Is it or isn't it?

Tom Gehrels writing in the second issue of the IAU's snappily titled conference newsletter - Dissertatio cum Nuncio Sidereo III - states the proposal for the definition of planets that has been put forward to the relevant IAU committees. The proposal keeps Pluto as a planet, as was agreed at the IAU GA in Manchester (2000), and adopts 2003 UB313 (or Xena if you must) as a planet because it is intrinsically brighter than Pluto. If accepted, the definition would be that to classify as a planet the body must have an absolute V magnitude greater than -0.76 (the V magnitude of Pluto). Gehrels points out that this is much simpler than using a classification based on sphericity as it can be very difficult to work out how circular these things are at such a great distance. I'm all for simple and I'm quite happy with Pluto remaining a planet. We just have to wait for the decision.

As I mentioned on my previous post, Thomas Marquart is blogging from the IAU now. Check out his blog for reports on the sessions he has been attending.

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Posted in astro blog by Stuart on Monday 14th Aug 2006 (23:34 BST) | Permalink
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