#238 – Pluto

#238 – Pluto


  • chortle says:

    I can understand why new bodies not be called a Planet but why didn’t Pluto grandfather as a planet? What is next will Australia and Antarctica suddenly stop being continents?

  • Hannah says:

    I wish we’d gotten three new planets with super cool names [sigh]. Mostly I am sad that the honor of Sailor Pluto was crushed, but that is me.

  • Not only IS Pluto still a planet, but we do have several new planets as well, for a total of 13 in our solar system. They are Mercury, Venus, Earth, Mars, Ceres, Jupiter, Saturn, Uranus, Neptune, Pluto, Haumea, Makemake, and Eris.

    What you may not be aware of is that only four percent of the International Astronomical Union (IAU) voted to demote Pluto and did so in a controversial process that violated the group’s own bylaws. Most who voted on this were not planetary scientists at all but other types of astronomers. Their decision was immediately opposed in a petition of over 300 professional astronomers led by Dr. Alan Stern, Principal Investigator of NASA’s New Horizons mission to Pluto, all of whom decried the IAU planet definition as sloppy and said they will not use it. You can find the petition here: http://www.ipetitions.com/petition/planetprotest/

    The IAU planet definition makes no sense for two reasons. First, it states that a dwarf planet is not a planet at all. That’s like saying a grizzly bear is not a bear! Second, it defines objects solely by where they are while ignoring what they are. If Earth were in Pluto’s orbit, according to the IAU definition, it would not be a planet either.

    A better, alternative definition advocated by Stern and like-minded astronomers is that a planet is any non-self-luminous spheroidal body in orbit around a star. Being spheroidal, or round, is critical because it means an object has enough self gravity to pull itself into a round shape. When this happens, the object becomes geologically differentiated into core, mantle, and crust and develops geological processes, just like the bigger planets and unlike inert, shapeless asteroids. You can find Dr. Stern’s discussion of this planet definition here: http://www.sciencenews.org/index/generic/activity/view/id/38770/title/Debates_over_definition_of_planet_continue_and_inspire and you can also find audio and video transcripts of a conference held this summer, titled the Great Planet Debate, which involved much dissention from the IAU definition, here: http://gpd.jhuapl.edu/index.php

    In summary, there is no need to blindly accept a dictate by a tiny minority of astronomers that does not even have consensus among those in the profession. Viewing Pluto as still being a planet is a legitimate scientific position.