Posts Tagged ‘planet’

It may be small but Pluto is still a planet

July 13, 2015

It orbits the Sun. It has five moons. It is the tenth most massive object orbiting the Sun. It is not that Pluto is not a planet, but that there are many more planets than the “big ten”. The asteroid belt and the Kuiper belt objects are all also planets. Inventing new definitions and calling them “dwarf planets” or “planetoids” doesn’t change the fundamentals.

The International Astronomical Union (IAU) defines a planet thus:

A planet is a celestial body which:

  1. is in orbit around a Star,
  2. has sufficient mass to assume hydrostatic equilibrium (a nearly round shape), and
  3. has “cleared the neighbourhood” around its orbit.

Calling Pluto a “dwarf planet” rather than a “planet” has nothing to do with its properties or the properties of the Sun. It is not even a matter of language or semantics. It is merely for the convenience of a bunch of lazy astronomers who were afraid of having too many planets to classify.

Ultimately it is just a matter of usage. For me any celestial body orbiting another is and remains a planetary body. And every body which orbits the Sun directly (and not by virtue of orbiting a planetary body first) is a planet. Every asteroid is a planet of the Sun. Jupiters moons remain planets of Jupiter. And that makes Pluto a planet. New planets may well have been found in the Kuiper belt – but Pluto remains a planet for me, in spite of the failings of the IAU.

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