A moment of silence for Pluto

In case you missed the science news in the last week, we now only have 8 planets in our Solar System with Pluto demoted to “dwarf planet” status, 76 years after it was discovered.

I must admit that while studying Astronomy at Uni I was never 100% convinced that Pluto should be called a planet. It is afterall tiny, in a binary orbit with its moon Charon (the centre of gravity of the pair is located between them), and its orbit is higly tilted from that of the remainder of the planets and crosses inside Neptune’s.

The decision was made by scientists meeting recently in Prague who agreed that a planet (put simply):

  1. orbits the Sun
  2. is big enough to be nearly round
  3. has “cleared the neighbourhood around its orbit”

Point 3 is a little strange since other planets don’t pass this test – including Earth, which orbits the sun with many near earth asteroids (ie our neighbourhood is NOT clear).

That aside, the result is that we now have 8 planets, and currently 3 dwarf planets – Ceres, Pluto and “2003 UB313” (how’s that for a stupid name!) Ceres orbits in the asteroid belt between Mars and Jupiter, Pluto’s binary companion Charon is NOT a dwarf planet as it’s classifed as a “satellite” (or moon), and lastly “2003 UB313” orbits beyond Pluto.

While I tend to agree with the decision from a technical point of view, it has divided the scientific community. Many disagree with the change and reckon things should have been left alone, and to complicate matters only 424 of the 2500+ attending voted on the issue.

One group happy with the decision might be the publishers of school and uni text books – just a few are now out of date and in need of reprinting!

For more, see the following Wikipedia entries,


About Chris
A self confessed geek, meteorologist (aka weather forecaster), father & proud kiwi mainlander living, working & playing in Wellington, New Zealand.

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