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Pluto as a Collisional Family

  1. Mar 25, 2014 #1
    I realize that some people may still be sensitive concerning Pluto's declassification as a "planet" by the IAU. However, what the IAU did not do was establish exactly what Pluto is. As a result, Pluto is now considered a "Trans-Neptunian Object", a "Kuiper Belt Object", a "Plutoid", a "Dwarf Planet", a "Minor Planet", and a "Planetoid."

    One thing that does set Pluto apart from all the other planets is that its orbit is not in the same ecliptic plane as the rest of the planets. While its eccentric orbit does bring Pluto within the orbit of Neptune, it never actually crosses Neptune's orbit because Pluto's orbit is at a completely different angle. So there is no gravitational influence by Neptune on Pluto, or visa versa.

    Considering the four new moons recently discovered around Pluto, Charon making five moons, perhaps Pluto might be considered a "collisional family." What do you think?
  2. jcsd
  3. Mar 25, 2014 #2
    Pluto has been categorized as a dwarf planet. It can also be called a TNO if you want. However, not all dwarf planets are a TNOs

  4. Mar 26, 2014 #3
    I'm not sure if we can consider them a collisional family with the data we currently have on Pluto. Perhaps in the future when we obtain more data from the New Horizons probe, we could verify whether or not they originated from a common object.
  5. Mar 27, 2014 #4
    while the fact that Pluto's orbital plane lies outside the ecliptic does make it unique with respect to the planets, the rest of what you said here isn't quite true. Pluto's orbital path doesn't literally have to cross that of Neptune's in order to influence it gravitationally. they simply have to be close enough to one another in their orbits to influence each other gravitationally. in fact, the two objects actually never stop influencing one another gravitationally. of course the magnitude of that influence is negligible when Neptune and Pluto are more or less on opposite sides of the Sun/solar system. and sometimes Uranus, even from a greater distance (though still sufficiently close), can still exert more gravity on Neptune than Pluto...so even in situations where Pluto is fairly close to Neptune (and can therefore exert more gravity on it), the gravitational influence between them is still negligible in the grand scheme of things. that said, rest assured that Neptune and Pluto are always exerting gravitational influence on one another, however unnoticeable it may be.
  6. Mar 27, 2014 #5
    I will grant you that gravitationally speaking, every object tugs on every other object, even if that tug is negligible. An apple falling from a tree, while being tugged by Earth's gravity toward the surface, also exerts a negligible tug against the Earth due to the apple's tiny gravity.

    If it is considered that Pluto has not "cleared its neighbourhood", gravitationally speaking, due to the presence of Neptune, even though they are separated by several million miles at their closest approach. Then would that not also exclude Neptune from "planet" status since it has also not "cleared its neighbourhood"?

    This is another example of the failure of the IAU to make a proper definition. Just how much gravitational influence on an object must another object have before it is no longer considered a planet?
  7. Mar 27, 2014 #6
    I agree. The limited data we currently have is inconclusive. I am looking forward to the New Horizons probe reaching Pluto next July. That will give us a lot more answers, and hopefully a few new questions.

    Personally, I do not care if Pluto is a "planet" or a "dwarf planet" or a "collisional family." Unlike the IAU, I am more interested in determining what Pluto really is, rather than what it is not.
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