9, 12, or 8 planets?
Pluto has always been controversial as a "planet". It has a strange orbit but it no longer meets the requirements of a planet according to IAU.
The decision at a conference of 2,500 astronomers from 75 countries was a dramatic shift from just a week ago, when the group's leaders floated a proposal that would have reaffirmed Pluto's planetary status and made planets of its largest moon and two other objects.
That plan proved highly unpopular, splitting astronomers into factions and triggering days of sometimes combative debate that led to Pluto's undoing
Now, two of the objects that at one point were cruising toward possible full-fledged planethood will join Pluto as dwarfs: the asteroid Ceres, which was a planet in the 1800s before it got demoted, and 2003 UB313, an icy object slightly larger than Pluto whose discoverer, Michael Brown of the California Institute of Technology, has nicknamed Xena.
Pluto now belongs to a new Trans-Neptunian family of planets that still have to be named. Wikipedia impressed me again as it did not take long before all Pluto related articles were updated. A community effort like Wikipedia will always have problems with vandalism but the benefits compared to a normal bookshelf encyclopedia is enormous. Kids will continue to learn about Pluto The Planet for many years (decades?) to come.
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