The Bullet Cluster

Chris Lintott ... 17 October 2006

One of the fundamental motivations behind the writing of Bang! was that - for the first time in many decades - most of the observational tests astronomers can think of produce results which agree with a single model of how the Universe evolves. In the trade, this has become known as the 'concordance cosmology', and we concentrated on telling that story alone. (We did chicken out when it came to selecting from the many possible ends of our Universe, but that's another story altogether) However, you shouldn't get the idea that the world's cosmologists are now comfortably resting on their laurels, perhaps with a nice cup of tea (or something stronger); the model is deeply unsatisfactory, relying as it does on two as yet unknown components of the Universe which we label dark matter and dark energy. Any theory which can dispose of the need for such mysterious actors on the Universe's stage therefore deserves to be taken seriously.

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Nine Planets - or Eight?

Sir Patrick Moore ... 15 October 2006

One very new development comes under the heading of terminology rather than true astronomy. We are used to talking about nine planets, from Mercury to Pluto, but Pluto has always been an enigma; it is small, and has an orbit which is both inclined and eccentric. We have now found that
it is not a solitary wanderer in this remote part of the Solar System; there are hundreds, no doubt many thousands, of others, making up the Kuiper Belt, and Pluto is not even the largest member of the swarm. For example Eris, discovered in 2003, is decidedly bigger. At its latest general assembly, held in Prague, the International Astronomical Union decided to re-classify Pluto as a 'dwarf planet', along with Eris and the largest main-belt asteroid, Ceres.

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