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You are in: Curriculum issues > Science issues > Message from Pluto
The relegation of Pluto poses a real challenge to conventional science education, illustrating as it does that science changes.
As most people will know, a recent meeting of the International Astronomical Union (IAU) has reduced the number of planets in the Solar System by one. (See the BBC news item with photo of Jocelyn Bell and Pluto.)
A ‘planet’ is now defined as a celestial body that:
(a) is in orbit around the Sun,
(b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and
(c) has cleared the neighbourhood around its orbit.
One member of the Planet Definition Committee said: "Our goal was to find a scientific basis for a new definition of planet and we chose gravity as the determining factor. Nature decides whether or not an object is a planet."
A new class of objects called ‘dwarf planets’ was also decided. The first members of the dwarf planet category are Ceres, Pluto and 2003 UB313 (called Xena, this is the largest). More dwarf planet are expected to be announced by the IAU in the coming months and years, as new objects are found and the physics of existing candidates becomes better known.
This is a good example of science in the making. GCSE Science, in the Twenty First Century Science suite of courses, explores how scientific explanations develop. In the module Earth in the Universe, there are many examples of observations and new insights together reshaping scientific ideas. Not only is this a truer portrait of science, it also more inviting: young people can see how one day, as future scientists, they could make their own mark within the scientific community. The IAU’s decision this year adds yet another encouraging example.
Last Updated Tue, 29 August 2006