs (large comets in orbits ranging between Neptune and Jupiter; the first one to be discovered was Chiron, in 1977);
7) The Oort Cloud, a hypothesized spherical cloud of comets which may lie roughly 50,000 AU, or nearly a light-year, from the Sun. This places the cloud at nearly a quarter of the distance to Proxima Centauri, the nearest star to the Sun. The Kuiper belt and scattered disc, the other two reservoirs of trans-Neptunian objects, are less than one thousandth the Oort cloud's distance. The outer extent of the Oort cloud defines the gravitational boundary of our Solar System. The Oort cloud is thought to comprise two separate regions: a spherical outer Oort cloud and a disc-shaped inner Oort cloud, or Hills cloud. Objects in the Oort cloud are largely composed of ices, such as water, ammonia, and methane. Astronomers believe that the matter comprising the Oort cloud formed closer to the Sun and was scattered far out into space by the gravitational effects of the giant planets early in the Solar System's evolution. Although no confirmed direct observations of the Oort cloud have been made, astronomers believe that it is the source of all long-period and Halley-type comets entering the inner Solar System and many of the Centaurs and Jupiter-family comets as well. The outer Oort cloud is only loosely bound to the Solar System, and thus is easily affected by the gravitational pull both of passing stars and of the Milky Way Galaxy itself. These forces occasionally dislodge comets from their orbits within the cloud and send them towards the inner Solar System. Based on their orbits, most of the short-period comets may come from the scattered disc, but some may still have originated from the Oort cloud. Although the Kuiper belt and the farther scattered disc have been observed and mapped, only four currently known trans-Neptunian objects-90377 Sedna, 2000 CR105, 2006 SQ372 and 2008 KV42-are considered possible members of the inner Oort cloud.
8) The Aten asteroids, a group of near-Earth asteroids, named after the first of the group to be discovered (2062 Aten, discovered January 7, 1976 by Eleanor F. Helin). They are defined by having semi-major axes of less than one astronomical unit (the distance from the Earth to the Sun). Note that, because asteroids' orbits can be highly eccentric, an Aten orbit need not be entirely contained within Earth's orbit; in fact, nearly all known Aten asteroids have their aphelion greater than one AU.
9) The Apohele asteroids (alternatively, Inner Earth Objects (IEOs) or Atira asteroids, a subclass of Aten asteroids. They have not only their perihelion within Earth's orbit, but also their aphelion; that is, their entire orbit is within Earth's (which has a perihelion of 0.983 AU).
10) The Apollo asteroids, a group of near-Earth asteroids named after 1862 Apollo, the first asteroid of this group to be discovered by Karl Wilhelm Reinmuth. They are Earth-crosser asteroids that have orbital semi-major axes greater than that of the Earth (> 1 AU) and a perihelion distance (q) < 1.017 AU. Some can get very close to the Earth, making them a potential threat to our planet (the closer their semi-major axis is to Earth's, the less eccentricity is needed for the orbits to cross).
11) The Amor asteroids, a group of near-Earth asteroids named after the asteroid 1221 Amor. They approach the orbit of the Earth from beyond, but do not cross it. Most Amors do cross the orbit of Mars. The two moons of Mars, Deimos and Phobos, may be Amor asteroids that were captured by Mars's gravity.
12) The Trojan asteroids, minor planets and natural satellites (moons) that share orbits with a larger planet or moon, but don't collide with them, because they orbits around one of the two Lagrangian points of stability, L4 and L5, which lie 60° ahead of and behind the larger body. The term trojan originally referred to the Trojan asteroids orbiting around Jupiter's Lagrangian points (which are by convention named after figures from the Trojan War), and asteroids at the Lagrangian points of other planets may be called Lagrangian asteroids. Subsequently objects have been found orbiting the Lagrangian points of Neptune and Mars. In addition, trojan moons are known to orbit the Lagrangian points of two of Saturn's mid-sized moons.
13) Hirayama families of asteroids, which are groups of minor planets that share similar orbital elements, such as semimajor axis, eccentricity, and orbital inclination. The members of the families are thought to be fragments of past asteroid collisions. Strictly speaking, families and their membership are identified by analysing the so-called proper orbital elements rather than the current osculating orbital elements, which regularly fluctuate on timescales of tens of thousands of years. The proper elements are related constants of motion that are thought to remain almost constant for times of at least tens of millions of years.
13) And, of course, the Sun.
Clearly, using this type of categorization of Solar System bodies tells you right away not only where in the Solar System a body is located, but what its general physical and chemical makeup is, what its orbital characteristics are, and alll sorts of other useful information. Other potentially useful types of classifications of the Solar System bodies might be, e.g., any moons they might have, and the sizes of those moons relative to their parent bodies, or whether, like Titan, a moon of Saturn, or Triton, a moon of Neptune, their moons have substantial atmospheres. And so on.
So why did the International Astronomers Union declare in 2006 that henceforth, Pluto and other Kuyper Belt bodies were to be called "dwarf planets," an utterly stupid classification that tells one nothing particularly useful about where those bodies are in the Solar System, what their chemical makeup is, or anything else of value?
One possible reason for that which everyone seems to have overlooked -- or danced around because it's just too uncomfortable -- is psychodynamic in nature. Pluto, the flagship of Kuyper-Belt bodies, was named after the Roman avatar of Hades, the Greek God of the Underworld, including the realm of the dead. By "demoting" Pluto and its neighbors in the Kuyper Belt to "dwarf" status, those who upheld that stupid, stupid decision of the IAU are trumpeting to the world their fear of death and denial of its reality. Which is the sort of decision a frightened child might make, the act of a bombastic and equally terrified adolescent. It is not the decision or act of true adults. Make death your friend, kids, because there is no other healthy way to get past that fear and do something useful with your lives. Death is here to stay, so get the hell used to it.
Much more useful definitions and classifications of Solar System bodies do exist, e.g., one classifying them according to where they are in the Solar System and the general population of other bodies they belong to:
1) The small, rocky planets (Mercury, Venus, Earth, Mars);
2) The Main-Belt asteroids (Ceres, Vesta, Juno, Pallas, etc.);
3) The gas giants (Jupiter, Saturn);
4) The ice giants (Uranus, Neptune);
5) The Kuyper-Belt bodies (Pluto, Eris, Haumea, etc.);
6) The Centaurs (large comets in orbits ranging between Neptune and Jupiter; the first one to be discovered was Chiron, in 1977);
7) The Oort Cloud, a hypothesized spherical cloud of comets which may lie roughly 50,000 AU, or nearly a light-year, from the Sun. This places the cloud at nearly a quarter of the distance to Proxima Centauri, the nearest star to the Sun. The Kuiper belt and scattered disc, the other two reservoirs of trans-Neptunian objects, are less than one thousandth the Oort cloud's distance. The outer extent of the Oort cloud defines the gravitational boundary of our Solar System. The Oort cloud is thought to comprise two separate regions: a spherical outer Oort cloud and a disc-shaped inner Oort cloud, or Hills cloud. Objects in the Oort cloud are largely composed of ices, such as water, ammonia, and methane. Astronomers believe that the matter comprising the Oort cloud formed closer to the Sun and was scattered far out into space by the gravitational effects of the giant planets early in the Solar System's evolution. Although no confirmed direct observations of the Oort cloud have been made, astronomers believe that it is the source of all long-period and Halley-type comets entering the inner Solar System and many of the Centaurs and Jupiter-family comets as well. The outer Oort cloud is only loosely bound to the Solar System, and thus is easily affected by the gravitational pull both of passing stars and of the Milky Way Galaxy itself. These forces occasionally dislodge comets from their orbits within the cloud and send them towards the inner Solar System. Based on their orbits, most of the short-period comets may come from the scattered disc, but some may still have originated from the Oort cloud. Although the Kuiper belt and the farther scattered disc have been observed and mapped, only four currently known trans-Neptunian objects-90377 Sedna, 2000 CR105, 2006 SQ372 and 2008 KV42-are considered possible members of the inner Oort cloud.
8) The Aten asteroids, a group of near-Earth asteroids, named after the first of the group to be discovered (2062 Aten, discovered January 7, 1976 by Eleanor F. Helin). They are defined by having semi-major axes of less than one astronomical unit (the distance from the Earth to the Sun). Note that, because asteroids' orbits can be highly eccentric, an Aten orbit need not be entirely contained within Earth's orbit; in fact, nearly all known Aten asteroids have their aphelion greater than one AU.
9) The Apohele asteroids (alternatively, Inner Earth Objects (IEOs) or Atira asteroids, a subclass of Aten asteroids. They have not only their perihelion within Earth's orbit, but also their aphelion; that is, their entire orbit is within Earth's (which has a perihelion of 0.983 AU).
10) The Apollo asteroids, a group of near-Earth asteroids named after 1862 Apollo, the first asteroid of this group to be discovered by Karl Wilhelm Reinmuth. They are Earth-crosser asteroids that have orbital semi-major axes greater than that of the Earth (> 1 AU) and a perihelion distance (q) < 1.017 AU. Some can get very close to the Earth, making them a potential threat to our planet (the closer their semi-major axis is to Earth's, the less eccentricity is needed for the orbits to cross).
11) The Amor asteroids, a group of near-Earth asteroids named after the asteroid 1221 Amor. They approach the orbit of the Earth from beyond, but do not cross it. Most Amors do cross the orbit of Mars. The two moons of Mars, Deimos and Phobos, may be Amor asteroids that were captured by Mars's gravity.
12) The Trojan asteroids, minor planets and natural satellites (moons) that share orbits with a larger planet or moon, but don't collide with them, because they orbits around one of the two Lagrangian points of stability, L4 and L5, which lie 60° ahead of and behind the larger body. The term trojan originally referred to the Trojan asteroids orbiting around Jupiter's Lagrangian points (which are by convention named after figures from the Trojan War), and asteroids at the Lagrangian points of other planets may be called Lagrangian asteroids. Subsequently objects have been found orbiting the Lagrangian points of Neptune and Mars. In addition, trojan moons are known to orbit the Lagrangian points of two of Saturn's mid-sized moons.
13) Hirayama families of asteroids, which are groups of minor planets that share similar orbital elements, such as semimajor axis, eccentricity, and orbital inclination. The members of the families are thought to be fragments of past asteroid collisions. Strictly speaking, families and their membership are identified by analysing the so-called proper orbital elements rather than the current osculating orbital elements, which regularly fluctuate on timescales of tens of thousands of years. The proper elements are related constants of motion that are thought to remain almost constant for times of at least tens of millions of years.
13) And, of course, the Sun.
Clearly, using this type of categorization of Solar System bodies tells you right away not only where in the Solar System a body is located, but what its general physical and chemical makeup is, what its orbital characteristics are, and alll sorts of other useful information. Other potentially useful types of classifications of the Solar System bodies might be, e.g., any moons they might have, and the sizes of those moons relative to their parent bodies, or whether, like Titan, a moon of Saturn, or Triton, a moon of Neptune, their moons have substantial atmospheres. And so on.
So why did the International Astronomers Union declare in 2006 that henceforth, Pluto and other Kuyper Belt bodies were to be called "dwarf planets," an utterly stupid classification that tells one nothing particularly useful about where those bodies are in the Solar System, what their chemical makeup is, or anything else of value?
One possible reason for that which everyone seems to have overlooked -- or danced around because it's just too uncomfortable -- is psychodynamic in nature. Pluto, the flagship of Kuyper-Belt bodies, was named after the Roman avatar of Hades, the Greek God of the Underworld, including the realm of the dead. By "demoting" Pluto and its neighbors in the Kuyper Belt to "dwarf" status, those who upheld that stupid, stupid decision of the IAU are trumpeting to the world their fear of death and denial of its reality. Which is the sort of decision a frightened child might make, the act of a bombastic and equally terrified adolescent. It is not the decision or act of true adults. Make death your friend, kids, because there is no other healthy way to get past that fear and do something useful with your lives. Death is here to stay, so get the hell used to it.