1, 2, 3, Planète
In the wake of continuous discoveries of many object beyond planet Neptune, starting in 1992, the International Astronomical Union decided in 2006 to reclassify the objects of the Solar System by defining three main group of objects: the planets, the dwarf planets and the small bodies (see a more extended explanation at the website of the IAU). Pluto, which has been named the ninth planet since its discovery in 1930, has been reclassified as a dwarf planet.
In this educational film, Alain Doressoundiram, astrophysicists at the Paris Observatory and his colleagues Danielle Briot (Paris Observatory) and Bernard Schmitt (University Joseph Fourier de Grenoble) explore the history of our understanding of the Solar System. They explain why Pluto is not considered a planet anymore and how modern research is done on Trans Neptunian Objects, the small icy bodies at the very edge of the Solar System.
A DVD was produced as well and the disk image (french-only version) can be downloaded from ufe.obspm.fr/article424.html.
[Lightcurve Films for Science à l’Ecole / French Ministry of Education; 25:47 min.; May 2008]